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Optimal Oocyte Retrieval and Embryo Transfer Techniques: Where We Are and How We Got Here Micah J. Hill, DO1

Eric D. Levens, MD2

1 Department of Reproductive and Adult Endocrinology, National

Institute of Child Health and Human Development, Bethesda, Maryland 2 Shady Grove Fertility Reproductive Science Center, Rockville, Maryland

Address for correspondence Eric D. Levens, MD, Shady Grove Fertility Reproductive Science Center, 15001 Shady Grove Road, Suite 340, Rockville, MD 20850 (e-mail: [email protected]).

Semin Reprod Med 2015;33:83–91

Abstract

Keywords

► oocyte retrieval ► embryo transfer ► in vitro fertilization

Oocyte retrieval is most safely accomplished with conscious sedation via a transvaginal approach under ultrasound guidance with low-pressure aspiration. Follicle flushing has not been shown to improve outcomes. The type of vaginal surgical preparation and the use of antibiotics have not been demonstrated to affect outcomes. As the final step in a rigorous assisted reproductive technology (ART) cycle, precise technique in embryo transfer is essential. Based on current findings, the recommended embryo transfer technique includes the use of an ultrasound-guided transcervical approach with a full bladder using a soft catheter. The transfer depth of the embryo should be in the midportion of the uterus with a quick steady insertion followed by pressure on the syringe during withdrawal of the catheter. It is acceptable to encourage immediate ambulation after embryo transfer.

The history of assisted reproductive technology (ART) dates back more than a century when Walter Heape, a professor at the University of Cambridge, reported the first case of embryo transfer in rabbits in the 1890s.1 Several decades later, Aldous Huxley conceptualized the technique of in vitro fertilization (IVF) in his science fiction novel Brave New World (c. 1932). After successful mammalian experiments, attempts at human IVF began in the 1940s when Miriam Menken and John Rock exposed human oocytes recovered via laparotomy to spermatozoa in vitro.2 Three decades later, Louise Brown was born after successful IVF.3 In the nearly 40 years since the first successful human birth, ART has undergone continuous improvement. Significant advances have been made in oocyte fertilization and embryo culture, resulting in ever-increased treatment success. Often overlooked, however, have been the developments in oocyte recovery and embryo transfer techniques that have led to increased safety and success of ART treatment. This document sets out to review the history oocyte recovery and

Issue Theme Best Practices in In Vitro Fertilization; Guest Editor, Bradley J. Van Voorhis, MD

embryo transfer techniques, and to provide recommendations for current best practices.

Approaches of Oocyte Recovery Oocyte recovery aims to maximize the number of oocytes extracted from the ovarian follicles while minimizing the surgical risk to the patient. Optimizing this balance has driven the evolution of oocyte recovery techniques (►Fig. 1).4–16 In the early days of IVF experimentation, abdominal laparotomy was performed to collect oocytes during tubal ligation procedures. Surgery would be scheduled immediately prior to expected ovulation, timed by basal body temperatures.17 Follicles were extracted by needle aspiration or ovarian wedge resection. Techniques described for follicle aspiration involved puncturing follicles over 5 mm in diameter with a 20-gauge needle. The aspiration needle was connected to tubing and emptied into a test tube through a metal inlet with a rubber stopper sealing the tube. A second needle was introduced through the stopper and connected to surgical suction tubing

Copyright © 2015 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.

DOI http://dx.doi.org/ 10.1055/s-0035-1545365. ISSN 1526-8004.

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Mae Wu Healy, DO1

Optimal Oocyte Retrieval and Embryo Transfer Techniques

Healy et al.

Fig. 1 Evolution of oocyte retrieval.

via a three-way plastic connector. Aspiration was achieved by covering the free opening in the three-way connector to create suction to 200 mm Hg. Each follicle was aspirated into individual tubes.17 The technique described for wedge resection involved incising follicles with a scalpel under microscopy subsequently releasing the oocytes into the culture medium for further observation.17 Using these techniques, the reported oocyte recovery rate was 30.2% for aspiration and 93.3% for wedge resection.17,18 Although these techniques are a viable option to obtain oocytes, laparotomies carry surgical risks to include bleeding, infection, increased pain, potential injury to surrounding pelvic and abdominal organs, and longer recovery times. The risks of laparotomy to retrieve oocytes for IVF encouraged the pursuit of alternative surgical options. In the 1950s and 1960s there was great interest in developing less invasive techniques for performing gynecologic surgery. Raoul Palmer was developing laparoscopic surgery in France for sterilization procedures whereas Hans Fragenheim was working with “cold-light” illumination in Germany.4 This work paved the way for laparoscopic techniques. Patrick Steptoe, searching for alternatives to laparotomy in gynecologic surgery, sought out to learn laparoscopic techniques and began using laparoscopy for sterilizations in England as a method of family planning by the mid-1960s.12 Concurrently, Professor Robert Edwards was developing mammalian in vitro techniques. Based on his experiments with mice embryos, he began fertilizing human oocytes in vitro and returning the resulting embryos to the uterus.11 However, as a nonphysician scientist, Edwards encountered barriers to initiating clinical trials. It was not until 1968 when he encountered Steptoe’s article on “Laparoscopy and Ovulation” in the Lancet13 that a connection was made. Together they set out to recover oocytes via laparoscopy and subsequently perform IVF11; thus they began the work of Edwards and Steptoe.14 Using the laparoscopic techniques described by Palmer in 1961, Steptoe and Edwards successfully recovered oocytes for Seminars in Reproductive Medicine

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IVF in 1970.14 The technique described utilized general anesthesia with an umbilical laparoscopic port with a second laparoscopic port placed 7 to 10 cm to the right of the midline, between the pubic bone and the umbilicus. Using forceps to stabilize the ovary and for rotation to obtain adequate visualization, the thin-walled follicles were aspirated using a 20-gauge needle and a syringe for suction. This suction technique was described by Steptoe to be unsatisfactory, which led to the development of an aspiration device. A short-beveled needle was placed directly through the skin into the abdominal cavity, and then cleared of blood and tissue with a heparinized saline solution. Serving as an outer guide to insert the aspiration needle, the follicles were penetrated and suction was obtained by placing a finger over a bypass valve on the aspiration needle.14 The needle and tube were cleaned after each follicle was aspirated. The maximum pressure for the vacuum suction was 12 cm Hg due to concern that higher pressures would damage the oocytes.14 This technique pioneered minimally invasive oocyte retrieval. Laparoscopy slowly gained acceptance after studies demonstrated similar oocyte yields compared with laparotomy. Lopata and colleagues demonstrated no significant difference between laparoscopy and laparotomy in the mean number of oocytes obtained per patient.17 When laparoscopy was performed with CO2 pneumoperitoneum, there likewise was no significant difference in oocyte fertilization rates.19 Advantages of laparoscopy included shorter recovery time, less bleeding, fewer infectious risks, and decreased pain. However, even with these improvements, the disadvantages of requiring general anesthesia and poor visualization of follicles within ovarian stroma led to the pursuit of improved techniques of oocyte recovery. Advances in ultrasound aided in overcoming poor ovarian follicle visualization. In 1972, Kratochwil’s publication on the ultrasonic tomography of the ovaries provided a new window of opportunity.20 The improved visualization of follicles offered safer and more accurate methods for oocyte

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Recommended Techniques for Oocyte Retrievals Comparing Transvesical and Transvaginal Approaches Although the transvaginal approach to oocyte recovery was quickly accepted as a preferred approach, there were initial concerns of reduced pregnancy outcomes when compared with laparoscopic or transvesical approaches.26 This prompted Brinsmead and colleagues to perform a randomized trial

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comparing the two modalities in 94 couples undergoing IVF. The authors concluded that the rate of oocyte recovery, the number of embryos available for transfer, and the pregnancy rates per oocyte did not differ significantly between the two groups.26 It was concluded that the transvaginal approach was as efficacious as the laparoscopic approach.26,27 The transvaginal route has been found to be the simplest, least invasive, and the most effective approach for oocyte retrievals,22 making it the current preferred method for oocyte retrievals in ART clinics around the world.

Anesthesia with Oocyte Retrieval The use of anesthesia has been an integral part of performing oocyte retrievals. Anesthetic options include general anesthesia, neuraxial anesthesia, paracervical block, and conscious sedation. The choice of an anesthetic agent should be based on the ease of administration and monitoring with short-term reversible effects.28 In addition, the agent of choice should not have any toxic effects on the oocytes and subsequent embryos. Adequate pain control is critical, not only for the well-being of the patient but also for the safety of the procedure as the retrieval needle is inserted in close proximity to adjacent vital organs and vessels. With laparoscopic oocyte recovery, general anesthesia with endotracheal intubation and intermittent positive pressure ventilation is required to ensure airway protection, to assist with the maintenance of normocarbia,29,30 and to provide muscle paralysis.31 With less invasive techniques of oocyte recovery (transvesical and transvaginal routes), the need for general anesthesia has declined allowing for methods such as regional anesthesia. Advantages of regional anesthesia include limited absorption of anesthetic agents into the circulation and thus minimal effect on the oocytes.32 However, adverse effects such as spinal headache, back pain, urinary retention, hypotension, high spinal, epidural hematoma, abscess, and significant nerve damage limit its potential use.28 For transvaginal oocyte retrieval procedures, local anesthesia is commonly used. However, local anesthesia in the form of a paracervical block has been found to be inadequate for many women. In a survey of 65 women, 43% undergoing oocyte retrieval with a paracervical block for anesthesia reported the procedure as “very painful” or “painful.” Moreover, 28% of patients required additional analgesia to complete the procedure.33 Despite the decreased cost and ease of administration, a paracervical block is best used in conjunction with another form of anesthesia to provide adequate pain relief. Conscious sedation combining propofol, fentanyl, and midazolam has become one of the most common types of anesthesia for oocyte retrievals. Previously pentothal was used; however, a randomized controlled trial with 156 patients demonstrated that the use of pentothal during oocyte retrieval decreased the clinical pregnancy rate when compared with propofol. In addition, the time under anesthesia and the reported postoperative nausea and dizziness rates were significantly increased with pentothal as compared with propofol.34 Propofol has been shown to have no Seminars in Reproductive Medicine

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retrieval.16,21 In addition, ultrasound is inexpensive and has minimal risks.22 This led to the beginning of ultrasoundguided approaches of oocyte retrieval.23 In 1982, Lenz and colleagues reported the first ultrasoundguided trans-vesical route of oocyte recovery using local anesthesia.16,23 By use of an abdominal ultrasound with a full bladder, a large-bore needle connected to a syringe was passed directly through the abdominal wall through the bladder into the underlying ovaries. Suction was then applied to aspirate the follicular fluid and oocytes. The oocyte yield was similar with transvesicular aspiration compared with laparoscopy. However, the technique was associated with fewer complications and greater ovarian accessibility.7 As experience was gained with ultrasound-guided transvesical techniques, the oocyte yield was found to exceed 80% of the total follicles with a skilled provider.10,15 However, because of the intentional route through the bladder, complications were reported. Ashkenazi and colleagues reported among 140 patients who underwent oocyte retrievals, 11.5% had abdominal pain, 2.9% experienced an exacerbation of preexisting pelvic inflammatory disease, 2.9% had mild hemoperitoneum, 5.8% had urinary tract infections, and 5.8% had transient macroscopic hematuria.24 Despite these complications, this approach remained in favor among physicians and patients alike, because of the advantages of avoiding general anesthesia and being an outpatient procedure. In addition, this method was safer than laparoscopy in patients with extensive abdominal or pelvic adhesive disease.10 This method quickly became the preferred route of oocyte retrieval. Shortly thereafter, an abdominal ultrasound-guided vaginal retrieval was described.5,9 This allowed for increased accuracy and closer proximity of the needle to the ovaries. However, there still remained a significant distance between the abdominal ultrasound probe and the ovaries. The introduction of vaginal ultrasound probes provided a solution. In 1985, Wikland and colleagues described the first transvaginal ultrasound-guided oocyte retrieval.25 In this technique, a needle was guided along the vaginal ultrasound probe to perform an accurate puncture of the ovaries to harvest the oocytes. The improved visualization of the ovaries due to the proximity of the ultrasound probe led to more precise oocyte aspiration. Operation time was also notably shortened and only local anesthesia was required.6 This approach was more cost-effective, with fewer complications including infection, bleeding, and pain, helping the technique to gain widespread popularity among the patient population.8

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negative effect on fertilization rates, pregnancy rates, or live birth rates,34 thus making it a better anesthetic to use during oocyte retrievals.34,35 The rapid onset and recovery, adequate pain control, good safety profile, and lack of impact on oocyte and embryo quality make conscious sedation with propofol a good choice for transvaginal oocyte retrievals.

addition, it increases the length of the procedure and time under anesthesia. Thus, follicle flushing is not recommended in this population. Whether there remains a role for follicular flushing among poor responding patients remains to be determined; however, studies have suggested similar results as seen among normal responding patients.45

Preoperative Prophylactic Antibiotics

Aspiration Setup

The question of prophylactic antibiotics arises for all gynecologic surgeries and procedures. Specifically for oocyte retrievals, studies have shown a potential benefit for antibiotics prior to this procedure. In a study of 526 oocyte donors who received prophylactic antibiotics compared with 625 who did not, the rate of postoperative infection was 0.4% with prophylaxis and 0% without prophylactic antibiotics (p ¼ 0.21).36 The effect of antibiotics on pregnancy outcomes has also been controversial.37,38 Currently, no data convincingly support the use of prophylactic antibiotics to improve pregnancy outcomes. Additional research is needed to evaluate live birth rates as the primary outcome and to assess microbial colonization as a secondary outcome to be able to fully offer recommendations.38 Until further data are published, the use of prophylactic antibiotics for oocyte retrieval should be at the discretion of the provider.

The optimal follicle aspiration setup with the needle, vacuum, and media culture has not been definitively established. Currently, the most common needle sizes range from 16 to 20 gauge; however, there is no consensus on which results in the best outcomes. The vacuum aspirator pressure has been described to be safe for oocytes between the negative pressures of 80 and 300 mm Hg.46,47 However, recent studies show oocytes develop better after a lower aspiration pressure (180 mm Hg) as opposed to a higher pressure (300 mm Hg).47 Similarly, there is no clear agreement over the most effective in vitro oocyte culture media. Currently, most media are supplemented with pyruvic acid with essential and nonessential amino acids. However, further studies need to be performed to help optimize this setup.48

Vaginal Preparation Prior to Oocyte Retrieval

The Beginning

Vaginal preparation solutions used to reduce vaginal microbial concentrations prior to oocyte retrievals have been shown to impact pregnancy outcomes. The two most common disinfectants are 1% povidone-iodine solution and normal saline. In a comparison study, there was no difference in postoperative infection rates between those undergoing saline or 1% povidone-iodine vaginal preparations.39 Moreover, oocyte fertilization and embryo cleavage were similar; however, pregnancy rates were significantly higher in those undergoing normal saline preparation (30.3 vs. 17.2%).39 In addition, chemical pregnancies were increased among those undergoing 1% povidone-iodine preparation (7 from 2.5%).40 Based on these findings, the use of saline irrigation for vaginal preparation prior to oocyte retrieval appears to be the optimal vaginal preparation method for oocyte retrievals.

During an ART treatment cycle, the embryo transfer is the final critical procedure that can impact the outcome of a treatment cycle (►Fig. 2).3,49–58 One of the first reported embryo transfers was in 1891 by Walter Heape. Working out of a laboratory in Cambridge, the United Kingdom, Heape successfully transferred two ova from an Angora doe rabbit into the fallopian tube of a Belgian hare doe rabbit. The doe rabbit delivered six babies, two with Angora phenotypes and four with Belgian phenotypes.50 In the next several years, numerous experiments were performed using rabbits, guinea pigs, sea urchins, and starfish.51 Unfortunately, these attempts were unsuccessful. Almost 60 years later in 1956, McLaren and Michie developed and optimized embryo transfer techniques of blastocysts in mice.49 This report was published in Nature, and was given the heading “Brave New Mice” by the London Daily Telegraph.51 Making the transition to human embryos, Steptoe and Edwards performed embryo transfers for years to no avail. There are many reasons why the initial attempts at pregnancy were ineffective. One key potential contributor for pregnancy failure was poor technique in the transfer of the embryos into the uterus. In the next several years, incremental improvements were made to the embryo transfer process, to include using smaller-diameter transfer catheters, decreased transfer fluid volume from an average of 50 to 70 μL to 20 to 30 μL, and inclusion of a high proportion of serum in the transfer medium, resulting in increased pregnancy rates.59 This showed the importance of the transfer technique; however, the procedure has remained relatively unchanged for the past 30 years.54 Studies have demonstrated that poor technique during a transfer may account for as high as 30% of all

Does Follicle Flushing Improve ART Outcomes? The goal of oocyte retrieval is to maximize the number of oocytes recovered. In the past decade, there have been attempts to refine equipment to increase the number of oocytes retrieved.41 The double-lumen retrieval needle was developed to reintroduce additional fluid into an aspirated follicle to increase the likelihood of recovering a retained oocyte.42 Initial studies produced conflicting results as to the utility of follicular flushing with some studies demonstrating benefit when compared with aspiration alone. Bagtharia and Haloob demonstrated 82% of oocytes could be recovered with two flushes and up to 97% of oocytes could be retrieved in up to four flushes, compared with only 40% with the initial first aspiration.42 However, a recent meta-analysis and a Cochran review have both found that follicle flushing does not appear to improve ART outcomes in normal-responding patients.43,44 In Seminars in Reproductive Medicine

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Evolution of Embryo Transfer

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Healy et al.

Fig. 2 Evolution of embryo transfer.

pregnancy failures in ART.60 In addition, significantly different pregnancy rates after embryo transfers by different providers suggest a direct correlation between technique and pregnancy outcomes.61,62 This highlights the importance of precise technique during the transfer of embryos. Optimizing each step of the process will help facilitate successful implantation and improve pregnancy rates.57

Recommended Techniques for Embryo Transfer Evaluation of the Endometrial Lining, Uterus, and Cervical Canal The improvement of ultrasonography has proven to be an invaluable tool in embryo transfers. Transabdominal ultrasounds have provided a noninvasive technique to navigate the embryo transfer catheter through the internal cervical os, especially in patients with difficult anatomy (e.g., anteverted or retroverted uteri, a tortuous or long cervical canal). If needed, providers can use this information to mold the tip of the embryo catheter to match that of the patient’s uterocervical angle and decrease difficult or bloody entries and transfers.63 It also allows for direct visualization of the catheter tip during the entire passage to avoid disruption of the endometrium or touching against the fundal wall. Embryo transfers performed under direct visualization using an abdominal ultrasound have been shown to increase pregnancy rates by 4 to 8% when compared with the clinical touch64–66 and is currently the recommended technique.67,68

Is a Full Bladder Helpful? An essential concern during embryo transfer is to limit uterine trauma and thus decrease bleeding and uterine contractions that may cause the expulsion of the embryo after transfer.69 The insertion of the catheter has been shown to be easier with an axial uterus. When a patient presents with an anteflexed uterus, the options would include attempting catheter insertion accepting the potential for trauma during passage through

the curved uterocervical junction, using a tenaculum to straighten out the uterus but causing inevitable cramping, or having the patient present for transfer with a full bladder to straighten the uterus. An early randomized controlled trial with 142 women showed no significant differences in the difficulty during transfer and the chance of pregnancy with and without a full bladder.70 However, more recent studies, to include a systematic review and meta-analysis, have shown an increased ongoing pregnancy rate (odds ratio [OR] ¼ 1.44) and clinical pregnancy rate (OR ¼ 1.55) in addition to easier transfer with a full bladder during an embryo transfer. In these studies, there was also a significantly decreased need for instrumental assistance during the transfer with a full bladder.69,71–73 Moreover, improved visualization of the transfer catheter is achieved through a full bladder with transabdominal ultrasound. Though the disadvantages of a full bladder include the need for a second assistant to perform the ultrasound, inconvenience of having the patient fill her bladder,54 and the discomfort of a full bladder during the transfer, the advantages still outweigh the negatives. Thus, it is recommended that patients have a full bladder during embryo transfer.

Prepping For Transfer Once the patient is positioned in the dorsal lithotomy position,74 a speculum is placed in the vagina to visualize the cervix. The cervix is then cleaned with either culture media or saline solution. The presence of cervical mucous may act as a plug to the tip of the catheter that may cause the embryo to remain in the catheter during withdrawal, increasing the risk of a retained embryo within the catheter and the need for a retransfer.75 Techniques described to remove mucous from the cervix include swabbing with a sterile cotton Q-tip, aspirating the mucous using a sterile syringe, or using a cytobrush.76 Results from a prospective trial with 286 women showed an increased pregnancy rate when the cervical mucous was removed (OR ¼ 2.18).77 Other randomized controlled trials, however, have not shown a significant Seminars in Reproductive Medicine

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Optimal Oocyte Retrieval and Embryo Transfer Techniques

Optimal Oocyte Retrieval and Embryo Transfer Techniques difference in pregnancy outcomes (cervical swabbing: 24% live birth rate, control: 21% live birth rate; p ¼ NS).78,79 It remains at the discretion of the provider as to whether remove cervical mucus prior to embryo transfer.

Catheter Choice and Technique When selecting a catheter for embryo transfers, the provider should consider the ease of use and the ability to pass through the endocervix while avoiding trauma. There are numerous embryo transfer catheters on the market that can largely be divided into soft and firm catheters. Soft catheters (e.g., Cook and Wallace catheters) have been shown to have higher pregnancy rates when compared with firmer catheters, presumably because of decreased cervical and endometrial trauma caused to the cervix and the endometrium.80,81 Thus, if given the choice, it would be recommended using a soft embryo transfer catheter. Potential trauma to the endometrium or cervix may lead to blood on the transfer catheter. This can be encountered during difficult passes through the endocervix or touching the fundal wall. This is associated with lower implantation and pregnancy rates in addition to potentially increasing the rate of retained embryos.82,83 Additional factors that would classify an embryo transfer as difficult include an extended length of time of transfer; a high degree of resistance; a need to change catheter; or a need to dilate the cervix. It has been demonstrated that the level of difficulty of the transfer is an independent prognostic predictor of pregnancy rates with easy or intermediate transfers associated with a 1.7-fold higher pregnancy rate compared with difficult transfers (p < 0.0001).84 Thus providers should plan ahead if there is an anticipated difficult transfer. Potential tools to facilitate the embryo transfer include a full bladder, a transabdominal ultrasound approach, in addition to a soft catheter with an opaque appearance on ultrasound for better visualization.85 Traditionally, the best location of the droplet carrying the embryo has been thought to be near the fundal endometrial surface.86 However, recent studies have suggested a distance of 15 to 20 mm away from the fundus may have higher pregnancy rates.87 For every additional millimeter away from the fundus that the embryo is transferred, the odds of clinical pregnancy increases by 11%. When the fluid droplet carrying the embryo was placed at the fundus compared with greater than 5 mm away from the fundus, the clinical pregnancy rates was 11.2% compared with 48.6%. In addition, if an embryo transfer occurred at the fundus, the ectopic rate was increased by 4.2% (7.4 vs. 3.2%).88–90 Thus current evidence would suggest that the depth of embryo placement can significantly alter implantation87,91,92 with the ideal transfer location at the mid-portion of the uterus.87,91,93,94 After the correct position of the embryo transfer catheter has been identified by ultrasound, the embryo is injected through the catheter in a quick motion.57,95 After complete ejection of the fluid media carrying the embryo, some advocate for a small twist of the catheter to attempt to detach the embryo from the catheter tip prior to withdrawal should the embryo adhere to the catheter.62 Pressure on the plunger should be maintained while withdrawing the catheter slowly Seminars in Reproductive Medicine

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Healy et al. to minimize negative pressure.55,61 It may be beneficial for the outer sheath to remain in place if there is a need to retransfer for a retained embryo, especially in the case of a difficult entry to pass the endocervix. There are conflicting studies evaluating whether pregnancy rates are affected by the time between loading the embryo into the catheter and the actual transfer. In one study by Ciray and colleagues, there were no significant difference among pregnancy rates between groups split based on duration of embryo transfer (0–60 seconds, 61–120 seconds, 121–180 seconds, and >181 seconds). Comparatively, Matorras and colleagues found a significant decrease in pregnancy rates of 19.1% when transfer time was greater than 120 seconds versus 31.6–38.9% when transfer time was less (p < 0.05).96,97 With the potential for embryos to be adversely affected by exposure to the environment, the safest technique may be to attempt to minimize the interval time as much as possible.

Is a Mock Embryo Transfer Beneficial? Prior to ART, a mock (or trial) embryo transfer is commonly performed to evaluate the uterine position, depth, and the degree of difficulty in passing the catheter into the uterine cavity.55,57,98,99 However, during controlled ovarian stimulation, ovarian enlargement may alter the position of the uterus. For instance, if the ovaries settle in the posterior cul-de-sac or if the bladder is full on the day of transfer, a retroverted uterus may be converted to an anteverted uterus.100 Similarly, if the ovaries lie above the uterus, an anteverted uterus may be in a retroverted position.100 Thus, during the embryo transfer, assuming a position based on a mock embryo transfer may be misleading and increase the risk of potential uterine trauma.75,100,101 With ultrasound guidance, the risk of trauma may be decreased, resulting in improved clinical pregnancy rates (38% with ultrasound guidance vs. 25% without; p < 0.002).57,100,102 By allowing for advanced planning, mock transfers increase the chance of an atraumatic transfer and thus improve implantation (7.2 vs. 4.3% without mock transfer) and pregnancy rates (22.8 vs. 13.1% without mock transfer).57,98

Alternative Embryo Transfer Routes An alternative technique for embryo transfer that bypasses the cervical canal is the Towako method, otherwise known as a transmyometrial embryo transfer.103 This is a potential option for patients with severe cervical stenosis, or a history of difficult embryo transfers.54,104 The described procedure involves using an endovaginal ultrasound probe and a special needle with a stylet attached. Under direct visualization, the needle is inserted through the myometrium and guided to the endometrial cavity. The stylet is then removed and the transfer catheter with the embryo is passed through the needle for transfer. Per Kato and colleagues, there was a 44.9% pregnancy rate over their 4 years of experience with 1,298 cases.103 However, a more recent prospective randomized study has shown limited pregnancy rates using the transmyometrial transfer approach (1 clinical pregnancy rate in 20 patients) when compared with difficult transcervical transfer approaches (3 clinical pregnancies in

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6 Deutinger J, Reinthaller A, Csaicsich P, et al. Follicular aspiration

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Posttransfer Activity Traditionally, after an embryo transfer, patients would be placed on bed rest to improve embryo retention within the uterus.54,57 However, studies in the past 20 years have shown that bed rest does not improve pregnancy outcomes.106–109 Patients who immediately ambulated after following embryo transfer had similar clinical and ongoing pregnancy rates when compared with those who assumed bed rest for 30 minutes (OR ¼ 1.0).110 Thus, it is not recommended that a patient undergo prolonged bed rest immediately following an embryo transfer.

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Summary As the final step in a rigorous ART cycle, precise technique in embryo transfer is essential. Based on current findings, the recommended embryo transfer technique includes the use of an ultrasound-guided transcervical approach with a full bladder using a soft catheter for the transfer. The transfer depth of the embryo should be in the mid-portion of the uterus with a quick steady insertion followed by pressure on the syringe during withdrawal of the catheter. It is acceptable to encourage immediate ambulation after embryo transfer.

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Disclaimer The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government. Financial Support This work was supported, in part, by the Program in Reproductive and Adult Endocrinology, NICHD, NIH, Bethesda, MD. Conflict of Interest None for any authors.

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References 1 Betteridge KJ. A history of farm animal embryo transfer and some 2 3 4 5

associated techniques. Anim Reprod Sci 2003;79(3–4):203–244 Menkin MF, Rock J. In vitro fertilization and cleavage of human ovarian eggs. Am J Obstet Gynecol 1948;55(3):440–452 Steptoe PC, Edwards RG. Birth after the reimplantation of a human embryo. Lancet 1978;2(8085):366 Edwards R, Steptoe PC. A Matter of Life. The Story of a Medical Breakthrough. London, UK: Hutchinson Publishers; 1980 Dellenbach P, Nisand I, Moreau L, et al. Transvaginal, sonographically controlled ovarian follicle puncture for egg retrieval. Lancet 1984;1(8392):1467

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for in vitro fertilization: sonographically guided transvaginal versus laparoscopic approach. Eur J Obstet Gynecol Reprod Biol 1987;26(2):127–133 Feichtinger W, Kemeter P. Laparoscopic or ultrasonically guided follicle aspiration for in vitro fertilization? J In Vitro Fert Embryo Transf 1984;1(4):244–249 Feldberg D, Goldman JA, Ashkenazi J, Shelef M, Dicker D, Samuel N. Transvaginal oocyte retrieval controlled by vaginal probe for in vitro fertilization: a comparative study. J Ultrasound Med 1988; 7(6):339–343 Gleicher N, Friberg J, Fullan N, et al. EGG retrieval for in vitro fertilisation by sonographically controlled vaginal culdocentesis. Lancet 1983;2(8348):508–509 Lenz S. Percutaneous oocyte recovery using ultrasound. Clin Obstet Gynaecol 1985;12(4):785–798 Litynski GS. Patrick C. Steptoe: laparoscopy, sterilization, the testtube baby, and mass media. JSLS 1998;2(1):99–101 Steptoe PC. Gynecological endoscopy–laparoscopy and culdoscopy. J Obstet Gynaecol Br Commonw 1965;72:535–543 Steptoe PC. Laparoscopy and ovulation. Lancet 1968;2(7574):913 Steptoe PC, Edwards RG. Laparoscopic recovery of preovulatory human oocytes after priming of ovaries with gonadotrophins. Lancet 1970;1(7649):683–689 Sterzik K, Jonatha W, Keckstein G, Rossmanith W, Traub E, Wolf A. Ultrasonically guided follicle aspiration for oocyte retrieval in an in vitro fertilization program: further simplification. Int J Gynaecol Obstet 1987;25(4):309–314 Wikland M, Nilsson L, Hansson R, Hamberger L, Janson PO. Collection of human oocytes by the use of sonography. Fertil Steril 1983;39(5):603–608 Lopata A, Johnston IW, Leeton JF, Muchnicki D, Talbot JM, Wood C. Collection of human oocytes at laparoscopy and laparotomy. Fertil Steril 1974;25(12):1030–1038 Morgenstern LL, Soupart P. Oocyte recovery from the human ovary. Fertil Steril 1972;23(10):751–758 Khan I, Devroey P, Van den Bergh M, et al. The effect of pneumoperitoneum gases on fertilization, cleavage and pregnancy in human in-vitro fertilization and gamete intra-fallopian transfer. Hum Reprod 1989;4(3):323–326 Kratochwil A, Urban G, Friedrich F. Ultrasonic tomography of the ovaries. Ann Chir Gynaecol Fenn 1972;61(4):211–214 Lenz S, Lauritsen JG. Ultrasonically guided percutaneous aspiration of human follicles under local anesthesia: a new method of collecting oocytes for in vitro fertilization. Fertil Steril 1982; 38(6):673–677 Cohen J, Debache C, Pez JP, Junca AM, Cohen-Bacrie P. Transvaginal sonographically controlled ovarian puncture for oocyte retrieval for in vitro fertilization. J In Vitro Fert Embryo Transf 1986;3(5):309–313 Wikland M, Hamberger L. Ultrasound as a diagnostic and operative tool for in vitro fertilization and embryo replacement (IVF/ ER) programs. J In Vitro Fert Embryo Transf 1984;1(4):213–216 Ashkenazi J, Ben David M, Feldberg D, Shelef M, Dicker D, Goldman JA. Abdominal complications following ultrasonically guided percutaneous transvesical collection of oocytes for in vitro fertilization. J In Vitro Fert Embryo Transf 1987;4(6):316–318 Wikland M, Enk L, Hamberger L. Transvesical and transvaginal approaches for the aspiration of follicles by use of ultrasound. Ann N Y Acad Sci 1985;442:182–194 Brinsmead M, Stanger J, Oliver M, Shumack J, Raymond S, Clark L. A randomized trial of laparoscopy and transvaginal ultrasounddirected oocyte pickup for in vitro fertilization. J In Vitro Fert Embryo Transf 1989;6(3):149–154 Torode HW, Picker RH, Porter RN, et al. Oocyte pickup by laparoscopy replaced by transvaginal aspiration in an in vitro fertilization program. J In Vitro Fert Embryo Transf 1987;4(3): 148–152 Seminars in Reproductive Medicine

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another 20 patients).105 Disadvantages include pain and discomfort during the procedure in addition to concern of uterine contractions causing expulsion of the transferred embryo.54,104 At this time, further investigation is still needed prior to recommending this technique as an alternative to the conventional transcervical embryo transfer.

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anesthesia for assisted reproductive technologies. Int J Gynaecol Obstet 2009;105(3):201–205 Montalva M, Das B. Carbon dioxide homeostasis during laparoscopy. South Med J 1976;69(5):602–603 Ohlgisser M, Sorokin Y, Heifetz M. Gynecologic laparoscopy. A review article. Obstet Gynecol Surv 1985;40(7):385–396 Marco AP, Yeo CJ, Rock P. Anesthesia for a patient undergoing laparoscopic cholecystectomy. Anesthesiology 1990;73(6): 1268–1270 Kogosowski A, Lessing JB, Amit A, Rudick V, Peyser MR, David MP. Epidural block: a preferred method of anesthesia for ultrasonically guided oocyte retrieval. Fertil Steril 1987;47(1):166–168 Hammarberg K, Wikland M, Nilsson L, Enk L. Patients’ experience of transvaginal follicle aspiration under local anesthesia. Ann N Y Acad Sci 1988;541:134–137 Goutziomitrou E, Kolibianakis EM, et al. The use of pentothal for anesthesia during oocyte retrieval is associated with decreased pregnancy rates as compared to propofol: A randomised controlled trial. Hum Reprod 2011;26:i96 Jarahzadeh MH, Jouya R, Mousavi FS, Dehghan-Tezerjani M, Behdad S, Soltani HR. Propofol or Thiopental sodium in patients undergoing reproductive assisted technologies: differences in hemodynamic recovery and outcome of oocyte retrieval: a randomized clinical trial. Iran J Reprod Med 2014;12(1):77–82 Weinreb EB, Cholst IN, Ledger WJ, Danis RB, Rosenwaks Z. Should all oocyte donors receive prophylactic antibiotics for retrieval? Fertil Steril 2010;94(7):2935–2937 Brook N, Khalaf Y, Coomarasamy A, Edgeworth J, Braude P. A randomized controlled trial of prophylactic antibiotics (co-amoxiclav) prior to embryo transfer. Hum Reprod 2006;21(11): 2911–2915 Kroon B, Hart RJ, Wong BM, Ford E, Yazdani A. Antibiotics prior to embryo transfer in ART. Cochrane Database Syst Rev 2012;3: CD008995 van Os HC, Roozenburg BJ, Janssen-Caspers HA, et al. Vaginal disinfection with povidon iodine and the outcome of in-vitro fertilization. Hum Reprod 1992;7(3):349–350 Hannoun A, Awwad J, Zreik T, Ghaziri G, Abu-Musa A. Effect of Betadine vaginal preparation during oocyte aspiration in in vitro fertilization cycles on pregnancy outcome. Gynecol Obstet Invest 2008;66(4):274–278 Miller KA, Elkind-Hirsch K, Benson M, Bergh P, Drews M, Scott RT. A new follicle aspiration needle set is equally effective and as well tolerated as the standard needle when used in a prospective randomized trial in a large in vitro fertilization program. Fertil Steril 2004;81(1):191–193 Bagtharia S, Haloob AR. Is there a benefit from routine follicular flushing for oocyte retrieval? J Obstet Gynaecol 2005;25(4): 374–376 Levy G, Hill MJ, Ramirez CI, et al. The use of follicle flushing during oocyte retrieval in assisted reproductive technologies: a systematic review and meta-analysis. Hum Reprod 2012;27(8): 2373–2379 Wongtra-Ngan S, Vutyavanich T, Brown J. Follicular flushing during oocyte retrieval in assisted reproductive techniques. Cochrane Database Syst Rev 2010;(9):CD004634 Levens ED, Whitcomb BW, Payson MD, Larsen FW. Ovarian follicular flushing among low-responding patients undergoing assisted reproductive technology. Fertil Steril 2009;91(4, Suppl) 1381–1384 Wynn P, Picton HM, Krapez JA, Rutherford AJ, Balen AH, Gosden RG. Pretreatment with follicle stimulating hormone promotes the numbers of human oocytes reaching metaphase II by in-vitro maturation. Hum Reprod 1998;13(11):3132–3138 Hashimoto S, Fukuda A, Murata Y, et al. Effect of aspiration vacuum on the developmental competence of immature human

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oocytes retrieved using a 20-gauge needle. Reprod Biomed Online 2007;14(4):444–449 Practice Committees of the American Society for Reproductive Medicine and the Society for Assisted Reproductive Technology. In vitro maturation: a committee opinion. Fertil Steril 2013; 99(3):663–666 Mclaren A, Michib D. Studies on the transfer of fertilized mouse eggs to uterine foster-mothers. I. Factors affecting the implantation’ and survival of native and transferred eggs. J Exp Biol 1956; 33:394–416 Killick SR, Leary C, Trussell J, Guthrie KA. Sperm content of preejaculatory fluid. Hum Fertil (Camb) 2011;14(1):48–52 Biggers JD. IVF and embryo transfer: historical origin and development. Reprod Biomed Online 2012;25(2):118–127 Chang MC. Fertilization of rabbit ova in vitro. Nature 1959;184 (Suppl 7):466–467 De Kretzer D, Dennis P, Hudson B, et al. Transfer of a human zygote. Lancet 1973;2(7831):728–729 Mains L, Van Voorhis BJ. Optimizing the technique of embryo transfer. Fertil Steril 2010;94(3):785–790 Mansour RT, Aboulghar MA. Optimizing the embryo transfer technique. Hum Reprod 2002;17(5):1149–1153 Neithardt AB, Segars JH, Hennessy S, James AN, McKeeby JL. Embryo afterloading: a refinement in embryo transfer technique that may increase clinical pregnancy. Fertil Steril 2005;83(3): 710–714 Schoolcraft WB, Surrey ES, Gardner DK. Embryo transfer: techniques and variables affecting success. Fertil Steril 2001;76(5): 863–870 Steptoe PC, Edwards RG. Reimplantation of a human embryo with subsequent tubal pregnancy. Lancet 1976;1(7965):880–882 Nayudu PL, Lopata A, Leung PC, Johnston WI. Current problems in human in vitro fertilization and embryo implantation. J Exp Zool 1983;228(2):203–213 Cohen J. Embryo replacement technology. San Francisco 1998 31 Annual post graduate course. ASRM. 1998 Hearns-Stokes RM, Miller BT, Scott L, Creuss D, Chakraborty PK, Segars JH. Pregnancy rates after embryo transfer depend on the provider at embryo transfer. Fertil Steril 2000;74(1):80–86 Karande VC, Morris R, Chapman C, Rinehart J, Gleicher N. Impact of the “physician factor” on pregnancy rates in a large assisted reproductive technology program: do too many cooks spoil the broth? Fertil Steril 1999;71(6):1001–1009 Sallam HN, Agameya AF, Rahman AF, Ezzeldin F, Sallam AN. Ultrasound measurement of the uterocervical angle before embryo transfer: a prospective controlled study. Hum Reprod 2002; 17(7):1767–1772 Buckett WM. A meta-analysis of ultrasound-guided versus clinical touch embryo transfer. Fertil Steril 2003;80(4):1037–1041 Mirkin S, Jones EL, Mayer JF, Stadtmauer L, Gibbons WE, Oehninger S. Impact of transabdominal ultrasound guidance on performance and outcome of transcervical uterine embryo transfer. J Assist Reprod Genet 2003;20(8):318–322 Sallam HN, Sadek SS. Ultrasound-guided embryo transfer: a meta-analysis of randomized controlled trials. Fertil Steril 2003;80(4):1042–1046 Matorras R, Urquijo E, Mendoza R, Corcóstegui B, Expósito A, Rodríguez-Escudero FJ. Ultrasound-guided embryo transfer improves pregnancy rates and increases the frequency of easy transfers. Hum Reprod 2002;17(7):1762–1766 Tang OS, Ng EH, So WW, Ho PC. Ultrasound-guided embryo transfer: a prospective randomized controlled trial. Hum Reprod 2001;16(11):2310–2315 Lewin A, Schenker JG, Avrech O, Shapira S, Safran A, Friedler S. The role of uterine straightening by passive bladder distension before embryo transfer in IVF cycles. J Assist Reprod Genet 1997;14(1): 32–34

This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.

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Healy et al.

70 Mitchell JD, Wardle PG, Foster PA, Hull MG. Effect of bladder

89 Pope CS, Cook EK, Arny M, Novak A, Grow DR. Influence of embryo

filling on embryo transfer. J In Vitro Fert Embryo Transf 1989; 6(4):263–265 Abou-Setta AM. Effect of passive uterine straightening during embryo transfer: a systematic review and meta-analysis. Acta Obstet Gynecol Scand 2007;86(5):516–522 Lorusso F, Depalo R, Bettocchi S, Vacca M, Vimercati A, Selvaggi L. Outcome of in vitro fertilization after transabdominal ultrasound-assisted embryo transfer with a full or empty bladder. Fertil Steril 2005;84(4):1046–1048 Sundström P, Wramsby H, Persson PH, Liedholm P. Filled bladder simplifies human embryo transfer. Br J Obstet Gynaecol 1984; 91(5):506–507 Egbase PE, Al-Sharhan M, Grudzinskas JG. Influence of position and length of uterus on implantation and clinical pregnancy rates in IVF and embryo transfer treatment cycles. Hum Reprod 2000; 15(9):1943–1946 Nabi A, Awonuga A, Birch H, Barlow S, Stewart B. Multiple attempts at embryo transfer: does this affect in-vitro fertilization treatment outcome? Hum Reprod 1997;12(6):1188–1190 McNamee P, Huang T, Carwile A. Significant increase in pregnancy rates achieved by vigorous irrigation of endocervical mucus prior to embryo transfer with a Wallace catheter in an IVF-ET program. Fertil Steril 1998;70:S228 Eskandar MA, Abou-Setta AM, El-Amin M, Almushait MA, Sobande AA. Removal of cervical mucus prior to embryo transfer improves pregnancy rates in women undergoing assisted reproduction. Reprod Biomed Online 2007;14(3):308–313 Visschers BA, Bots RS, Peeters MF, Mol BW, van Dessel HJ. Removal of cervical mucus: effect on pregnancy rates in IVF/ICSI. Reprod Biomed Online 2007;15(3):310–315 Craciunas L, Tsampras N, Fitzgerald C. Cervical mucus removal before embryo transfer in women undergoing in vitro fertilization/intracytoplasmic sperm injection: a systematic review and meta-analysis of randomized controlled trials. Fertil Steril 2014; 101(5):1302–1307 Abou-Setta AM, Al-Inany HG, Mansour RT, Serour GI, Aboulghar MA. Soft versus firm embryo transfer catheters for assisted reproduction: a systematic review and meta-analysis. Hum Reprod 2005;20(11):3114–3121 McDonald JA, Norman RJ. A randomized controlled trial of a soft double lumen embryo transfer catheter versus a firm single lumen catheter: significant improvements in pregnancy rates. Hum Reprod 2002;17(6):1502–1506 Alvero R, Hearns-Stokes RM, Catherino WH, Leondires MP, Segars JH. The presence of blood in the transfer catheter negatively influences outcome at embryo transfer. Hum Reprod 2003;18(9):1848–1852 Goudas VT, Hammitt DG, Damario MA, Session DR, Singh AP, Dumesic DA. Blood on the embryo transfer catheter is associated with decreased rates of embryo implantation and clinical pregnancy with the use of in vitro fertilization-embryo transfer. Fertil Steril 1998;70(5):878–882 Tomás C, Tikkinen K, Tuomivaara L, Tapanainen JS, Martikainen H. The degree of difficulty of embryo transfer is an independent factor for predicting pregnancy. Hum Reprod 2002;17(10):2632–2635 Allahbadia GN, Kadam K, Gandhi G, et al. Embryo transfer using the SureView catheter-beacon in the womb. Fertil Steril 2010; 93(2):344–350 Rosenlund B, Sjöblom P, Hillensjö T. Pregnancy outcome related to the site of embryo deposition in the uterus. J Assist Reprod Genet 1996;13(6):511–513 Coroleu B, Barri PN, Carreras O, et al. The influence of the depth of embryo replacement into the uterine cavity on implantation rates after IVF: a controlled, ultrasound-guided study. Hum Reprod 2002;17(2):341–346 Nazari A, Askari HA, Check JH, O’Shaughnessy A. Embryo transfer technique as a cause of ectopic pregnancy in in vitro fertilization. Fertil Steril 1993;60(5):919–921

transfer depth on in vitro fertilization and embryo transfer outcomes. Fertil Steril 2004;81(1):51–58 Yovich JL, Turner SR, Murphy AJ. Embryo transfer technique as a cause of ectopic pregnancies in in vitro fertilization. Fertil Steril 1985;44(3):318–321 Franco JG Jr, Martins AM, Baruffi RL, et al. Best site for embryo transfer: the upper or lower half of endometrial cavity? Hum Reprod 2004;19(8):1785–1790 van de Pas MM, Weima S, Looman CW, Broekmans FJ. The use of fixed distance embryo transfer after IVF/ICSI equalizes the success rates among physicians. Hum Reprod 2003;18(4):774–780 Frankfurter D, Silva CP, Mota F, Trimarchi JB, Keefe DL. The transfer point is a novel measure of embryo placement. Fertil Steril 2003; 79(6):1416–1421 Waterstone J, Curson R, Parsons J. Embryo transfer to low uterine cavity. Lancet 1991;337(8754):1413 Leong M, Leung C, Tucker M, Wong C, Chan H. Ultrasoundassisted embryo transfer. J In Vitro Fert Embryo Transf 1986; 3(6):383–385 Ciray HN, Tosun S, Hacifazlioglu O, Mesut A, Bahceci M. Prolonged duration of transfer does not affect outcome in cycles with good embryo quality. Fertil Steril 2007;87(5):1218–1221 Matorras R, Mendoza R, Expósito A, Rodriguez-Escudero FJ. Influence of the time interval between embryo catheter loading and discharging on the success of IVF. Hum Reprod 2004;19(9): 2027–2030 Mansour R, Aboulghar M, Serour G. Dummy embryo transfer: a technique that minimizes the problems of embryo transfer and improves the pregnancy rate in human in vitro fertilization. Fertil Steril 1990;54(4):678–681 Sharif K, Afnan M, Lenton W. Mock embryo transfer with a full bladder immediately before the real transfer for in-vitro fertilization treatment: the Birmingham experience of 113 cases. Hum Reprod 1995;10(7):1715–1718 Henne MB, Milki AA. Uterine position at real embryo transfer compared with mock embryo transfer. Hum Reprod 2004;19(3): 570–572 Kan AK, Abdalla HI, Gafar AH, et al. Embryo transfer: ultrasoundguided versus clinical touch. Hum Reprod 1999;14(5):1259–1261 Wood EG, Batzer FR, Go KJ, Gutmann JN, Corson SL. Ultrasoundguided soft catheter embryo transfers will improve pregnancy rates in in-vitro fertilization. Hum Reprod 2000;15(1):107–112 Kato O, Takatsuka R, Asch RH. Transvaginal-transmyometrial embryo transfer: the Towako method; experiences of 104 cases. Fertil Steril 1993;59(1):51–53 Biervliet FP, Lesny P, Maguiness SD, Robinson J, Killick SR. Transmyometrial embryo transfer and junctional zone contractions. Hum Reprod 2002;17(2):347–350 Groutz A, Lessing JB, Wolf Y, Azem F, Yovel I, Amit A. Comparison of transmyometrial and transcervical embryo transfer in patients with previously failed in vitro fertilization-embryo transfer cycles and/or cervical stenosis. Fertil Steril 1997;67(6):1073–1076 Amarin ZO, Obeidat BR. Bed rest versus free mobilisation following embryo transfer: a prospective randomised study. BJOG 2004; 111(11):1273–1276 Botta G, Grudzinskas G. Is a prolonged bed rest following embryo transfer useful? Hum Reprod 1997;12(11):2489–2492 Sharif K, Afnan M, Lenton W, et al. Do patients need to remain in bed following embryo transfer? The Birmingham experience of 103 in-vitro fertilization cycles with no bed rest following embryo transfer. Hum Reprod 1995;10(6):1427–1429 Woolcott R, Stanger J. Ultrasound tracking of the movement of embryo-associated air bubbles on standing after transfer. Hum Reprod 1998;13(8):2107–2109 Purcell KJ, Schembri M, Telles TL, Fujimoto VY, Cedars MI. Bed rest after embryo transfer: a randomized controlled trial. Fertil Steril 2007;87(6):1322–1326

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Optimal Oocyte Retrieval and Embryo Transfer Techniques

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