Original Paper Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
Received: May 15, 2013 Accepted after revision: August 30, 2013 Published online: October 23, 2013
Radiofrequency Ablation for Selective Reduction in Complicated Monochorionic Multiple Pregnancies Jing Lu a Yuen Ha Ting b Kwok Ming Law b Tze Kin Lau c Tak Yeung Leung b a
Department of Ultrasound Medicine, Prenatal Diagnosis Center of Xiamen, Maternal and Child Health Hospital, Xiamen, b Fetal Medicine Unit, Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Prince of Wales Hospital, and c Fetal Medicine Centre, Paramount Clinic, Hong Kong, SAR, China
Key Words Monochorionic multiple pregnancy · Radiofrequency ablation · Selective feticide
Conclusions: RFA is a promising technique for selective reduction in complicated MC multiple pregnancies with a high survival rate and low complication rate. © 2013 S. Karger AG, Basel
© 2013 S. Karger AG, Basel 1015–3837/13/0344–0211$38.00/0 E-Mail [email protected] www.karger.com/fdt
Introduction
Although monochorionic (MC) multiple pregnancies are less frequent than dichorionic pregnancies, they are associated with a much higher risk of perinatal morbidity and mortality [1]. This is related to the fact that almost all MC placentas have vascular anastomoses connecting the circulations of the fetuses [2]. These communicating placental vessels lead to complications specific to MC pregnancies, such as twin-twin transfusion syndrome (TTTS), twin reversed arterial perfusion (TRAP) sequence, and acute feto-fetal exsanguination of the survivor after single twin intrauterine demise (IUD) [3]. Moreover, MC pregnancies with unequal placental share may result in selective intrauterine growth restriction (sIUGR) [4]. Furthermore, structural anomalies of MC twins are three times higher than those found in dichorionic twins [5]. When such MC pregnancy complications occur, selective reduction may be needed to reduce perinatal mortality and morbidity [6]. For singleton pregnancies or dichoProf. Tak Yeung Leung, MD Department of Obstetrics and Gynaecology Prince of Wales Hospital Shatin, Hong Kong, SAR (China) E-Mail tyleung @ cuhk.edu.hk
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Abstract Objective: To evaluate the perinatal outcome of monochorionic (MC) multiple pregnancies after selective reduction by radiofrequency ablation (RFA). Methods: A case series of all MC multiple pregnancies with selective reduction by RFA in one single institution was reviewed. Results: Ten consecutive patients with an MC pregnancy (9 pairs of twins and 1 set of triplets) underwent RFA. The median gestational age at the time of the procedure was 15.6 weeks (range, 12.3– 19.6). The indications for selective reduction included discordance for fetal anomalies (4 cases), twin reversed arterial perfusion sequence (3 cases), selective intrauterine growth restriction (2 cases) and severe twin-twin transfusion syndrome (1 case). All procedures were technically successful in achieving selective reduction. The overall survival rate of the cotwin was 81.8% (9/11), and the median gestational age at delivery was 35.9 weeks (range, 32.4–38.6). There was one preterm delivery before 34 weeks of gestation (11.1%). Preterm premature rupture of the membranes occurred in 2 patients (20%); however, this was not observed within 4 weeks postoperatively, nor did they deliver before 32 weeks.
Color version available online
rionic pregnancies, feticide can easily be achieved by fetal intracardiac potassium chloride injection. However, this method is not suitable for MC pregnancies because of the inevitable presence of vascular anastomosis in the MC placentas which can cause acute transfusion from the cotwin to the dying twin through these connecting circulations [7]. Death of one twin in an MC pair can result in death of or neurologic abnormality in the co-twin in 12 and 18% of cases, respectively [8]. Therefore, selective reduction in MC pregnancies can only be done by cord occlusion techniques, which interrupt the blood flow of the targeted twin while avoiding exsanguination of the cotwin. Among the cord occlusion techniques, the most commonly performed procedure is bipolar cord coagulation (BCC) [9]. Radiofrequency ablation (RFA) is a relatively new method used in selective reduction [9]. RFA achieves cord coagulation by high-frequency alternating current inducing high temperature. We report our initial experience with RFA for selective reduction in complicated MC pregnancies.
Materials and Methods
212
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
Fig. 1. An abortus after RFA: note the iatrogenic necrosis in the lower abdomen corresponding to the ablation site.
Energy was applied until no blood flow was demonstrated in the umbilical cord by color Doppler and pulsed-wave Doppler. The prongs were retracted back and the probe was removed. Ultrasound examination was performed after the procedure to confirm persistent bradycardia or cardiac asystole in the targeted twin and normal heart pulsation of the co-twin. A zone of probable thermal injury might also have been seen on ultrasound examination. Postoperatively, the patient was observed overnight in the hospital and discharged on the following day after ultrasound examination confirming cardiac asystole in the targeted twin and normal heart pulsation of the co-twin. Figure 1 shows an abortus after RFA with iatrogenic necrosis in the lower abdomen corresponding to the ablation site.
Results
There were 10 MC pregnancies that had selective reduction by RFA, including 7 pairs of MC diamniotic twins, 2 pairs of MC monoamniotic twins and 1 set of MC triamniotic triplets (table 1). The median maternal age was 29 years (range, 27–31). The median gestational age at the time of the procedure was 15.6 weeks (range, 12.3– Lu/Ting/Law/Lau/Leung
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This is a retrospective case series of all the selective reductions in MC pregnancies by RFA performed in the Fetal Medicine Unit, Prince of Wales Hospital, the Chinese University of Hong Kong from December 2011 to September 2012. The antenatal course, operation and delivery details of all the cases were reviewed. All RFA procedures were performed with ultrasound guidance using the Philips iU22 xMATRIX ultrasound system under local anesthesia by maternal fetal medicine subspecialists. All patients underwent ultrasound examination to determine the chorionicity and to confirm the indication for selective reduction. They were admitted on the day of surgery and informed consent was obtained. Augmentin 1.2 g was given intravenously before the procedure, and maternal sedation was not required. Ultrasound examination was performed to locate the placenta and the abdominal umbilical cord insertion of the targeted twin in order to determine the site of entrance. Bilateral grounding pads were placed on maternal thighs. After the abdominal skin had been sterilized, 10 ml 1% Xylocaine was infiltrated subcutaneously over the site of entry. A small skin incision was made and the radiofrequency probe (LeVeen Superslim Needle Electrode radiofrequency probe, 17 G, 15 cm long) was inserted percutaneously into the amniotic cavity of the targeted fetus under ultrasound guidance, with caution to avoid puncturing the amniotic sac of the co-twin as far as possible. The probe was then inserted into the fetal abdomen around the fetal umbilical cord insertion site. No anesthetic drug for fetal relaxation was used. After confirmation of the probe location, the prongs of the device were deployed. A radiofrequency generator (RF 3000TM, MEDI-TECH, Boston Scientific) was used and radiofrequency energy was applied in a stepwise fashion starting from 30 W and progressing to a maximum of 100 W, each energy level lasting for no more than 2 min.
Table 1. List of perinatal outcome of the 10 complicated MC pregnancies with selective reduction by RFA in chorological order
Case n
Amnionicity Indication
Gestation at procedure, weeks
Number of RFA cycles
Gestation at delivery, weeks
Outcome of co-twin
birth weight g
1
MCMA
discordant malformation
17.9
2
36.9
live-born
2,530
2
MCDA
discordant malformation
19.6
2
35.7
live-born
2,010
3
MCDA
TRAP sequence
13
4
38.6
live-born
2,620
4
MCTA
discordant malformation
12.3
3
35
live-born
2,215/2,195
5
MCMA
TRAP sequence
13.1
4
–
IUD 7 days after the procedure
–
6
MCDA
TRAP sequence
13.4
2
32.4
live-born
2,245
7
MCDA
sIUGR
19.6
1
34.4
live-born
1,845
8
MCDA
discordant malformation
13
1
38.4
live-born
2,135
9
MCDA
stage 4 TTTS
19.3
1
35.4
stillborn
1,700
10
MCDA
sIUGR
17.9
3
35.7
live-born
2,040
MCMA = MC monoamniotic; MCDA = MC diamniotic; MCTA = MC triamniotic.
19.6). The indications for selective reduction included discordance for fetal anomalies (4 cases), TRAP sequence (3 cases), sIUGR (2 cases) and severe TTTS (1 case). All procedures were technically successful in achieving selective reduction without the need for amnioinfusion. All procedures were completed within 4 radiofrequency cycles and most were completed after 1–2 radiofrequency cycles. Cardiac asystole of the targeted fetuses was confirmed by ultrasound after 24 h for all procedures. There were no maternal complications observed and no inadvertent septostomy or chorioamniotic separation. The perinatal outcome of all cases is summarized in table 1. There were 2 cases of IUD of the co-twin. One case (case 5) was an MC monoamniotic twin pregnancy complicated by TRAP sequence. The pump twin was already hydropic before the procedure at 13 weeks of gestation. Placental cord insertion sites were close together and there was cord entanglement near the placental cord insertion sites. The co-twin had normal cardiac pulsation 1 day after completion of the procedure, but was found to have absent cardiac pulsation 7 days later. The other case (case 9) was an MC diamniotic twin pregnancy complicated by stage 4 TTTS with an uneventful RFA performed at 19.3 weeks. The donor twin’s umbilical vessels were ablated and the hydropic changes of the recipient gradually resolved. However, the recipient twin was found to have IUD unexpectedly at 35.4 weeks. Hence the overall survival rate of the co-twins was 81.8% (9/11).
For the remaining 9 live births, the median gestational age at delivery was 35.9 weeks (range, 32.4–38.6) with the median birth weight being 2,204 g (range, 1,845– 2,620). The median procedure-to-delivery interval was 20.4 weeks (range, 14.9–25.6). There was one preterm delivery before 34 weeks of gestation (11.1%). Preterm premature rupture of membranes (PPROM) occurred in 2 cases (20%). One case (case 4) had PPROM at 35 weeks, which resulted in delivery within 24 h. The other one (case 7) had PPROM at 27 weeks and delivered at 34.4 weeks. Neither of the PPROM occurred within 4 weeks postoperatively, nor did these women deliver before 34 weeks.
Radiofrequency Ablation for Selective Reduction
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
For the last 10 years, RFA has been used for in utero therapy for MC pregnancy complications, fetal sacrococcygeal teratoma and fetal chest mass [10–12]. The mechanism of action of RFA is by thermal effect generated by the alternating electric current operated in the range of radiofrequency waves. The electric current agitating the ions in the tissue surrounding the electrodes causes frictional heat which is conducted into the adjacent tissue. The needle electrode itself is not heated up but the very high temperature generated in the tissue results in protein denaturation and local coagulation [13]. Therefore, for 213
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Discussion
Table 2. List of publications on selective reduction using RFA
Authors
Type of pregnancies (n)
Case series on selective reduction for TRAP sequence TRAP (5) Paramasivam et al. [5]
Average gestation week at procedure (range)
18.1 (16.3–19.4)
Survival of co-twins/triplets (rate per pregnancy, %) 4 (80%)
Average gestation week at delivery (range) 37.8 (36–41)
Cabassa et al. [19]
TRAP (7)
Lee et al. [22]a
TRAP (98)
20.2±2.4
Our study
TRAP (3)
13.2 (13–13.4)
All case series for TRAP sequence
total 113 pregnancies
–
89 (78.8%)
–
18.4 (12.7–27.1)
27 (90.0%)
35.4 (26–40.4)
6 (66.7%)
36.1 (26–39.2)
17 (14–23)
Case series on selective feticide for indications other than TRAP Paramasivam et al. [5] total (30) malformed (9); sIUGR (4); TTTS (11); fetal reduction (6)
5 (71.4%)
33 (31–39)
78 (79.6%)
37 (27.9–38.9)
2 (66.7%)
35.5 (32.4–38.6)
Moise et al. [17]
total (9) TTTS (5); malformed (4)
19.5 (18.6–22.2)
Roman et al. [20]
total (14)
–
Our study
total (7) malformed (4); sIUGR (2); TTTS (1)
17.1 (12.3–19.6)
All case series for indications other than TRAP
total 60 pregnancies
–
51 (85%)
–
All case series for all indications
total 173 pregnancies
–
140 (80.9%)
–
Retrospective comparative studies (RFA vs. BCC) Roman et al. [20] RFA (20) BCC (40) Bebbington et al. [21] a
RFA (58) BCC (88)
12 (85.7%)
–
6 (85.7%)
20.3 (17–29) 21.5 (17–29)
(87%) (88%)
20.2±2.2 20.9±2.7
(70.7%) (85.2%)
36 (34.4–38.4)
36 (26–41) 39 (19–40) 34.7 [29.2–38.6]b 33.0 [23.4–38.9]b
Cases recruited in this series were also reported in other references [15, 16, 18, 20, 21] which were excluded to avoid double counting. are interquartile ranges.
selective reduction, RFA is not aimed at umbilical cord occlusion, but targets on ablation of intrafetal umbilical vessels beneath the cord insertion site. Coagulation of the cord takes place secondarily [14]. Tsao et al. [10] was the first one to report the use of RFA in treating acardiac twins. In their 13 cases of TRAP sequence, the average gestational age at intervention was 20.7 weeks, and the average gestational age at delivery was 36.2 weeks. The preterm delivery rate before 34 weeks was 23.1% with only 1 neonate who died of prematurity. Subsequently, there were at least 8 other case series with varying sample sizes [5, 15–22]. The largest series has recently been published with a sample size of 98 cases [22], though it might have included some cases from 214
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
previously published series [15, 16, 18, 20, 21]. Combining our cases with these case series (excluding those case series which might have been included in the largest series), the overall survival rate reached 80.9% [5, 17, 19, 20, 22] (table 2). The average gestational age at delivery ranged from 33 to 38 weeks. When compared to these series, our initial local experience with RFA is promising with a co-twin survival rate of 81.8%. We had only 1 preterm delivery before 34 weeks of gestation (11.1%) [5, 10]. The PPROM rate of our series (20%) is also comparable with that reported in the literature (5–23.1%) [10, 15, 20]. RFA has several potential advantages over BCC. First, the diameter of an RFA probe is only 1.4 mm and is much Lu/Ting/Law/Lau/Leung
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b Figures
cases. In addition, it is worth noticing that in the study by Bebbington et al. [21], the chances of PROM (27.3%) and preterm labor (22.4%) after BCC were higher than after RFA (13.7 and 7%, respectively). However, because of a relatively higher rate of fetal death after RFA that required iatrogenic preterm induction of labor, the overall reported preterm delivery rate was not different between the two groups. Based on the existing two retrospective comparative studies, it is yet controversial whether RFA is inferior to BCC, but several case series including ours show a satisfactory success rate with a low complication rate. Other potential risks of RFA include hyperkalemia from massive tissue necrosis, hyperthermia due to the very high thermal energy produced during the procedure and embolization of generated microbubbles causing thromboembolism. However, none of them has been reported. Radiofrequency engenders an electromagnetic conflict causing disturbance to the Doppler signal. Thus, Doppler evaluation is not available during the procedure. Another disadvantage of RFA is that it is a more expensive procedure than BCC because of the disposable RFA needle and the special radiofrequeny generator [17, 21]. The limitation of this study is that it is a small retrospective cohort study. The main aim of our study was to compare our initial experience with RFA with that reported in the literature. As there is no randomized controlled trial comparing RFA and BCC, more extensive research in this area is urgently needed. In conclusion, RFA is a safe and effective procedure for selective reduction in different kinds of complicated MC pregnancies. Apart from the need for a randomized controlled trial to compare RFA and BCC, research on longterm neurological and developmental outcome of the survivors is also urgently warranted.
Radiofrequency Ablation for Selective Reduction
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
References
1 Acosta-Rojas R, Becker J, Munoz-Abellana B, Ruiz C, Carreras E, Gratacos E, Catalunya and Balears Monochorionic Network: Twin chorionicity and the risk of adverse perinatal outcome. Int J Gynaecol Obstet 2007;96:98–102. 2 Denbow ML, Cox P, Taylor M, Hammal DM, Fisk NM: Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome. Am J Obstet Gynecol 2000;182:417–426. 3 Lewi L, Van Schoubroeck D, Gratacos E, Witters I, Timmerman D, Deprest J: Monochorionic diamniotic twins: complications and management options. Curr Opin Obstet Gynecol 2003;15:177–194.
215
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finer than the bipolar forceps (3–5 mm diameter including the additional cannula) [17, 21]. Therefore, it is more suitable for earlier gestation with limited access, and even in the presence of severe oligohydramnios. With a smaller puncture, RFA should theoretically lead to a lower chance of PPROM and preterm delivery than BCC. Second, RFA may be technically easier, as the RFA probe is just targeted at the immobile intrafetal portion of the umbilical vessels, and the chance of slipping out is very low once the tip of the probe is anchored by its protruded tines. On the other hand, during BCC, the forceps blades have to grasp the floating umbilical cord, which is smooth and thick and hence may slip out from the blades. While there is yet no randomized controlled trial to compare the effectiveness and risk between RFA and BCC, two retrospective studies [20, 21] had compared RFA and BCC with conflicting results. In the study by Roman et al. [20], the authors first conducted a computergenerated random sampling to match patients who had undergone BCC with patients who had undergone RFA in a 2:1 ratio, controlling for gestational age and indication. The survival rate of the 20 pregnancies following RFA was 87%, and was not different from that of their 40 matched cases treated by BCC (88%). Although the chance of PPROM within 2 weeks after RFA was 0% compared to 12.5% following BCC, the difference had not reached statistical difference, or had translated to a significant difference in early preterm delivery rate (
Received: May 15, 2013 Accepted after revision: August 30, 2013 Published online: October 23, 2013
Radiofrequency Ablation for Selective Reduction in Complicated Monochorionic Multiple Pregnancies Jing Lu a Yuen Ha Ting b Kwok Ming Law b Tze Kin Lau c Tak Yeung Leung b a
Department of Ultrasound Medicine, Prenatal Diagnosis Center of Xiamen, Maternal and Child Health Hospital, Xiamen, b Fetal Medicine Unit, Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Prince of Wales Hospital, and c Fetal Medicine Centre, Paramount Clinic, Hong Kong, SAR, China
Key Words Monochorionic multiple pregnancy · Radiofrequency ablation · Selective feticide
Conclusions: RFA is a promising technique for selective reduction in complicated MC multiple pregnancies with a high survival rate and low complication rate. © 2013 S. Karger AG, Basel
© 2013 S. Karger AG, Basel 1015–3837/13/0344–0211$38.00/0 E-Mail [email protected] www.karger.com/fdt
Introduction
Although monochorionic (MC) multiple pregnancies are less frequent than dichorionic pregnancies, they are associated with a much higher risk of perinatal morbidity and mortality [1]. This is related to the fact that almost all MC placentas have vascular anastomoses connecting the circulations of the fetuses [2]. These communicating placental vessels lead to complications specific to MC pregnancies, such as twin-twin transfusion syndrome (TTTS), twin reversed arterial perfusion (TRAP) sequence, and acute feto-fetal exsanguination of the survivor after single twin intrauterine demise (IUD) [3]. Moreover, MC pregnancies with unequal placental share may result in selective intrauterine growth restriction (sIUGR) [4]. Furthermore, structural anomalies of MC twins are three times higher than those found in dichorionic twins [5]. When such MC pregnancy complications occur, selective reduction may be needed to reduce perinatal mortality and morbidity [6]. For singleton pregnancies or dichoProf. Tak Yeung Leung, MD Department of Obstetrics and Gynaecology Prince of Wales Hospital Shatin, Hong Kong, SAR (China) E-Mail tyleung @ cuhk.edu.hk
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Abstract Objective: To evaluate the perinatal outcome of monochorionic (MC) multiple pregnancies after selective reduction by radiofrequency ablation (RFA). Methods: A case series of all MC multiple pregnancies with selective reduction by RFA in one single institution was reviewed. Results: Ten consecutive patients with an MC pregnancy (9 pairs of twins and 1 set of triplets) underwent RFA. The median gestational age at the time of the procedure was 15.6 weeks (range, 12.3– 19.6). The indications for selective reduction included discordance for fetal anomalies (4 cases), twin reversed arterial perfusion sequence (3 cases), selective intrauterine growth restriction (2 cases) and severe twin-twin transfusion syndrome (1 case). All procedures were technically successful in achieving selective reduction. The overall survival rate of the cotwin was 81.8% (9/11), and the median gestational age at delivery was 35.9 weeks (range, 32.4–38.6). There was one preterm delivery before 34 weeks of gestation (11.1%). Preterm premature rupture of the membranes occurred in 2 patients (20%); however, this was not observed within 4 weeks postoperatively, nor did they deliver before 32 weeks.
Color version available online
rionic pregnancies, feticide can easily be achieved by fetal intracardiac potassium chloride injection. However, this method is not suitable for MC pregnancies because of the inevitable presence of vascular anastomosis in the MC placentas which can cause acute transfusion from the cotwin to the dying twin through these connecting circulations [7]. Death of one twin in an MC pair can result in death of or neurologic abnormality in the co-twin in 12 and 18% of cases, respectively [8]. Therefore, selective reduction in MC pregnancies can only be done by cord occlusion techniques, which interrupt the blood flow of the targeted twin while avoiding exsanguination of the cotwin. Among the cord occlusion techniques, the most commonly performed procedure is bipolar cord coagulation (BCC) [9]. Radiofrequency ablation (RFA) is a relatively new method used in selective reduction [9]. RFA achieves cord coagulation by high-frequency alternating current inducing high temperature. We report our initial experience with RFA for selective reduction in complicated MC pregnancies.
Materials and Methods
212
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
Fig. 1. An abortus after RFA: note the iatrogenic necrosis in the lower abdomen corresponding to the ablation site.
Energy was applied until no blood flow was demonstrated in the umbilical cord by color Doppler and pulsed-wave Doppler. The prongs were retracted back and the probe was removed. Ultrasound examination was performed after the procedure to confirm persistent bradycardia or cardiac asystole in the targeted twin and normal heart pulsation of the co-twin. A zone of probable thermal injury might also have been seen on ultrasound examination. Postoperatively, the patient was observed overnight in the hospital and discharged on the following day after ultrasound examination confirming cardiac asystole in the targeted twin and normal heart pulsation of the co-twin. Figure 1 shows an abortus after RFA with iatrogenic necrosis in the lower abdomen corresponding to the ablation site.
Results
There were 10 MC pregnancies that had selective reduction by RFA, including 7 pairs of MC diamniotic twins, 2 pairs of MC monoamniotic twins and 1 set of MC triamniotic triplets (table 1). The median maternal age was 29 years (range, 27–31). The median gestational age at the time of the procedure was 15.6 weeks (range, 12.3– Lu/Ting/Law/Lau/Leung
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This is a retrospective case series of all the selective reductions in MC pregnancies by RFA performed in the Fetal Medicine Unit, Prince of Wales Hospital, the Chinese University of Hong Kong from December 2011 to September 2012. The antenatal course, operation and delivery details of all the cases were reviewed. All RFA procedures were performed with ultrasound guidance using the Philips iU22 xMATRIX ultrasound system under local anesthesia by maternal fetal medicine subspecialists. All patients underwent ultrasound examination to determine the chorionicity and to confirm the indication for selective reduction. They were admitted on the day of surgery and informed consent was obtained. Augmentin 1.2 g was given intravenously before the procedure, and maternal sedation was not required. Ultrasound examination was performed to locate the placenta and the abdominal umbilical cord insertion of the targeted twin in order to determine the site of entrance. Bilateral grounding pads were placed on maternal thighs. After the abdominal skin had been sterilized, 10 ml 1% Xylocaine was infiltrated subcutaneously over the site of entry. A small skin incision was made and the radiofrequency probe (LeVeen Superslim Needle Electrode radiofrequency probe, 17 G, 15 cm long) was inserted percutaneously into the amniotic cavity of the targeted fetus under ultrasound guidance, with caution to avoid puncturing the amniotic sac of the co-twin as far as possible. The probe was then inserted into the fetal abdomen around the fetal umbilical cord insertion site. No anesthetic drug for fetal relaxation was used. After confirmation of the probe location, the prongs of the device were deployed. A radiofrequency generator (RF 3000TM, MEDI-TECH, Boston Scientific) was used and radiofrequency energy was applied in a stepwise fashion starting from 30 W and progressing to a maximum of 100 W, each energy level lasting for no more than 2 min.
Table 1. List of perinatal outcome of the 10 complicated MC pregnancies with selective reduction by RFA in chorological order
Case n
Amnionicity Indication
Gestation at procedure, weeks
Number of RFA cycles
Gestation at delivery, weeks
Outcome of co-twin
birth weight g
1
MCMA
discordant malformation
17.9
2
36.9
live-born
2,530
2
MCDA
discordant malformation
19.6
2
35.7
live-born
2,010
3
MCDA
TRAP sequence
13
4
38.6
live-born
2,620
4
MCTA
discordant malformation
12.3
3
35
live-born
2,215/2,195
5
MCMA
TRAP sequence
13.1
4
–
IUD 7 days after the procedure
–
6
MCDA
TRAP sequence
13.4
2
32.4
live-born
2,245
7
MCDA
sIUGR
19.6
1
34.4
live-born
1,845
8
MCDA
discordant malformation
13
1
38.4
live-born
2,135
9
MCDA
stage 4 TTTS
19.3
1
35.4
stillborn
1,700
10
MCDA
sIUGR
17.9
3
35.7
live-born
2,040
MCMA = MC monoamniotic; MCDA = MC diamniotic; MCTA = MC triamniotic.
19.6). The indications for selective reduction included discordance for fetal anomalies (4 cases), TRAP sequence (3 cases), sIUGR (2 cases) and severe TTTS (1 case). All procedures were technically successful in achieving selective reduction without the need for amnioinfusion. All procedures were completed within 4 radiofrequency cycles and most were completed after 1–2 radiofrequency cycles. Cardiac asystole of the targeted fetuses was confirmed by ultrasound after 24 h for all procedures. There were no maternal complications observed and no inadvertent septostomy or chorioamniotic separation. The perinatal outcome of all cases is summarized in table 1. There were 2 cases of IUD of the co-twin. One case (case 5) was an MC monoamniotic twin pregnancy complicated by TRAP sequence. The pump twin was already hydropic before the procedure at 13 weeks of gestation. Placental cord insertion sites were close together and there was cord entanglement near the placental cord insertion sites. The co-twin had normal cardiac pulsation 1 day after completion of the procedure, but was found to have absent cardiac pulsation 7 days later. The other case (case 9) was an MC diamniotic twin pregnancy complicated by stage 4 TTTS with an uneventful RFA performed at 19.3 weeks. The donor twin’s umbilical vessels were ablated and the hydropic changes of the recipient gradually resolved. However, the recipient twin was found to have IUD unexpectedly at 35.4 weeks. Hence the overall survival rate of the co-twins was 81.8% (9/11).
For the remaining 9 live births, the median gestational age at delivery was 35.9 weeks (range, 32.4–38.6) with the median birth weight being 2,204 g (range, 1,845– 2,620). The median procedure-to-delivery interval was 20.4 weeks (range, 14.9–25.6). There was one preterm delivery before 34 weeks of gestation (11.1%). Preterm premature rupture of membranes (PPROM) occurred in 2 cases (20%). One case (case 4) had PPROM at 35 weeks, which resulted in delivery within 24 h. The other one (case 7) had PPROM at 27 weeks and delivered at 34.4 weeks. Neither of the PPROM occurred within 4 weeks postoperatively, nor did these women deliver before 34 weeks.
Radiofrequency Ablation for Selective Reduction
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
For the last 10 years, RFA has been used for in utero therapy for MC pregnancy complications, fetal sacrococcygeal teratoma and fetal chest mass [10–12]. The mechanism of action of RFA is by thermal effect generated by the alternating electric current operated in the range of radiofrequency waves. The electric current agitating the ions in the tissue surrounding the electrodes causes frictional heat which is conducted into the adjacent tissue. The needle electrode itself is not heated up but the very high temperature generated in the tissue results in protein denaturation and local coagulation [13]. Therefore, for 213
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Discussion
Table 2. List of publications on selective reduction using RFA
Authors
Type of pregnancies (n)
Case series on selective reduction for TRAP sequence TRAP (5) Paramasivam et al. [5]
Average gestation week at procedure (range)
18.1 (16.3–19.4)
Survival of co-twins/triplets (rate per pregnancy, %) 4 (80%)
Average gestation week at delivery (range) 37.8 (36–41)
Cabassa et al. [19]
TRAP (7)
Lee et al. [22]a
TRAP (98)
20.2±2.4
Our study
TRAP (3)
13.2 (13–13.4)
All case series for TRAP sequence
total 113 pregnancies
–
89 (78.8%)
–
18.4 (12.7–27.1)
27 (90.0%)
35.4 (26–40.4)
6 (66.7%)
36.1 (26–39.2)
17 (14–23)
Case series on selective feticide for indications other than TRAP Paramasivam et al. [5] total (30) malformed (9); sIUGR (4); TTTS (11); fetal reduction (6)
5 (71.4%)
33 (31–39)
78 (79.6%)
37 (27.9–38.9)
2 (66.7%)
35.5 (32.4–38.6)
Moise et al. [17]
total (9) TTTS (5); malformed (4)
19.5 (18.6–22.2)
Roman et al. [20]
total (14)
–
Our study
total (7) malformed (4); sIUGR (2); TTTS (1)
17.1 (12.3–19.6)
All case series for indications other than TRAP
total 60 pregnancies
–
51 (85%)
–
All case series for all indications
total 173 pregnancies
–
140 (80.9%)
–
Retrospective comparative studies (RFA vs. BCC) Roman et al. [20] RFA (20) BCC (40) Bebbington et al. [21] a
RFA (58) BCC (88)
12 (85.7%)
–
6 (85.7%)
20.3 (17–29) 21.5 (17–29)
(87%) (88%)
20.2±2.2 20.9±2.7
(70.7%) (85.2%)
36 (34.4–38.4)
36 (26–41) 39 (19–40) 34.7 [29.2–38.6]b 33.0 [23.4–38.9]b
Cases recruited in this series were also reported in other references [15, 16, 18, 20, 21] which were excluded to avoid double counting. are interquartile ranges.
selective reduction, RFA is not aimed at umbilical cord occlusion, but targets on ablation of intrafetal umbilical vessels beneath the cord insertion site. Coagulation of the cord takes place secondarily [14]. Tsao et al. [10] was the first one to report the use of RFA in treating acardiac twins. In their 13 cases of TRAP sequence, the average gestational age at intervention was 20.7 weeks, and the average gestational age at delivery was 36.2 weeks. The preterm delivery rate before 34 weeks was 23.1% with only 1 neonate who died of prematurity. Subsequently, there were at least 8 other case series with varying sample sizes [5, 15–22]. The largest series has recently been published with a sample size of 98 cases [22], though it might have included some cases from 214
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
previously published series [15, 16, 18, 20, 21]. Combining our cases with these case series (excluding those case series which might have been included in the largest series), the overall survival rate reached 80.9% [5, 17, 19, 20, 22] (table 2). The average gestational age at delivery ranged from 33 to 38 weeks. When compared to these series, our initial local experience with RFA is promising with a co-twin survival rate of 81.8%. We had only 1 preterm delivery before 34 weeks of gestation (11.1%) [5, 10]. The PPROM rate of our series (20%) is also comparable with that reported in the literature (5–23.1%) [10, 15, 20]. RFA has several potential advantages over BCC. First, the diameter of an RFA probe is only 1.4 mm and is much Lu/Ting/Law/Lau/Leung
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b Figures
cases. In addition, it is worth noticing that in the study by Bebbington et al. [21], the chances of PROM (27.3%) and preterm labor (22.4%) after BCC were higher than after RFA (13.7 and 7%, respectively). However, because of a relatively higher rate of fetal death after RFA that required iatrogenic preterm induction of labor, the overall reported preterm delivery rate was not different between the two groups. Based on the existing two retrospective comparative studies, it is yet controversial whether RFA is inferior to BCC, but several case series including ours show a satisfactory success rate with a low complication rate. Other potential risks of RFA include hyperkalemia from massive tissue necrosis, hyperthermia due to the very high thermal energy produced during the procedure and embolization of generated microbubbles causing thromboembolism. However, none of them has been reported. Radiofrequency engenders an electromagnetic conflict causing disturbance to the Doppler signal. Thus, Doppler evaluation is not available during the procedure. Another disadvantage of RFA is that it is a more expensive procedure than BCC because of the disposable RFA needle and the special radiofrequeny generator [17, 21]. The limitation of this study is that it is a small retrospective cohort study. The main aim of our study was to compare our initial experience with RFA with that reported in the literature. As there is no randomized controlled trial comparing RFA and BCC, more extensive research in this area is urgently needed. In conclusion, RFA is a safe and effective procedure for selective reduction in different kinds of complicated MC pregnancies. Apart from the need for a randomized controlled trial to compare RFA and BCC, research on longterm neurological and developmental outcome of the survivors is also urgently warranted.
Radiofrequency Ablation for Selective Reduction
Fetal Diagn Ther 2013;34:211–216 DOI: 10.1159/000355406
References
1 Acosta-Rojas R, Becker J, Munoz-Abellana B, Ruiz C, Carreras E, Gratacos E, Catalunya and Balears Monochorionic Network: Twin chorionicity and the risk of adverse perinatal outcome. Int J Gynaecol Obstet 2007;96:98–102. 2 Denbow ML, Cox P, Taylor M, Hammal DM, Fisk NM: Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome. Am J Obstet Gynecol 2000;182:417–426. 3 Lewi L, Van Schoubroeck D, Gratacos E, Witters I, Timmerman D, Deprest J: Monochorionic diamniotic twins: complications and management options. Curr Opin Obstet Gynecol 2003;15:177–194.
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finer than the bipolar forceps (3–5 mm diameter including the additional cannula) [17, 21]. Therefore, it is more suitable for earlier gestation with limited access, and even in the presence of severe oligohydramnios. With a smaller puncture, RFA should theoretically lead to a lower chance of PPROM and preterm delivery than BCC. Second, RFA may be technically easier, as the RFA probe is just targeted at the immobile intrafetal portion of the umbilical vessels, and the chance of slipping out is very low once the tip of the probe is anchored by its protruded tines. On the other hand, during BCC, the forceps blades have to grasp the floating umbilical cord, which is smooth and thick and hence may slip out from the blades. While there is yet no randomized controlled trial to compare the effectiveness and risk between RFA and BCC, two retrospective studies [20, 21] had compared RFA and BCC with conflicting results. In the study by Roman et al. [20], the authors first conducted a computergenerated random sampling to match patients who had undergone BCC with patients who had undergone RFA in a 2:1 ratio, controlling for gestational age and indication. The survival rate of the 20 pregnancies following RFA was 87%, and was not different from that of their 40 matched cases treated by BCC (88%). Although the chance of PPROM within 2 weeks after RFA was 0% compared to 12.5% following BCC, the difference had not reached statistical difference, or had translated to a significant difference in early preterm delivery rate (
