Shoulder dystocia: Prevention and treatment James A. O'Leary, MD, and Helene B. Leonetti, MD Jersey City, New Jersey Although shoulder dystocia is an infrequent event it has assumed a position of great clinical importance because of our litigious environment. Many cases are preventable by the proper identification of risk factors, especially glucose intolerance, macrosomia, obesity, and postdate pregnancies. The severity of the problem can be rapidly graded or determined by the response to a systematic treatment plan; such a plan is outlined. (AM J OBSTET GVNECOL 1990;162:5-9.)
Key words: Shoulder dystocia, prevention, treatment Shoulder dystocia has replaced or at least is about to fill the void being created by the disappearance of breech presentations and Scanzoni and Kielland forceps rotations as possible causes of damaged babies and medicolegal liability. It is highly probable that in the future all shoulder impaction dystocias with a bad outcome will be litigated. This situation demands our attention to prevent further problems, since the axiom is that shoulder dystocia occurs cataclysmically and many, if not a majority, can and should be anticipated.' Dignam 2 has defined the "absolute essentials" in the management of shoulder dystocia as (1) prior consideration, (2) accurate knowledge, (3) a well-conceived plan of action, and (4) rapidity of execution. Williams' Obstetrics3 has emphasized that the practitioner of obstetrics must be well versed in the management principles of this occasionally devastating complication. The purpose of this presentation is twofold : one, to outline a thoughtful approach to the prevention of shoulder dystocia, and, second, to detail a rapid treatment plan that includes cephalic replacement.
Incidence The incidence of shoulder dystocia appears to be increasing} This may be a reflection of improved prenatal care, increasing maternal age, obesity, pregnancy weight gain, and a decrease in factors leading to preterm delivery. Hopwood 4 has observed a fivefold increase in shoulder dystocia in a community hospital over the past 15 years. A greater frequency of postdate pregnancies also may account for this. As with all infrequent occurrences it is difficult to establish the incidence accurately, but it is clearly < I %, probably about 0.2% to 0.4%. The decreased incidence at Los Angeles County Hospital from 0.3% to 0.13% is a reflection of
From the Jersey City Medical Center. Reprint requests: James A . O'Leary, MD, Department of Obstetncs and Gynecology, Jersey City Medical Center, 50 Baldwin Ave., Jersey City, NJ 07304 . 611116073
an increased incidence of cesarean section for macrosomia and prolonged second stage of labor.5 Prepregnancy risk factors. Maternal glucose intolerance will account for 10% of macrosomic infants. After those cases attributed to large maternal stature or excessive weight gain are eliminated, at least one third of cases of macrosomia remain unexplained. The value of ascertaining maternal birth weight has recently been reconfirmed . The study of Klebanoff et al. 6 demonstrates that a mother's birth weight has a strong influence on her child's birth weight. In fact, maternal birth weight is more strongly associated with accelerated fetal growth than is either current maternal height or weight. The history of a previous delivery of a large baby or a history of shoulder dystocia clearly identifies a woman at high risk for shoulder dystocia. The concept of a "proved pelvis" because of an uncomplicated passage of a macrosomic infant is untenable. The dictum "once a shoulder dystocia, always a cesarean" may come to pass, especially if the subsequent infant is of a similar size. Women who will be delivered of a macrosomic infant tend to be older, to be of increased parity and to have one or both of two problems, obesity and diabetes. Macrosomia would be expected in obese and diabetic pregnant women because the principal substrate for fetal growth is glucose. The risk of macrosomia increases from 15.1 % to 31.5% when more than one risk factor is present. Preconception counseling will help to identify eight key potential predictors of shoulder dystocia (Table I) and experience suggests that the predictability of these factors may be not only additive but also synergistic. Prepartal risk factors. Pregnancy-induced glucose intolerance, which includes one or two abnormal values on a 3-hour glucose tolerance test or two borderline values, is a risk factor for macrosomia and shoulder dystocia. All pregnant women should be screened for pregnancy-induced glucose intolerance in the second trimester. Patients at high risk should undergo a 3-hour glucose tolerance test. Those patients at high risk but
5
6 O'Leary and Leonetti
Table I. Key prep regnancy historic risk factors Maternal birth weight Prior shoulder dystocia Prior macrosomia Diabetes-preexisting Obesity Multiparity Prior gestational diabetes Advanced maternal age
Table II. Antepartal risk factors Glucose intolerance or excess Excessive weight gain Macrosomia Short stature Abnormal pelvic shape Abnormal pelvic size Postdatism
with negative test results should be rescreened in the third trimester. The nonfasting 50 gm glucose screen ("a cola and candy bar") should be used. Values> 135 mg/dl are considered abnormal. Five to ten percent of patients with pregnancy-induced glucose intolerance and insulin dependence will have infants who show signs of macrosomia. The presence of glucose excess, especially the fasting blood glucose, will greatly increase the risk for shoulder dystocia, especially if any prepregnancy risk factors are present. Maternal weight gain ranks high as a factor leading to macrosomia. Boyd et al. 7 found that a weight gain of 20 kg is additive to the risk factors of obesity and postdate gestations 7 days. The risk of excess weight gain has been detailed by Dor et al. a but questioned by Parks and Ziel." It is safe to assume that the excess glucose intake exposes the infant to a greater growth stimulus and adds greater risk if prep regnancy abnormalities have been noted . Excessive weight gain increases the incidence of macrosomia from 1.4% to 15.2%. Antenatal suspicion of macrosomia requires careful ultrasonographic evaluation. Infants estimated to be >4500 gm should be delivered by primary cesarean section. Spellacy et al. IO recommend abdominal delivery for a weight of 5000 gm while Dor et al.a suggest a weight of 4000 gm. The presence of other risk factors makes the decision more obvious. A report" in 1982 described an ultrasonographic macrosomia index. In this study cesarean section for delivery of all fetuses with chest-biparietal diameter > 1.4 cm would have reduced the incidence oftraumatic morbidity from 27% to 9%. The large-for-gestationalage fetuses of diabetic gravid patients seem to have disproportionately accelerated abdominal growth as compared with that of large-for-gestational-age and appropriate-for-gestational-age fetuses of nondiabetic
January 1990 Am J Obstet Gynecol
gravid patients and appropriate-for-gestational-age fetuses of diabetic gravid patients. Neonates experiencing shoulder dystocia have significantly greater shoulderto-head and chest-to-head proportions than macrosomic neonates delivered by cesarean section because of failed progress in labor. Elliott et al. 11 recommended that a chest-to-head circumference difference of 1.6 cm or a shoulder-to-chest circumference difference of 4.8 cm be considered the anthropometic proportions indicating the possibility of shoulder dystocia. Postdate gestation is a very important risk factor for shoulder dystocia and is one of the ominous components of a triad, the other components being obesity and diabetes. Boyd et al. reported a 21 % incidence of macrosomia with infants delivered at 42 weeks but only 12% with those delivered at 40 weeks and suggested induction of labor as a means to prevent shoulder dystocia. In the study of Spellacy et al. the frequency of postdate pregnancy was 10.2% among the infants with mild macrosomia and 14.8% among those with more severe macrosomia. When multiple risk factors were present in association with postdate pregnancy, the fetal risks increased even further. Other antenatal risks that impact on the frequency of shoulder dystocia are short stature, abnormal pelvic morphologic characteristics (especially the flat pelvis), and reduced pelvic size (Table II). Each of these is of greater significance when considered in light of prepregnancy and other antenatal risk factors. Intrapartal risk factors. Labor abnormalities can help identify women at risk for shoulder dystocia. Dor et al. a reported a 46% incidence of failure to progress in labor in a group of macrosomic infants, while others l2 have described a 63.3% incidence of cephalopelvic disproportion and a 21.1 % incidence of failure to progress in a similar group of patients. The value of a prolonged second stage as a marker for shoulder dystocia has been clearly defined by Benedetti and Gabbe. 12 An abnormal second stage with macrosomia is associated with an increase in the incidence of shoulder dystocia from 1.2% to 23%. A significant reduction in dystocia from 23.0% to 11.1 % was accomplished by a liberal cesarean section policy. Acker et al. 13 in analyzing nondiabetic infants weighing 4000 to 4499 gm, observed normal labor in 70.1 %, protraction in 21.5%, and arrest in 8.4%. In infants >4500 gm with an arrest disorder, it appeared to be a predictive tool, although 17.3% had a normal pattern. In their diabetic population with a cesarean section rate of 46.3%, only 27.3% of the dystocias could be predicted on the basis of an abnormal labor. Hopwood in a community hospital study reported a prolonged decelerative phase in 38 of 62 cases and confirmed the findings of Benedetti and Gabbe. The abnormalities of labor, when they occur, unfortunately are late phenomena. Arrest of descent, failure of descent, protracted
Shoulder dystocia
Volume 162 Numher I
descent, or a prolonged second stage occurs at a point in time when all parties concerned would like to conclude the process. Intrapartal risk factors are summarized in Table III. The temptation to perform a mid pelvic delivery in women with abnormal descent curves and prolonged second stage and the tragic outcomes have been well defined .'" The use of epidural and saddle block anesthesia also has been incriminated as predisposing to shoulder dystocia.~ Maternal glucose intolerance and macrosomia associated with an abnormal labor are more than sufficient reason to perform a cesarean section. Benedetti and Gabbe showed a higher incidence with the vacuum extractor than with mid forceps. They proposed that the difference between the two modalities was the result of the capacity of the vacuum extractor to deliver a laI'ger infant than Kielland's forceps could deliver.
Table III. Intrapartal risk factors Prolonged second stage Protracted descent Arrest of descent Failure of descent Macrosomia Abnormal first stage Molding Need for mid pelvic delivery
Table IV. Severity of shoulder dystocia and suggested treatment Grade
I. Mild
Treatment The treatment must be preplanned and carefully understood by the obstetrician. There is insufficient time for reflective meditation and/ or consultation. The physician must be forewarned of the three P's resulting from panic-pulling, pushing, and pivoting. Further pulling or traction will increase the impactation, while fundal pressure will do the same. Pivoting or twisting the neck adds nothing good and only leads to neurologic damage. Adequate help must be obtained. Anesthesia is important as are a pediatrician and additional nursing care. The airway must be cleared. Rapidity of action is critical to grade the severity of the dystocia and to determine which procedure should be used. Once the head has emerged and it is evident that shoulder dystocia exists, several courses of action are available. As the first step, it is essential that any possible interference from the soft tissues of the lower binh canal be eliminated by a truly adequate episiotomy. Our experience supports the contention that a deliberate perineotomy, which divides the anal sphincter and extends well up the rectovaginal septum furnishes the needed space. It can be expected that a carefully repaired perineotomy will result in a better anatomic restoration of the vagina and perineum than a repaired wide mediolateral episiotomy. A question frequently asked is how much time do I have? More than lO years ago Wood et al! described serial pH determinations between delivery of the head and trunk. The pH declined at the ratio of 0.04 unit per minute or 0 .2 unit in 5 minutes. Thus there is adequate time to proceed in a well-organized manner. Mild dystocia (grade 1) We prefer to grade shoulder dystocias on the basis of the response to treatment, going from the easiest to
7
2. Moderate 3. Severe 4. Undeliverable
Treatment
Suprapubic pressure 1. Directed posteriorly (Mazzanti) 2. Directed to one side (Rubin) Wood maneuver Rubin maneuver (reverse Wood) Posterior shoulder Hibbard technique McRo berts maneuver All of the above combined Cephalic replacement
a combination of more involved procedures (Table IV). The first and simplest step is direct suprapubic pressure in the midline, directed slightly away from behind the pubic bone. This pressure also may be to one side of the midline of the maternal abdomen or the other, alternately, to force the shoulder into an oblique diameter of the pelvis. ' These techniques are usually successful only with milder forms (grade 1) of shoulder dystocia. The Wood screw maneuver or its modification, a reverse rotation, should be applied next if the dystocia is mild. These are usually unsuccessful in the more severe grades of dystocia and one should not waste much time with them. In the presence of shoulder dystocia the screwing motion should be effected by exerting pressure on the anterior surface of the posterior shoulder of the infant (Wood maneuver). The pressure on the anterior surface of the posterior shoulder should be exerted in the deltopectoral triangle of the posterior arm. However, the importance of having both the infant's shoulders brought forward toward the chest should be emphasized . The Wood maneuver results in abduction of the shoulder, and in this position the circumference of the baby's body is greater than when the shoulders are adducted. The latter would result from use of the Wood maneuver. Therefore the more recommended movement is a reverse of the Wood maneuver, with pressure on the posterior surface of the posterior shoulder. The infant's shoulder may be rocked from side to
8 O'Leary and Leonetti
side by pusing on the mother's suprapubic area. This results in adduction of both the baby's shoulders, and if they are at first located in the anteroposterior diameter of the pelvis, the maneuver displaces them into the longer oblique diameter of the pelvis. Moderate dystocia (grade 2)
In the moderate forms of dystocia the Hibbard 15 and posterior shoulder techniques are more effective. Hibbard described a maneuver in which pressure on the head results in directing it back into the vagina, the infant's anterior shoulder being pushed toward the rectum to displace it from the symphysis. This requires an assistant capable of applying a sufficient amount of suprapubic and then fundal pressure. The steps are as follows: Press firmly with a flattened hand against the infant's head, jaw, and upper neck, carrying the head and neck posteriorly toward the rectum and slightly upward to facilitate the release of the anterior shoulder. As the anterior shoulder slips free of the superior surface of the symphysis, strong fundal pressure is applied. At the same time, continuing pressure against the jaw and neck is shifted slightly, aiming directly at the rectal area. The method has several advantages. It is easily learned and requires only that an assistant be available to apply strong, steady fundal pressure. When the procedure is properly performed, the infant's cervical nerves are not injured and the hypoxic damage of a prolonged delivery is avoided. We also favor delivery of the posterior arm as the most efficacious and expeditious means of overcoming shoulder dystocia. The definitive move is to introduce one hand into the vagina posteriorly to determine the reason for difficulty. If shoulder dystocia is due to a very large baby, the true pelvis is tightly filled with the baby's torso, and it will be impossible or extremely difficult to insert the examining hand very far into the vagina. 2 The baby's posterior hand is located and pulled across the chest. Pressure can be applied in the antecubital space to flex the arm and make the hand more accessible. We have found that this is difficult to do when the arm and hand are tightly wedged in the pelvis. As the posterior hand is brought down across the baby's chest, the posterior arm and shoulder are delivered outside the vagina and the remainder of the delivery usually can be completed without undue difficulty. Severe dystocia (grade 3)
With moderate to severe dystocia where the above techniques fail, it has been our policy to perform a McRoberts maneuver. The procedure, although requiring two assistants (its only drawback), has been highly successful. Successful resolution of the dystocia has occurred in all but four of 44 cases. The
January 1990 Am J Obslel Gyneco1
McRoberts maneuver is easy and safe and can be performed rapidly. We concur strongly in the recommendation that every obstetrician should know how to perform it. The McRoberts maneuver has been recommended by Gonik et al. 16 It consists of removing the patient'S legs from the stirrups and sharply flexing them against the abdomen. This results in straightening ofthe sacrum relative to the lumbar spine, with rotation of the symphysis pubis cephalad and a decrease of the angle of inclination. Although this maneuver does not change the dimensions of the pelvis, the superior rotation of the symphysis tends to free the impacted anterior shoulder. As part of the McRoberts maneuver, if the shoulder is not released immediately, we combine all of the above techniques. The Hibbard technique is repeated, plus suprapubic pressure, followed by attempts at rotation and/or grasping of the posterior arm. Undeliverable dystocia (grade 4)cephalic replacement
After the diagnosis of irreducible or undeliverable bilateral severe shoulder dystocia is made, the following steps should be taken: Prepare for abdominal delivery. Initiate tocolysis (subcutaneous terbutaline 0.25 mg), if necessary, monitor the fetal heart rate, and rapidly perform a cephalic replacement. The episiotomy repair can be deferred and hemostats placed on any major bleeding vessels. The head is easily replaced by constant but firm pressure with the palm of the hand. The head must be "reflexed" and kept in the position of flexion; then the vertex is pushed as far cephalad as possible (usually to the zero station) and held in that position by an assistant, if necessary. This technique should be used only when continued vaginal manipulation would lead to a predictably poor outcome for all concerned. If the infant has been damaged, the placenta separated, or severe hypoxia has occurred, it should not be used. There must be a reasonable chance of a safe delivery for the mother and a good outcome for the baby. We feel that cephalic replacement is worthy of further investigation and reporting of all outcomes to see if it will become a permanent part of our regimen for management of severe shoulder dystocia. Success has occurred in 23 cases. Comment
The optimum method of treatment of shoulder dystocia, once it occurs, remains debatable; however, everyone would agree that prevention is the best practice. The prevention of shoulder dystocia begins with the first prenatal visit, where the preconceptual and prenatal risk factors all can be determined except for total pregnancy weight gain . Early identification and proper counseling, frequent ultrasonographic testing,
Volume 162 Number I
and perhaps induction of labor at 40 weeks might help to reduce the severity of this problem. However, it must be emphasized that even under optimal circumstances and in the best of hands an unexpected shoulder dystocia can occur. As cesarean section rates have increased in our institution, the number of shoulder dystocias appears to have decreased; thus one important criterion for a safe vaginal delivery is becoming more and more difficult to fulfill; that is, residency training programs may not provide sufficient opportunity to acquire adequate experience. In-depth teaching, memorizing a plan of action, and periodically reviewing these procedures (a socalled "fire drill") is imperative. A high level of suspicion for shoulder dystocia is a reasonable indication for cesarean section if founded on a solid data base of known risk factors. The patients who fit the mnemonic DOPE (Diabetes, Obesity, Postdatism, and Excessive fetal weight or maternal weight gain) are at greatest risk. Poor labor progress, especially arrest patterns and abnormal descent patterns, as well as knowledge of maternal birth weight, will further increase the index of suspicion for shoulder dystocia. Only a liberal policy for cesarean section for these indications will decrease the frequency of shoulder dystocia. It canot be emphasized too strongly that shoulder dystocia can be largely prevented by the use of cesarean delivery instead of mid forceps or vacuum extraction when the head of a large infant arrests in the mid pelvis. This has been proved true in our institution. Meticulous antenatal care consisting of frequent ultrasonographic examinations, glucose screening, and proper diet should help to reduce the incidence of macrosomia and to properly identify women at greatest risk. REFERENCES I. McLeod A. In discussion: Hopwood HG Jr. Shoulder dystocia: fifteen years' experience in a community hospital. AMJ OBSTET GYNECOL 1982;144:162.
Shoulder dystocia 9
2. Dignam WJ. Difficulties in delivery, including shoulder dystocia and mal presentations of the fetus. Clin Obstet GynecoI1976;19:577. 3. Williams' obstetrics. 17th ed. Norwalk, Connecticut: Appleton-Century-Crofts, 1985:669. 4. Hopwood HGO Jr. Shoulder dystocia: fifteen years' experience in a community hospital. AMJ OB5TET GYNECOL 1982;144:162. 5. Benedetti TJ. Managing shoulder dystocia. Contemp Ob Gyn 1979; 14:33. 6. Klebanoff MA, Mills JL, Berendes HW. Mother's birth weight as a predictor of macrosomia. AM J OBSTET GyNECOL 1985; 153:253. 7. Boyd ME, Usher RH, McLean FH. Fetal macrosomia: prediction, risks, proposed management. Obstet Gynecol 1983;61:715. 8. Dor N, Mosberg H, Stern W, Jagani N. Schulman H. Complications in fetal macrosomia. NY State J Med 1984;84:302. 9. Parks GD, Ziel HK. Macrosomia: a proposed mdication for primary cesarean section. Obstet Gynecol 1987; 52:407. 10. Spellacy WN, Miller S, Winegar A, Peterson PQ. Macrosomia-maternal characteristics and infant complications. Obstet Gynecol 1985;66: 158. II. Elliott JP, Garite TJ, Freeman RK, et al. Ultrasonic prediction of fetal macrosomia in diabetic patients. Obstet Gynecol 1982;60: 159. 12. Benedetti TJ. Gabbe SG. Shoulder dystocia: a complication of fetal macrosomia and prolonged second stage with mid-pelvic delivery. Obstet Gynecol 1978;52:526. 13. Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985;66:762. 14. Wood C, Ng KH, Hounslow D, Benning H. Time: an important variable in normal delivery. J Obstet Gynaecol Br Commonw 1973;80:295. IS. Hibbard LT. Coping with shoulder dystocia. Contemp Ob Gyn 1982;20:229. 16. Gonik B, Stringer CA, Held B. An alternate maneuver for the management of shoulder dystocia. AM J OBSTET GYNECOL 1983; 145:882.
Key words: Shoulder dystocia, prevention, treatment Shoulder dystocia has replaced or at least is about to fill the void being created by the disappearance of breech presentations and Scanzoni and Kielland forceps rotations as possible causes of damaged babies and medicolegal liability. It is highly probable that in the future all shoulder impaction dystocias with a bad outcome will be litigated. This situation demands our attention to prevent further problems, since the axiom is that shoulder dystocia occurs cataclysmically and many, if not a majority, can and should be anticipated.' Dignam 2 has defined the "absolute essentials" in the management of shoulder dystocia as (1) prior consideration, (2) accurate knowledge, (3) a well-conceived plan of action, and (4) rapidity of execution. Williams' Obstetrics3 has emphasized that the practitioner of obstetrics must be well versed in the management principles of this occasionally devastating complication. The purpose of this presentation is twofold : one, to outline a thoughtful approach to the prevention of shoulder dystocia, and, second, to detail a rapid treatment plan that includes cephalic replacement.
Incidence The incidence of shoulder dystocia appears to be increasing} This may be a reflection of improved prenatal care, increasing maternal age, obesity, pregnancy weight gain, and a decrease in factors leading to preterm delivery. Hopwood 4 has observed a fivefold increase in shoulder dystocia in a community hospital over the past 15 years. A greater frequency of postdate pregnancies also may account for this. As with all infrequent occurrences it is difficult to establish the incidence accurately, but it is clearly < I %, probably about 0.2% to 0.4%. The decreased incidence at Los Angeles County Hospital from 0.3% to 0.13% is a reflection of
From the Jersey City Medical Center. Reprint requests: James A . O'Leary, MD, Department of Obstetncs and Gynecology, Jersey City Medical Center, 50 Baldwin Ave., Jersey City, NJ 07304 . 611116073
an increased incidence of cesarean section for macrosomia and prolonged second stage of labor.5 Prepregnancy risk factors. Maternal glucose intolerance will account for 10% of macrosomic infants. After those cases attributed to large maternal stature or excessive weight gain are eliminated, at least one third of cases of macrosomia remain unexplained. The value of ascertaining maternal birth weight has recently been reconfirmed . The study of Klebanoff et al. 6 demonstrates that a mother's birth weight has a strong influence on her child's birth weight. In fact, maternal birth weight is more strongly associated with accelerated fetal growth than is either current maternal height or weight. The history of a previous delivery of a large baby or a history of shoulder dystocia clearly identifies a woman at high risk for shoulder dystocia. The concept of a "proved pelvis" because of an uncomplicated passage of a macrosomic infant is untenable. The dictum "once a shoulder dystocia, always a cesarean" may come to pass, especially if the subsequent infant is of a similar size. Women who will be delivered of a macrosomic infant tend to be older, to be of increased parity and to have one or both of two problems, obesity and diabetes. Macrosomia would be expected in obese and diabetic pregnant women because the principal substrate for fetal growth is glucose. The risk of macrosomia increases from 15.1 % to 31.5% when more than one risk factor is present. Preconception counseling will help to identify eight key potential predictors of shoulder dystocia (Table I) and experience suggests that the predictability of these factors may be not only additive but also synergistic. Prepartal risk factors. Pregnancy-induced glucose intolerance, which includes one or two abnormal values on a 3-hour glucose tolerance test or two borderline values, is a risk factor for macrosomia and shoulder dystocia. All pregnant women should be screened for pregnancy-induced glucose intolerance in the second trimester. Patients at high risk should undergo a 3-hour glucose tolerance test. Those patients at high risk but
5
6 O'Leary and Leonetti
Table I. Key prep regnancy historic risk factors Maternal birth weight Prior shoulder dystocia Prior macrosomia Diabetes-preexisting Obesity Multiparity Prior gestational diabetes Advanced maternal age
Table II. Antepartal risk factors Glucose intolerance or excess Excessive weight gain Macrosomia Short stature Abnormal pelvic shape Abnormal pelvic size Postdatism
with negative test results should be rescreened in the third trimester. The nonfasting 50 gm glucose screen ("a cola and candy bar") should be used. Values> 135 mg/dl are considered abnormal. Five to ten percent of patients with pregnancy-induced glucose intolerance and insulin dependence will have infants who show signs of macrosomia. The presence of glucose excess, especially the fasting blood glucose, will greatly increase the risk for shoulder dystocia, especially if any prepregnancy risk factors are present. Maternal weight gain ranks high as a factor leading to macrosomia. Boyd et al. 7 found that a weight gain of 20 kg is additive to the risk factors of obesity and postdate gestations 7 days. The risk of excess weight gain has been detailed by Dor et al. a but questioned by Parks and Ziel." It is safe to assume that the excess glucose intake exposes the infant to a greater growth stimulus and adds greater risk if prep regnancy abnormalities have been noted . Excessive weight gain increases the incidence of macrosomia from 1.4% to 15.2%. Antenatal suspicion of macrosomia requires careful ultrasonographic evaluation. Infants estimated to be >4500 gm should be delivered by primary cesarean section. Spellacy et al. IO recommend abdominal delivery for a weight of 5000 gm while Dor et al.a suggest a weight of 4000 gm. The presence of other risk factors makes the decision more obvious. A report" in 1982 described an ultrasonographic macrosomia index. In this study cesarean section for delivery of all fetuses with chest-biparietal diameter > 1.4 cm would have reduced the incidence oftraumatic morbidity from 27% to 9%. The large-for-gestationalage fetuses of diabetic gravid patients seem to have disproportionately accelerated abdominal growth as compared with that of large-for-gestational-age and appropriate-for-gestational-age fetuses of nondiabetic
January 1990 Am J Obstet Gynecol
gravid patients and appropriate-for-gestational-age fetuses of diabetic gravid patients. Neonates experiencing shoulder dystocia have significantly greater shoulderto-head and chest-to-head proportions than macrosomic neonates delivered by cesarean section because of failed progress in labor. Elliott et al. 11 recommended that a chest-to-head circumference difference of 1.6 cm or a shoulder-to-chest circumference difference of 4.8 cm be considered the anthropometic proportions indicating the possibility of shoulder dystocia. Postdate gestation is a very important risk factor for shoulder dystocia and is one of the ominous components of a triad, the other components being obesity and diabetes. Boyd et al. reported a 21 % incidence of macrosomia with infants delivered at 42 weeks but only 12% with those delivered at 40 weeks and suggested induction of labor as a means to prevent shoulder dystocia. In the study of Spellacy et al. the frequency of postdate pregnancy was 10.2% among the infants with mild macrosomia and 14.8% among those with more severe macrosomia. When multiple risk factors were present in association with postdate pregnancy, the fetal risks increased even further. Other antenatal risks that impact on the frequency of shoulder dystocia are short stature, abnormal pelvic morphologic characteristics (especially the flat pelvis), and reduced pelvic size (Table II). Each of these is of greater significance when considered in light of prepregnancy and other antenatal risk factors. Intrapartal risk factors. Labor abnormalities can help identify women at risk for shoulder dystocia. Dor et al. a reported a 46% incidence of failure to progress in labor in a group of macrosomic infants, while others l2 have described a 63.3% incidence of cephalopelvic disproportion and a 21.1 % incidence of failure to progress in a similar group of patients. The value of a prolonged second stage as a marker for shoulder dystocia has been clearly defined by Benedetti and Gabbe. 12 An abnormal second stage with macrosomia is associated with an increase in the incidence of shoulder dystocia from 1.2% to 23%. A significant reduction in dystocia from 23.0% to 11.1 % was accomplished by a liberal cesarean section policy. Acker et al. 13 in analyzing nondiabetic infants weighing 4000 to 4499 gm, observed normal labor in 70.1 %, protraction in 21.5%, and arrest in 8.4%. In infants >4500 gm with an arrest disorder, it appeared to be a predictive tool, although 17.3% had a normal pattern. In their diabetic population with a cesarean section rate of 46.3%, only 27.3% of the dystocias could be predicted on the basis of an abnormal labor. Hopwood in a community hospital study reported a prolonged decelerative phase in 38 of 62 cases and confirmed the findings of Benedetti and Gabbe. The abnormalities of labor, when they occur, unfortunately are late phenomena. Arrest of descent, failure of descent, protracted
Shoulder dystocia
Volume 162 Numher I
descent, or a prolonged second stage occurs at a point in time when all parties concerned would like to conclude the process. Intrapartal risk factors are summarized in Table III. The temptation to perform a mid pelvic delivery in women with abnormal descent curves and prolonged second stage and the tragic outcomes have been well defined .'" The use of epidural and saddle block anesthesia also has been incriminated as predisposing to shoulder dystocia.~ Maternal glucose intolerance and macrosomia associated with an abnormal labor are more than sufficient reason to perform a cesarean section. Benedetti and Gabbe showed a higher incidence with the vacuum extractor than with mid forceps. They proposed that the difference between the two modalities was the result of the capacity of the vacuum extractor to deliver a laI'ger infant than Kielland's forceps could deliver.
Table III. Intrapartal risk factors Prolonged second stage Protracted descent Arrest of descent Failure of descent Macrosomia Abnormal first stage Molding Need for mid pelvic delivery
Table IV. Severity of shoulder dystocia and suggested treatment Grade
I. Mild
Treatment The treatment must be preplanned and carefully understood by the obstetrician. There is insufficient time for reflective meditation and/ or consultation. The physician must be forewarned of the three P's resulting from panic-pulling, pushing, and pivoting. Further pulling or traction will increase the impactation, while fundal pressure will do the same. Pivoting or twisting the neck adds nothing good and only leads to neurologic damage. Adequate help must be obtained. Anesthesia is important as are a pediatrician and additional nursing care. The airway must be cleared. Rapidity of action is critical to grade the severity of the dystocia and to determine which procedure should be used. Once the head has emerged and it is evident that shoulder dystocia exists, several courses of action are available. As the first step, it is essential that any possible interference from the soft tissues of the lower binh canal be eliminated by a truly adequate episiotomy. Our experience supports the contention that a deliberate perineotomy, which divides the anal sphincter and extends well up the rectovaginal septum furnishes the needed space. It can be expected that a carefully repaired perineotomy will result in a better anatomic restoration of the vagina and perineum than a repaired wide mediolateral episiotomy. A question frequently asked is how much time do I have? More than lO years ago Wood et al! described serial pH determinations between delivery of the head and trunk. The pH declined at the ratio of 0.04 unit per minute or 0 .2 unit in 5 minutes. Thus there is adequate time to proceed in a well-organized manner. Mild dystocia (grade 1) We prefer to grade shoulder dystocias on the basis of the response to treatment, going from the easiest to
7
2. Moderate 3. Severe 4. Undeliverable
Treatment
Suprapubic pressure 1. Directed posteriorly (Mazzanti) 2. Directed to one side (Rubin) Wood maneuver Rubin maneuver (reverse Wood) Posterior shoulder Hibbard technique McRo berts maneuver All of the above combined Cephalic replacement
a combination of more involved procedures (Table IV). The first and simplest step is direct suprapubic pressure in the midline, directed slightly away from behind the pubic bone. This pressure also may be to one side of the midline of the maternal abdomen or the other, alternately, to force the shoulder into an oblique diameter of the pelvis. ' These techniques are usually successful only with milder forms (grade 1) of shoulder dystocia. The Wood screw maneuver or its modification, a reverse rotation, should be applied next if the dystocia is mild. These are usually unsuccessful in the more severe grades of dystocia and one should not waste much time with them. In the presence of shoulder dystocia the screwing motion should be effected by exerting pressure on the anterior surface of the posterior shoulder of the infant (Wood maneuver). The pressure on the anterior surface of the posterior shoulder should be exerted in the deltopectoral triangle of the posterior arm. However, the importance of having both the infant's shoulders brought forward toward the chest should be emphasized . The Wood maneuver results in abduction of the shoulder, and in this position the circumference of the baby's body is greater than when the shoulders are adducted. The latter would result from use of the Wood maneuver. Therefore the more recommended movement is a reverse of the Wood maneuver, with pressure on the posterior surface of the posterior shoulder. The infant's shoulder may be rocked from side to
8 O'Leary and Leonetti
side by pusing on the mother's suprapubic area. This results in adduction of both the baby's shoulders, and if they are at first located in the anteroposterior diameter of the pelvis, the maneuver displaces them into the longer oblique diameter of the pelvis. Moderate dystocia (grade 2)
In the moderate forms of dystocia the Hibbard 15 and posterior shoulder techniques are more effective. Hibbard described a maneuver in which pressure on the head results in directing it back into the vagina, the infant's anterior shoulder being pushed toward the rectum to displace it from the symphysis. This requires an assistant capable of applying a sufficient amount of suprapubic and then fundal pressure. The steps are as follows: Press firmly with a flattened hand against the infant's head, jaw, and upper neck, carrying the head and neck posteriorly toward the rectum and slightly upward to facilitate the release of the anterior shoulder. As the anterior shoulder slips free of the superior surface of the symphysis, strong fundal pressure is applied. At the same time, continuing pressure against the jaw and neck is shifted slightly, aiming directly at the rectal area. The method has several advantages. It is easily learned and requires only that an assistant be available to apply strong, steady fundal pressure. When the procedure is properly performed, the infant's cervical nerves are not injured and the hypoxic damage of a prolonged delivery is avoided. We also favor delivery of the posterior arm as the most efficacious and expeditious means of overcoming shoulder dystocia. The definitive move is to introduce one hand into the vagina posteriorly to determine the reason for difficulty. If shoulder dystocia is due to a very large baby, the true pelvis is tightly filled with the baby's torso, and it will be impossible or extremely difficult to insert the examining hand very far into the vagina. 2 The baby's posterior hand is located and pulled across the chest. Pressure can be applied in the antecubital space to flex the arm and make the hand more accessible. We have found that this is difficult to do when the arm and hand are tightly wedged in the pelvis. As the posterior hand is brought down across the baby's chest, the posterior arm and shoulder are delivered outside the vagina and the remainder of the delivery usually can be completed without undue difficulty. Severe dystocia (grade 3)
With moderate to severe dystocia where the above techniques fail, it has been our policy to perform a McRoberts maneuver. The procedure, although requiring two assistants (its only drawback), has been highly successful. Successful resolution of the dystocia has occurred in all but four of 44 cases. The
January 1990 Am J Obslel Gyneco1
McRoberts maneuver is easy and safe and can be performed rapidly. We concur strongly in the recommendation that every obstetrician should know how to perform it. The McRoberts maneuver has been recommended by Gonik et al. 16 It consists of removing the patient'S legs from the stirrups and sharply flexing them against the abdomen. This results in straightening ofthe sacrum relative to the lumbar spine, with rotation of the symphysis pubis cephalad and a decrease of the angle of inclination. Although this maneuver does not change the dimensions of the pelvis, the superior rotation of the symphysis tends to free the impacted anterior shoulder. As part of the McRoberts maneuver, if the shoulder is not released immediately, we combine all of the above techniques. The Hibbard technique is repeated, plus suprapubic pressure, followed by attempts at rotation and/or grasping of the posterior arm. Undeliverable dystocia (grade 4)cephalic replacement
After the diagnosis of irreducible or undeliverable bilateral severe shoulder dystocia is made, the following steps should be taken: Prepare for abdominal delivery. Initiate tocolysis (subcutaneous terbutaline 0.25 mg), if necessary, monitor the fetal heart rate, and rapidly perform a cephalic replacement. The episiotomy repair can be deferred and hemostats placed on any major bleeding vessels. The head is easily replaced by constant but firm pressure with the palm of the hand. The head must be "reflexed" and kept in the position of flexion; then the vertex is pushed as far cephalad as possible (usually to the zero station) and held in that position by an assistant, if necessary. This technique should be used only when continued vaginal manipulation would lead to a predictably poor outcome for all concerned. If the infant has been damaged, the placenta separated, or severe hypoxia has occurred, it should not be used. There must be a reasonable chance of a safe delivery for the mother and a good outcome for the baby. We feel that cephalic replacement is worthy of further investigation and reporting of all outcomes to see if it will become a permanent part of our regimen for management of severe shoulder dystocia. Success has occurred in 23 cases. Comment
The optimum method of treatment of shoulder dystocia, once it occurs, remains debatable; however, everyone would agree that prevention is the best practice. The prevention of shoulder dystocia begins with the first prenatal visit, where the preconceptual and prenatal risk factors all can be determined except for total pregnancy weight gain . Early identification and proper counseling, frequent ultrasonographic testing,
Volume 162 Number I
and perhaps induction of labor at 40 weeks might help to reduce the severity of this problem. However, it must be emphasized that even under optimal circumstances and in the best of hands an unexpected shoulder dystocia can occur. As cesarean section rates have increased in our institution, the number of shoulder dystocias appears to have decreased; thus one important criterion for a safe vaginal delivery is becoming more and more difficult to fulfill; that is, residency training programs may not provide sufficient opportunity to acquire adequate experience. In-depth teaching, memorizing a plan of action, and periodically reviewing these procedures (a socalled "fire drill") is imperative. A high level of suspicion for shoulder dystocia is a reasonable indication for cesarean section if founded on a solid data base of known risk factors. The patients who fit the mnemonic DOPE (Diabetes, Obesity, Postdatism, and Excessive fetal weight or maternal weight gain) are at greatest risk. Poor labor progress, especially arrest patterns and abnormal descent patterns, as well as knowledge of maternal birth weight, will further increase the index of suspicion for shoulder dystocia. Only a liberal policy for cesarean section for these indications will decrease the frequency of shoulder dystocia. It canot be emphasized too strongly that shoulder dystocia can be largely prevented by the use of cesarean delivery instead of mid forceps or vacuum extraction when the head of a large infant arrests in the mid pelvis. This has been proved true in our institution. Meticulous antenatal care consisting of frequent ultrasonographic examinations, glucose screening, and proper diet should help to reduce the incidence of macrosomia and to properly identify women at greatest risk. REFERENCES I. McLeod A. In discussion: Hopwood HG Jr. Shoulder dystocia: fifteen years' experience in a community hospital. AMJ OBSTET GYNECOL 1982;144:162.
Shoulder dystocia 9
2. Dignam WJ. Difficulties in delivery, including shoulder dystocia and mal presentations of the fetus. Clin Obstet GynecoI1976;19:577. 3. Williams' obstetrics. 17th ed. Norwalk, Connecticut: Appleton-Century-Crofts, 1985:669. 4. Hopwood HGO Jr. Shoulder dystocia: fifteen years' experience in a community hospital. AMJ OB5TET GYNECOL 1982;144:162. 5. Benedetti TJ. Managing shoulder dystocia. Contemp Ob Gyn 1979; 14:33. 6. Klebanoff MA, Mills JL, Berendes HW. Mother's birth weight as a predictor of macrosomia. AM J OBSTET GyNECOL 1985; 153:253. 7. Boyd ME, Usher RH, McLean FH. Fetal macrosomia: prediction, risks, proposed management. Obstet Gynecol 1983;61:715. 8. Dor N, Mosberg H, Stern W, Jagani N. Schulman H. Complications in fetal macrosomia. NY State J Med 1984;84:302. 9. Parks GD, Ziel HK. Macrosomia: a proposed mdication for primary cesarean section. Obstet Gynecol 1987; 52:407. 10. Spellacy WN, Miller S, Winegar A, Peterson PQ. Macrosomia-maternal characteristics and infant complications. Obstet Gynecol 1985;66: 158. II. Elliott JP, Garite TJ, Freeman RK, et al. Ultrasonic prediction of fetal macrosomia in diabetic patients. Obstet Gynecol 1982;60: 159. 12. Benedetti TJ. Gabbe SG. Shoulder dystocia: a complication of fetal macrosomia and prolonged second stage with mid-pelvic delivery. Obstet Gynecol 1978;52:526. 13. Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985;66:762. 14. Wood C, Ng KH, Hounslow D, Benning H. Time: an important variable in normal delivery. J Obstet Gynaecol Br Commonw 1973;80:295. IS. Hibbard LT. Coping with shoulder dystocia. Contemp Ob Gyn 1982;20:229. 16. Gonik B, Stringer CA, Held B. An alternate maneuver for the management of shoulder dystocia. AM J OBSTET GYNECOL 1983; 145:882.
