ACOG 1997

0

Purpose

~ Objectives

Methods

International 4ournal ol

GYNECOLOGY & OBSTETRICS

Intemational Joumal of Gynecology & Obstetrics 60 (1998) 306-313

ACOG practice patterns

Shoulder dystocia

Number 7, October 1997

Shoulder dystocia is an obstetric emergency. Failure of the shoulders to deliver sponta- neously immediately places both the pregnant woman and fetus at risk for injury. Re- ported incidence ranges from less than 1% to slightly more than 4% among vaginal cephalic deliveries. Differences in reported rates are partly due to clinical variation in describing shoulder dystocia. The diagnosis of shoulder dystocia has a subjective com- ponent. Although severe cases are readily apparent, milder forms may be over- or un- derestimated. As a result, researchers differ in their approaches to defining shoulder dystocia. Some accept a clinician's judgment, noted in the chart, that shoulder dystocia occurred. Others require documentation of specific release maneuvers or other procedures to substantiate a diagnosis of shoulder dystocia. As a result, incidence figures vary. Over time, several maneuvers to release impacted shoulders have been developed, but the rarity and urgency of this event makes prospective studies to compare them impractical. Prevention is largely confined to planned cesarean delivery for pregnancies considered to be most at risk for shoulder dystocia.

The purpose of this document is to provide information based on published studies regarding the prediction, prevention, and management of deliveries complicated by shoulder dystocia to assist obstetrician-gynecologists in providing care to their patients.

These practice guidelines will enable physicians to:

Determine whether shoulder dystocia can be predicted Identify strategies to manage shoulder dystocia Determine whether elective cesarean delivery is an effective strategy to prevent

shoulder dystocia

The MEDLINE database was used to conduct a literature search to locate relevant articles published between 1985 and 1997. The search was restricted to articles published in the English language. Articles reporting results of original research were given prior- ity, although review articles and commentaries were consulted as well. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion in this document. Guidelines published by organizations or institutions such as the National Institutes of Health and the American College of Obstetricians and Gynecologists were reviewed, and additional studies were located by reviewing bibli- ographies of articles located via MEDLINE. Studies were collected and grouped according to topic. In most cases, studies involving fewer than 50 subjects were not evaluated. When reliable research was not available, expert opinions from obstetrician-gynecologists were used.

ACOG practice patterns / International Journal of Gynecology & Obstetrics 60 (1998) 306-313 307

Studies were reviewed and evaluated for quality according to the method outlined by the U.S. Preventive Services Task Force:

I Evidence obtained from at least one properly designed randomized controlled trial

II-1 Evidence obtained from well-designed controlled trials without randomization II-2 Evidence obtained from well-designed cohort or case-control analytic studies,

preferably from more than one center or research group 1I-3 Evidence obtained from multiple time series with or without the intervention.

Dramatic results in uncontrolled experiments could also be regarded as this type of eviderice

III Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees

Results Can shoulder dystocia be accurately predicted and prevented? The ideal management strategy for shoulder dystocia is prevention. Theoretically, most cases of shoulder dystocia could be avoided if fetuses at risk were identified before labor and selected for elective cesarean delivery. However, this strategy relies on several underlying assumptions that, in reality, are not true. These erroneous assumptions are

Risk factors for shoulder dystocia can always be identified prior to labor. The presence of risk factors is highly predictive of shoulder dystocia. Risks associated with shoulder dystocia are greater than risks associated with

planned cesarean deliveries to avoid shoulder dystocia. Costs associated with planned cesarean deliveries to avoid shoulder dystocia

are less than the costs associated with shoulder dystocia-related injuries.

Predictors of shoulder dystocia There have been many efforts to identify risk factors. Macrosomia and maternal diabetes consistently appear across many studies as the two risk factors most strongly associated with shoulder dystocia (Level II-2: 1-5) (Level II-3: 6). Pregnant women who have diabetes are two to six times more likely to experience shoulder dystocia than women who do not have diabetes (Level I1-2: 1, 3, 5). The incidence of shoulder dystocia increases in direct proportion to infant birth weight whether or not the woman has diabetes, although women who have diabetes experience significantly greater rates of shoulder dystocia in each weight group (Level 11-2: 2, 4, 5, 7-9) (see Tables 1 and 2).

TABLE 1. Risk of Shoulder Dystocia According to Diabetic Status

Author Increase in Risk Associated with Diabetic Status

Acker et a119851

Bahar 1996 ~

Langer et al 1991 ~

Sandmire et al 19884

Rate ratio 5.2

Odds ratio 4.3; 95% CI 2.2-8.3

Relative risk 4,000 g 3.6; 95% CI 2.37-4.76

Relative risk 6.5; 95% CI 1.5-27.1

308 ACOG practice patterns /International Journal of Gynecology & Obstetrics 60 (1998) 306-313

TABLE 2. Rate of Shoulder Dystocia Related to Birth Weight and Diabet!c Status

Birth Weight (g) Women Without Diabetes (%) Women with Diabetes (%)

4,500 4.1-22.6 20.0-50.0

Sources: Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985;66:762-768; aI-Najashi S, aI-Suleiman SA, eI-Yahia A, Rahman MS, Rahman J. Shoulder dystocia: a clinical study of 56 cases. Aust N Z J Obstet Gynaeco11989;29:129-132; Langer 0, Berkus MD, Huff RW, Samueloff A. Shoulder dystocia: should the fetus weighing __4,000 grams be delivered by cesarean section? Am J Obstet Gyneco11991 ;165:831--837.

Although risk increases with birth weight and diabetic status, a substantial proportion of cases occur among women who do not have diabetes and among infants with birth weights of less than 4,000 g. Predicting which patients are likely to experience shoulder dystocia based on the presence of risk factors has been unsuccessful. Acker et al reported a low sensitivity when diabetes mellitus and macrosomia were used to predict cases of shoulder dystocia; the presence of these risk factors accurately predicted only 55% of cases (Level II-2: 1). Additional studies failed to find any combination of risk factors that could predict which pregnancies would be complicated by shoulder dystocia (Level II-2: 3, 4, 7, 8, 10). In each case, risk factors could be identified, but their predictive value was not high enough to be useful in a clinical setting.

Planned cesarean delivery Because identification of antenatal risk factors has not proved useful in preventing shoulder dystocia, a broad policy of planned cesarean delivery for macrosomic fetuses has been suggested. This strategy seeks to prevent shoulder dystocia by identifying a sub- group with a known risk factor, macrosomia, and selecting those fetuses for cesarean delivery. To be successful, several elements must exist. There must be a high correla- tion between macrosomia and shoulder dystocia, as well as a reliable method for identifying fetal macrosomia. In addition, the risks associated with shoulder dystocia must be greater than the risks associated with the additional cesarean deliveries resulting from the policy.

For women who do not have diabetes, the policy is unfeasible. Although there is a greater incidence of shoulder dystocia among macrosomic infants, most do not experience this complication. Consequently, if all fetuses suspected of being macrosomic underwent cesarean delivery, there would be a disproportionate impact on the increased cesarean rate compared with the reduction in rate of shoulder dystocia (Level II-2: 5, 8) (Level II-3:11). For example, Gross et al projected a 27% increase in the total cesarean rate (rising from 15.1% to 19.1%) if cesarean deliveries were performed for all patients with fetuses that weighed 4,000 g or more; unfortunately, the number of shoulder dystocia cases would be reduced by only 42% (Level II-2: 8). Delpapa et al reported similar results among fetuses with estimated birth weights of 4,000 g or more; in their study, an additional 76 cesarean deliveries would have prevented only five cases of shoulder dystocia, none of which resulted in permanent injury (Level II-3:11). A recently published decision analysis estimated an additional 2,345 cesarean deliveries would be required, at a cost of $4.9 million annually, to prevent one permanent injury resulting from shoulder dystocia if all fetuses suspected of weighing 4,000 g or more underwent cesarean delivery (Level III: 12).


Even if the weight threshold were increased to 4,500 g, the policy remains ques- tionable. Opinion is divided over whether the benefits outweigh the risks. More cases of shoulder dystocia would be prevented, but the impact on the cesarean delivery rate would also be greater. Depending on the distribution of shoulder dystocia cases within a given population, planned cesarean delivery may provide more benefits than risks. Two investigators reported more than 50% of their cases occurred among infants weighing 4,500 g or more, but this finding was unusual (Level I1-3: 6, 13). Others report that 20% or less of shoulder dystocia cases could be prevented by cesarean delivery for infants with birth weights of 4,500 g or more (Level 11-2: 1, 5, 7) (Level I1-3:14).

Gross et al argued that despite preventing fewer cases overall, infants weighing 4,500 g or more could benefit from planned cesarean delivery without adversely affect- ing the cesarean delivery rate; within the population studied, 20 cases of shoulder dystocia would have been prevented among 42 spontaneous vaginal deliveries with birth weights of 4,500 g or greater, and the cesarean delivery rate would only have increased from 15.1% to 15.7% (Level 1I-2: 8). Another investigator supporting routine cesarean delivery for birth weights greater than 4,500 g calculated the policy would reduce the incidence of shoulder dystocia by more than 50% while increasing the cesarean rate by only 1.7% (Level 11-3: 6). At the other end of the spectrum, Baskett et al projected that implementing the policy within their study population would have resulted in an additional 817 cesarean deliveries while preventing only 69 cases of shoulder dystocia and 15 cases of brachial plexus palsy (Level 11-2: 7). A separate study of 590 vaginal deliveries of infants weighing 4,500 g or more found only 54 cases of shoulder dystocia, with five brachial palsies, three fractured clavicles, and no permanent injuries (Level 11-3: 15). According to a decision analysis, the national impact of this policy would be $8.7 million annually, with an additional 3,695 cesarean deliveries required to prevent one permanent injury (Level 111: 12). The cesarean delivery rate would be projected to rise from 19.1% to 27.6% (Level 111: 12). According to the evidence, the costs associated with routine cesarean delivery for estimated fetal weights of 4,500 g or more would be costly without commensurate benefits.

Among women with diabetes, shoulder dystocia cases are more concentrated within the heavier birth weight classes (Level I1-2: 1, 2, 5). Approximately 70% of cases among women with diabetes occur at infant birth weights of 4,000 g or more, compared with 50% among those of women without diabetes. Therefore, a policy of planned cesarean delivery is more likely to prevent shoulder dystocia cases among pregnant women with diabetes. The evidence confirms this finding. Acker et al reported that almost 55% of shoulder dystocia among women with diabetes could be prevented if fetuses that weighed 4,000 g or more underwent cesarean delivery (Level 11-2: 1). Langer et al found that 76% of shoulder dystocia cases among pregnant women with diabetes could be prevented if fetuses weighing 4,250 g or more underwent cesarean delivery (Level II-2: 5). In contrast, Keller et al found no justification for a 4,000-g threshold among women with gestational diabetes because more than half the cases occurred in infants weighing less than 4,000 g and the ultrasound estimates of fetal weight were inaccurate (Level II- 2: 9). A decision analysis projected that a 4,500-g threshold for fetuses of women with diabetes would require an additional 443 procedures to prevent one permanent brachial plexus injury, at a cost of $930,000 (Level 111: 12). The studies indicate that for pregnant women with diabetes who are suspected of carrying macrosomic fetuses, a planned cesarean delivery may be a reasonable course of action, depending on the incidence of shoulder dystocia, the accuracy of predicting macrosomia, and the cesarean delivery rate within a specific population.

310 ACOG practice patterns / International Journal of Gynecology & Obstetrics 60 (1998) 306-313

The policy of planned cesarean delivery relies also on accurate estimates of fetal weight. Fetal weights are calculated from measurements taken during ultrasound ex- aminations. Ultrasonography is an inaccurate predictor of macrosomia. Among the general population, ultrasonography could correctly identify macrosomia only about 60% of the time, according to a pooled estimate of 13 studies (Level III: 12). Within the diabetic population, ultrasonography has provided mixed results. There is evidence of accelerated fetal growth, most notably in the abdominal circumference and chest-to- head ratio (Level 11-2: 16-18). However, the clinical usefulness of this information has been limited. One study correctly predicted 88.8% of macrosomia cases among pregnant women with diabetes, based on measurements of abdominal circumference and estimated fetal weight (Level 11-2: 17). However, there are no studies documenting the usefulness of identifying macrosomic fetuses for planned cesarean delivery among women with diabetes.

How often does shoulder dystocia result in an injury to the newborn? Brachial plexus injuries and fractures of the clavicle and humerus are associated with shoulder dystocia. The most potentially serious, brachial plexus injuries, can be caused by extreme amounts of traction and flexion exerted on the infant's neck. These injuries may result in permanent disability. The reported incidence of brachial plexus injuries following a delivery complicated by shoulder dystocia varies widely from 4% to 40% (1,2, 6-9, 13, 14, 19-22). Fortunately, most cases resolve without permanent disability. Reports indicate between 9% and 25% of brachial plexus injuries persist (2, 7, 9, 14). Placed in perspective, fewer than 10% of all shoulder dystocia cases result in a persistent brachial plexus injury (2, 7, 9, 14). Moreover, brachial plexus injuries can occur without shoulder dystocia and at birth weights of less than 4,000 g (23).

Are any of the maneuvers used to release impacted shoulders either more likely to cause injuries or more likely to be successful? Because of the rarity and urgency of shoulder dystocia, only a limited amount of data exists comparing management techniques. Two separate studies confirm that the combination of traction and fundal pressure is associated with brachial plexus injuries as well as with fractures of the humerus and clavicle (Level II-2: 7) (Level II-3: 20). There is no indication, however, that any particular management technique is superior to another once shoulder dystocia occurs.

There is evidence that injuries might and do occur despite application of appropriate obstetric maneuvers (Level 11-3: 24). During a series of deliveries, the obstetrician wore a tactile-sensing device that recorded the peak and duration of forces applied to the head and neck of the fetus. During the study, two cases of shoulder dystocia occurred to infants with similar birth weights and obstetric protocols. One infant sus- tained a shoulder dystocia-related injury and the other did not (Level II-3: 24).

The McRoberts maneuver relies on maternal manipulation and is reported to be effective (Level 11-2: 7, 19) (Level 11-3: 25). Successful use of the McRoberts maneuver is documented in the scientific literature. The maneuver involves sharply flexing the patient's legs against her abdomen. Results from a laboratory study using models of the maternal pelvis, fetal head, and fetal shoulders demonstrated that less force was required to deliver fetuses using the McRoberts maneuver compared with the standard lithotomy position (26).


Summary and Based on this highest level of evidence found in the data, the following recommenda- Recommendations tions are provided and graded according to the following categories:

A There is good evidence to support the recommendation. B There is fair evidence to support the recommendation. C There is insufficient evidence to support the recommendation; however, the rec-

ommendation may be made on other grounds.

Prediction and prevention of shoulder dystocia Most cases of shoulder dystocia cannot be predicted or prevented because accurate

methods for identifying which fetuses will experience this complication do not exist, and performing cesarean deliveries for all women suspected of carrying a macrosomic fetus is not appropriate (B: 11-2).

Ultrasonographic measurements to estimate macrosomia have limited accuracy (B: 1I-2).

Planned cesarean delivery on the basis of suspected macrosomia in the general population is not a reasonable strategy because the number and cost of additional cesarean deliveries required to prevent one permanent injury is excessive (B: I1-2).

Planned cesarean delivery may be a reasonable strategy for diabetic pregnant women with estimated fetal weights exceeding 4,250--4,500 g (B: 1/-2).

Shoulder dystocia as a cause of injury to newborns Injuries are a common outcome associated with shoulder dystocia and may occur

despite use of appropriate standard obstetric maneuvers (B: I1-3). Brachial plexus injuries, fractures of the humerus, and fractures of the clavicle are the most com- monly reported injuries associated with shoulder dystocia (A: 11-2).

Fewer than 10% of all deliveries complicated by shoulder dystocia will result in a persistent brachial plexus injury (A:II-2).

References

Release techniques There is no evidence that any one maneuver is superior to another in releasing an

impacted shoulder or reducing the chance of injury. However, the McRoberts maneuver is easily facilitated and has a high success rate without an associated increase in risk of injury to the newborn (B: 1I-2).

Traction combined with fundal pressure has been associated with a high rate of brachial plexus injuries and fractures (B: 1I-2).

I. Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985;66:762- 768

2. al-Najashi S, al-Suleiman SA, el-Yahia A, Rahman MS, Rahman J. Shoulder dystocia: a clinical study of 56 cases. Aust N Z J Obstet Gynaecol 1989;29:129-132

3. Bahar AM. Risk factors and fetal outcome in cases of shoulder dystocia compared with normal deliveries of a similar birthweight. Br J Obstet Gynaecol 1996;103:868-872

4. Sandmire HF, O'Halloin TJ. Shoulder dystocia: its incidence and associated risk factors. Int J Gynaecol Obstet 1988;26:65-73

5. Langer O, Berkus MD, Huff RW, Samueloff A. Shoulder dystocia: should the fetus weighing >4000 grams be delivered by cesarean section? Am J Obstet Gynecol 1991;165:831-837

6. el Madany AA, Jallad KB, Radi FA, el Hamdan H, O'deh HM. Shoulder dystocia: anticipation and outcome. Int J Gynecol Obstet 1990;34:7-12

7. Baskett TF, Allen AC. Perinatal implications of shoulder dystocia. Obstet Gynecol 1995;86:14-17

312 ACOG practice patterns / International Journal of Gynecology & Obstetrics 60 (1998) 306-313

8. Gross TL, Sokol RJ, Williams T, Thompson K. Shoulder dystocia: a fetal-p.hysician risk. Am J Obstet Gynecol 1987;156:1408-1418

9. Keller JD, Lopez-Zeno JA, Dooley SL, Socol ML. Shoulder dystocia and birth trauma in gestational diabetes: a five-year experience. Am J Obstet Gynecol 1991;165:928-930

10. Nocon JJ, McKenzie DK, Thomas LJ, Hansell RS. Shoulder dystocia: an analysis of risks and obstetric maneuvers. Am J Obstet Gynecol 1993;168:1732-1739

11. Delpapa EH, Mueller-Heubach E. Pregnancy outcome following ultrasound diagnosis of macrosomia. Obstet Gynecol 1991;78:340-343

12. Rouse DJ, Owen J, Goldenberg RL, Cliver SP. The effectiveness and costs of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound. JAMA 1996;276:1480-1486

13. Hassan AA. Shoulder dystocia: risk factors and prevention. Aust N Z J Obstet Gynaecol 1988;28:107- 109

14. Mordson JC, Sanders JR, Magann EF, Wiser WL. The diagnosis and management of dystocia of the shoulder. Surg Gynecol Obstet 1992;175:515-522

15. Menticoglou SM, Manning FA, Morrison I, Harman CR. Must macrosomic fetuses be delivered by a cesarean section? A review of outcome for 786 babies greater than or equal to 4,500 g. Aust N Z J Obstet Gynaecol 1992;32:100-103

16. Bracero LA, Baxi LV, Rey HR, Yeh MN. Use of ultrasound in antenatal diagnosis of large-for-gestational age infants in diabetic gravid patients. Am J Obstet Gynecol 1985;152:43-47

17. Tamura RK, Sabbagha RE, Depp R, Dooley SL, Socol ML. Diabetic macrosomia: accuracy of third trimester ultrasound. Obstet Gynecol 1986;67:828-832

18. Modanlou HD, Komatsu G, Dorchester W, Freeman RK, Bosu SK. Large-for-gestational-age neo- nates: anthropometric reasons for shoulder dystocia. Obstet Gynecol 1982;60:417-423

19. Gonik B, Hollyer L, Allen R. Shoulder dystocia recognition: differences in neonatal risks for injury. Am J Perinatol 1991 ;8:31-34

20. Gross SJ, Shime J, Farine D. Shoulder dystocia: predictors and outcome. A five-year review. Am J Obstet Gynecol 1987; 156:334-336

21. Hopwood HG Jr. Shoulder dystocia: fifteen years' experience in a community hospital. Am J Obstet Gynecol 1982;144:162-166

22. Lurie S, Insler V, Hagay ZJ. Induction of labor at 38 to 39 weeks of gestation reduces the incidence of shoulder dystocia in gestational diabetic patients class A2. Am J Perinatol 1996;13:293-296

23. Graham EM, Forouzan I, Morgan MA. A retrospective analysis of Erb's palsy cases and their relation to birth weight and trauma at delivery. J Matern Fetal Med 1997;6:1-5

24. Allen R, Sorah J, Gonik B. Risk factors for shoulder dystocia: an engineering study of clinician- applied forces. Obstet Gynecol 1991 ;77:352-355

25. Smeltzer JS. Prevention and management of shoulder dystocia. Clin Obstet Gynecol 1986;29:299-308 26. Gonik B, Allen R, Sorab J. Objective evaluation of the shoulder dystocia phenomenon: effect of mater-

nal pelvic orientation on force reduction. Obstet Gynecol 1989;74:44-48


Practice Patterns are clinical practice guidelines developed by The American College of Obstetricians and Gynecologists (ACOG) to assist practitioners and patients in making decisions about appropriate obstetric and gynecologic care. Each Practice Pattern focuses on a clinical issue and is based on a review and analysis of the scientific literature. The information and recommendations reflect scientific and clinical knowledge current as of the publication date and are subject to change as advances in diagnostic techniques and treatments emerge. In addition, variations of practice, taking into account the needs of the individual patient, resources, and limitations unique to the institution or type of practice, may warrant alternative treatment or procedures to the recommendations outlined in this document. Therefore, these guidelines should not be construed as dictating an exclusive course of treatment or procedure.

Copyright 1997 The American College of Obstetricians and Gynecologists, 409 l~2th Street, SW, PO Box 96920, Washington, DC 20090-6920. Requests for authorization to make photocopies should be di- rected to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923; telephone (508) 750-8400.

ISSN 1083-3331 12345/10987

ACOG 1997

Documents

diagnosis of shoulder

published studies

prospective studies

additional studies

review articles

practice guidelines

reliable research

abstracts of research