Shoulder dystocia: A fetal-physician risk

Dietrich, Dolnicek, and Rayburn

a few people who have complained about some nausea. I think that we have had three or four people per quarter that had to have the test redone because they were unable to complete the test. It just has not been a major problem. I think that our concern once again is that no one interprets these as data that are to be automatically used in deciding whether patients are screened. I cannot answer the question as to whether a nonwhite, nonprivate practice group should have qualifications similar to those of our group. I think that is why we rec-

June 1987 Am J Obstet Gynecol

ommend that each one look at his or her own population group. Since there has been an increasing amount of pressure with litigation, we have several members of our group who are addressing the same issue and wondering whether they should screen everybody just because it is easier. At this point in time we have been resisting that, but we may very well end up in the same position. Up to now, however, we feel we have good data to support the fact that we are not routinely screening all patients.

Shoulder dystocia: A fetal-physician risk Thomas L. Gross, M.D., RobertJ. Sokol, M.D., Thomas Williams, M.A., and Karen Thompson Cleveland, Ohio, Detroit, Michigan, and Peoria, Illinois Trauma that occurs as a result of shoulder dystocia is an important cause of neonatal morbidity. If the occurrence of severe shoulder dystocia, resulting in fetal asphyxia and trauma, could be accurately predicted from maternal risk factors, then a cesarean section would be indicated to prevent the poor outcome. The information available in the obstetric literature, however, is contradictory regarding whether shoulder dystocia can be predicted. In the present study, the patients at greatest risk of shoulder dystocia (all 394 mothers delivering neonates with birth weights ;;.4000 gm over a 2-year period) were examined. A three-way discriminant analysis was used to determine if a model could be developed that could effectively predict those pati~nts who would be included in each of the groups of no shoulder dystocia, shoulder dystocia without trauma (29 patients), and shoulder dystocia with trauma (20 patients). Three factors, including birth weight, prolonged deceleration phase, and length of second stage labor, were found individually to contribute significantly to the classification. However, when examined in detail, it was noted that while 94% of cases with no shoulder dystocia would be detected, only 16% of the cases of shoulder dystocia with trauma would be predicted by this model. We conclude that in the group of pregnancies delivering neonates ;;.4000 gm, the occurrence of shoulder dystocia cannot be predicted from clinical characteristics or labor abnormalities, and that the occurrence of shoulder dystocia is not evidence of medical malpractice. (AM J 0BSTET GYNECOL 1987;156:1408-18.)

Key words: Shoulder dystocia, labor abnormalities, malpractice Trauma suffered during the birth process is a major risk for immediate and long-term infant morbidity. Significant birth trauma is rare; however, it remains a major cause oflitigation filed against the obstetrician/gynecologist. One of the primary complications resulting

From the Perinatal Clinical Research Center and the Department of Obstetrics and Gynecology, Cleveland Metropolitan General Hospital/Case Western Reserve University, the Department of Obstetrics and Gynecology, Hutzel Hospital, Detroit Medical Center, Wayne State University, and the Department of Obstetrics and Gynecology, the University of Illinois College of Medicine at Peoria. Presented at the Fiftyjourth Annual Meeting of The Central Association of Obstetricians and Gynecologists, Milwaukee, Wisconsin, October 7-11, 1986. Reprint requests: Thomas L. Gross, M.D., Department of Obstetrics and Gynecology, the University of Illinois College of Medicine at Peoria, Box 1649, Peoria, IL 61656.

1408

in traumatic delivery is shoulder dystocia.' Of the 103 obstetric- or gynecologic-related suits filed in the past 5 years at one of the author's hospitals, seven (6.8%) were related to shoulder dystocia. If the occurrence of severe shoulder dystocia resulting in fetal asphyxia and trauma can be accurately predicted from maternal risk factors, then a cesarean section would be indicated to prevent poor outcome! Plaintiff's attorneys bringing litigation against an obstetrician because trauma occurred after impacted fetal shoulders at delivery theorize that the clinician could have predicted and avoided the problem. However, the information that is available in the obstetric literature is contradictory regarding whether shoulder dystocia can be predicted. On the one hand, there are well-known risk factors for shoulder dystocia, such as fetal macrosomia. 3 In addition,

Shoulder dystocia 1409

Volume 156 Number 6

previous investigators have reported that individual labor abnormalities, including prolonged deceleration phase,' arrest disorders, 5 and prolonged second stage, 6 are significantly correlated with shoulder dystocia. There is a major difference, however, between a factor being statistically significant and its clinical usefulness as a predictor to the degree that it can be used to manage cases. Indeed, some investigators have stated that "shoulder dystocia, when it occurs, is usually unexpected."7 No studies have examined whether a group of risk factors for shoulder dystocia, including antepartum and labor data, can be used to develop a risk profile for predicting impacted fetal shoulders at delivery. The purpose of the present study was to examine the group of patients at greatest risk of shoulder dystocia (birth weights ~4000 gm), and thus those patients for whom the problem should be most predictable, to determine if a profile of antenatal abnormalities can be used to predict which patients are at greatest risk of suffering the trauma associated with impacted fetal shoulders. Methods

All women given antenatal care and consecutively delivered at our hospital during a 24-month period from January 1982 to December 1983 were included in this study. Repeat and primary cesarean section rates were determined for the 7013 women delivered of 7123 infants. In addition, they were divided into groups of increasing birth weight and evaluated for the occurrence of shoulder dystocia. Since the macrosomic fetus (defined as ~4000 gm) is at greatest risk for shoulder dystocia, this group was singled out for further study. All 394 pregnancies resulting in a macrosomic neonate during this 2-year period were included in the study group. The maternal charts of the 49 patients in whom the delivery record documented shoulder dystocia were examined to determine the type of delivery necessary for extracting the fetus. The neonatal charts were examined for signs of trauma sustained during birth. The vaginally delivered patients were stratified into three groups, those in whom no shoulder dystocia was recorded (no shoulder dystocia), those in whom shoulder dystocia was described by the obstetrician but no evidence of fetal trauma was recorded (shoulder dystocia without trauma), and those in whom shoulder dystocia was described, and obvious fetal trauma, including a fracture or a brachial plexus injury, was recorded (shoulder dystocia with trauma). For comparison, a fourth group of patients undergoing cesarean section because of a labor complication was also examined, since this is the intervention that can prevent the occurrence of shoulder dystocia. Pregnancy characteristics, including maternal com-

plications, estimates of gestational age, and birth weight and labor abnormalities, were compared among the four groups. Labor progress was recorded prospectively for each patient as part of a labor diagnostic system previously reported and validated. 8 For this study, the labor abnormalities were obtained by reviewing each patient's clinical chart. The labor abnormalities studied included the six m;:Uor dysfunctional labor patterns.9 In addition, "short arrest" of dilatation and length of second stage were recorded. A "short arrest" is an arrest pattern that does not quite meet the criteria for a 2-hour arrest of active-phase dilatation and has previously been reported to be associated with increased maternal and fetal morbidity. 10 To develop a better understanding of how shoulder dystocia could be predicted, nine perinatal factors previously associated with shoulder dystocia by other investigators were examined. In addition, five dysfunctional labor patterns that we have previously found to be present with increased frequency in mothers delivering macrosomic neonates and the diagnosis of "short arrest" and length of second stage were included. All factors were subjected to a three-way stepwise discriminant analysis to determine whether these preceding risks could effectively predict the patient that would be included in the groups of no shoulder dystocia, shoulder dystocia without trauma, or shoulder dystocia with trauma. In addition, a second discriminant analysis was performed in which the dysfunctional labor patterns were forced into the equation in clinical sequence. In stepwise discriminant analysis, the relationship of a factor to the outcome is measured by the F value of the factor. The F value is directly proportional to the strength of the relationship. The computer program then combines the individual factors by selecting the ones with the highest F values in succession until an improvement in classification is no longer significant. Finally, to examine the question of whether 4500 gm is a good break point for predicting shoulder dystocia, the patients were stratified into two groups (4000 to 4499 gm and ~4500 gm). The frequency with which shoulder dystocia occurred after labor abnormalities in these two groups was then calculated. Univariate differences among all groups were examined by x2 analysis or Student t test, as appropriate. A p of <0.01 was considered significant. Results

The frequency of shoulder dystocia occurring over the range of all birth weights in the 7013 mothers delivered during the 2-year study period is shown in Table I. As expected, the frequency of shoulder dystocia increased with each increment of fetal weight. The frequency of repeat and primary cesarean section that occurred in the overall obstetric population is shown

1410 Grosset al.

June 1987 Am J Obstet Gynecol

Table I. Frequency of shoulder dystocia shown for birth weight increments of 500 gm in the 7123 infants delivered on the entire delivery service during the time period of the study* Shoulder dystocia Birth weight (gm)

<2500 2500-2999 3000-3499 3500-3999 4000-4499 ""4500

No. of deliveries

1265 1704 2392 1368 338 14 with trauma 56 6 with trauma

No.

I

%

5 2 21 39 29

(0.5) (0.1) (0.8) (2.9) (8.6)

20

(35.7)

*There were 7013 pregnancies delivered.

in Table II. The total cesarean birth rate increased from a low of 14.4% in the <4000 gm group to 25% in the ;:;.4500 gm patients. The route of delivery for the 394 mothers with macrosomic infants was as follows: vaginal delivery, 293; repeat cesarean, 31; primary cesarean section before labor for breech presentation, 17; and primary cesarean section during labor, 53. On reviewing the maternal charts, the following descriptions of how the shoulder dystocias were managed was determined. The physician's delivery note indicated that in 21 of 49 patients, suprapubic and fundal pressure were the procedures used to deliver the baby after shoulder dystocia. In four charts delivery of the posterior arm was described, and a corkscrew maneuver was described in one chart. In 23 charts the physician's note did not describe any procedure used for the shoulder dystocia. In this final group there were seven fractured clavicles and one brachial palsy. The neonatal trauma that occurred in the entire group was as follows: 12 neonates had fractured clavicles, one had a fractured humerus, and 10 babies had suspected brachial plexus injury. Multiple injuries were present in some neonates. Table III shows the characteristics of the pregnancies delivered vaginally stratified into those with no shoulder dystocia, shoulder dystocia without trauma, and shoulder dystocia with trauma. In addition, the group of patients in whom labor was interrupted by a primary cesarean section because of a labor complication is shown. There are no differences in the maternal characteristics between the groups. Birth weight was significantly higher in the shoulder dystocia without trauma group (p < 0.01), but the increase in birth weight in the shoulder dystocia with trauma group did not reach statistical significance. One-minute Apgar scores were significantly lower in the shoulder dystocia without trauma (p < 0.01) and the shoulder dystocia

Table II. Frequency of cesarean section (repeat and primary) for the total population of 7013 mothers delivered during a 2-year period. Patients are stratified into non-macrosomic (<4000 gm) and macrosomic (;:;.4000 gm) populations Total non-macrosomic population < 4000 gm Repeat cesarean section Primary cesarean section Total cesarean section Total macrosomic population "" 4000 gm 4000-4499 gm Repeat cesarean section Primary cesarean section Total cesarean section ""4500 gm Repeat cesarean section Primary cesarean section Total cesarean section Entire obstetric population Cesarean section rate in entire population Repeat cesarean section Primary cesarean section Total cesarean section

6619 376 580 956

(5.7%) (8.7%) (14.4%) 394

338 24 63 87 56 7 7 14

(7.1%) (18.6%) (25.7%) (12.5%) (12.5%) (25.0%) 7013 (5.8%) (9.3%) (15.1 %)

with trauma groups (p < 0.001). Table IV shows the frequencies of the dysfunctional labor patterns in the same four groups. It can be noted that total labor abnormality, defined as the presence of one or more major dysfunctional labor patterns, occurred with nearly twice the frequency in the shoulder dystocia with trauma group compared with the no shoulder dystocia group (75% versus 43%, X2 = 18.9, p < 0.001). The frequency of shoulder dystocia for the different dysfunctional labor patterns in the patients delivering 4000 to 4499 gm infants and those delivering ;:;.4500 gm infants is shown in Table V. For the 4000 to 4499 gm infants, the maximum frequency of shoulder dystocia of 38% occurred after prolonged deceleration. For every dysfunctional labor pattern that occurred in this weight category, the most frequent outcome was normal vaginal delivery. In the ;:;.4500 gm group there is a trend toward increasing shoulder dystocia after many of the dysfunctional labor patterns, but the number of patients in this category is too small to be conclusive. The results of the first run of discriminant analysis in which all factors were allowed to compete are shown in Table VI. Three factors, including birth weight, length of second stage, and prolonged deceleration phase, were found individually to contribute significantly to the classification of no shoulder dystocia, shoulder dystocia with trauma, and shoulder dystocia without trauma, with birth weight showing the strongest relationship. As shown in the second column of F values, birth weight, length of second stage, and pro-

Shoulder dystocia

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1411

Table III. Clinical characteristics of the patients delivering macrosomic neonates vaginally are shown stratified into three groups: (1) no shoulder dystocia, (2) shoulder dystocia without trauma, and (3) shoulder dystocia with trauma; patients undergoing a primary cesarean section because of a complication during labor are shown; the data are shown as means ± SD or frequencies

Characteristics

Maternal weight (pounds) Pregnancy weight gain (pounds) Maternal age (yr) Parity Gestational age (wk) Birth weight (gm) Apgar score (1 and 5 minutes) Race White% Black% Other% Diabetes mellitus Class A% Class B-R% Maternal smoking % Male fetus%

No. shoulder dystocia, mean ± SD (244)

Shoulder dystocia without trauma, mean ± SD (29)

Shoulder dystocia with trauma, mean± SD (20)

Primary* cesarean section in labor (53)

167 ± 42 26 ± 14 25.0 ± 5.0 1.5 40.0 ± 1.4 4226 ± 211 7.2 ± 1.9, 8.7 ± l.l

159 ± 37 27 ± 15 26.0 ± 5.0 1.8 40.0 ± 1.4 4434 ± 322 6.1 ± 1.9, 8.4 ± 1.0

159 ± 35 31 ± 17 24.0 ± 6.0 1.0 40.0 ± 1.4 4383 ± 230 4.9 ± 2.1, 7.5 ± 1.9

166 ± 55 32 ± 18 24.0 ± 5 0.3 40.0 ± 1.9 4254 ± 203 6.5 ± 2.5, 8.5 ± l.l

63 27 10

44 34 22

68 32 0

58 32 9

7.7 4.6 22.0 58

3.7 11.0 13.0 67

10.0 10.0 20.0 58

11.0 13.0 36 70

*Seventeen patients who were known to have primary cesarean sections for reasons unrelated to labor complications were excluded.

Table IV. Frequencies of the dysfunctional labor patterns of the patients delivering macrosomic neonates vaginally are shown stratified into groups: (1) no shoulder dystocia, (2) shoulder dystocia without trauma, and (3) shoulder dystocia with trauma. The group of patients undergoing a primary cesarean section because of a complication during labor is shown for comparison purposes

Labor abnormality

Protraction active Arrest active Short arrest Prolonged deceleration Protraction descent Arrest descent Total No. dysfunctional labor patterns Length second stage (min)

No. shoulder dystocia (244)%

Shoulder dystocia without trauma (29)%

Shoulder dystocia with trauma (20)%

Primary* cesarean section in labor (53)%

34.0 6.1 3.6 4.5 8.1 3.6 43.0

34.4 13.7 6.8 17.2 3.4 6.8 58.6

55.0 15.0 10.0 15.0 10.0 15.0 75.0

50.9 43.3 7.5 9.4 11.3 13.2 69.8

37 ± 49

25 ± 28

81 ± 67

*Seventeen patients who were known to have primary cesarean sections for reasons unrelated to labor complications are excluded.

longed deceleration, used in combination, contributed significantly to the classification of shoulder dystocia. However, when examined in detail, it was noted that while 94% of patients in whom no shoulder dystocia occurred would be predicted by this model, only 16% of the patients with shoulder dystocia with trauma would be predicted. Additional discriminant analyses were performed with other combinations oflabor abnormalities, including one in which four dysfunctional labor patterns were forced into the equation in clinical sequence of progressing labor, protraction of active phase, arrest of active phase, protraction of descent, and arrest of de-

scent. Although this combination could predict more than 95% of the cases of no shoulder dystocia, it could predict less than 10% of the cases of shoulder dystocia. In all of the discriminant analyses examined, a maximum of 12% of the variance of abnormal outcome could be explained by any one of the classification models.

Comment In this study our goal was to design a model for clinical decision making to determine whether it was possible to predict shoulder dystocia in a high-risk group of patients. The key finding in this study is that

1412

Grosset al.

june 1987 Am J Obstet Gynecol

Table V. The frequency of shoulder dystocia that occurs after each dysfunctional labor pattern in gravida patients delivering macrosomic neonates (stratified into two groups, 4000 to 4499 gm and ;;;.4500 gm) is shown 4000-4499 gm

No.

Protraction Arrest Short arrest Prolonged deceleration Arrest descent Protracted descent Second stage > l hr

87 15 10 16

I

Shoulder dystocia

13 3 l

6 4 3 9

ll

22 51

?>4500 gm

I

I

Shoulder dystocia

%

No.

14.9 20.0 10.0 37.5 36.3 13.6 17.6

17 7 3 3 3

8 4 3 2

l

0 4

l

9

l

% 47.0 57.1 100.0 66.6 33.3 0.0 44.4

Table VI. Results of the three-way stepwise discriminant analysis for the classification of infants as having no shoulder dystocia, shoulder dystocia without trauma and shoulder dystocia with trauma

Maternal weight Pregnancy weight gain Diabetes mellitus Gestational age Previous infant ?> 4000 gm Maternal age Parity Birth weight Male fetus Smoking Arrest active phase Short arrest Protraction Prolonged deceleration Arrest descent Protraction descent Length second stage

Initial F values (2258)

p<

Final F values (2257)

p<

0.601 1.146 0.563 0.487 3.375 0.795 1.630 13.242 0.399 1.782 1.955 1.190 1.996 6.462 2.556 0.415 8.295

NS NS NS NS NS NS NS 0.001 NS NS NS NS NS 0.01 NS NS 0.001

1.002 0.904 0.377 0.484 4.159 0.511 1.601 13.242 0.372 1.907 0.635 0.993 1.941 5.980 2.506 0.349 8.224

NS NS NS NS NS NS NS 0.001 NS NS NS NS NS 0.01 NS NS 0.001

in the group of pregnancies in which the infant weighed ?>4000 gm, the occurrence of shoulder dystocia cannot be consistently predicted from clinical characteristics of the pregnancy or labor abnormalities. Previous investigators have reported multiple antepartum factors, including maternal obesity, pregnancy weight gain, diabetes mellitus, parity, postdate pregnancy, neonatal birth weight, and the presence of a male fetus to be related to macrosomia and shoulder dystocia. 11 · 14 In addition, several individual labor abnormalities have been reported to increase in labors that are followed by shoulder dystocia at delivery.<· 6 · 15 The present investigation extends the study design of the previous work in two ways. First, we have examined the question of whether the occurrence of shoulder dystocia could be predicted with a profile of multiple maternal antepartum complications ard labor abnormalities. Multiple discriminant analyses were attempted to find a model that could predict the three categories of outcome, no shoulder dystocia, shoulder dystocia without trauma, and shoulder dystocia with trauma. It is clear that none

of these models could successfully predict shoulder dystocia with an accuracy that is acceptable for clinical practice. The best classification obtained missed 85% of the shoulder dystocia without trauma and 84% of the shoulder dystocia with trauma. The second important change in the design of this study is that we have included two outcome variables for shoulder dystocia; those in whom there was no evidence of trauma in the neonate and those in whom there was evidence of immediate damage. This is important, since the definitions and thus the reported frequencies of shoulder dystocia vary between individual physicians and institutions. There is not likely to be agreement among studies on the definition of the degree of difficulty in delivering the shoulders that is necessary to diagnose shoulder dystocia. However, difficulty delivering the shoulders, in combination with fetal i~ury, is more likely to be accepted as true shoulder dystocia. The different definitions of shoulder dystocia used is probably the major reason for the variation in frequency reported by several authors. Another reason for dis-

Volume 156 Number 6

agreement among studies is that some authors report the frequency per vaginal deliveries and others report for the entire obstetric population. In our study, the frequency of shoulder dystocia in the entire group of mothers delivering a 4000 to 4499 gm infant was 8.6%. Although this is higher than some previous studies, 6 • 15 it is very similar to the 10% frequency in the same birth weight category in the nondiabetic patients reported by Acker et al. 5 Moreover, the incidence of 1.5% of shoulder dystocia in the overall obstetric population in our study is similar to the 1.1% reported by Hopwood 4 when he examined the same category of patients in his study. One remaining question is, can the clinician avoid shoulder dystocia, and thus reduce neonatal morbidity by choosing an appropriate group of mothers to deliver by cesarean section? To examine this, the group of patients at greatest risk of shoulder dystocia must first be defined and then the number of cesarean sections that would be needed if all the patients in this highrisk group were delivered abdominally must be determined. We have projected several approaches to this question from the present data base. We first examined the potential outcome if cesareans were performed in all patients with fetuses ;:;:4000 gm. In the present data base, this would increase the primary cesarean section rate from 9.3% to 13.3%, and the total rate from 15.1% to 19.1%. This would increase the primary cesarean birth rate by 44%, the total rate for the entire obstetric population by 27%, and would entail performing an additional283 cesareans to prevent 49 cases of shoulder dystocia. In the authors' opinion, performing nearly six additional cesareans for every case of shoulder dystocia prevented is too high a price to pay. The second projection we have examined is to determine the effect of delivering all fetuses ;:;:4500 gm by cesarean section. Delivering this entire group abdominally in the current series would result in an additional 42 cesarean births and increase the total cesarean rate in the overall obstetric population from 15.1% to 15.7%. There were 14 cases of shoulder dystocia without trauma and six cases of shoulder dystocia with trauma that occurred in the 42 vaginal deliveries in this group (>4500 gm). We believe that preventing this many cases of shoulder dystocia, with the small effect it would have on the overall cesarean rate, justifies recommending abdominal delivery when the clinical and ultrasound evidence strongly suggest a fetus in the weight range of >4500 gm (10 pounds). Previous investigators have also suggested liberalizing the cesarean rate in this group. 12 • 14 In the present analysis we found significantly increased labor abnormalities in the shoulder dystocia group, but we were unable to define a risk profile so that a large number of cases of fetal trauma could be

Shoulder dystocia

1413

avoided with only a selected increase in cesarean section. Acker et a!.' have found results similar to this in the macrosomic fetus. In the fetus ~4500 gm they reported 60% of patients with arrest patterns (defined as a combination of arrest of dilatation, prolonged deceleration, and arrest of descent) had their deliveries subsequently complicated by a shoulder dystocia, but they reported that a large percentage of the cases of shoulder dystocia would still be missed. The poor predictive potential that we found in our study occurred, even though we chose a high-risk group of patients to simplify the predictive potential, since a high prevalence of poor outcome will increase the ability to predict that outcome. In addition, even though estimating fetal weight with ultrasonography is improving, predicting the macrosomic fetus is still frequently inaccurate. 16 This means that errors in predicting fetal weight will decrease the ability to predict shoulder dystocia to an even greater extent. We believe that this suggests that the models for predicting shoulder dystocia used in the present study are close to the optimum that can be achieved. The answer to the question, can the occurrence of shoulder dystocia be prevented?, can be summarized as follows. Based on our reasoning as detailed it seems acceptable to deliver all fetuses who clinically seem very large (>4500 gm) by cesarean section. Even with this approach, however, over half of the cases of shoulder dystocia in macrosomic infants would still occur (in the 4000 to 4499 gm group). Thus these cases could not be prevented unless the clinician was willing to perform an abdominal delivery for all fetuses estimated to be >4000 gm, and we believe that the number of cesarean sections that would be performed to achieve this is excessive and unwarranted. Finally, even if one did perform cesarean sections for all pregnancies with macrosomic fetuses (>4000 gm), it is important to note that over half of the cases of shoulder dystocia would still occur. In the data base in the present study, more than 50% of shoulder dystocia occurred at birth weights <4000 gm. At present there is no way to predict those cases. Therefore, we conclude that the occurrence of shoulder dystocia cannot be predicted. However, for the clinician to ensure optimal patient management and be protected as much as possible from litigation, several rules need to be followed. First, all intrapartum records, including labor progress, must be written accurately and in detailed fashion, so that it can be documented that the usual management principles regarding dysfunctional labor have been followed. In addition, the findings in the present study show that the obstetrician should not be liable for failure to predict shoulder dystocia. Nonetheless, the management after shoulder dystocia occurs is not only important to ensure good neonatal outcome but also becomes the

1414 Grosset al.

major factor that the obstetrician may need to defend later. Each clinician must have a well-conceived approach planned in advance that can be instituted quickly and with the least possible maternal and fetal trauma, and this must be described in detail in the chart. The major efforts are directed toward disimpaction of the anterior shoulder by one of the maneuvers described in the major textbooks. When this approach is followed, we conclude that the occurrence and subsequent management by standard techniques of shoulder dystocia even with birth damage are not prima facie evidence of medical malpractice. REFERENCES I. Levine MG, Holroyde J, Woods JR, eta!. Birth trauma:

2. 3. 4. 5. 6. 7. 8.

9. 10. 11. 12. 13. 14. 15. 16.

incidence and predisposing factors. Obstet Gynecol 1984;63:792. Parks DG, Ziel HK. Macrosomia: a proposed indication for primary cesarean section. Obstet Gynecol 1978;52: 407. Golditch IM, Kirkman K. The large fetus: management and outcome. Obstet Gynecol 1978;52:26, Hopwood HG. Shoulder dystocia: fifteen years' experience in a community hospital. AM j 0BSTET GYNECOL 1982;144:163. Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985;66:762. Benedetti TJ, Gabbe SG. Shoulder dystocia. Obstet Gynecol 1978;52:527. Harris BA. Shoulder dystocia. Clin Obstet Gynecol 1984;27:106. Sokol RJ, Nussbaum R, Chik LC, eta!. Computer diagnosis of labor progression. Development of an on-line interactive digital computer program for the diagnosis of normal and abnormal cervical dilatation patterns. J Reprod Med 1973;ll:149. Friedman EA. Labor: clinical evaluation and management. New York: Appleton-Century-Crofts, 1978. Bottoms SF, Sokol RJ, Rosen MG. Short arrest of cervical dilatation: a risk for maternal/fetal/infant morbidity. AM .f 0BSTET GYNECOL 1981; 140:108. Spellacy WN, Miller S, Winegar A, et a!. Macrosomia: maternal characteristics and infant complications. Obstet Gynecol 1985;66: 158. Modanlou HD, Dorchester WL, Thorosian A, eta!. Macrosomia: maternal, fetal, and neonatalimp1ications. Obstet Gynecol 1980;55:420. Boyd ME, Usher RH, McLean FH. Fetal macrosomia: prediction, risks, proposed management. Obstet Gyneco1 1983;61:715. Sack RA. The large infant. AM J 0BSTET GYNECOL 1969; 104:195. Swartz DP. Shoulder girdle dystocia in vertex delivery. Obstet Gynecol 1960; 15:194. Hadlock FP, Harris T. Use of femur length/abdominal circumference ratio in detecting the macrosomic fetus. Radiology 1985; 154:503.

Editors' note: This manuscript was revised after these discussions were presented. Discussion DR. HERBERT F. SANDMIRE, Green Bay, Wisconsin. The authors have demonstrated in a statistical fashion what most of us have known from clinical experience.

June 1987 Am J Obstet Gynecol

Table I. Distribution of newborn weight of infants born in Cleveland and Green Bay >4000 gm

4000-4499 gm

>4500 gm

15.7 5.5

13.7 4.7

2.0 0.8

Green Bay Cleveland

Table II. Birth weight and cesarean section distribution for births in Green Bay from July 1, 1982, to June 30, 1983 Birth weight (gm)

<4000 4000-4499 >4500

I

No.

2905 471 ____ill!

3445

I

% 84.3 13.7 ___£,_Q 100.0

Cesarean birth

366 50 ...lQ

432

% 12.6 10.6 23.2 12.5

That is, by using clinical characteristics of the pregnancy or labor abnormalities, the predictability of shoulder dystocia is too low to be useful for choosing the route of delivery for a specific patient. What the present and all other authors have not done is to provide infant follow-up information identifying the severity and persistence or nonpersistence of the injuries incurred with their reported shoulder dystocia deliveries. For this, I am disappointed because the information is crucial to clinical decisions dependent on the balancing of maternal and fetal risks. The end point for the fetus is not the risk of shoulder dystocia but the risk of a persistent injury of significant severity. Fractures of the clavicle and humerous are neither significant nor persistent. Fortunately, most brachial plexus injuries are either transient or when persistent, result in mild residual arm weakness. On very rare occasions, the residual handicap may be substantial or fetal death may occur. Moreover, on very rare occasions, women die of cesarean section complications. The authors conclude that cesarean delivery is acceptable for all fetuses who seem very large (;;:.4500 gm). Considering the birth weight distribution (Table I) and the incidence of shoulder dystocia in their patient population, they may be right. However, until the severity and persistence of injuries associated with shoulder dystocia are considered, their conclusion has to be based on speculation. Two percent of all births occurring in Green Bay result in newborns weighing more than 4500 gm (Table II). Shoulder dystocia occurs with 7.4% of these deliveries (Table III). The 2.7% of73 deliveries complicated by shoulder dystocia in a patient population of 14,806 resulted in persistent mild arm weakness (Table IV). No severe or moderately severe persistent injuries occurred. Further analysis of the Green Bay obstetric population from July 1, 1982 to June 30, 1983 demonstrated 53 vaginal and 16 cesarean births in newborns weighing ;;:.4500 gm. Table V demonstrates the number of ad-

Shoulder dystocia

Volume 156 Number 6

Table III. Birth weight and shoulder dystocia distribution for births in Green Bay from July I, 1982, to June 30, 1983 Birth weight (gm)

<4000 4000-4499 >4500

% 2905 471

84.3 13.7

6 6

0.2

~

_&Q

_2

7.4

100.0

17

3445

1.2

Table IV. Brachial plexus palsy associated with 73 shoulder dystocia deliveries in the Green Bay obstetric population from 1980 to 1985

Transient Permanent

Table VI. Reduction in shoulder dystocia resulting from the additional 132 cesarean sections performed with a policy of cesarean section for all fetuses estimated to weigh > 4500 gm Birth weight (gm)

Shoulder dystocia*

Shoulder dystocia (new policy)

<4000 4000-4499 >4500

6 6

6 5

_2

_l

17

12

*132/5 = one shoulder dystocia delivery prevented for each additional 26 cesareans performed.

No.

%

10 2*

13.7 2.7

*Both mild arm weakness.

Table VII. Shoulder dystocia and reduction in newborn injuries attributable to a policy of cesarean birth for all fetuses estimated to weigh > 4500 gm 132 sections will prevent five shoulder dystocia deliveries and 0.135 permanent mild brachial palsies 978 cesarean sections would be required to prevent one persistent mild arm weakness handicap

Table V. Analysis of the 53 vaginal births with a strategy of cesarean section for all fetuses estimated to weigh > 4500 gm No.

Incorrectly estimated at <4500 gm* Correctly estimated at >4500 gm* Fetuses incorrectly estimated >4500 gm* Total estimated at >4500 gm Additional cesarean sections

1415

9 44 88 132 132

*By ultrasound measurement of femur length/abdominal circumference ratio, an abnormal value will indicate a macrosomic fetus in only 33% of cases. 16

ditional cesareans that would be performed with a strategy of performing cesarean sections on all fetuses estimated to weigh ""4500 gm. Nine fetuses would be incorrectly predicted at <4500 gm and would therefore not be delivered by cesarean section. These statistics are based on the reported accuracy of estimating fetal weight by the reference source 1 cited by the authors. Table VI demonstrates the prevention of five cases of shoulder dystocia by performing the 132 additional cesarean sections resulting from a policy of cesarean section for all fetuses estimated to weigh ""4500 gm. The 978 cesarean sections would be required to prevent one persistant mild arm weakness handicap. (Table VII). The maternal complications and risks of death associated with 978 cesarean sections would be of much greater importance than the prevention of one persistent mild arm weakness in the infant. Therefore in our obstetric population it would be inappropriate to perform cesarean sections on all women with fetuses estimated to weigh ""4500 gm. The authors state that the approach used in overcoming the shoulder dystocia "must be described in

Table VIII. Relationship between neonatal trauma* and the presence or absence of a chart note describing the procedure used in overcoming shoulder dystocia Procedure described

Procedure not described

(N = 26)

(n = 23)

Suspected brachial palsy Fractured clavicle Fracture humerous Brachial palsy

9

0

5 l

0

7

l 15

8

Data from study of Gross et a!. *Multiple injuries were present in some neonates.

detail in the chart," and yet this was not done in 23 of their 49 cases. Fetal injuries occurred more often in described than in undescribed deliveries (Table VIII). Description of delivery techniques will assist in the collection of data for research purposes but has no effect on infant outcome. Dr. Gross states that plaintiffs' attorneys theorize that the clinician can predict shoulder dystocia and therefore avoid it and associated fetal injuries by cesarean delivery. Actually, the plaintiffs' attorneys do not theorize at all but are told this by obstetricians acting as legal consultants and expert witnesses. Examples include the following statements by our next discussant, Dr. Leslie Iffy: "Significant possibility of shoulder dystocia is an unequivocal indication for cesarean section. If the cases are properly selected, the possibility of a shoulder dys-

1416

Grosset al.

June 1987 Am J Obstet Gynecol

Table I. Frequency of shoulder dystocia in the statewide perinatal center, Newark, New Jersey, between July 1, 1981, and June 30, 1984 No. of cases of shoulder dystocia

% of shoulder dystocia after vaginal deliveries

Birth weight (gm)

Deliveries

Cesarean section (%)

<4000 4000-4499 ;;.4500

6725 198 39

14.1 16.7 51.0

7 4 1

0.1 2.5 5.3

Total deliveries

6942

15.0

12

0.2

tocia, conducive to permanent damage, can be predicted with a considerable degree of accuracy." REFERENCE 1. Hadlock FP, Harris T. Use of femur length/abdominal circumference ratio in detecting the macrosomic fetus. Radiology 1985;154:503.

DR. LESLIE IFFY, Newark, New Jersey. The literature that the investigators quoted identifies about 20 predisposing factors for shoulder dystocia. Of these, the authors elected to investigate only those that they considered of major significance. However, some of the factors that they excluded are equ<'lly important. Nonetheless, the study of Gross et al. is a valuable investigation that provides a useful yardstick for clinicians. The recommendation of delivering babies with an estimated weight of 4500 gm or more by cesarean section is a useful rule of thumb and the warning concerning the potential risks in the 4000 to 4499 gm group is justifiable. I was surprised to find that in this material little more than 7000 deliveries involved 116 cases of shoulder dystocia. Therefore I reviewed a comparable number of cases in the material of the Perinatal Center in Newark, New Jersey, based on deliveries between July 1, 1981 and June 30, 1984. (Table I). Some of the differences between the frequency of shoulder dystocia in the two centers can be explained by our different demographic profiles. The high number of black patients in Newark tends to reduce the number of macrosomic fetuses. Our virtual abandonment of midforceps deliveries in recent years may also have played a role, although I note that the cesarean section rates in Detroit and Newark were essentially the same (15%). I am inclined to attribute significance to our routine method of delivery, which is widely favored in Great Britain. This technique, which is described in a textbook chapter of one of the authors of this paper, 1 calls for noninterference after the delivery of the head. Apart from releasing the cord if wrapped around the neck, the obstetrician waits for the next uterine contraction and extracts the shoulders at the peak of the same. We have used this protocol for more than 10 years in our service and encountered few cases of shoulder dystocia during this time. The authors correctly emphasize the medicolegal im-

portance of shoulder dystocia. I reported recently that of 100 claims pertaining to alleged fetal damage, not less than eight were related to this entity! In most of these cases, the struggle for overcoming shoulder dystocia started immediately after the delivery of the head, an endeavor that our residents are trained to avoid. Services with a high rate of specific complications are more likely to report their findings than those without. This circumstance may introduce a bias into the data base of otherwise impeccable studies, such as the one presented by Gross et al. Thus it is necessary to evaluate the subject based on material without an inflated incidence of shoulder dystocia and on the grounds of more parameters of investigation than what the authors elected to use. REFERENCES 1. Bottoms SF, Sokol RJ. Mechanisms and conduct of labor. In: Iffy L, Kaminetzky HA, eds. Principles and practice of obstetrics and perinatology. New York: John Wiley & Sons Inc., 1981:875. 2. Iffy L, Goldsmith LS. Obstetric background of malpractice claims involving fetal damage. In: Iffy L, ed. Second perinatal practice and malpractice symposium. New York: Healthmark Communications, 1985:95.

DR. BERNHARDT LAFALD PEDERSON, Bay City, Michigan. In the'authors' group of approximately 400 cases of patients delivering large infants, approximately I 00 had cesarean sections and of that I 00, 50 were delivered without labor. I would like to know how this group was chosen. I would then like to add my appreciation for the authors discussing the relationship of this problem to malpractice. DR. joE THOMPSON, Indianapolis, Indiana. I begin with a brief quotation for which I cannot claim credit: "30 years ago it was risky for a woman to have a baby but safe for the physician to deliver it. Now it is safe for a woman to have a baby but risky for the physician to deliver it." I have two questions. If I came to them as a family practitioner in the institution in which they practice, is there a biparietal diameter above which they would suggest that I deliver the baby by cesarean section, and then if I came to them the next day with the same question and told them that the woman had previously had a baby and shoulder dystocia, what would be their response? I would heartily endorse the fourth conclusion about

Volume 156 Number 6

documenting the maneuvers that you go through to deliver an infant in whom shoulder dystocia becomes apparent. In the medical malpractice panel system that we have in Indiana, it is generally held that a physician who goes through the usual maneuvers in attempting to correct shoulder dystocia has followed the standards of practice in the community. DR. WILLIAM). KEATING, Cleveland, Ohio. The article by Gross et a!. does not actually address the management of shoulder dystocia but management is more salutary if we have anticipated shoulder dystocia. This paper does not examine infants who are <4000 gm, but any obstetrician with any degree of experience has encountered babies of smaller weight who have had shoulder dystocia. My remarks are based on those two hypotheses or provisos and I have two points to make. The first is that a lack of precision in predicting shoulder dystocia using birth weight criteria alone to select the patients at risk is not all that surprising, since it ignores the passageway, the pelvis. Since shoulder dystocia virtually always occurs at the pelvic inlet and in the anteroposterior diameter, a flatter pelvis with a shorter anteroposterior diameter must increase the risk of shoulder dystocia, even at lower birth weights. A short anteroposterior diameter is easily detectable by clinical-that is, manual-pelvimetry, by measuring the diagonal conjugate. Thus in part this is a plea for us to resort to that oldest maneuver to assess pelvic capacity, the diagonal conjugate, which was first published by our honored colleague, William Smellie, in 1752. It is not new information. Of course, this would still not give us an actual prognosis, but would merely identify the risk group to a larger extent. Second, despite the pressure of consumers on we who have faced this (which is all of us), trying to manage shoulder dystocia in a patient attempting to deliver in a bed is an absolute disaster. Indeed, even on a proper delivery table, management efforts such as the McRoberts maneuver of acute thigh flexion are sharply impeded if the legs are strapped to the table, or if there is only one circulating attendant to help us. Thus identification of the at-risk group to alert the obstetrician in advance to the greater likelihood of shoulder dystocia would be in the best interest of fetal safety by assuring delivery on a delivery table, unfettered, and with enough help. I would like Dr. Gross to comment on the degree to which this study as it stands, admittedly without diagonal conjugate information, could be used simply as an early warning, a caution light, to give us some warning, not so much to choose another method of delivery but so that we may face shoulder dystocia and know how to manage it. DR. LEE B. STEVENSON, Southfield, Michigan. An honest effective opportunity for the obstetrician who is faced with a medicolegal challenge in this area, considering the alternative, is to convince the opposition that he is the best obstetrician in town; so if you can convince the opposition that you are in fact the best

Shoulder dystocia

1417

obstetrician in town, you are a long way toward winning your battle. DR. HARRY K. WADDINGTON, Olympia Fields, Illinois. I enjoyed the paper by Gross et a!. and invite him to appear before the Chicago Bar Association. DR. GROSS (Closing). First, as Dr. Sandmire noted, I did not present all the data in the article simply because there was not enough time. Dr. Sandmire asked, what would be the effect of routine abdominal delivery if we performed this on all babies who were >4000 gm or those >4500 gm? We projected several approaches to this question. In the present data base, if were were able to estimate all patients in whom the fetus was >4000 gm and deliver them abdominally, the primary cesarean section rate would increase from 9.3% to 13.3%. The total rate would go from 15.1% to 19.1%. This would increase the primary cesarean rate by 44% and the total rate by 27%. This would result in 283 additional cesarean sections to prevent the 49 cases of shoulder dystocia that we reported in this study. This would be 14 cesarean sections for every case of trauma and six cesarean sections for every case of shoulder dystocia. We believe that this large number of cesarean sections would be too high a price to pay. The second projection that we examined was the potential effect of routine cesarean section when the fetus weighed >4500 gm. This would increase our primary cesarean section rate by only 6% and our total cesarean section rate by only 4%. We would prevent 20 cases of shoulder dystocia, and in this data base we concluded that cesarean section for all babies weighing >4500 gm would be indicated. However, I agree with Dr. Sandmire that this may not be applicable to other data bases such as the one he presented in which there was a threefold higher rate of neonates weighing >4500 gm. I believe that it is a judgment call that must rest with the obstetrician because an accurate estimate of fetal weight is not available at this time. When this study was performed, we used biparietal diameters, and they are very imprecise. At present the estimate of fetal macrosomia is still very imprecise. Multiple methods are being attempted. In a review in the Journal of Clinical Ultrasound last year, Deter' suggested that at this time we cannot diagnose fetal macrosomia. Deter points out there is a 15% error even by the best sonographers. Spellacy, 2 in a reply to a "Letter to the Editor" to Dr. Iffy, the past year in Obstetrics and Gynecology agreed that the baby >4500 gm should be delivered by cesarean section. However, he concluded that to be confident that the birth weight would be >4500 gm, the estimated fetal weight would have to be at least 5000 gm. If one used this estimate, it would result in predicting very few cases of shoulder dystocia because even with large fetuses fetal weight is rarely estimated to be this size. Even though no ultrasound techniques are currently available that can accurately predict fetal macrosomia

1418 Grosset al.

or shoulder dystocia, some are being studied and some are looking at fetal growth profiles that include head, shoulder, abdominal, and thigh size to improve the estimated fetal weight. Dr. Sandmire stated that follow-up information on the infants would be very important. I agree with this, but follow-up studies are very difficult to perform and of course take many years. The population of patients who are studied are often indigent and are unavailable for long-term follow-up. If you used these rare longterm variables, it would mean that the ability to predict those patients who have a poor outcome would be even worse. I appreciate that Dr. Sandmire presented his fascinating data. He definitely deals with a population of patients with different social and demographic factors. In my data base, there was a large percentage of patients who were black, and this group frequently has smaller babies. Dr. Sandmire's population had three times more 4500 gm babies, which was probably due to the difference in population. In a different population, when there are more babies >4500 gm, the number of cesarean sections that would be needed to deliver all large babies abdominally would then obviously be increased. Dr. Iffy's comments questioned if we looked at the use of oxytocin and midforceps. We examined these variables, and they were not predictors for the outcome of shoulder dystocia. That is, they were not helpful in predicting which patients would develop shoulder dystocia. The studies that Dr. Iffy suggested showing midforceps delivery to be a risk factor for shoulder dystocia actually reported midpelvic delivery to be a major predictor. Most of those patients were not delivered by midforceps but by vacuum extraction. We did not use vacuum extraction, and we very rarely used midforceps delivery in our population; thus we could not examine these variables as predictors. We included them in our discriminant analysis, and they had no predictive value because of their low frequency. Dr. Iffy suggested that the frequency of shoulder dystocia in our study was high. The frequency of shoulder dystocia in our population is higher than some studies in the literature. However, there have been very few studies in the literature that have divided the patients into shoulder dystocia with and without trauma as we did. We feel that there are several possibilities to explain why our frequency is higher than some studies. First, it may be that the doctors in Cleveland are just more honest. The other possibility is that the patients who developed trauma may have had true shoulder dystocias that are categorized by other physicians. It should be noted that the frequency of shoulder dystocia in our study was nearly exactly the same as Friedman's data that was referred to earlier. The study of Acker et a!.' appeared in the literature just as we completed the first draft of this article, and thus we could compare our data to theirs. In the first column are the frequen-

June 1987 Am J Obstet Gynecol

cies of shoulder dystocias in the present study of neonates weighing >4000 gm. To answer one of Dr. Keating's questions, some babies develop shoulder dystocia weighing <4000 gm. In our study more than half of the infants with shoulder dystocias reported in our population weighed <4000 gm. This is in exact agreement with Dr. Friedman's data. If you compare our data with that of Acker eta!, you see that our frequency is almost exactly the same as theirs up until a birth weight of 4500 gm, at which point our frequency became higher. There are several possible explanations for this. Friedman separated his diabetic from his nondiabetic mothers. The frequency of shoulder dystocia in his diabetic babies is shown in brackets, 23% in the >4000 gm babies and a 50% rate of shoulder dystocia in the >4500 gm babies. This has been previously found. The fetus of the diabetic mother is at much greater risk of shoulder dystocia because apparently the shoulders grow faster than the fetal brain in the diabetic mother. Friedman separated his diabetic patients and looked at them separately. We did not, so our >4500 gm babies include many diabetic mothers, which explains some of our increase in shoulder dystocia in patients in whom a >4500 gm neonate was delivered. Next, let me answer the questions from the floor. Fifty patients had cesarean sections without labor for various reasons. In 17 patients the fetuses were in the breech position, and the physician estimated that a macrosomic fetus was present and did not want to do a breech deliyery on a macrosomic fetus. Dr. Keating stated that almost all studies on shoulder dystocia have ignored the maternal pelvis. I agree with this assessment, and I do not think that this is appropriate. We did not have pelvic data available in the present study, but I believe that we need a prospective study in which the maternal pelvic size is included. Finally, Dr. Keating asked if we use this as an early warning. I believe we can. In our >4500 gm babies, the presence of a labor abnormality, that is, an arrest pattern, was very high, and I think this should be an early warning sign that shoulder dystocia may be a slightly greater risk. The problem is that in this group, this group using the labor abnormalities as a predictor would have predicted only about 15% of cases with shoulder dystocia. It is again statistically related; however, it is not good to use for a predictor. REFERENCES I. Deter RL, Hadlock FP. Use of ultrasound in the detection of macrosomia: a review. J Clin Ultrasound 1985;13: 519-24. 2. Spellacy WN. Macrosomia. Obstet Gynecol 1986;68:140. 3. Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985;66:762.