Medline ® Abstracts for References 1,5-7

OBJECTIVE: The purpose of this study was to examine the 1-year incidence statewide in California of shoulder dystocia and its associated risk factors.

STUDY DESIGN: With a data set that contains computer-linked records from the birth certificate and hospital discharge records of both mother and baby, all births of infants>3500 g in>300 civilian acute care hospitals in California in 1992 were analyzed. All cases of shoulder dystocia were identified from discharge records, birth certificates, or both and were analyzed with both bivariate and multivariate techniques to identify specific risk factors.

RESULTS: A total of 175,886 vaginal births of infants>3500 g were included in our database, of which 6238 infants (3%) had shoulder dystocia. The percentages of births complicated by shoulder dystocia for unassisted births not complicated by diabetes were 5.2% for infants 4000 to 4250 g, 9.1% for those 4250 to 4500 g, 14.3% for 4500 to 4750, and 21.1% for those 4750 to 5000 g. Shoulder dystocia increased by approximately 35% to 45% in vacuum- or forceps-assisted births to nondiabetic mothers. Similar increases were seen in unassisted births to diabetic mothers. The risk of shoulder dystocia for assisted births to diabetic mothers was even more dramatic: 12.2% for infants 4000 to 4250 g, 16.7% for those 4250 to 4500 g, 27.3% for those 4500 to 4750 g, and 34.8% for those 4750 to 5000 g. After controlling for other parameters, there was an increased risk of shoulder dystocia associated with diabetes (odds ratio 1.7), assisted delivery (odds ratio 1.9), and induction of labor (odds ratio 1.3). Rates of birth trauma, asphyxia, and length of stay were all increased among births complicated by shoulder dystocia.

CONCLUSION: This information on the incidence of shoulder dystocia and associated risk factors for a large statewide population may assist providers of obstetric care in counseling patients when macrosomia is suspected. The inaccuracy of estimating fetal weight is a severe limitation in attempting to establish guidelines designed to prevent shoulder dystocia.

An unmatched comparative study is described to determine if routine clinical indicators are useful predictors for shoulder dystocia. Parity, maternal weight gain during pregnancy, and a history of a previous large baby and increased operative vaginal delivery rate were more often associated with shoulder dystocia. No other significant associations were found. However, shoulder dystocia can not be predicted accurately antepartum using routinely available clinical factors.

OBJECTIVE: Our purpose was to determine the rate of associated risk factors for shoulder dystocia from a large cohort of patients delivered within our Southern California perinatal program.

STUDY DESIGN: A retrospective analysis was performed of patients delivered from January 1991 to June 2001. Patients with and without shoulder dystocia were identified from our computer-stored perinatal database and compared. Statistical methods used included: chi 2 test, t test, calculation of odds ratios, and Fisher exact test, as indicated.

RESULTS: Among the 267,228 vaginal births during the study period, there were 1,686 cases of shoulder dystocia (rate 0.6%). Rates for operative vaginal delivery, diabetes, epidural use, multiparity, and postdatism were similar among cases with and without shoulder dystocia. The clinical triad of oxytocin use, labor induction, and birth weight greater than 4,500 g yielded a cumulative odds ratio of 23.2 (95% CI 17.3-31.0) for shoulder dystocia, but its sensitivity and positive predictive value were only 12.4% and 3.4%, respectively.

CONCLUSION: Historic obstetric risk factors for shoulder dystocia are not useful predictors for the event. Furthermore, although shoulder dystocia was observed more frequently with increasing birth weight, current limitations in estimating birth weight antenatally with accuracy preclude its practical use as a reliable predictor.