SHOULDER DYSTOCIA AND ASSOCIATED RISK-FACTORS WITH MACROSOMIC INFANTSBORN IN CALIFORNIA

OBJECTIVE: The purpose of this study was to examine the 1-year inciden ce statewide in California of shoulder dystocia and its associated ris k 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 a cute care hospitals in California in 1992 were analyzed. All cases of shoulder dystocia were identified from discharge records, birth certif icates, 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 b irths complicated by shoulder dystocia for unassisted births not compl icated by diabetes were 5.2% for infants 4000 to 4250 g, 9.1% for thos e 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 vac uum- or forceps-assisted births to nondiabetic mothers. Similar increa ses were seen in unassisted births to diabetic mothers. The risk of sh oulder 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 45 00 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 ris k of shoulder dystocia associated with diabetes (odds ratio 1.7), assi sted delivery (odds ratio 1.9), and induction of labor (odds ratio 1.3 ). Rates of birth trauma, asphyxia, and length of stay were all increa sed among births complicated by shoulder dystocia. CONCLUSION: This in formation on the incidence of shoulder dystocia and associated risk fa ctors for a large statewide population may assist providers of obstetr ic care in counseling patients when macrosomia is suspected. The inacc uracy of estimating fetal weight is a severe limitation in attempting to establish guidelines designed to prevent shoulder dystocia.