Newborn shoulder width: a prospective study of 2222 consecutive measurements

Objectives To relate maternal and infant characteristics to newborn shoulde r width and to evaluate the predictive value of newborn shoulder width meas urement in cases of shoulder dystocia. Design Newborn shoulder width was systematically measured at birth during a period of 18 months. Setting Department of Obstetrics and Gynaecology of Saint-Antoine Universit y Hospital, Paris, France. Population A total of 2222 newborn shoulder width measurements were perform ed and 22 cases of true shoulder dystocia occurred during the study period. Methods Newborn shoulder width measurements were reviewed and correlated wi th maternal age, par ity, nonpregnant weight, weight gain during pregnancy, height, race, fasting glucose and one hour glucose levels, gestational age , birthweight and sex of the neonate. A receiver-operating characteristics curve was constructed to evaluate newborn shoulder width as a test for pred icting shoulder dystocia. Results The mean newborn shoulder width was 122.06 mm (10.50 SD). Stepwise multiple regression showed that newborn shoulder width was significantly as sociated with birthweight (P < 0.001), parity (P = 0.04), and nonpregnant w eight (P = 0.04). We estimated that the best cut off for shoulder dystocia prediction was a newborn shoulder width measurement with a low false positi ve rate (< 10%) in association with a high sensitivity rate. Therefore, new born shoulder width measurement greater than or equal to 140 mm was selecte d. This measurement should have a low sensitivity of 27.27%, a specificity of 91.82%, a positive predictive value of 4.02%, and a negative predictive value of 99.01% for shoulder dystocia prediction. Nevertheless, birthweight greater than or equal to 4000 g should have a better predictive value retr ospectively for shoulder dystocia. Conclusions Newborn shoulder width measurement, which is strongly correlate d with birthweight, still remains a poor predictor for shoulder dystocia, e ven when this evaluation is correct antenatally.