August 23rd, 2019

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Use of Customized Birth Weight Percentiles for the Prediction of Shoulder Dystocia
Authors:  Nateya Carrington, M.D., Haleema Sadath, M.D., Haleh Sangi-Haghpeykar, Ph.D., and Christina Davidson, M.D.
  OBJECTIVE: To investigate the use of customized birth weight percentiles (CBWPs) as a predictor for shoulder dystocia (SD).

STUDY DESIGN: Over a 3-year period SD occurred among 99 of 11,493 deliveries, for an incidence of 0.9%. To conduct a case-cohort study, 386 deliveries with no SD were randomly selected. CBWP was determined for each woman using the estimated fetal weight (EFW) in the Gestation Related Optimal Weight software, which accounts for maternal height, weight, ethnicity, parity, gestational age, and infant sex. Relationship between CBWP and SD was examined using logistic regression and receiver operative characteristic (ROC) curve analysis.

RESULTS: The area under the ROC curve for CBWP was 0.84 (95% CI 0.80–0.88), indicating moderate performance of CBWP as a risk discriminator. The 70th percentile had both the highest sensitivity (79%) and specificity (76%) for prediction of SD (positive likelihood ratio=3.3, negative likelihood ratio=3.6). The area under the ROC curve for birth weight was also 0.84 (95% CI 0.79–0.88) and for EFW was 0.73 (95% CI 0.65–0.80). The average EFW was 3,678 g (SD 411) for the cases and 3,355 g (SD 303) for the controls (p<0.0001).

CONCLUSION: CBWP performs better than estimated fetal weight alone at predicting shoulder dystocia.
Keywords:  birth weight; body weight, fetal; childbirth; dystocia; fetal macrosomia; fetal weight; obstetric labor; shoulder dystocia
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