Predicting periviable birthweight and survival: bedside ultrasound versus anatomy scan gestational adjusted age projection

Objective: Two methods of birthweight (BW) prediction in the periviable period: bedside ultrasound proximate to delivery versus gestation-adjusted-projection (GAP) method was compared. Methods: Periviable births were identified over a 6-year period. The GAP method was applied to the estimated fetal weight (EFW) from anatomy scans and the gestational age at delivery to predict BW, designated EFW_GAP. EFW from the bedside ultrasound (EFW_US), and the EFW_GAP were compared to actual BW to calculate absolute values of error in BW estimates. Neonatal survival estimates were made utilizing a National Institute of Child Health and Human Development calculator. Results: EFW_US was more accurate than EFW_GAP in predicting BW as the mean absolute value of error with bedside ultrasound ǀEFW_US-BWǀ was significantly lower than mean absolute value of error with GAP method ǀEFW_GAP-BWǀ, 75.32 ± 74.64 g versus 125.68 ± 130.62 g, p = 0.01. Predicted neonatal survival based on EBW_US was closer to reference than predicted survival based on EBW_GAP 9.66% ± 9.43% versus 7.76% ± 7.78% p = 0.26. Conclusions: EFW_US is more accurate than EFW_GAP for predicting BW in this period. However, the GAP technique could have utility in survival predictions when timely performance of ultrasound is not feasible.