Can we improve the gestation-adjusted projection (GAP) method for prediction of birth weight in morbidly obese women?

AbstractObjective: The gestation-adjusted projection (GAP) is a method to predict birthweight using population birth data and third trimester ultrasound fetal weight. This method usually utilizes population birth weight data from almost 40 years ago. In 2011, a large cohort of racially diverse infants across the US was included to validate updated birth curves. Our objective was to determine if the updated data would improve the accuracy of the GAP method during the third trimester among obese women.Methods: This secondary analysis of a cohort study included singleton pregnancies of obese women who had fetal growth assessment(s) in the third trimester. The first subgroup (N = 235) included women with a BMI >40 kg/m2 who had ultrasounds during 30 + 0–35 + 0 weeks (EARLY) and greater than 35 + 0 weeks (LATE). The second subgroup (N = 431) included women with a BMI 30–35, 40–50, or >50 kg/m2 who had an ultrasound during 34 + 0–36 + 6 weeks. Mean absolute percent error was calculated for all GAP methods and c...