Customized fetal weight limits for antenatal detection of fetal growth restriction

Objective To define cut-offs limits for individually adjustable fetal weigh t standards for the detection of intrauterine growth restriction. Design Retrospective study: with the outcome measures small-for-gestational age (SGA) birth weight, operative delivery for fetal distress, umbilical a rtery pH < 7.15, and admission to the neonatal intensive care unit. Subjects and Methods;Two hundred and fifteen women considered to be at incr eased risk of uteroplacental insufficiency were recruited to a study of ser ial ultrasound scans. Fetal weights were derived using standards formula ar m, retrospectively, weight percentiles were calculated after individual adj ustment for maternal height, weight in early pregnancy: ethnic group, Parit y and fetal sex. Introduction One or more antenatal scans indicative of fetal weight below t he 10th customized percentile were predictive for a SGA neonate at birth (P < 0.001), operative delivery for fetal distress (P < 0.01) and admission t o neonatal intensive care (P < 0.01) but not for a low umbilical artery PH (P = 0.6). Receiver-operator curves,es showed the optimal customized fetal weight percentile limit for predicting all SGA neonate to be the 18th perce ntile (sensitivity 83%, specificity 79%, Positive predictive value 63% and negitive predictive value 92%). For the prediction of operative delivery fo r fetal distress and admission to neonatal intensive cave, the optional cus tomised cut-off value was the 8th Percentile. Conclusions Thc assessment of fetal weight using ultra-sound and an individ ually-adjusted standard is predictive of growth restriction and perinatal e vents associated with hypoxia or diminished reserve. The optimal cut-off va lue for Predicting operative delivery for fetal distress of admission to th e neonatal intensive care unit suggests that the 10th customized percentile is a good limit for clinical use.