Perinatal outcomes of babies predicted to be large‐for‐gestational age by universal third‐trimester ultrasound in non‐diabetic pregnancies

To describe perinatal outcomes of babies predicted to be large-for-gestational age in non-diabetic pregnancies for women attempting vaginal birth.This was a prospective population-based cohort study of patients from a single tertiary maternity unit in the UK offering universal third trimester ultrasound and practising expectant management of suspected large-for-gestational age until 41 to 42 weeks. All women with a singleton pregnancy and an estimated due date between January 2014 to September 2019 were included. Women delivering before 37 weeks, with pre-existing or gestational diabetes, fetal abnormalities, and those who did not have a third trimester scan were excluded for the assessment of perinatal outcomes of LGA by ultrasound after implementation of universal scan period. Association of LGA and perinatal adverse outcome were assessed for birth during universal ultrasound screening with the exposures of interest being EFW 90-95th , EFW>95th and EFW >99th centiles. The reference group was fetuses with EFW 30-70th . Analysis was performed using multivariate logistic regression. Neonatal composite adverse outcomes include: 1) Admission to NICU, APGARS <7 at 5 minutes, or arterial cord pH <7.1; 2) stillbirth, neonatal death, or hypoxic ischaemic encephalopathy. Secondary maternal outcomes were induction of labour, mode of birth, postpartum haemorrhage, shoulder dystocia, obstetric anal sphincter injury.Babies with an estimated fetal weight (EFW) on universal third trimester scan above 95th centile were at increased risk of CAO1 (aOR 2.18 [1.69-2.80]) and CAO2 (aOR 2.58 [1.05-16.0]). However, babies with EFW 90-95 had a smaller risk of CAO1 and were not at increased risk of CAO2. All pregnancies were at increased risk of secondary maternal outcomes except for obstetric anal sphincter injury; the risk of adverse maternal outcome was higher with increasing EFW. Post hoc exploration of data suggests shoulder dystocia has a limited contribution for neonatal composite adverse outcomes in LGA babies (population attributable fraction of 10.8% for CAO1 and 29.1% for CAO2) CONCLUSION: Babies with EFW >95th centile are at increased risk of adverse perinatal outcome and these results should aid antenatal counselling of the associated risks and birth options. This article is protected by copyright. All rights reserved.