Rethinking third trimester ultrasound measurements and risk of adverse neonatal outcomes in pregnancies complicated by hyperglycaemia: A retrospective study

Background: Antenatal ultrasound is used frequently in pregnancies complicated by hyperglycaemia; however, it is unclear which measurements have the greatest association with adverse neonatal outcomes. 

Aim: To assess the association between third trimester ultrasound parameters with adverse neonatal outcomes in pregnancies complicated by hyperglycaemia. 

Method: All pregnant women with gestational or type 2 diabetes who birthed in a regional hospital over 12 months were included. A composite adverse neonatal outcome was defined by one or more: admission to special care nursery, acidosis, hypoglycaemia, jaundice, shoulder dystocia, respiratory distress syndrome or 5-minute Apgar score < 5. Logistic regression was used to determine odds ratios (OR) for an adverse neonatal outcome, according to pre-specified cut points in both lower and upper percentiles of abdominal circumference (AC) and estimated fetal weight (EFW). 

Results: Of 275 births an adverse outcome occurred in 122 (44%). Unadjusted OR (95% CI) for AC ≤30^th was 3.2 (1.1–8.8) and >95^th percentile was 3.1 (1.5–6.0) compared with the reference group of 31–70^th percentile. Unadjusted OR for EFW ≤30^th was 1.5 (0.7–3.1) and >95^th percentile was 3.0 (1.4–6.3). After adjusting for maternal age, body mass index, diabetes type, ethnicity, gravidity, mode of delivery and gestation at birth the OR (95% CI) were as follows: AC ≤30^th percentile, 3.7 (1.1–12.4); AC >95^th, 2.2 (1.1–4.8); EFW ≤30^th, 2.6 (1.1–6.1); EFW >95^th, 2.5 (1.1–6.1). 

Conclusion: An AC and EFW up to the 30^th percentile may pose just as great a risk to the fetus as an AC or EFW >95^th percentile in pregnancies complicated by hyperglycaemia.