Ultrasound predictors of adverse outcome in pregnancy complicated by pre-existing and gestational diabetes

Abstract

Introduction: Ultrasound assessment of fetuses subjected to hyperglycemia is recommended but, apart from increased size, little is known about its interpretation, and the identification of which large fetuses of diabetic pregnancy are at risk is unclear. Newer markers of adverse outcomes, abdominal circumference growth velocity and cerebro-placental ratio, help to predict risk in non-diabetic pregnancy. Our study aims to assess their role in pregnancies complicated by diabetes.

Material and methods: This is a retrospective analysis of a cohort of singleton, non-anomalous fetuses of women with pre-existing or gestational diabetes mellitus, and estimated fetal weight at the 10th centile or above. Gestational diabetes was diagnosed by selective screening of at risk groups. A universal ultrasound scan was offered at 20 and 36 weeks of gestation. Estimated fetal weight, abdominal circumference growth velocity, presence of polyhydramnios, and cerebro-placental ratio were evaluated at the 36-week scan. A composite adverse outcome was defined as the presence of one or more of perinatal death, arterial cord pH less than 7.1, admission to Neonatal Unit, 5-minute Apgar less than 7, severe hypoglycemia, or cesarean section for fetal compromise. A chi-squared test was used to test the association of estimated fetal weight at the 90th centile or above, polyhydramnios, abdominal circumference growth velocity at the 90th centile or above, and cerebro-placental ratio at the 5th centile or below with the composite outcome. Logistic regression was used to assess which ultrasound markers were independent risk factors. Odds ratios of composite adverse outcome with combinations of independent ultrasound markers were calculated.

Results: A total of 1044 pregnancies were included, comprising 87 women with pre-existing diabetes mellitus and 957 with gestational diabetes. Estimated fetal weight at the 90th centile or above, abdominal circumference growth velocity at the 90th centile or above, cerebro-placental ratio at the 5th centile or below, but not polyhydramnios, were significantly associated with adverse outcomes: odds ratios (95% confidence intervals) 1.85 (1.21-2.84), 1.54 (1.02-2.31), 1.92 (1.21-3.30), and 1.53 (0.79-2.99), respectively. Only estimated fetal weight at the 90th centile or above and cerebro-placental ratio at the 5th centile or below were independent risk factors. The greatest risk (odds ratio 6.85, 95% confidence interval 2.06-22.78) was found where both the estimated fetal weight is at the 90th centile or above and the cerebro-placental ratio is at the 5th centile or below.

Conclusions: In diabetic pregnancies, a low cerebro-placental ratio, particularly in a macrosomic fetus, confers additional risk.

Keywords: cerebro-placental ratio; diabetes in pregnancy; estimated fetal weight; fetal Doppler; fetal growth.