Association of change in haemoglobin A1c with adverse perinatal outcomes in women with pregestational diabetes

Abstract

Aims: To determine whether a net decline in glycosylated haemoglobin (HbA_1c ) from early to late pregnancy is associated with lower risk of adverse perinatal outcomes at delivery among women with pregestational diabetes.

Methods: A retrospective analysis from 2012 to 2016 at a tertiary care centre. The exposure was the net change in HbA_1c from early (<20 weeks gestation) to late pregnancy (≥20 weeks gestation). Primary outcomes were large for gestational age (LGA) and neonatal hypoglycaemia. The association between outcomes per 6 mmol/mol (0.5%) absolute decrease in HbA_1c was evaluated using modified Poisson regression, and adjusted for age, body mass index, White Class, early HbA_1c and haemoglobin and gestational age at HbA_1c measurement and delivery.

Results: Among 347 women with pregestational diabetes, HbA_1c was assessed in early (9 weeks [IQR 7,13]) and late pregnancy (31 weeks [IQR 29,34]). Mean HbA_1c decreased from early (59 mmol/mol [7.5%]) to late (47 mmol/mol [6.5%]) pregnancy. Each 6 mmol/mol (0.5%) absolute decrease in HbA_1c was associated with a 12% reduced risk of LGA infant (30%, aRR:0.88; 95% CI:0.81,0.95), and a 7% reduced risk of neonatal hypoglycaemia (35%, aRR:0.93; 95% CI:0.87,0.99). Preterm birth (36%, aRR:0.93; 95% CI:0.89,0.98) and neonatal intensive care unit admission (55%, aRR:0.95; 95% CI:0.91,0.98) decreased with a net decline in HbA_1c , but not caesarean delivery, pre-eclampsia, shoulder dystocia and respiratory distress syndrome.

Conclusions: Women with pregestational diabetes with a reduction in HbA_1c may have fewer infants born LGA or with neonatal hypoglycaemia. Repeated assessment of HbA_1c may provide an additional measure of glycaemic control.

Keywords: complications; diabetes; diabetes mellitus; glycosylated haemoglobin; haemoglobin A1c; pregestational diabetes; pregnancy.