Pregnancy outcomes in women with booking HbA1c ≤ 40 mmol/mol compared with 41-49 mmol/mol in South Auckland, New Zealand

Aims There are few data on pregnancy outcomes in women with pre-diabetes (HbA1c 41-49 mmol/mmol) at pregnancy booking. We aimed to (i) identify the proportion of women in Counties Manukau Health (CMH), South Auckland, New Zealand (NZ), with pre-diabetes at booking and (ii) compare outcomes between women with normal HbA1c and pre-diabetes. Materials and methods Using data from a multi-ethnic population of 10,869 singleton pregnancies, booked at <20 weeks from January 2017 to December 2018 in CMH, we compared outcomes between those with normal HbA1c (<= 40 mmol/mol) and those with pre-diabetes (HbA1c 41-49 mmol/mol). The primary outcomes were gestational diabetes mellitus (GDM) by NZ criteria and large for gestational age (LGA) defined as birthweight >90th customised centile. Logistic regression determined the contribution of HbA1c 41-49 mmol/mol to the development of GDM. Results Among 10,869 participants, 193 (1.78%) had an HbA1c 41-49 mmol/mol at <20 weeks' gestation. Those with HbA1c 41-49 mmol/mol were 11 times more likely to develop GDM (59.6 vs 7.9%; adjusted odds ratio (aOR) 11.16 (7.59, 16.41)) and were more likely to have an LGA baby (47 (24.4%) vs 1436 (13.5%) aOR 1.63 (1.10, 2.41)) versus those with normal HbA1c. They also had significantly higher rates of pre-eclampsia, caesarean sections, preterm births and perinatal deaths. Conclusions: Nearly two-thirds of women with a booking HbA1c of 41-49 mmol/mmol developed GDM as well as multiple other perinatal complications compared to women with HbA1c <= 40. Trials to evaluate the impact of treatment in early pregnancy on the risk of late-pregnancy complications are required.