Hemoglobin A1c Trajectories During Pregnancy and Adverse Outcomes in Women with Type 2 Diabetes: A Danish National Population-based Cohort Study.

Objective: To identify and characterize groups of pregnant women with type 2 diabetes with distinct hemoglobin A1c (HbA1c) trajectories across gestation and to examine the association with adverse obstetric and perinatal outcomes.

Research Design and Methods: A retrospective Danish national cohort study including all singleton pregnancies in women with type 2 diabetes, giving birth to a liveborn infant, between 2004 and 2019. HbA1c trajectories were identified using latent class linear mixed model analysis. Associations with adverse outcomes were examined with logistic regression models.

Results: In total, 1129 pregnancies were included. Three HbA1c trajectory groups were identified and named according to the glycemic control in early pregnancy (good 59%, moderate 32%, poor 9%). According to the model, all groups attained an estimated HbA1c < 6.5 % (48 mmol/mol) during pregnancy, with no differences between groups in the 3rd trimester. Women with poor glycemic control in early pregnancy had lower odds of having an infant with large-for-gestational-age (LGA) birthweight (adjusted odds ratio (aOR) 0.57, 95% CI 0.40–0.83), and higher odds of having an infant with small-for-gestational-age (SGA) birthweight (aOR 2.49, 95% CI 2.00–3.10) and congenital malformation (CM) (aOR 4.60 95% CI 3.39–6.26) compared to women with good glycemic control. There was no evidence of a difference in odds of preeclampsia, preterm birth and caesarean section between groups.

Conclusions: Women with poor glycemic control in early pregnancy have lower odds of having an infant with LGA birthweight, but higher odds of having an infant with SGA birthweight and CM.