Poor periconceptional glycaemic control magnifies pre-eclampsia risk in T1D

Women with type 1 diabetes (T1D) have an increased risk of developing pre-eclampsia during pregnancy, and this risk gets is commensurate with worsening blood sugar control around the time of conception, according to a study from Sweden.

The analysis included 1,689,301 singleton pregnancies, including 4,429 in women with a pre-gestational diagnosis of T1D (first diagnosis anytime ≤91 days after conception and at least one HbA1c measurement within ±90 days from conception). Periconceptional glycaemic control was categorized based on the most recent HbA1c measurement: <48, 48–61, 62–75, ≥76 mmol/mol. Data were obtained from the National Diabetes Register and other health registers.

Pre-eclampsia, the main study outcome, was categorized according to completed gestational weeks at delivery with pre-eclampsia diagnosis: early preterm pre-eclampsia (<34 + 0), late preterm pre-eclampsia (34 + 0 to 36 + 6), or term pre-eclampsia (≥ 37 + 0).

Pre-eclampsia occurred in 16.8 percent of women with T1DM vs 2.9 percent of women without any diabetes diagnosis (≤91 days after conception; unexposed group) (adjusted risk ratio [aRR], 4.7, 95 percent confidence interval [CI], 4.4–5.0). Of note, pre-eclampsia risk increased with peri-conceptional HbA1c, from 11.6 percent in the <48 mmol/mol category to 23.3 percent in the ≥76 mmol/mol category.

A dose–response relationship between HbA1c and pre-eclampsia was observed in the T1D group vs the unexposed group (HbA1c <48 mmol/mol: aRR, 3.4; HbA1c 48–61 mmol/mol: aRR, 4.6; HbA1c 62–75 mmol/mol: aRR, 5.7; HbA1c ≥76 mmol/mol: aRR, 6.3).

Compared with the unexposed group, the T1D group showed a more than threefold greater risk of term pre-eclampsia (aRR, 3.5, 95 percent CI, 3.1–3.9), more than sevenfold greater risk of early preterm pre-eclampsia (aRR, 7.2, 95 percent CI, 6.1–8.5), and approximately tenfold greater risk of late preterm pre-eclampsia (aRR, 9.9, 95 percent CI, 8.8–11.1).