Does recurrent gestational diabetes mellitus increase the risk of preterm birth? A population-based cohort study

To investigate whether recurrent gestational diabetes mellitus (GDM) is associated with an increased risk of preterm birth.

We conducted a prospective population-based cohort study covering all live singleton births born to nulliparous and multiparous mothers aged 20 years and older in Qingdao, from 2018 to 2020 (n = 105,528). Preterm birth (<37 gestational weeks) was classified into moderate preterm birth (32-36 weeks of gestation) and very preterm birth (<32 weeks). Logistic regression analysis was performed to estimate the risk and severity of prematurity in relation to parity among mothers with previous GDM, current GDM, and recurrent GDM (previous and current GDM), using mothers without GDM as the reference group. Z-test and ratio of odds ratios (ROR) were used to determine subgroup differences.

Maternal GDM increased the risk of preterm birth in both nullipara (OR_adj = 1.28, 95 %CI: 1.14-1.45) and multipara (OR_adj = 1.26, 95 %CI: 1.14-1.40). However, the risk of premature delivery in multiparous mothers with recurrent GDM and those with current GDM did not differ significantly, with a ROR of 0.89 (95 %CI: 0.71-1.12). The risk of recurrent GDM on preterm birth was most pronounced among multiparous mothers with pre-pregnancy BMI above 30 kg/m² (OR_adj = 2.18, 95 %CI: 1.25-3.82) as compared with those with current GDM alone (ROR = 2.20, 95 %CI: 1.07-4.52). The risk of GDM for moderate preterm birth was similar to that of overall preterm birth. In contrast, GDM was not associated with very preterm birth irrespective of parity (all P values > 0.05).

Maternal GDM increased the risk of preterm birth in nullipara and multipara, whereas recurrent GDM was not associated with a further increase in the risk of prematurity in multiparous mothers. Maternal GDM did not contribute to very preterm birth irrespective of parity. Our findings can be useful for facilitating more targeted preventive strategies for adverse pregnancy outcomes.