Preterm delivery and maternal obesity remain common complications in pregnancies with type 1 diabetes-A nationwide study in Sweden

AimA primary goal of obstetric care of women with type 1 diabetes (T1D) is to reduce the risks of preterm birth (PTB). Besides hyperglycaemia, maternal obesity is an important risk factor for PTB in T1D. However, it's unclear if public health efforts decreased risks of maternal obesity and PTB in pregnancies with T1D. We examined time-trends over the last 20 years in the distribution of gestational ages at birth (GA) in offspring of women with T1D in Sweden, and in maternal BMI in the same mothers.MethodsPopulation-based cohort study, using data from national registries in Sweden. To capture differences not only in the median values, we used quantile regression models to compare the whole distributions of GA's and early pregnancy BMI between deliveries in 1998-2007 (P1) and 2008-2016 (P2). Multivariable models were adjusted for differences in maternal age, smoking and education between periods 1 and 2.ResultsThe study included 7639 offspring of women with T1D between 1998 and 2016. The 10% percentile GA, increased with 0.09 days (95% CI: -0.11 to 0.35) between P1 and P2. The 90% percentile for BMI was 1.20 kg/m2 higher (95% CI: 0.57 to 1.83) in P2. Risks of PTB remained stable over time also when adjusting for maternal BMI.ConclusionDespite modern diabetes management, the distribution of GA, and consequently the risk of PTB in T1D, remained unchanged from 1998 to 2016. During the same time, maternal BMI increased, particularly in the already obese.