Maternal BMI and weight gain in singleton pregnancies: has something changed in the last decade?

To assess the trend of the pregravid body mass index (BMI), pregnancy weight gain, and BMI gain in singleton pregnancies delivered at ≥38 completed weeks during the last decade. We used data from a population-based dataset for the period of 2006-2015. Linear regression was used to assess the relationship between BMI, pregnancy weight gain, and BMI change over time. A total of 70,866 women were included and stratified as primiparous and multiparous. The average BMI in the primiparous women increased 0.52 kg/m in the past decade, increasing for 0.05 kg/m every year. The average pregnancy weight gain in this group decreased in this period by 0.7 kg, consequently lowering for 0.07 kg per year, the average BMI change during pregnancy decreased overall by 0.26 kg/m (0.026 kg/m/year). However, in multiparous women, the average pregravid BMI did not change over time, but the average pregnancy weight gain decreased by 0.21 kg (0.021 kg/year), and the average BMI change decreased for 0.10 kg/m. Our study showed that the pregravid BMI is increasing in the pregnant primiparous women, but the BMI gain, as well as the pregnancy weight gain, decreased irrespective of parity. Given that the range of differences is not clinically significant, we conclude that pregravid BMI, pregnancy weight gain, and BMI change during pregnancy did not change in the last decade.