Social inequality in pre-pregnancy BMI and gestational weight gain in the first and second pregnancy among women in Sweden

Background High pre-pregnancy body mass index (BMI) and inappropriate gestational weight gain (GWG) are associated with adverse short and long-term maternal and neonatal outcomes and may act as modifiable risk factors on the path to overweight/obesity, but their social patterning is not well established. This study investigates the association of education with BMI and GWG across two consecutive pregnancies. Methods The study includes 163 352 Swedish women, having their first and second singleton birth in 1982-2010. In both pregnancies, we investigated the association of women's education with (1) pre-pregnancy weight status and (2) adequacy of GWG. We used multinomial logistic regression, adjusting for child's birth year, mother's age and smoking status. Results Overall, the odds of starting either pregnancy at an unhealthy BMI were higher among women with a low education compared to more highly-educated women. Lower education also predicted a greater increase in BMI between pregnancies, with this effect greatest among women with excessive GWG in the first pregnancy (p<0.0001 for interaction). Education was also inversely associated with odds of excessive GWG in both pregnancies among healthy weight status women, but this association was absent or even weakly reversed among overweight and obese women. Conclusions Lower educated women had the largest BMI increase between pregnancies, and these inequalities were greatest among women with excessive GWG in the first pregnancy. The importance of a healthy pre-pregnancy BMI, appropriate GWG and a healthy postpartum weight should be communicated to all women, which may assist in reducing existing social inequalities in body weight.