Background: Weight gain is common after pregnancy. Most studies suggest that weight gain associated with a pregnancy is between 0.5 and 3.8 kg up to 2.5 y of follow-up. However, 73% of the female patients at our obesity clinic identified pregnancy as an important trigger for marked weight retention. The majority retained more than 10 kg after each pregnancy. The aim of this study was to examine long-term weight development after pregnancy in a 15 y follow-up of women who took part in the Stockholm Pregnancy And Women's Nutrition (SPAWN) study.
Method and subjects: The SPAWN study is a long-term follow-up study of women who delivered children in 1984-85 in Stockholm (n=2342). A total of 1423 participants (response rate=61%) completed questionnaires, which covered eating behaviour and exercise, demographic information including social situation and status and details of the pregnancy before, during and up to 1 y after pregnancy. After 15 y, these women were invited to take part in the follow-up study. Anthropometric measurements and the same questionnaire data were collected from the 563 women who participated (response rate=40%). The sample was divided into two main groups: those who were normal weight before pregnancy and remained normal weight, and those who were normal weight before pregnancy and had become overweight at 15 y follow-up.
Results: Those women who became overweight had a higher pre-pregnant body mass index (BMI) (22.3+/-1.5 vs 20.5+/-1.6 kg/m(2), P<0.001), gained more weight during pregnancy (16.3+/-4.3 vs 13.6+/-3.7 kg, P<0.001) and had retained more at 1 y follow-up. The women who became overweight had a steeper weight trajectory gaining more from 1 y follow-up to 15 y follow-up (11.1+/-6.5 vs 4.5+/-6.5 kg, P<0.001), with a higher BMI at 15 y follow-up of 27.5+/-2.6 vs 22.5+/-2.3 5 kg/m(2) (P<0.001). However, differences between those who became overweight and those who did not could not be explained by age, number of children and various socioeconomic factors. Features of pregnancy that did differ between the two groups were breastfeeding and smoking cessation. However, women who became overweight had lower lactation scores than women who remained normal weight. Relatively more subjects of the group that became overweight stopped smoking during pregnancy.
Discussion: Pregnancy is a vulnerability factor for some women to become overweight. This study attempted to identify those factors that place initially normal weight women on a steeper weight trajectory as a result of pregnancy. Demographic, behavioural, physical and psychological characteristics only partly explain the weight gain observed at 15 y follow-up. Further research is required to investigate the relative role of these characteristics in predicting postpregnancy weight development.