Background Pregnancy is frequently associated with postdelivery weight retention in women. Most studies suggest weight retention associated with pregnancy of between 0.5 to 3.8 kg with up to 2.5 years of follow-up. However, 73% of the female patients at our obesity clinic report that their pregnancies have been important trigger factors for marked weight gain and that they had gained more than 10 kg after each pregnancy. The aim of this study was to examine correlations in weight gain and weight retention after pregnancy in the long-term perspective.
Method and subjects. The SPAWN (Stockholm Pregnancy and Women's Nutrition) study is a long-term follow-up study of women who delivered children in 1984–85 in Stockholm (n = 2342). The participants filled out questionnaires about their eating and exercise habits, social condition, etc. before, during and up to 1 year after pregnancy. Antropometric data were also sampled. One thousand four hundred and twenty-three women completed the study and filled out all questionnaires up to 1 year after pregnancy. Fifteen years later, these 1423 women were invited to the follow-up study. Five hundred and sixty-three women participated and filled out extended questionnaires, and antropometric data were also sampled. Data from the Swedish Medical Birth Register (MBR) about weight before and weight gain during pregnancy were collected. The sample was divided into groups regarding four critical time periods: (1) Time interval between first and second pregnancy, less and more than 2 years. (2) Overweight and normal weights before first pregnancy based on initial body mass index (BMI). (3) Low and high weight gainers during pregnancy by mean split. (4) Low and high weight retainers at 1 year after first pregnancy by mean split.
Results. 1) There were no differences between those women who have more than 2 years between their pregnancies regarding weight gain during and weight retention after the first and second pregnancy. (2) Overweight women did not gain more weight during pregnancy or retain more weight at 1 year of follow-up after the first and second pregnancy. (3) High weight gainers retained more weight at 1 year after both the first and second pregnancy. (4) High weight retainers had gained more during pregnancy and retained it into the second pregnancy, and also gained more during and retained more after the second pregnancy.
Discussion. To our knowledge, the SPAWN study is the longest follow-up study of factors affecting weight development after pregnancy. Women overweight before pregnancy did not have any higher risks of postpartum weight retention than normal weight women. Weight gain during pregnancy and weight retention up to 1 year after delivery is of predictive value for the weight development in the second pregnancy. Obviously the environmental variation is an important determinant of the differences in weight increase, which follow a pregnancy. Pregnancies time interval does not seem to be of any importance. There are practical implications of these findings: Women who plan their later pregnancy several years after the first pregnancy have no reason to assume that the weight development during subsequent pregnancies will be worse than before. On the other hand, women who have increased considerably in weight during the first pregnancy or retained weight after delivery have a higher risk of doing so in the subsequent pregnancies and should receive appropriate advise and support.