Combined effect of education and reproductive history on weight trajectories of young Australian women: A longitudinal study

Objective: To investigate the combined effect of education and reproductive history on weight trajectory. Methods: The association of education with weight trajectory (1996–2012) in relation to reproductive history was analyzed among 9,336 women (born 1973–1978) from the Australian Longitudinal Study on Women's Health using random effects models. 

Results: Compared with women with a university degree/higher, lower-educated women were 2 kg heavier at baseline and gained an additional 0.24 kg/year. Giving birth was associated with an increase in weight which was more pronounced among women having their first birth <26 years of age (2.1 kg, 95% CI: 1.5–2.7), compared with 26 to 32 years or >32 years. While younger first-time mothers had a steeper weight trajectory (∼+0.16 kg/year, 95% CI: 0.1–0.3), this was less steep among lower-educated women. High-educated women with a second birth between 26 and 32 years had 0.9 kg decreased weight after this birth, while low-educated women gained 0.9 kg. 

Conclusions: While the effect of having children on weight in young adulthood was minimal, women having their first birth <26 years of age had increased risk of weight gain, particularly primiparous women. Educational differences in weight persisted after accounting for reproductive history, suggesting a need to explore alternative mechanisms through which social differences in weight are generated.