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.