Parity, lactation, and long-term weight change in Mexican women.

One post-partum behaviour that may be protective against post-partum weight retention and long-term weight gain among women of reproductive age is lactation because of its potential role in resetting maternal metabolism after pregnancy. However, most of the evidence focuses on weight retention at 6, 12, or 24 months post-partum, and data beyond 2 years after birth are sparse, and findings are inconclusive. Therefore, our aim was to assess the association of parity and mean duration of lactation per child with long-term weight change in Mexican women. We assessed the association of parity and mean duration of lactation per child with long-term weight change in 75,421 women from the Mexican Teachers' Cohort. Several multivariable regression models were fit to assess these associations. We also examined the non-linear association between duration of lactation and weight change using restricted cubic splines. We found that parous women (≥4 children) gained 2.81 kg more (95% CI [2.52, 3.10]) than did nulliparous women. The association between mean duration of lactation per child and weight change appeared to be non-linear. Women who breastfed on average 3-6 months per child had lower gain weight (-1.10, 95% CI [-1.58, -0.47 kg]) than had women who did not breastfeed. This association was linear up to 6 months of lactation per child. Our findings suggest that parity alters weight-gain trajectory in women and that lactation could reduce this alteration. These findings are important in the prevention of excessive weight gain through reproductive years and their future health implications.