Maternal Weight after Childbirth versus Aging-Related Weight Changes

Pregnancy weight gain is believed to contribute to female overweight and obesity. However, most studies do not account for the changes in body weight expected to occur as women age. We examined the long-term weight trajectory of childbearing women relative to weight progression that could be expected in the absence of pregnancy.

From the hospital records of 32,187 women with two births in Wisconsin during 2006 to 2013, we extracted the maternal weight at pregravid, delivery, and subsequent pregravid. We predicted the corresponding aging-progressed weights using a weight-for-age equation adjusted for sociodemographic variables. Nonparametric mixed effects models estimated the average maternal weight trajectory and the corresponding aging-related progression through 5 years after birth.

The estimated aging-related progression predicted a gradual annual weight increase of 1.94 pounds (95% confidence interval 1.90-1.98), from 152.79 pounds at pregravid to 163.76 pounds by 5 years after birth. Actual maternal weight followed a sinusoidal pattern: increasing during gestation, decreasing during the first postbirth year, converging with the aging-related progression during the second postbirth year, and then increasing at 2.89 pounds (95% confidence interval 2.23-3.55) annually and diverging upward from the aging-related progression to 168.03 pounds by 5 years after birth.

Pregnancy weight gain did not contribute to the aging-related trend, but lifestyle changes of parenthood may later exacerbate the long-term trend.