levels, providing some support to the estrogen hypothesis; however, higher GWG was associated with lower levels of maternal progesterone and of sex hormone-binding globulin (−0.7 percent [95% CI: −1.5, 0.0] at 16 weeks and −1.2 percent [95% CI: −2.0, −0.4] at 27 weeks, respectively, for every 1-kg increment in GWG.
In addition, one study directly addressed the association of GWG with incident breast cancer. Analyzing data from the Finnish Cancer Registry, Kinnunen et al. (2004) found that offspring of mothers in the upper tertile of GWG (> 15 kg) had a 1.62-fold higher breast cancer risk than mothers who gained within the recommended range (11-15 kg) after adjusting for parity; mother’s age at menarche, at first birth, and at index pregnancy; and prepregnancy BMI. Together these findings provide some support for the hypothesis that excessive weight gain in pregnancy could lead to elevated breast cancer risk in the offspring.
Attention deficit hyperactivity disorder Because the human brain develops rapidly during both gestation and the early postnatal period, it is possible that maternal body fat reserves and GWG can influence fetal central nervous pathways in a manner that ultimately results in long-term behavioral disorders such as attention deficit hyperactivity disorder (ADHD). Only one study was able to identify associations between either early pregnancy BMI or GWG and ADHD (Rodriguez et al., 2008). Within three cohorts of 7- to 12-year-old Scandinavian children, teachers used standard questionnaires to rate the children’s inattention and hyperactivity symptoms; about 8.5 percent of children were classified as having ADHD symptoms. A large majority of the mothers (86.4 percent) had a normal prepregnancy BMI and adequate GWG (mean gestational age = 39.6 ± 1.6 weeks, mean birth weight = 3.6 ± 0.5 kg). Multivariate linear regression analyses showed that among women with a high prepregnancy BMI, GWG (measured weekly and in 100-g increments) was associated with increased odds of child ADHD (OR = 1.24, 95% CI: 1.07-1.44). Among lean women, those who experienced weight loss during pregnancy also had higher odds of having a child that would later develop ADHD compared to their counterparts who did not lose weight during gestation (OR: 1.52, 95% CI: 1.07-2.15). The mechanisms for these effects are unknown, although the authors speculated on the possibility of neurotoxin transfer from maternal adipose tissue to the developing fetal brain.
Assessing the impact of GWG on child outcomes requires both a short-and long-term outlook. Strong observational evidence links GWG directly with fetal growth, so that higher weight gain predicts LGA and lower