Maternal Obesity, Birth Size, and Risk of Childhood Cancer Development.

Infants and children are particularly vulnerable to in utero and early-life exposures. Thus, a mother's exposures before and during pregnancy could have important consequences for her child's health, including cancer development. We examined whether birth certificate-derived maternal anthropometric characteristics were associated with increased risk of subsequent childhood cancer development, accounting for established maternal and infant risk factors. Pennsylvania birth and cancer registry files were linked by the state Department of Health, yielding a virtual cohort of births and childhood cancers from 2003 through 2016. The analysis included 1,827,875 infants (13,785,309 person-years at risk), with 2,352 children diagnosed with any cancer and 747 with leukemia before age 14 years. Children born to mothers with a body mass index (weight (kg)/height (m)2) of ≥40 had a 57% (95% confidence interval: 12, 120) higher leukemia risk. Newborn size of ≥30% higher than expected was associated with 2.2-fold and 1.8-fold hazard ratios for total childhood cancer and leukemia, respectively, relative to those with expected size. Being <30% below expected size also increased the overall cancer risk (P for curvilinearity < 0.0001). Newborn size did not mediate the association between maternal obesity and childhood cancer. The results suggest a significant role of early-life exposure to maternal obesity- and fetal growth-related factors in childhood cancer development.