OBJECTIVE The associations of prenatal exposures to maternal prepregnancy overweight and gestational diabetes mellitus (GDM) with offspring overweight are controversial. Research estimating risk for offspring overweight due to these exposures, separately and concomitantly, is limited.

RESEARCH DESIGN AND METHODS Prevalence of overweight and abdominal obesity at age 16 years and odds ratios (ORs) for prenatal exposures to maternal prepregnancy overweight and GDM were estimated in participants of the prospective longitudinal Northern Finland Birth Cohort of 1986 (N = 4,168).

RESULTS The prevalence and estimates of risk for overweight and abdominal obesity were highest in those exposed to both maternal prepregnancy overweight and GDM (overweight prevalence 40% [OR 4.05], abdominal obesity prevalence 25.7% [3.82]). Even in offspring of mothers with a normal oral glucose tolerance test during pregnancy, maternal prepregnancy overweight is associated with increased risk for these outcomes (overweight prevalence 27.9% [2.56], abdominal obesity prevalence 19.5% [2.60]). In offspring of women with prepregnancy normal weight, the prevalence or risks of the outcomes were not increased by prenatal exposure to GDM. These estimates of risk were adjusted for parental prepregnancy smoking, paternal overweight, and offspring sex and size at birth.

CONCLUSIONS Maternal prepregnancy overweight is an independent risk factor for offspring overweight and abdominal obesity at age 16 years. The risks are highest in offspring with concomitant prenatal exposure to maternal prepregnancy overweight and GDM, whereas the risks associated with GDM are only small.