BACKGROUND: Gestational weight gain (GWG) is associated with a range of health outcomes, but little is known about the factors that influence it.

OBJECTIVE: The objective was to test the hypothesis that maternal and fetal genetic variants that are reliably associated with adiposity are associated with GWG.

DESIGN: We examined the association of a risk allele score by using 4 adiposity-related single nucleotide polymorphisms (SNPs; rs9939609 in FTO, rs17782313 near MC4R, rs6548238 near TMEM18, and rs10938397 near GNPDA2) with GWG in a pregnancy cohort in which women had detailed repeated assessment of GWG (median number of weight measurements: 10; interquartile range: 8, 11). The numbers included in our analyses varied between 2324 and 7563 for different variant-outcome analyses. A linear spline random-effects model was used to model weight change with gestational age and to relate genetic variants to this. This modeling confirmed 3 distinct periods of GWG: 0-18, 19-28, and ≥29 wk of gestation.

RESULTS: Maternal risk allele score and SNPs in FTO, MC4R, and TMEM18 were positively associated with prepregnancy weight. Maternal allele score was inversely associated with GWG in the first 18 wk of pregnancy (-14.46 g/wk per allele; 95% CI: -24.75, -4.17 g/wk per allele) but was not associated with other periods of GWG. Offspring allele score and maternal and offspring individual SNPs were not associated with GWG in any period or with birth weight or postnatal weight retention.

CONCLUSIONS: Our findings suggest that neither maternal nor fetal adiposity-related genetic variants are associated with greater GWG. The inverse association of maternal allele score with GWG in the first 18 wk requires replication.