Body Mass Index, Overweight, and Obesity in Swedish Women Born Post‐term

Abstract Background There is increasing evidence that post‐term birth (≥42 weeks of gestation) is associated with adverse long‐term outcomes. We assessed whether women born post‐term displayed increased risk of overweight and obesity in adulthood. Methods Data were collected at first antenatal visit (~10–12 weeks of gestation) on singleton Swedish women aged ≥18 years in 1991–2009 (mean age 26.1 years), who were born post‐term ( n = 27 153) or at term (37–41 weeks of gestation; n = 184 245). Study outcomes were evaluated for continuous associations with gestational age. Stratified analyses were carried out comparing women born post‐term or at term. Analyses were also run with a 2‐week buffer between groups to account for possible errors in gestational age estimation, comparing women born very post‐term (≥43 weeks of gestation; n = 5761) to those born within a narrower term window (38–40 weeks of gestation; n = 130 110). Results Increasing gestational age was associated with greater adult weight and body mass index ( BMI ). Stratified analyses showed that women born post‐term were 0.5 kg heavier and had BMI 0.2 kg/m 2 greater than those born at term. Differences were more marked between women born very post‐term (≥43 weeks) vs. a narrower term group (38–40 weeks): 1.0 kg and 0.3 kg/m 2 . The adjusted relative risks of overweight/obesity and obesity in women born very post‐term were 1.13 and 1.12 times higher, respectively, than in those born at term. Conclusions Post‐term birth is associated with greater BMI and increased risk of overweight and obesity in adulthood, particularly among women born ≥43 weeks of gestation.