High birth weight and obesity--a vicious circle across generations.

OBJECTIVES: Rates of high birth weight infants, overweight and obese children and adults are increasing. The associations between birth weight and adult weight may have consequences for the obesity epidemic across generations. We examined the association between mothers' birth weight for gestational age and adult body mass index (BMI) and these factors' joint effect on risk of having a large-for-gestational-age (LGA) offspring (>+2 s.d. above the mean).

DESIGN: A cohort of 162 676 mothers and their first-born offspring with birth information recorded on mothers and offspring in the nation-wide Swedish Medical Birth Register 1973-2006.

RESULTS: Compared with mothers with appropriate birth weight for gestational age (AGA; -1 to +1 s.d.), mothers born LGA had increased risks of overweight (BMI 25.0-29.9; odds ratio (OR), 1.50; 95% CI 1.39-1.61), obesity class I (BMI 30.0-34.9; OR 1.77; 95% CI 1.59-1.98), obesity class II (BMI 35.0-39.9; OR 2.77; 95% CI 2.37-3.24) and obesity class III (BMI ≥40.0; OR 2.04; 95% CI 1.49-2.80). In each stratum of mother's birth weight for gestational age, risk of having an LGA offspring increased with mother's BMI. The risk of an LGA offspring was highest among women with a high (≥30) BMI who also had a high birth weight for gestational age (>+1 s.d.). In these groups, the ORs for LGA offspring ranged from 5 to 14 when compared with mothers born AGA with normal BMI (≤24.9). However, the strongest increase in risk by BMI was seen among mothers born SGA: the OR of having an LGA offspring was 13 times as high among SGA mothers with BMI ≥35.0 compared with the OR among SGA mothers with normal BMI (ORs=4.61 and 0.35, respectively).

CONCLUSIONS: Prenatal conditions are important for the obesity epidemic. Prevention of LGA births may contribute to curtail the intergenerational vicious cycle of obesity.