Maternal healthy lifestyle during early pregnancy and offspring birthweight: differences by offspring sex

Purpose: Individual maternal lifestyle factors during pregnancy have been associated with offspring birthweight; however, associations of combined lifestyle factors with birthweight and potential differences by offspring sex have not been examined.

Materials and methods: Participants (N?=?2924) were identified from a pregnancy cohort in Washington state. Lifestyle factors during early pregnancy were dichotomized based on Alternate Healthy Eating Index score ≥62, leisure time physical activity (LTPA)?≥?150?min/week, not smoking during pregnancy and Perceived Stress Scale score ≤3, then combined into a lifestyle score (0–4). Regression models were run overall and stratified by offspring sex, prepregnancy overweight/obese (BMI ≥25?kg/m²) and prepregnancy LTPA.

Results: Overall, 20% of participants had healthy diet, 95% were nonsmokers, 55% had low stress levels, and 66% were physically active. Lifestyle score was not associated with birthweight (β?=?3.3?g; 95% CI: ?14.5, 21.0); however, associations differed by offspring sex (p?=?.009). For each unit increase in lifestyle score, there was a suggested 22.4?g higher birthweight (95% CI: ?2.7, 47.6) among males and 14.6?g lower birthweight (95% CI: ?39.9, 10.7) among females. Prepregnancy BMI and LTPA did not modify associations.

Conclusions: Healthy lifestyle score in early pregnancy may be associated with greater birthweight among male offspring, but lower birthweight among female offspring.