LAUSR

Objective Animal studies and epidemiological studies have shown that there is potential sex-specific sensitivity to the intrauterine environment in relation to the developmental programming of obesity. The objective of this study was to assess the sex-specific association between prenatal antibiotics exposure and body mass index (BMI) in offspring from 1 to 4 years. Methods A total of 10,163 mother–child pairs from the Medical Birth Registry in Xiamen, China, were included in this prospective cohort study. Data on prenatal antibiotics exposure were collected from the prescription database. Results A total of 4909 (48.3%) offspring had prenatal antibiotics exposure. The associations between prenatal antibiotics exposure and offspring’s BMI were significantly different among female offspring and male offspring ( P for interaction: 0.034 at 1 year of age; 0.033 at 2 years of age; 0.020 at 3 years of age; and 0.021 at 4 years of age). In female offspring, prenatal antibiotic use was significantly associated with a higher BMI Z -score from 1 to 4 years old (difference in BMI Z -score: 0.11 [95% CI: 0.05–0.17] at 1 years of age; 0.10 [95% CI: 0.05–0.16] at 2 years of age; 0.14 [95% CI: 0.09–0.21] at 3 years of age; and 0.13 [95% CI: 0.07–0.19] at 4 years of age) after adjustment for confounder. Prenatal antibiotics use was not associated with offspring BMI Z -score from 1 to 4 years in male offspring. Conclusions The association of prenatal antibiotics exposure and BMI Z -score from 1 to 4 years old may differ by sex of offspring.