BACKGROUND: Fetal exposure to endocrine disrupting chemicals may increase the risk for adverse health effects at birth or later in life. OBJECTIVES: The objective of this study is to analyze the combined effect of xenoestrogens on reproductive and perinatal growth outcomes (child birthweight, early rapid growth and body mass index (BMI) at 14months) using the biomarker total effective xenoestrogen burden (TEXB). METHODS: 490 placentas were randomly collected in the Spanish prospective birth cohort Environment and Childhood (INMA) project. TEXB was used to assess the estrogenicity of placental samples in two fractions: that largely attributable to environmental organohalogenated xenoestrogens (TEXB-alpha), and that mostly due to endogenous estrogens (TEXB-beta), both expressed in estrogen equivalent units (Eeq) per gram of tissue. Linear or logistic regression models were performed adjusting for cohort and confounders. Sex interactions were investigated. RESULTS: The median TEXB-alpha level was 0.76pMEeq/g (interquartile range (iqr): 1.14). In multivariate models, higher TEXB-alpha levels (third tertile, >1.22pMEeq/g; iqr: 1.73) were associated with increased birthweight in boys but not in girls (β=148.2g, 95% CI: 14.01, 282.53, p(int)=0.057). Additionally, higher TEXB-alpha values in boys were related with a lower risk of early rapid growth (OR=0.37; 95% CI: 0.15, 0.88) and with a non significant association with larger BMI z-scores at 14months of age (β=0.29; 95% CI: -0.11, 0.69). CONCLUSIONS: These findings suggest that prenatal exposure to xenoestrogens may increase birthweight in boys, which might have an impact on child obesity and other later health outcomes.