['Animal studies have indicated that maternal androgen levels influence the intrauterine environment and development of the offspring. Human data are missing. We therefore investigated the possible association between maternal androgens and offspring size at birth in humans.', 'A random sample of parous Caucasian women (n=147) was followed prospectively through pregnancy.', 'Maternal serum levels of dehydroepiandrosterone sulfate (DHEAS), androstenedione, testosterone and sex hormone-binding globulin (SHBG) were measured at gestational weeks 17 and 33. The main outcome measures were weight and length at birth. Associations between maternal androgen levels and offspring birth weight and length were investigated using multiple linear regression modeling adjusted for potential confounding by maternal height, pre-pregnancy body mass index, smoking, parity, offspring gender and gestational age at birth.', 'Elevated maternal testosterone levels at week 17 and 33 were both associated with lower birth weights and lengths. Accordingly, at week 17, an increase in maternal testosterone levels from the 25th to the 75th percentile was associated with a decrease in birth weight by 160 g (95% confidence interval (CI); 29-290 g), while at week 33 that estimate was 115 g (95% CI; 21-207 g). No similar associations were observed for DHEAS, androstenedione or SHBG.'] Are maternal testosterone levels during pregnancy associated with offspring size at birth?