The aetiology of polycystic ovary syndrome (PCOS) is poorly understood, but an intrauterine hyperandrogenic environment has been implicated. This study was designed to assess whether the female offspring of mothers with PCOS are exposed to raised levels of testosterone (T) in utero. In this case–control study, three groups of pregnant women were recruited from the labour ward: PCOS women with a female baby (n = 10, PCOS girls); control women with a female baby (n = 20, control girls) and control women with a male baby (n = 10, control boys). Maternal and umbilical vein (UV) blood was assayed for T levels. UV T in PCOS girls was significantly raised, compared with control girls (p < 0.012). The difference in UV T between PCOS girls and control boys was not significant (p < 0.254). This is the first demonstration of a hyperandrogenic in utero environment in PCOS pregnancies; UV T in female infants is raised to male levels.