Risk factors for undescended testis.

The hypothesis that undescended testis is caused by an excess of maternal oestrogen in pregnancy has been tested indirectly in a case-control study comparing mothers of boys with undescended testis (83) and mothers of normal boys (129) born on the same day. The study concentrated on the gestation of the boys, but also investigated the mother's previous obstetric history and postnatal events in the boys. The hypothesis predicted that there should be an excess of nausea, vomiting and hypertension in mothers of cases, but in fact the pregnancies of the case and control mothers were similar in all respects except one. The exception was the increased liability of the mothers of cases to threatened abortion. Mothers of cases also had an increased tendency to miscarry in previous conceptions, a reduced number of deliberate terminations and evidence of decreased fertility. An alternative hypothesis is suggested which would explain these findings. This is that placental function is impaired in the gestation of affected boys and the secretion of human chorionic gonadotrophin is reduced. This leads to changes in fetal testicular function and possible maldescent. Those born with undescended testis were more likely to present to a general practitioner with illness in the first three years after birth and this difference was mainly due to asthma, eczema, jaundice and feeding difficulties.