Case control study of hypospadias, based on registry information.

With the aid of data in the Swedish Medical Birth Registry for infants with hypospadias and controls, a number of variables were compared. Records of infants born in 1982-1983 (188 cases and 376 matched controls) contained information on involuntary infertility, previous spontaneous and induced abortions, use of oral contraceptives or a remaining IUD at conception, smoking in early pregnancy, occupation in early pregnancy, family situation, and diagnoses given during pregnancy and at delivery, including information on caesarean section and vacuum extraction. Among all variables studied, only one group of statistically significant differences appeared: women whose sons had hypospadias more often than controls had a diagnosis of weak contractions, a higher rate of induced deliveries, and also a higher rate of caesarean sections. The finding of a higher caesarean section rate in infants with hypospadias was verified in a separate study of 1,736 hypospadic infants delivered in 1973-1981 and compared with all births in Sweden during that period. No difference in the rate of vacuum extractions was seen. This finding is interpreted as a result of an abnormality of the fetal-placental-maternal organism interaction, perhaps also disturbing the early pregnancy and increasing the risk for hypospadias.