Pre-natal and early life risk factors for diabetes, cryptorchism and inguinal hernia in children
Findings are presented from matched case-control studies of risk factors for diabetes, cryptorchidism and inguinal hernia in children using routine data collected by the Oxford Record Linkage Study since 1965. There were 315 cases born 1965-85 in the diabetes study, 947 and 1449 cases in studies of cryptorchidism diagnosed at birth and at orchidopexy respectively, and 1701 male and 347 female cases in the study of inguinal hernia. Each case was individually matched with up to eight controls on sex, year, and hospital or place of birth. A potential bias caused by differential migration of cases and controls was identified. A sample of 753 controls born in Oxfordshire was checked against the Oxfordshire Family Health Services Authority register to determine migration out of the study area in relation to perinatal risk factors. A general procedure was developed to estimate the strength of the migration bias. Pre-eclampsia was identified as a significant pre-natal risk factor for diabetes. The studies of cryptorchidism identified significantly raised risks with low birth weight, low social class and breech presentation. The results suggested that asymmetric growth retardation in the third trimester may be involved in the aetiology of undescended testes that do not spontaneously descend in later life. Analysis of risk factors among siblings of cases and controls suggested that permanent changes to the mother may occur around the time of the pregnancy involving the affected child. Low birth weight, short gestation and smoking during pregnancy were associated with significantly raised risks of inguinal hernia among boys. Among girls the results were similar, suggesting that mechanisms independent of the sex of the child may be important in the aetiology of this condition. Estimates of disease risk in siblings showed a strong familial aggregation, especially among girls.