Reported influenza in pregnancy and subsequent cancer in the child.

A longitudinal study of 1,959 infants born in the first week of March 1958 to mothers who were reported to have had influenza during pregnancy revealed an incidence of cancer of 4.1 per 1,000 compared with only 0.8 per 1,000 among the 14,791 infants of mothers who had not had influenza.This increase was caused by cases of leukaemia and other neoplasms of lymphatic and haematopoietic tissue (I.C.D. 200-209) (P <0.0001).Data from the reports of the Registrar General for England and Wales were used to estimate the number of infants born in each year from 1955 to 1964 who subsequently died of cancer before 5 years of age. The rates for each year were compared with an estimate of the prevalence of influenza during the preceding winter. After allowing for the overall trend in the cancer death rate, a highly significant correlation was shown with deaths attributed to causes classified as I.C.D. 200-209 (P <0.005), but not with deaths attributed to other cancers. The increase in the risk of developing these neoplasms among children whose mothers had influenza is estimated to be not less than fourfold. Even so the risk remains small (3 to 4 per 1,000).