Cancer in mothers of dizygotic twins.

For the determination of whether mothers of dizygous (DZ) male-female twins or other polyzygous (unlike sexed) multiple births have cancer incidence different from that of controls, a cohort study was conducted with the use of the records of the Connecticut Twin Registry and the Connecticut Tumor Registry (CTR). A total of 3,982 women born between 1885 and 1935 who had borne DZ (male-female) twins or who had experienced other polyzygous multiple births in Connecticut during 1925-59 and a control group of 3,982 women, matched pairwise on year of childbirth, age, number of previous children, race, and national origin, were searched in the CTR for the incidence of cancer of all sites. Women who have DZ twins have a higher level of gonadotropins than women in the general population. A hypothesis that mothers of DZ twins may have a higher incidence of breast cancers than other women was investigated; the results did not support the hypothesis. There was, however, an excess incidence of cancer of the pancreas among mothers of twins. The relative risk was 3.2 (P = 0.026, exact two-tail probability) with exact 95% confidence limits (1.12, 11.16). These results are consistent with findings from autopsy data which suggested that among women but not among men with pancreatic duct cell carcinoma, there is excessive gonadotropic activity. These results are also consistent with early findings of high follicle-stimulating hormone (FSH) in the urine of diabetics and high FSH in the urine of postmenopausal women.