ABO blood-groups and the risk of gestational trophoblastic disease

The relation between ABO blood group, mating patterns of patient/husband blood group, and the risk of gestational trophoblastic disease was investigated in a case-control study conducted in Milan on 286 women with histologically confirmed trophoblastic disease (245 benign hydatidiform moles and 41 persistent trophoblastic disease) and 433 control subjects admitted for normal delivery to the same hospitals where cases had been identified. ABO blood groups were associated with the risk of gestational trophoblastic disease (chi 2(6) for heterogeneity = 14.46, p = 0.02). Compared to women of group O or B, women of group A and AB had an elevated relative risk (RR) of benign mole (RR = 1.4 and 2.3, respectively). The risk estimates were higher for persistent trophoblastic disease, i.e., 2.2 for women of group A and 4.8 of group AB. The tests for linear trend in risk from benign to persistent disease were statistically significant in both A and AB groups. There was a significant interaction between blood group and age, since the ABO-related risk was elevated only for women over the age of 35. When mating combinations of maternal/paternal blood groups were considered, women of group A married to males of group O had a risk estimate not substantially different than those married to group A males.