Risk of partial and complete hydatidiform molar pregnancy in relation to maternal age.

All cases of first histologically confirmed complete and partial moles registered between 1985 and 1999 were identified from the database of a Trophoblastic Disease Registration Centre. The maternal age distribution at diagnosis was calculated for the 7916 molar pregnancies and compared with the maternal age distribution of an unselected population of women from a routine obstetric database. Likelihood ratios were calculated for complete and partial molar pregnancies by maternal age. A positive relationship was found between the risk of molar pregnancy and both upper and lower extremes of maternal age (> or = 45 years and < or = 15 years, respectively). This association, although present for both complete and partial moles, is much greater for complete mole at all maternal ages, and the degree of risk is much greater with older (> or = 45 years) rather than younger (< or = 15 years) maternal age. This study provides, for the first time, data regarding specific risk of partial versus complete hydatidiform mole with maternal age.