Search for maternal factors associated with malformed human embryos: a prospective study

Using data from 3,474 human embryos derived form induced abortion, various maternal factors ascertained prior to morphologic examination of the specimens were analyzed in association with the frequency of malformed embryos. The overall frequency of malformed embryos was 3.3%; polydactyly, holoprosencephaly, exencephaly with or without myeloschisis, and cleft lip accounted for 88% of the total malformations. Mothers of low parity showed an increased frequency of malformed embryos. There were nine embryos form mothers with thyroid disorders, of which one was affected with exencephaly and myeloschisis and another with holoprosencephaly and polydactyly; this finding may support the relation of maternal hyperthyroidism with anencephaly suggested by previoius case reports. The frequency of malformed embryos from mothers who drank alcohol was significantly lower than from those who did not. Several possibilities were suggested to interpret this unexpected finding. No association was verified with maternal age, irregular menstrual cycles, irradiation, contraceptive methods, maternal occupation, and a smoking habit, or with parental consanguinity. The limitation of this study is discussed in relation to both negative and positive results.