Sir.—In a study on the possible role of genetic polymorphisms in the etiology of unexplained habitual abortion, we have observed a significant relation between the gestational duration of aborted fetuses and both maternal phosphoglucomutase locus 1 (PGM1) and Ss genotypes.1 Aborted fetuses from mothers with the PGM1 2-1 genotype and those from mothers with the SS genotype showed a longer gestational duration as compared with fetuses from mothers with other PGM1 and Ss genotypes, respectively. Genotype distributions of these two polymorphisms in couples with habitual abortion were also statistically different from distributions in a control population. These observations prompted us to search for possible effects of maternal PGM1 and Ss genotypes on the gestational duration in normal pregnancies.
A consecutive series of 142 women who were delivered of a single liveborn infant was studied. Through the use of standard techniques, the MNSs genotype was determined