[MNSs system mother-newborn segregation distortions]

We present segregation distortions for the MNSs system and for the sex ratio found among 400 mother-newborn pairs, from the northern Area of Santiago and the middle-low and low socioeconomic strata. Three subsamples were taken: from the non private patients of the Clinical Hospital of the University of Chile; from the Hospital San José, a public hospital of this Area; controls of malformed newborns belonging to an international study from the Clinical Hospital of the University of Chile. In spite of the almost homogeneity of socioeconomic strata and area, the differences among these subsamples did not allow us to take them as only one sample. We found excess of heterozygous individuals for the MN locus, specially among mothers. Ss heterozygotes had a higher sex ratio than ss homozygotes. Several distortions could not be dealt with as having a regular pattern in the three subsamples. A possible technical error is discussed.