Spontaneous abortion and aging of human ova and spermatozoa

To test the hypothesis that aging of human gametes within the genital tract increases the chance of abortion, we measured the probabilities of abortion after insemination on a given day of the menstrual cycle in relation to the day of the shift in the basal body temperature in 965 patients. Cases came from family-planning and sterility clinics where basal body temperature and coital records are kept routinely. The probability of abortion diminished significantly (P less than 0.001) as the shift in temperature was approached and the increased to its highest point (24 per cent) three days later. Animal experiments have shown that aging of both spermatozoa and ova before fertilization is accompanied by higher probabilities of abortion. Present evidence indicates that this higher prevalence is also true for human beings.