Fecundability and the Frequency of Marital Intercourse: New Models Incorporating the Ageing of Gametes

This paper a companion to one published in the Journals previous issue examines the processes that affect fecundability when intercoital intervals vary between 66 and 24 hours. A new model incorporates the following assumptions that influence fertilization and impregnation rates: 1) womans aging 2) mans aging 3) ovums aging 4) spermatozoas aging 5) post-ovulatory aging of the ovum in the oviduct and 6) spermatozoa aging in the female genital tract. Using new deductive models the authors examine the last 2 categories of gamete aging. Several models yield very different fecundability predictions based on 1) the cycle being favorable 2) the 2nd of 2 matching inseminations antedating the fertile period taking full precedence over the other and 3) constant coital intervals. After examining 7 models the authors are unable to comment on fecundability at higher coital frequencies. Larger samples based on coital and basal body temperature charts must determine whether fecundability declines when coital frequency increases from high to very high levels.