Published online by Cambridge University Press: 31 July 2008
The laws observed among Orthodox Jews regulating coital activity according to menstrual cycle phase (the laws of Taharat HaMishpacha), in a population that generally does not use contraception, have potentially important effects on fertility. Analysis of these effects based on menstrual cycle and ovulatory phase lengths for women in the childbearing years shows that the majority of cycles are potentially exposed to coital activity during a fertile period and the increased likelihood of coitus following abstinence has potentially fertility-enhancing effects. For the individual woman with a predominance of short cycles, delays in conception are probable.