On Getting Pregnant

Abstract For a woman to conceive, she must have intercourse close to the time of ovulation—but how close? The number of days in each cycle on which intercourse can produce pregnancy depends on how long the sperm survive in the female reproductive tract and on how long the egg is available for fertilization. As it happens, this basic reproductive information has come not from physiology or clinical studies but from epidemiology. Women’s fertile days are the five days before ovulation and the day of ovulation itself. The highest chance of conceiving a clinical pregnancy occurs on the two days before ovulation. In the absence of information on ovulation, almost any day of the menstrual cycle could be fertile, given the variability in ovulation day.