Many studies have been published over the years in an attempt to understand the factors that influence fertility and the process of conception.
The "Fertile Window" has been defined as the days of the menstrual cycle during which intercourse is most likely to result in pregnancy. This fertile window extends runs for 6 days starting at 5 days before ovulation until the day of ovulation. Your most fertile days are the 4-5 days before and the day of ovulation.
Making love the day after established ovulation is unlikely to improve your chances getting pregnant.
Increasing amounts of estrogen in the cervical mucus and reproductive tract of a women approaching ovulation generally allows the sperm to live for up to 6 days.
Studies have shown that even in women with regular cycles, ovulation can possibly happen any time, so "timing" of intercourse has never been shown to improve your pregnancy chances. You are probably not improving your chances of getting pregnant if you wait with intercourse until the temperature goes up or the OPK has become positive. You may already have ovulated by that time, and sex after ovulation is unlikely to get you pregnant.
Couples who tried to get pregnant were previously told to have sex once every other day during their fertile days. Recent studies have shown that the average couple who is trying to conceive should make love regularly 2-3 times a week, every week because you don't know exactly when ovulation happens.
In addition, you may improve your chances if you have sex once a day (as long as his sperm are OK) during the fertile 4-5 days prior to, and the day of, ovulation. In those rare circumstances when the man does not have enough sperm (oligospermia), the old rule of once every other day still holds true. For a more extensive explanation please read Here Sex during fertile days: % Pregnancy (% Live Birth) Sex every day: 37% Pregnancy Sex every other day: 33% Pregnancy Sex once a week: 15% Pregnancy From: "Timing of Sexual Intercourse in Relation to Ovulation -- Effects on the Probability of Conception, Survival of the Pregnancy, and Sex of the Baby" was published in The New England Journal of Medicine (December 7, 1995 -- Vol. 333, No. 23). Allen J. Wilcox, Clarice R. Weinberg, Donna D. Bair