If menstruation is regular, ovulation is calculated as the 14th day before the next menstrual period, 5 days before and 4 days after, plus the day of ovulation, a total of 10 days, the entire period of ovulation, the chances of conception can reach 60% -70%; clear monitoring of ovulation, in the 24 hours before and after ovulation coitus, the chances of pregnancy can reach 80%; ovulation on the fourth day of ovulation, basically close to the day of ovulation, the chances of pregnancy with coitus is very high, it should be able to reach 70%; if you want to increase the chances of conception, you can coitus every other day during the period of ovulation, so that there is always a viable spermatozoa inside the vagina, the chances of pregnancy will be even higher.