A woman gets pregnancy
when she had intercourse with her husband at the time when her egg rupture and sperms reaches the ovaries at the same time and fertilization
takes place. This time varies from person to person depending on your cycle, egg formation start from 7th or 8th day of periods, like if your periods start on 1st of any month, then gradually increase in size and rupture. It varies in every individual women. So roughly your fertile period
is from 8th day of periods till 20th day, it can be any day, so you need to have intercourse every alternate day during this time. So there will be maximum chances of conception.