On the contrary, the high hormone level immediately after childbirth prevents ovulation and so pregnancy is virtually unknown if intercourse is within 21 days of delivery. If the baby is totally breastfed and the woman remains amenorrhoeic (isn’t having periods), then the contraceptive effect continues for at least six months. If the baby is totally bottle-fed, the hormone levels return to normal more quickly and ovulation usually occurs from about a month after delivery so that the first period would occur from about six weeks.