Menstruation comes before a week can you be pregnant together

Take menstrual cycle 28 days as an example, about 14 days before menstruation is ovulation day, ovulation day 5 days after 4 days belong to ovulation period, because most of the previous week has passed ovulation period, the probability of pregnancy in the same room is relatively small, but if ovulation is delayed or menstrual cycle is not allowed, it is still possible to be pregnant in the same room one week before menstruation.