Hi If you have had sex on the ovulation day, then pregnancy test can be done on the 7th day after sex. The logic is implantation of baby into uterus occurs on the 6th-7th day after ovulation. With implantation, pregnancy hormone is secreted and it can be detected by tests. This is the earliest time to do pregnancy test. urine test may not detect it. You need to do blood pregnancy test. So only when you have sex at the time /just after ovulation pregnancy test can be done after 6-7 days. What you have heard is right. The first week and the last week of a menstrual cycle are safe. A woman cannot get pregnant if she has unprotected sex during this period. I hope I have answered your concerns.