Can a woman know she is pregnant a week after sex?

A woman may not typically know she is pregnant just a week after sex, as it usually takes time for a fertilized egg to implant in the uterus and for pregnancy hormones to build up to detectable levels. Most home pregnancy tests can reliably detect pregnancy about one to two weeks after a missed period, which is usually around two to three weeks after conception. Some early signs, like missed periods or symptoms such as nausea, might occur, but they vary widely among individuals.