Morning sickness can start quite early in pregnancy, typically between 4 and 9 weeks of pregnancy. According to information from multiple sources, it most commonly begins around week 5 or 6 but can start as early as 8 to 10 days after ovulation (which is shortly after conception). For most women, it peaks between weeks 8 and 10 and usually improves or ends by the 14th to 16th week of pregnancy, although some women may experience it longer or even throughout pregnancy. The symptoms can happen at any time of day, not just in the morning, despite the name "morning sickness".
