Nausea as a symptom of pregnancy typically starts about 8 to 10 days after ovulation, which closely aligns with the time of implantation. Research shows that nausea and vomiting during early pregnancy tend to begin within a narrow 3-day window after implantation occurs, highlighting a likely biological basis for this timing. Some sources suggest that nausea can occasionally be experienced as early as 6 to 12 days after ovulation or conception, but it most commonly appears around this 8 to 10-day mark after fertilization when implantation is successful. This means nausea often begins very soon after implantation, generally within a few days of the embryo attaching to the uterus lining and before the classic 4 to 6 weeks of pregnancy when morning sickness usually becomes noticeable. Hormonal changes, particularly rising levels of hCG and progesterone after implantation, are believed to trigger the onset of nausea.