How many days of delayed menstruation are needed to detect pregnancy?

Generally, for women with regular menstrual cycles, pregnancy can usually be detected by a home pregnancy test about 7 days after a missed period. For women with irregular menstrual cycles, it is recommended to wait 10-14 days after the missed period before testing, or to calculate based on the date of sexual intercourse, in order to improve the accuracy of the test. Detailed explanation is as follows:

If a woman has a regular menstrual cycle and ovulation time is relatively fixed, after conception, the level of human chorionic gonadotropin (hCG) in her body will gradually rise. When the menstrual period is delayed by 7 days, the concentration of hCG in the urine is typically sufficient for a pregnancy test to show a positive result, making the test highly accurate at this stage. However, if the test is performed too early, the hCG level may be too low, which could lead to a false negative result and thus misdiagnosis.

For women with irregular menstrual cycles, ovulation times can vary greatly, making it difficult to accurately determine the appropriate testing time based solely on the number of days the period is delayed. These women can perform a pregnancy test about two weeks after unprotected intercourse, or wait until their period is 10-14 days late before testing, by which time hCG levels are likely to have reached a detectable range.

In daily life, it is recommended to use first-morning urine when testing for pregnancy, as it contains a higher concentration of hCG, thereby providing a more accurate result. If the test result indicates pregnancy, further medical examination is advised for confirmation.