How many days after conception can a pregnancy be detected?

Typically, about 6 to 10 days after implantation of the fertilized egg—roughly 7 to 14 days after the first day of the expected menstrual period—pregnancy can be initially determined by detecting the presence of human chorionic gonadotropin (hCG) in urine or blood.

Blood hCG testing is more sensitive and can be performed approximately 8 to 10 days after sexual intercourse. By quantitatively measuring hCG concentration in the blood, pregnancy can be detected as early as one week after conception. In contrast, when using a home pregnancy test strip or urine test stick, a more accurate result is usually obtained only after a delay of 3 to 7 days in the menstrual period, because the hCG concentration in urine rises relatively slowly, and testing too early may lead to a false-negative result.

In addition, the timing of testing is also related to the woman's menstrual cycle. Women with regular menstrual cycles can test according to the timing mentioned above; however, women with irregular menstrual cycles may have uncertain ovulation and conception times. They should wait patiently, using methods such as basal body temperature tracking and observing physical changes to assist in judgment. If necessary, they should extend the testing interval and perform multiple tests to confirm the result.