Does being 42 days pregnant refer to 42 days after intercourse?

Generally, the calculation of pregnancy duration starts from the first day of the last menstrual period, rather than from the date of intercourse. Therefore, 42 days of pregnancy does not directly correspond to 42 days after intercourse. The detailed explanation is as follows:

The number of days of pregnancy is counted from the first day of a woman's last menstrual period, not from the date of intercourse. This is because there are individual differences in women's menstrual cycles and ovulation timing, and the exact time of fertilization may be difficult to determine precisely. Women with irregular menstrual cycles may need an ultrasound examination to accurately determine the gestational age. In cases where pregnancy is achieved through assisted reproductive technologies such as in vitro fertilization (IVF), the gestational age may be calculated based on the date of embryo transfer and the developmental stage of the embryo.

To ensure accuracy, it is recommended that when pregnancy is suspected, a urine pregnancy test or blood hCG test be performed to confirm the pregnancy status, and medical consultation should be sought for more detailed prenatal information and guidance.