When does pregnancy begin, and how is the timing accurately calculated?

Pregnancy is typically calculated from the first day of the woman's last menstrual period, which is referred to as gestational age or pregnancy age.

The first day of the menstrual cycle is relatively easy to determine, and for most women ovulation and conception generally occur around the midpoint of the menstrual cycle. In a standard 28-day menstrual cycle, ovulation usually occurs around day 14, when fertilization is most likely to happen. Therefore, calculating 40 weeks, or 280 days, from the first day of the last menstrual period is considered the full duration of pregnancy. If a pregnant woman has irregular menstrual cycles or irregular ovulation, ultrasound examination is generally required to estimate gestational age based on the appearance of fetal indicators such as fetal heart activity and embryo development, rather than relying on the last menstrual period.

During pregnancy, regular prenatal checkups at the hospital are necessary. Pregnant women should ensure adequate rest and avoid excessive fatigue to prevent adverse effects on fetal growth and development. Additionally, maintaining a balanced diet is important. Consuming foods rich in proteins and vitamins, such as eggs and tomatoes, can help provide essential nutrients and support fetal development. If any discomfort occurs, prompt medical consultation is recommended.