Is preterm birth calculated based on actual birth date or full-term gestation?

Preterm birth is generally determined based on whether the fetus has reached full term. The specific analysis is as follows:

The standard for full-term pregnancy in pregnant women is calculated from the first day of the last menstrual period, with each 7-day period constituting one gestational week. Delivery at or after 37 weeks is considered full-term pregnancy, 40 weeks corresponds to the expected delivery date, and delivery beyond 42 weeks is classified as post-term pregnancy. Clinically, infants born between 28 and 37 weeks of gestation who survive are referred to as preterm infants. Therefore, preterm birth is defined relative to full-term pregnancy.

Both preterm and post-term pregnancies are considered abnormal conditions. Therefore, during early pregnancy, strenuous exercise should be avoided, as it may increase abdominal pressure. Light physical activities such as walking or practicing yoga are acceptable and recommended.