How to Calculate Pregnancy Duration Most Accurately

Methods for calculating the time of pregnancy:

1. If a woman has regular menstrual cycles, the most commonly used method is to calculate from the first day of the last menstrual period (LMP). The entire pregnancy typically lasts about 280 days (or 40 weeks). This method is simple and widely accepted because most women have relatively stable menstrual cycles.

2. For women with irregular menstrual cycles or those who have forgotten the date of their last menstrual period, ultrasound examination becomes an important auxiliary tool. An ultrasound can estimate the gestational age based on measurements of fetal size and developmental status. Especially during early pregnancy, calculations based on the size of the gestational sac and embryo provide relatively accurate results.

3. If conception occurred through ovulation monitoring or in vitro fertilization (IVF) embryo transfer, the pregnancy date can be calculated based on the results of ovulation tests or the date of embryo transfer. These methods can also provide relatively accurate estimations of gestational age.

Due to individual differences and variations in fetal growth rates, there may be some margin of error in the calculated results. Therefore, pregnant women should attend prenatal checkups regularly during pregnancy, allowing doctors to comprehensively assess fetal development and gestational age based on multiple examination findings.