Pregnancy cycle refers to the period between conception and delivery, the whole pregnancy period is 280 days, a total of 10 gestational months, pregnant women within 38-42 weeks of gestation delivery are full term. The main calculation methods are as follows: 1, according to the last menstrual period: this method is the most common and simple, if the pregnant woman’s menstrual cycle is regular, every 28-30 days, you can use the formula, that is, from the first day of the last menstrual period, the month minus 3 or plus 9, the number of days plus 7. As the length of women’s menstrual cycle varies, the estimated due date and the actual due date of 1-2 weeks difference can also be regarded as normal; 2, according to the emergence of fetal movement, the pregnancy cycle is the period between conception and delivery. 2.Calculated by the date of fetal movement: the fetal movement of primiparous mothers appears in the 18th week, and that of menstruating mothers is about 2 weeks earlier than that of primiparous mothers due to their experience, i.e. they can feel the fetal movement at the end of the 16th week, and the formula for calculation is: The expected date of birth of primiparous mothers = the date of fetal movement + 22 weeks; the expected date of birth of menstruating mothers = the date of fetal movement + 24 weeks; through the above methods, pregnant women can project the date of birth of their babies; 3.Calculated by ultrasound Calculation by ultrasound results: Measure the diameter of fetal sac, fetal sitting height, fetal biparietal diameter or fetal femur length under ultrasound, and use the measured value to compare with the table of normal values, then we can know the gestational week that matches with it.