The pregnancy cycle can be estimated by the last menstrual period or by early pregnancy ultrasound. If your menstrual cycle is normal, you can count from the first day of your last menstrual period, and every 7 days will be 1 week, and so on. In clinical practice, the last menstrual period is often used to predict the expected date of delivery, which is simple and accurate. If the usual menstrual cycle is irregular, or if the last menstrual period is not known, an ultrasound examination is needed to accurately determine the week of pregnancy. During pregnancy, pregnant women can download the pregnancy week calculator and check the pregnancy week and due date according to the date of the last menstrual period. Before 12 weeks of pregnancy, it is recommended to improve the ultrasound examination to estimate the size of the fetus by ultrasound and further verify the accuracy of the gestational week. Secondly, you need to pay attention to regular maternity checkups during pregnancy to know the growth and development of the fetus.