Natural childbirth is the delivery of a fetus vaginally, usually without manual intervention, provided that it is safe and secure. The most basic condition for a natural birth is that the three factors that determine the birth are normal and compatible: labor, birth canal and fetus. When deciding to have a natural birth, pregnant women should know when they are expected to give birth and the whole process of birth. 1. Estimation of due date Estimation of due date is an essential part of the preparation of pregnant women for childbirth. The estimated due date is the first day of the last menstruation, the month minus 3 or plus 9, the number of days plus 7, for example, the first day of the last menstruation is March 31, 2000, then the expected date of birth is January 7, 2001. If the projection is based on the lunar calendar, the month is subtracted by 3 or added by 9 and the number of days is added by 15, e.g., if the first day of the last menstrual period is August 10, 2000, the expected date of delivery is May 25, 2001. The actual date of delivery is affected by a number of factors and can vary from the expected date of delivery by 1 to 2 weeks, which is normal. For pregnant women who are not sure about their last menstruation or those who are pregnant without menstruation during breastfeeding, it can be estimated according to the time when early pregnancy reaction starts, the time when fetal movement starts, the height of the uterus measured by hand or the length of the uterus on the pubic side measured by a ruler. 2.Prenatal fetal and maternal examination For pregnant women who give birth naturally, they should know the whole process of birth and do the corresponding examination during pregnancy so that they can have a comprehensive understanding of the situation of the pregnant woman and the fetus. Pregnant women should have general checkups and prenatal checkups for early detection of abnormalities and early treatment; the fetus should also be examined accordingly, such as placental function, fetal maturity, intrauterine diagnosis of fetal congenital malformations and intrauterine diagnosis of fetal genetic diseases, so that the development of the fetus and the fetal delivery style can be accurately grasped. The fetal position is the relationship between the longitudinal axis of the fetus and the longitudinal axis of the mother. Usually, most of them are in the longitudinal birth position, and only a very small number of them are in the transverse birth position, which often causes difficult delivery. For pregnant women in natural delivery, abnormal fetal birth position such as brachial or transverse birth position can easily lead to obstructed labor. However, the fetal birth position is not fixed in different periods of pregnancy, and some of them can change to normal fetal position naturally. However, if the fetal position does not change to normal after 30 to 32 weeks of gestation, it must be corrected manually. The methods of manual correction include knee-chest position, 2 to 6 times a month for 10 to 15 minutes each time; or external inversion, i.e. the fetal position is corrected by the obstetrician by force (the force mentioned here is not the use of violence, but the use of manual methods to correct the abnormal fetal position under close monitoring). After the fetal position is successfully corrected, the fetal position should be fixed to prevent the reoccurrence of abnormal fetal position and regular antenatal checkups should be done. Of course, some pregnant women with abnormal fetal position can also deliver naturally, but accordingly, the risks involved will be greater. With sound medical supervision, the success rate of natural delivery is also very high.