Definition of a duration of gestation. For an establishment of a duration of gestation and date of sorts use data on time of last menses, date of the first movement of a fetus and data of objective inspection of the pregnant woman. Normal pregnancy lasts 280 days, that is 40 weeks, or 10 obstetric months, including from the first day of last menses. At some women pregnancy can proceed less than this term or more it.

Definition of a duration of gestation on size of a uterus:
1) in 6 weeks a uterus is a little bit enlarged, the spherical form, there are attributes of the Snegiryov;
2) in 8 weeks the uterus reaches the sizes of a female fist, its bottom at a level of a pubic symphysis;
3) in 12 weeks a uterus in size with a man's fist, its bottom on a diameter of one finger above a pubic symphysis;
4) in 16 weeks the uterine fundus is on the middle of distance between a pubic symphysis and a belly-button;
5) in 20 weeks it is noticeably enlarged a stomach, the uterine fundus is located on a diameter of two fingers below a belly-button, there are movements of a fetus and its intimate tones are auscultated;
6) in 24 weeks a uterine fundus at a level of a belly-button;
7) in 28 weeks a uterine fundus on a diameter of two fingers above a belly-button;
8) in 32 weeks a belly-button smooths out, the uterine fundus is defined between a belly-button and a xiphoid process;
9) in 36 weeks the uterine fundus reaches a xiphoid process and costal arches;
10) the uterine fundus falls to 40 weeks up to a level on which was at 32-week pregnancy. At primapara the head of a fetus is fixed in an input of a small basin whereas at multipara it remains mobile above an input in a basin. For practical obstetrics diagnostics of 32-week pregnancy as in this term of pregnant women receive antenatal holiday has great value. This term can be defined by date of last menses, the first movement of a fetus (in 20 weeks at primapara and in 18 weeks at multipara), size of a uterus at the first arrival to female consultation (at earlier arrival the diagnosis establish more precisely). Alongside with it consider height of standing of a uterus above a bosom, the attitude of a presenting part of a fetus to an input in a small basin, length of a fetus or its frontooccipital size, measured by a pelvimeter, and also data of a ultrasonic fetometry - size of of the coccygeal parietal size, a circle of a stomach, the biparietal size of a head of a fetus, etc. Are offered various formulas for definition of a duration of gestation and calendars for definition of term of sorts.