Calendar method. In the calendar, find the date of the first day of your last period and counting the number of weeks that have passed since that time. The result is divided by 4. For example, it took 17 weeks and 3 days, so the period of pregnancy 17-18 weeks or 4 months 1 week and 3 days.
The definition of the term. There are special tables, which can determine the term of pregnancy, matching today's date with the date of the first day of the last menstrual period. In fact it is a modified calendar method.
Ultrasound. This method is the most accurate at the initial time. To 12 weeks period is determined with an error of 1-3 days. Then every month the error increases in the second trimester to 7 days, and the third error can reach 2 – 3 weeks. The fact that in this case, doctors are guided by the size of the fetus. In early pregnancy it depends on the length and time of birth the size and weight of the child depends on the individual.
Definition of term pregnancy gynecological examination. An experienced doctor in the early pregnancy quite accurately defines her life by the size of the uterus. 4 weeks (1 month) the uterus is the size of a hen's egg, in 8 weeks (2 months) with a goose egg in 12 weeks (3 months) a man's fist.
More late terms of pregnancy are determined by the height of standing of bottom of uterus. In 4 months (16 weeks), the fundus is midway between the vagina (pubic bones) and the navel. 5 months (20 weeks), the fundus is at a distance of 11-12 cm above the fold. 6 months – level of umbilicus. 7 months (28 weeks) at 4 cm above the navel. 8 months – midway between the umbilicus and xiphoid process of the sternum. In obstetric 9 months (36 weeks) the bottom of the uterus in rib, at the level of the xiphoid. At the time of birth (40 weeks) the uterus descends to the middle between the navel and xiphoid process.
The length of the uterus. Measuring tape measure the distance between the fold and the bottom of the uterus. The number of centimeters equal to the number of weeks of time. Dividing the result by 4, will receive a month of pregnancy.
Previously used the definition of pregnancy in the first movement of the fetus, but currently this method is not popular because it is not precise enough.