One way of determining the date of the last menstrual period. However, this method can only be used in women with regular menstrual cycles. Otherwise, a possible error in the calculations. Take your personal calendar and count how many weeks have passed since her first day. This will be the period of pregnancy. To determine the date of birth is used the formula of Negele. Count from the first day of periods back 3 months and add to them the 7 days.
To know the duration of pregnancy and date of births by the ovulation date. Ovulation happens mid-cycle, usually 12-16 days, counting from the first day of menstruation. Often in this period and that is conception. With the selected point, count the period of pregnancy and add 2 weeks. For finding date of birth from the date of ovulation, subtract 3 months and 7 days, or add 38 weeks. This method is ideal for women who become pregnant by artificial means.
To set the duration of the pregnancy can gynecologist according to the vaginal examination. It determines the size of the uterus, which gradually increases in size. At a later period, the uterus becomes palpable through the abdomen, and the doctor measures the volume of the stomach and the height of standing of bottom of uterus above the vagina with the help of the tape measure. It should be noted that this method is not always reliable. Often uterine size may be larger (if polyhydramnios, fibroids, multiple gestation) or less (if of fetal malnutrition, water scarcity) laid norms.
Another method - ultrasonography (us). During the procedure, measurements of the size of the fetus, which correspond to a certain term of the pregnancy. The most accurate method in the first trimester. In time possible errors in determining the number of weeks of pregnancy, because the growing fetus has its own constitutional peculiarities. Sometimes the expectant mother and child can be some pathology (for example, diabetes in women, fetal malnutrition) contributing to the growth and development of the embryo or its excessive growth.
To find the duration of pregnancy and date of birth can on the first movement of the fetus. Usually primipara expectant mother feels it in 20-21 weeks of pregnancy, powernotes – since 18-19 weeks. To calculate the gestational age, the date of the first stirring add 5 lunar months. If labor is the second – 5.5 months.