Determination of the gestational age is necessary for its correct management and determination of the expected date of birth. The term can be calculated in calendar months - a normal pregnancy lasts an average of nine months and seven days from the first day of the last menstruation. But more often obstetric months are used, each of which is equal to 28 days. In this case, the pregnancy lasts 10 months or 40 weeks. There are several ways to determine the term.
Instructions
Step 1
Calendar method. In the calendar, we find the date of the first day of the last menstruation and count the number of weeks that have passed since that time. Divide the result by 4. For example, 17 weeks and 3 days have passed, which means that the gestation period is 17-18 weeks or 4 months 1 week and 3 days.
Step 2
Determination of the term using tables. There are special tables by which you can determine the duration of pregnancy by combining today's date with the date of the first day of the last menstruation. In fact, this is a modified calendar method.
Step 3
Ultrasound procedure. This method is the most accurate in the initial stages. Up to 12 weeks, the period is determined with an error of 1-3 days. Then every month the error increases, in the second trimester up to 7 days, and in the third trimester the error can go up to 2 - 3 weeks. The fact is that in this case, doctors are guided by the size of the fetus. At the beginning of pregnancy, it depends on the period, and by the time of delivery, the size and weight of the child depends on individual characteristics.
Step 4
Determination of gestational age during gynecological examination. An experienced doctor at the beginning of pregnancy quite accurately determines its duration by the size of the uterus. At 4 weeks (1 month) the uterus is the size of a chicken egg, at 8 weeks (2 months) with a goose egg, at 12 weeks (3 months) with a man's fist.
Step 5
Later stages of pregnancy are determined by the height of the fundus of the uterus. At 4 months (16 weeks), the bottom of the uterus is located in the middle between the loons (pubic bones) and the navel. At 5 months (20 weeks), the fundus of the uterus is 11-12 cm above the bosom. At 6 months - at the level of the navel. At 7 months (28 weeks) 4 cm above the navel. At 8 months - in the middle between the navel and the xiphoid process of the sternum. At 9 obstetric months (36 weeks), the fundus of the uterus at the costal arches, at the level of the xiphoid process. By the time of delivery (40 weeks), the uterus descends to the middle between the navel and the xiphoid process.
Step 6
Along the length of the uterus. The distance between the bosom and the fundus of the uterus is measured with a measuring tape. The number of centimeters is equal to the number of weeks of the term. Dividing the result by 4 gives the month of pregnancy.
