You will need
- - the calendar.
The first method of determining the delivery date - formula Nagle. To the date of the first day of the last menstrual period, add nine months and seven days. A simple method for these calculations: from the first day of your last period count back three months and add seven days.
To determine the date of childbirth, counting from the first day of the last menstrual cycle 40 weeks.
Another way: add to the estimated day of conception 268 days.
The most accurate method of determine gestational age - ultrasound examination in early pregnancy. Having an ultrasound until 12 weeks of pregnancy, you can know the date of conception to within a few days, and, on this basis, to calculate the approximate date of delivery. In the second and third trimester the chance of error of determining the delivery date increases, this is justified by the peculiarities of the development of the fetus.
To determine the duration of pregnancy is possible by bimanual examination. The gynecologist can establish the period of pregnancy during the measurement of the size of the uterus — determination of the level or height of standing of bottom of uterus, circumference of the abdomen. For a period of 4 weeks of pregnancy the uterus is about the size of a chicken egg in 8 weeks — with a goose egg. At 12 weeks the uterus is increased to the size of a male fist, the bottom of the uterus extends to the upper edge of the pubic bone. At 16 weeks of pregnancy the fundus midway between the womb and the navel, and at 24 weeks it is at the level of the navel. The largest size uterus gets to 36 weeks (abdominal circumference up to 90 cm), by this time the bottom of the uterus rises to the ribs, and then 40 weeks lowered a couple of inches. Lowering of the uterus means that the baby is preparing to leave.
Also expected delivery date is determined the first movement of the fetus. In nulliparous women it occurs usually at 20 weeks, and multiparous with 18 weeks of pregnancy.