According to the date of ovulation (or conception). This method is one of the most accurate. But for this it is necessary to systematically measure the rectal temperature. The procedure should be carried out daily at the same time - in the morning, without getting out of bed. In the first half of the menstrual cycle, the temperature does not exceed 37 degrees, and on the day of ovulation it rises. By the day of sexual intercourse you can not navigate: spermatozoa get into the uterus and fallopian tubes and can live there 3-4, and sometimes up to 7 days, waiting for the release of the egg from the follicle. That is, the day of sexual intercourse does not necessarily coincide with the day of conception, and the day of ovulation is the day of conception, since the egg after exiting from the ovary can exist for no more than a day. It follows that women seeking to become pregnant should have sexual intercourse several days before ovulation, than be late for one day.
According to the date of the last menstruation. This method of calculation allows an error of one to two weeks. Pregnancy can occur only after ovulation, which occurs with a 28-day cycle between 12-16 days, therefore, to count the gestational age after the calendar should be two weeks after the first day of the last menstruation. But this countdown will be quite reliable for women with a regular menstrual cycle. If you add 280 days to the last menstruation, you will receive an approximate date of delivery.
The first stir is not a very accurate way to determine the timing. Moreover, it is only available in the second half of pregnancy. But gynecologists use it along with other methods. It is believed that primiparous women feel the movements of the baby at the 20th week of pregnancy, and the moles on the 18th. In this case, another 20-22 weeks are added by this time and calculations are made. But all this is very individual. Often happens, that the mummy starts to feel the kid already on 16th week and even earlier!
According to the size of the uterus. The length of the uterus in centimeters is approximately equal to the period of pregnancy in weeks. It is measured using a standard centimeter tape. A gynecologist will take measurements during each of your visits. This will allow him to judge the development of the fetus.
- At the end of 1 month (4 weeks), the uterus reaches the size of a chicken egg.
- By the end of 2 months (8 weeks), the uterus is the size of a female fist.
- At the end of 3 months (12 weeks), the uterus is the size of a newborn's head, its bottom reaches the upper edge of the womb.
- By the end of 4 months (16 weeks) the bottom of the uterus is 6 cm above the womb.
- By the end of 5 months (20 weeks) -12cm.
- By the end of 6 months (24 weeks) -20cm.
- By the end of 7 months (28 weeks) -on 24cm.
- By the end of 8 months (32 weeks) -28-30cm.
- By the end of 9 months (36 weeks) -34-36cm.
- By the end of the 10th month the uterus is lowered and is determined at the same level as at 32 weeks.
According to the data of ultrasound, it is possible to make very accurate calculations at the earliest possible dates - up to 6-7 weeks. At this time, the fetus develops proportionally and for all women at the same time it will have the same size. Later, development takes on an individual character.
According to the level of hCG (chorionic gonadotropin) in the blood. So, at a period of 1-2 weeks, the content of hCG in the blood is 150 mU / ml, and at the 8th week it is already 70,000 mU / ml. Small errors in one direction or another are allowed. But if the level of hCG does not match the time, then this may be a sign of any pathology, evidence of a "fading" of pregnancy or implantation of a fetal egg outside the uterus (ectopic pregnancy).