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How to determine the week of pregnancy
The dates of maternity leave and expected births depend on the accuracy of setting the gestational age. Women, as a rule, count from the day of possible conception. Doctors are guided by the date of the last menstruation, ultrasound and gynecological examinations.
How to determine how many weeks of pregnancy yourself?
During the first visit of the pregnant woman, the gynecologist determines the preliminary date of birth according to the Negele formula. To set the deadline, he uses a special obstetric calendar, but a woman can make simple calculations on her own.
Using the calendar, the week of pregnancy is determined using the Negele formula
To find out when the pregnancy began, you need to add 7 days to the first day of the last menstruation and subtract 3 months. 40 weeks are counted from the date received – this will be the preliminary day of birth.
Important! The obstetric method is far from accurate, especially for women with irregular menstrual cycles
For women who maintain a monthly calendar, it is easier to calculate the onset of pregnancy by the embryonic method. The likelihood of conceiving a child is highest during ovulation. It is possible to determine this favorable period for fertilization by subtracting two weeks from the day of the beginning of the last menstruation.
Errors in determining the week of pregnancy by the date of ovulation are due to the fact that there is a probability, albeit less, of conceiving a child on other days of the menstrual cycle.
Medical methods to help determine the week of pregnancy
Over the course of 9 months, a woman undergoes three planned ultrasounds: for a period of 10-14, 20-24 and 32-34 weeks. Research helps to timely identify fetal malformations, monitor the course of pregnancy. The tasks of obstetric ultrasound scanning include the clarification of the week of pregnancy. In this regard, the first ultrasound scan is of particular value for gynecologists, since it provides the most accurate information.
Ultrasound allows you to relatively accurately determine the week of pregnancy
The diagnostician determines the age of the fetus by measuring:
- the size of the child’s head;
- distance from coccyx to crown;
- chest diameter;
- abdominal circumference;
- thigh length.
By comparing the data obtained and the average values indicated in the table, the doctor determines the week of pregnancy.
During the examination, the gynecologist can set a deadline for the size of the uterus. The easiest way to do this is at the beginning of pregnancy: in the fourth week, the female organ is the size of a hen’s egg, in the eighth week – the size of a goose egg. The first movement of the fetus is also important to determine the period. Women feel the movements of the first child from the 20th week, the next children – from the 18th week.
So, the gestational age is calculated by the date of the beginning of the last menstruation. More accurate data is provided by the first ultrasound study conducted in the third month.