The obstetric calendar of current pregnancy counts, as a rule, from the last day of the previous pregnancy of the menstrual cycle. By this time the ovum has not yet been fertilized, as the process of its maturation is just beginning. Immediately fertilization occurs after the egg is released into the peritoneal cavity - ovulation. Usually this process occurs in the body of each woman 14 days after the menstrual period. That's why the obstetric period differs from that established by the gynecologist for 2 weeks.
What is an obstetric calendar?
To calculate the time, gynecologists use a special device - the obstetric calendar. It allows you to quickly and easily determine the duration of the current pregnancy. For this purpose, the date of the last menstruation is displayed on the scale and the expected date of delivery is calculated.
The round obstetric calendar is divided into individual weeks, months and so-called trimesters (a period of 3 months). The duration of a normal pregnancy is 40 weeks, which is exactly 10 obstetric months.
The entire period of any pregnancy is usually divided into 3 terms:
- from 0 to 12 weeks - the first;
- from 13 to 24 weeks - the second;
- from 25 to 40 weeks - the third.
In this case, each of the above periods has its own characteristics.
First trimester
This period is characterized by a sharp change in the hormonal background of the female body. Since the organism of the future mother is preparing for the maintenance of pregnancy, a large amount of progesterone is released, which leads to a change in the condition of the woman. It is during this period of the midwifery calendar that the sex of the child is determined.
Second trimester
At this time, special attention is paid to numerous studies, the main of which is ultrasound. With his help, doctors constantly monitor the growth and addition of the child's mass, as well as the functioning of the fetal organs.
Third trimester
This period is characterized by active growth of the fetus, which leads to an increase in the load on the female organs, in particular, pressure on the diaphragm increases. The successful completion of this period of the obstetric calendar is childbirth.