Why do you need to know the gestational age? After all, childbirth will occur sooner or later in every woman. This is true, however, it must be borne in mind that knowing the exact duration of pregnancy, the doctor will not only set the most correct PDD (the estimated day of birth), but will also track whether the baby is developing correctly at each stage by weeks.
In gynecology, it is customary to start counting pregnancy from the first day of the last menstruation. This is the so-called obstetric term. Strictly speaking, the woman is not pregnant for the first two weeks of this period, but if we consider that it is impossible to determine the exact day of ovulation and conception without measuring the basal temperature, then this method allows you to fairly correctly calculate the date of birth. After all, almost every woman is capable of calling the day of the last menstruation. The date of birth by obstetric time is determined as follows: 7 days are added to the number of the first day of menstruation, and 3 months are taken away. This will be the PDR.
After visiting the ultrasound office, many ladies are perplexed by the fact that the period according to the results of the study is about 2 weeks less than the obstetric one. This is correct, and should not cause concern: the ultrasound specialist sets the actual period of fetal development, and it just should be less than obstetric.
According to the results of ultrasound, you can very accurately find out the gestational age up to 8 weeks: at this time, all embryos develop in the same way, and you can even talk not about weeks, but about the days of pregnancy. At later stages, the development of the fetus occurs according to an individual schedule, which is enclosed in special tables that allow doctors to judge how correctly the pregnancy is proceeding.
In the early stages, pregnancy is diagnosed by analyzing the level of the specific hormone human chorionic gonadotropin (hCG). An increase in the content of this hormone in the blood indicates pregnancy, and the term is determined by its amount. However, this method is not the most accurate, since the range of hCG levels in women is too wide.
Starting from about the twelfth week, an observing obstetrician-gynecologist will measure the height of the fundus of the uterus above the bosom:
- for a period of 12 weeks, the uterus is located on the upper edge of the bosom, - at 14 weeks - 3-5 centimeters above the bosom, - at 16 weeks, the bottom of the uterus is felt between the bosom and the navel, - at 24 weeks at the navel level, - at 32 weeks, the height is 28-30 centimeters, - at 36 weeks, the fundus of the uterus supports the ribs, - by the end of the pregnancy, it drops to the level of thirty-two weeks, since the presenting part of the child drops lower into the pelvis.
Development is considered to be within the normal range if the deviation from the average is up to 3 centimeters. Measuring the height of the fundus of the uterus allows not only to make sure of the timing and normal development of pregnancy, but also to diagnose in time such troubles as oligohydramnios or polyhydramnios and a number of others.