At 18-21 weeks a woman is prescribed a mandatory second screening examination. Since only up to 24 weeks, pregnancy can be interrupted due to medical conditions, it is on the second screening examination that doctors should be convinced of the absence of severe congenital malformations in the child. If necessary, during this period it is possible to undergo consultative examinations at appropriate medical centers - to confirm the defect or to remove the diagnosis and the deadline for this is 21 weeks of pregnancy. Sometimes it may seem that 3-D ultrasound at this time will help better diagnose a different pathology, but ultrasound examination all depends not only on the capabilities of the device, but also on the qualification of the doctor.
Norm of ultrasound at 21 weeks of gestation
In 20 - 21 weeks of pregnancy, the main dimensions for ultrasound are as follows:
- at week 21, the average weight of the fetus is 300 g;
- length of body - up to 16 - 18 cm;
- BDP (biparietal size of the skull) - 48.4 - 51.6 mm;
- LTE (frontal parietal size of the skull) - 60 - 64 mm;
- DB (length of the thigh) - 33.1 - 35.3 mm;
- SJ (mean diameter of the abdomen) - 49.3 - 52.5 mm;
- SDHK (mean diameter of the chest) - 43.2 - 46.4 mm;
- thickness of the placenta - 25 - 26 mm, homogeneous without pathological inclusions, zero degree of maturity;
- the height of the column of amniotic fluid is from 35 to 70 mm, the water must be clean.
During this period, it is necessary to check the presence of all 4 chambers of the heart and the condition of the valves, check the course of the main vessels, the fetal heart rate during this period - from 120 to 160 per minute, rhythmic heartbeat , active movements - no less than 15 per hour.
Just at this time the woman should feel the first movements of the fetus, but they are still weak and irregular, but on ultrasound seen well. The position of the fetus in the uterus is still unstable - during the day, it can several times turn as you like. Results of ultrasound, when 21 weeks of pregnancy began, should include measurements of individual brain structures: the ventricles of the brain, the cerebellum, a large cistern. Be sure to measure the length of all the tubular bones of the child, check the structure of the hands and feet. In the abdomen of the fetus, the structure of the liver, the presence of the stomach and bladder, the state of the kidneys and intestines are observed.
Ultrasound in pregnancy at week 21-22
In a week, the basic parameters of ultrasound are already significantly changing and have the following norms:
- BDP (biparietal size of the skull) - 51.6 - 54.2 mm;
- DB (length of the thigh) - 35.3 - 38.3 mm;
- LTE (frontal parietal size of the skull) - 64 - 67 mm;
- SJ (mean diameter of the abdomen) - 52.5 - 56.4 mm;
- SDHK (mean diameter of the chest) - 46.4 - 49.4 mm.
All fetal condition examinations, which should be performed on a screening test, continue to be performed at this time. 21 weeks of pregnancy is the period when the sex of the fetus is clearly visible on the ultrasound: a girl or a boy. At this time, any deviations from the norm for ultrasound should be consulted with the appropriate specialists for the diagnosis of compatible and incompatible with the fetal life of the developmental disorders.