When 21 weeks of pregnancy occur, the anatomy of the fetus is almost similar to the structure of the child after birth. He already has all the internal organs and systems, and in the future only their development and growth will occur. And therefore 21 weeks - the end period for the second screening ultrasound - a study in which all organs of the fetus are tested for the presence of congenital malformations.
Pregnancy Week 21 - development of the fetus
At 21 weeks of pregnancy, the weight and size of the fetus are rarely measured for screening - these are indicators that are not very informative, although the body length reaches 18 cm and the weight is up to 300 g.
Until that time, a woman must feel the fetal movement , if at 21 weeks they are not yet - this can be cause for concern.
Week 21 - screening dimensions of the fetus
At 21 weeks, according to the protocol, almost all bones, internal organs and special sizes of the fetus are measured. The first important fetal size at week 21 is biparietal (51.6 mm between the two temporal bones), the second size of the skull is frontal-parietal (64 mm), while the structure of the brain resembles that of a newborn.
At week 21, all tubular bones are measured, while:
- length of thigh - 35.3 mm;
- length of humerus - 33.5 mm;
- length of tibia - 31.7 mm;
- the length of the bones of the forearm is 29.5 mm.
The diameter of the chest at 21 weeks is 46.4 mm, the fetal heart size is 21.2 mm in diameter, 21.5 mm in length, there are all the chambers of the heart, its rhythmic cuts, with a frequency of 120-160 per minute.
The average diameter of the stomach at 21 weeks is 52.5 mm, the stomach is clearly visible, the intestinal loops are not inflated, the anterior wall of the abdominal cavity is whole.
Both kidneys are visible up to 20.3 mm long, 11.1 mm across, bowls and pelvis are not dilated, the bladder is small, is in the small pelvis, after urinating the fetus, it is almost invisible.
Fetus at week 21 of pregnancy
The position of the fetus is often the head, but even if the gluteal, in this period the child can turn during the day in the uterus, and therefore, until 30 weeks of pregnancy, it is not worth worrying about it.
The placenta is uniform, 25.6 mm thick, the thickness of the column of amniotic fluid in a place free from parts of the fetus is from 35 to 70 mm. The cervix is closed at this time.