Screening examinations of pregnant women are done in order to timely identify any deviations from the norm in the development of the fetus and take timely measures. Ultrasound screening examinations must be conducted 3 times in a strictly defined time. The first screening ultrasound examination is carried out from 11 weeks and 1 day to 14 weeks. In this line, check whether there are signs of gross genetic abnormalities (signs of Down's syndrome, major malformations of the brain and spine, the presence of limbs), abnormalities in the course of the pregnancy itself (hematoma, placental abruption, threat of miscarriage).
The second screening ultrasound during pregnancy is carried out in the interval of 18 weeks and one day and until the end of 21 weeks, during this period, the fetal heart is examined for the presence of defects, all tubular bones of the limbs, hands and feet are checked, the presence of the stomach, bladder, the brain structure, the size of the cerebellum and the ventricles of the brain, the correspondence of the development of pregnancy according to the string, reveal deviations that were not seen in the first screening).
If abnormalities incompatible with fetal life were observed in the first or second screening, then the woman may be recommended to terminate the pregnancy for medical reasons (after this period, pregnancy can not be interrupted). If there is a violation of the development of the fetus or deviation from the norm, according to the indications, the treatment and supervision of the patient in the subsequent periods of pregnancy are prescribed.
The third screening ultrasound is carried out in the term 31-33 weeks, during this period, the fetal presentation, the maturity of the pregnancy, the condition of the placenta, identify all possible complications that may occur during childbirth and prescribe appropriate treatment according to the indications.
Ultrasound parameters at 20 weeks
Although the second ultrasound examination is conducted at 18-21 weeks, but most often the pregnant woman is sent to the ultrasound in 20 weeks of pregnancy. Usually, the parameters fluctuate within 1-2 weeks, but for most of the average indicators determine the term of pregnancy by ultrasound. Key indicators for determining the period:
- biparietal size of the skull (BPR) - between the parietal bones of the skull - the right outer and the left inner and vice versa;
- length of femur;
- mean diameter of the chest (SDHC); mean abdomen diameter (SJ);
- frontal-occipital cranial size (LZR);
- thickness of the placenta and other parameters.
- Ultrasound in 18-19 weeks of pregnancy has the following standards: BPR 41.8-44.8 mm, LZR 51-55 mm, length of the femur 23,1-27,9 mm, SDH 37,5-40,2 mm, SJ 43 , 2-45,6 mm, thickness of the placenta 26,2-25,1 mm, amount of amniotic fluid 30-70 mm (until the end of pregnancy).
- Ultrasound in 19-20 weeks of pregnancy : BPR 44.8-48.4 mm, LZR 55-60 mm, femur length 27.9-33.1 mm, SDHC 40.2-43.2 mm, SDJ 45.6- 49,3 mm, thickness of the placenta 25,1-25,6 mm.
- Ultrasound in the 20-21 week of pregnancy - normal parameters: BPR 48,4-56,1 mm, LZR 60-64 mm, length of the femur 33,1-35,3 mm, SDHC 43,2-46,4 mm, SJ 49 , 3-52.5 mm, thickness of the placenta 25.6-25.8 mm.
In addition, on ultrasound at 20 weeks, the rate of heart rate of the fetus (heart rate) from 130 to 160 beats per minute, rhythmic. The size of the heart on ultrasound in 20 weeks of pregnancy is 18-20 mm, while it is necessary to check the presence of all 4 chambers of the heart, the correctness of the main vessels, the presence of heart valves, the absence of defects in ventricular septums and so on.
It is for the examination of the heart that the ultrasound of the fetus is targeted at 20 weeks: in the presence of incompatible vices, it is recommended to terminate pregnancy on medical grounds. And if the vices can be operated in the first days of the child's life and ensure his future viability, the pregnant woman is forwarded in advance to specialized medical centers for delivery and subsequent surgical intervention in the heart of the child.