How is the trimester screening done?
At the specified time, the woman undergoes a comprehensive examination. It is not only in ultrasound (to determine how physically and externally the baby is developing), but also in conducting a blood test of the mother. This is done in order to identify possible changes that are characteristic of various fetal malformations (in particular, Down syndrome, Edwards syndrome, as well as disorders in the development of the nervous system and other organs and systems). Ultrasound, as a rule, measures the magnitude of the cervical fold, deviations from the norm of which are a sign of congenital diseases. It also examines how the blood flow of the child, works his heart, and how long his body is. It is for this reason that such a study is called a "double test". The term of 11-13 weeks of pregnancy is important because if any abnormalities are revealed, the expectant mother will be able to make a decision about the termination of pregnancy .
Preparing for a 1-term screening
The most important element of training is the choice of the clinic, which should be equipped with the best and most sensitive equipment. Before going through the ultrasound, in most cases, you just need to fill the bladder (drink ½ liter of water an hour before admission), but in modern clinics from this inconvenience relieve transvaginal sensors that do not require that the bladder is full. Conversely, for transvaginal ultrasound, a bladder must be emptied (a few minutes before admission). So the effectiveness will be higher.
To donate blood from the vein, you need to refrain from eating at least 4 hours before the fence, although it is optimal to take it in the morning, on an empty stomach. Also, you should adhere to a special diet for maximum accuracy of the result, namely: to refrain from fatty, meat, chocolate and seafood. The diet before the screening of the first trimester is very important, as all possible errors will be treated not in favor of the child.
Biochemical screening of the first trimester, the norms of which are determined comprehensively for each indicator, consists of an analysis of:
- HCG (human chorionic gonadotropin), which allows to identify Down syndrome, or the presence of twins - when it increases, as well as a stop in the development of the fetus - when it decreases.
- Protein A, produced by the placenta, which should increase steadily as the fetus develops.
Indicators of screening for the first trimester (the norms for hCG depend on the week when the analysis is done) are as follows:
- from 25.8 to 181.6 ng / ml at week 10;
- from 17.4 to 130.3 ng / ml - at the 11th week;
- from 13,4 to 128,5 ng / ml - at week 12;
- from 14.2 to 114.8 ng / ml at the 13th week.
If you, like most mothers, undergo a first-trimester screening at week 12, ultrasound results will be as follows:
- coccygeal parietal size - from 51 to 73 mm;
- The thickness of the collar zone - from 1,6 to 2,7 mm;
- nasal bone - not less than 3 mm;
- heart rate - from 150 to 174 beats per minute.
Genetic screening of the first trimester should not inspire fear, because this is what allows you to abandon the gestation of an unequivocally inferior fetus or to get used to the idea that it will be special. However, the decision in favor of one or the other option is taken solely by parents who have undergone a perinatal screening of the first trimester.