Down Syndrome is one of the most common genetic disorders. It occurs even at the stage of formation of the oocyte or sperm or at the time of their fusion during fertilization. Moreover, the child has an extra 21st chromosome and as a result, in the cells of the body there is not 46, as expected, but 47 chromosomes.
How to identify Down's syndrome during pregnancy?
There are several ways to identify Down syndrome during pregnancy. Among them - invasive methods, ultrasound, screening for pregnancy . Authentically, Down's syndrome can be diagnosed in the fetus only with the help of invasive methods:
- a chorionic biopsy at 10-12 weeks - the result is obtained after a few days. However, the procedure is dangerous because it can cause spontaneous miscarriage in 3% of cases;
- placentocentosis at 13-18 weeks - the result will be told to you after a few days. The risk of complications is the same - 3-4% of cases end in spontaneous miscarriage;
- amniocentesis at 17-22 weeks - in this case the risk of miscarriage is about 0.5%;
- Cordocentesis at 21-23 weeks - 1-2% of cases end in miscarriage.
If during the manipulations the presence of Down's syndrome is detected, it is possible to terminate the pregnancy for up to 22 weeks.
Of course, the risk of spontaneous miscarriage - a pretty unpleasant payment for the authenticity, especially if it turns out that the baby was all right. Therefore, not all are solved for such manipulations. With a certain degree of probability, Down's syndrome can be judged by the results of an ultrasound study.
Ultrasound of a fetus with Down syndrome
Symptoms of Down's syndrome in a fetus during pregnancy are difficult to determine with the help of ultrasound, since such a study allows to determine with a high degree of reliability only obviously gross anatomical disorders. However, there are a number of markers by which the doctor may suspect that the fetus has an extra chromosome. And if in the process of examination the fetus has signs of Down's syndrome, their study in aggregate will enable to integrate an integral picture and ascertain trisomy 21 with a certain probability.
So, these features include:
- enlargement of the collar space (large thickness of the cervical fold or accumulation of subcutaneous fluid on the back of the fetal neck). Normally, this parameter should not exceed 2.5 mm for vaginal examination and 3 mm for examination through the abdominal wall. Such a study is conducted at 10-13 weeks;
- the length of the bones of the nose of the fetus - is determined in the second trimester. Hypoplasia of nasal bones is present in every 2nd child with Down syndrome;
- enlarged bladder;
- reduced maxillary bone;
- moderate tachycardia (more than 170 beats per minute);
- violation of the waveform of blood flow in the venous duct.
If you have found one or more signs on ultrasound, this does not mean a hundred percent birth of a child with Down's syndrome. You are recommended to undergo one of the laboratory tests described above, when a woman through the abdominal wall takes genetic material.
Ultrasound is most informative on the period of 12-14 weeks - in this period the specialist can more accurately determine the degree of risk and help to take further necessary measures.
Screening for Down's syndrome - transcript
Another method of detecting Down's syndrome in pregnancy is a biochemical blood test of a pregnant woman taken from a vein. Analysis of pregnant women for Down's syndrome involves the determination of the concentration in her blood of alfa-fetoproteins and the hormone hCG.
Alfafetoprotein is a protein produced by the fetal liver protein. It enters the woman's blood through amniotic fluid. And a low level of this protein may indicate the development of Down syndrome. It is most advisable to do this analysis at 16-18 weeks gestation.