Diagnosis of birth defects

The development of birth defects is associated with a genetic factor and chromosomal abnormalities. Congenital defects can significantly affect the child's subsequent life or determine the quality of the whole life.

Congenital defects include:

• Genetic disorders: Down syndrome and trisomy 18.
• Hereditary diseases: sickle-cell anemia, cystic fibrosis.
• Structural disorders: congenital heart defects and neural tube defect, including spina bifida.

Pregnant women and their partners themselves must decide whether to conduct a test for birth defects. If you decide to do this, talk with a geneticist. The psychologist will help to make the right decision or refer to another specialist.

Birth Defects - Diagnosis

Testing of birth defects in the first trimester

These include:

• Test for transparency of the cervical fold. With the help of ultrasound, the accumulation of subcutaneous fluid on the posterior surface of the fetal neck in the first trimester of pregnancy is determined. The increase in width is a sign of an early birth defect. This test can only be done by a doctor who has been specially trained.
• Blood tests for β-hCG and PAPP-A in the first trimester. During the analysis, the amount of two substances in the blood is measured, namely human beta-chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein A (PAPP-A). β-hCG is a hormone produced by the placenta and its high level indicates certain birth defects. PAPP-A is a protein in the blood, and its low level also indicates the presence of defects. The attending physician compares the levels of these substances according to age and other factors, and determines the risk of developing birth defects in the child.

The first trimester is tested for 10-13 weeks of pregnancy, depending on the type of test. Sometimes, several tests are assigned at the same time. The test for the transparency of the cervical fold is often carried out simultaneously with the analysis of blood.

• A sample of the villous chorion is performed for the purpose of analyzing the cells of the placenta at 10-12 weeks of gestation. The doctor takes samples of the placenta cells with a transvaginal plastic catheter. Based on the results of this test, chromosome birth defects such as Down's syndrome and hereditary diseases, for example, sickle cell anemia and cystic fibrosis, can be judged. But it does not determine the defects of the neural tube.

This testing is carried out by a highly qualified specialist, therefore the risk of preterm labor is 1: 400, according to one study.

Second trimester testing

These include:

• A triple or quadruple biochemical blood test. Such tests determine the amount of three or four substances in the blood of a pregnant woman. Triple screening tests the level of alpha-fetoprotein (AFP, a-Fetoprotein), human chorionic gonadotropin (hCG, beta-hCG, b-HCG, Human Chorionic gonadotropin, HCG) and type of free estriol (unconjugated estriol). Such screening determines the level of three substances and the hormone inhibin A. The specialist compares the levels of these substances with age and other factors and determines the risk of developing birth defects in the child.
• Ultrasound. The doctor on the screen sees the image of the developing fetus. It is conducted between 18-20 weeks of pregnancy in order to identify certain traits that are associated with chromosomal abnormalities (Down syndrome). Ultrasound helps to identify structural changes in organs, namely, the heart, ridge, abdominal cavity or other organs.

Screening for the second trimester of pregnancy is carried out at 15-20 weeks of pregnancy. A triple and quadruplicate blood test is also called an extended AFP test. In some cases, comprehensive screening is carried out. A full report of the results is provided after the tests in the second trimester of pregnancy.

• Amniocentesis (puncture of the bladder) is performed to identify chromosomal changes by analyzing the cells of the amniotic fluid. The procedure is performed transplacentally - choose the thinnest part of the placenta - between 15-20 weeks of pregnancy. Amniocentesis determines the defects of the neural tube (spina bifida).

Definition of birth defects - testing accuracy

No test is accurate at 100%. Sometimes it happens that with negative results of screening the child still has birth defects. This is called a false negative test result. But it also happens that the test results deviate from the norm, but the child does not have an anomaly of development.

Therefore, screening only determines the possible risk of fetal pathology. If the results indicate an increased risk, the doctor will prescribe additional tests: a villous chorion sample or an amniocentesis for an accurate diagnosis.

Screening for the first trimester defines Down syndrome in 85%. Complex screening guarantees the accuracy of diagnosis in 95%.

With the help of ultrasound, a neural tube defect and anencephaly (congenital absence of the brain) are detected in almost all cases. The results of a sample of villous chorion and amniocentesis accurately show Down's syndrome in 99% of cases.

Definition of birth defects - should I get diagnosed?

Every pregnant woman makes this important decision herself. You must take into account the hereditary factor, the age, the need for this procedure and what you will do after receiving the results. At the same time, spiritual convictions and other moral values play an important role in the decision-making process.

Some congenital defects, for example, cleft of the upper lip or palate, or certain heart diseases are surgically removed after birth, and sometimes even during pregnancy. Other birth defects can not be eliminated.

Diagnosis should be done in such cases:

• If you are thinking of interrupting pregnancy in case of birth defects.
• You have hereditary diseases, for example, cystic fibrosis, Tay-Sachs disease or hemophilia.
• You need to know if the fetus has a developmental disorder.
• In case of a defect, you would like to know everything about the care and upbringing of a child with developmental disabilities.
• You would like to choose a hospital and pick up the attending physician, with whom you will cooperate, for the full care and treatment of the child.

Diagnosis of birth defects - why should not you go through this diagnosis?

You can opt out of the diagnosis if:

• You want to give birth to a child in spite of the test results. Sometimes the test results are positive, but a child can be born healthy. While waiting for the results, future mothers are very worried.
• This diagnosis does not reveal all possible deviations.
• You are concerned about the risk of premature birth, since a sample of a villous chorion or amniocentesis is not always safe. According to one study, in which the procedure was carried out by highly qualified specialists, the risk level was 1: 400. Other studies showed a higher risk of 2: 400 and 4: 400, but with less qualified specialists.
• Diagnosis is expensive.

[1], [2], [3], [4], [5]