Diagnosis of birth defects

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

Congenital defects include:

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

Pregnant women and their partners should decide for themselves whether to test for birth defects. If you decide to do so, talk to a geneticist. A psychologist can help you make the right decision or refer you to another specialist.……..

Congenital defects - diagnostics

First Trimester Birth Defect Testing

These include:

• Nuchal translucency test. Using ultrasound, this test detects the accumulation of subcutaneous fluid on the back of the fetus's neck in the first trimester of pregnancy. An increase in width is a sign of an early birth defect. This test can only be performed by a doctor who has undergone special training.
• Blood tests for β-hCG and PAPP-A in the first trimester. The test measures the amounts of two substances in the blood, namely, beta human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein A (PAPP-A). β-hCG is a hormone produced by the placenta, and high levels of it indicate certain birth defects. PAPP-A is a protein in the blood, and low levels of it also indicate the presence of defects. The attending physician compares the levels of these substances according to age and other factors, and determines the risk of birth defects in the child.

First trimester testing is done between 10 and 13 weeks of pregnancy, depending on the type of test. Sometimes several tests are ordered at the same time. The nuchal translucency test is often done at the same time as a blood test.

• A chorionic villus sampling (CVS) is a test done to look at the cells in the placenta at 10 to 12 weeks of pregnancy. The doctor takes samples of the placenta using a transvaginal plastic catheter. The results of this test can look for chromosomal birth defects such as Down syndrome and hereditary diseases such as sickle cell anemia and cystic fibrosis. However, it does not look for neural tube defects.

This testing is performed by a highly trained professional, so the risk of preterm birth is considered to be 1 in 400, according to one study.

Second trimester testing

These include:

• Triple or quadruple blood chemistry. These tests measure the amount of three or four substances in a pregnant woman’s blood. Triple screening checks the levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG, beta-hCG, b-hCG, Human Chorionic gonadotropin, HCG) and the type of free estriol (unconjugated estriol). This screening measures the levels 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 birth defects in the child.
• Ultrasound. The doctor sees an image of the developing fetus on the screen. It is performed between 18-20 weeks of pregnancy to identify certain features that are associated with chromosomal abnormalities (Down syndrome). Ultrasound helps to identify structural changes in organs, namely, the heart, spine, abdominal cavity or other organs.

Second trimester screening is done at 15-20 weeks of pregnancy. Triple and quadruple blood tests are also called extended AFP tests. In some cases, a comprehensive screening is done. A full report of the results is provided after the second trimester tests.

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

Birth Defect Detection - Testing Accuracy

No test is 100% accurate. Sometimes it happens that a child with negative screening results 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 a developmental anomaly.

Therefore, screening only determines the possible risk of developing pathology in the fetus. If the results indicate an increased risk, the doctor will prescribe additional tests: a chorionic villus sample or amniocentesis for an accurate diagnosis.

First trimester screening detects Down syndrome in 85% of cases. Comprehensive screening guarantees a diagnostic accuracy of 95%.

Ultrasound detects neural tube defects and anencephaly (congenital absence of the brain) in almost all cases. Chorionic villus sampling and amniocentesis accurately detect Down syndrome in 99% of cases.

Birth Defect Screening - Should I Get Tested?

Every pregnant woman makes this important decision herself. You must consider the hereditary factor, age, the necessity of this procedure and what you will do after receiving the results. At the same time, spiritual beliefs and other moral values play an important role in making the decision.

Some birth defects, such as cleft lip or palate, or certain heart conditions, can be surgically corrected after birth, or sometimes even during pregnancy. Other birth defects cannot be corrected.

Diagnostics should be done in the following cases:

• If you are thinking of terminating a pregnancy in case of birth defects.
• You have a hereditary disease, such as cystic fibrosis, Tay-Sachs disease, or hemophilia.
• You definitely 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 select a treating physician with whom you will cooperate for the full care and treatment of your child.

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

You can refuse diagnostics if:

• You want to have a baby despite the test results. Sometimes the test results are positive, but the baby can be born healthy. While waiting for the results, expectant mothers are very worried.
• This diagnostic does not reveal all possible deviations.
• You are concerned about the risk of preterm labor because chorionic villus sampling or amniocentesis is not always safe. One study in which highly trained professionals performed the procedure found a risk of 1:400. Other studies have found higher risks of 2:400 and 4:400, but in less trained professionals.
• Diagnostics are expensive.

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