There are various genetic tests aimed at detecting fetal genetic mutations, conducting carrier screening for parents, and diagnosing genetic diseases in children.
Accordingly, some tests are performed by parents at the pre-conception stage, or on cell cultures before implantation. Other tests are preformed prenatally (during pregnancy), while certain tests are performed postnatally (after birth).
This article discusses a prenatal procedure known as fetal skin sampling, or fetal tissue biopsy.
Which prenatal tests can help detect diseases?
Some prenatal tests are more commonly offered than others. Here are several popular prenatal tests available today:
Triple screen (also known as triple marker test): a blood test performed around week 17 into pregnancy. A blood sample is taken from the pregnant woman to measure the level of several substances: the hormone hCG (human chorionic gonadotropin) that is produced in the placenta, AFP (alpha-fetoprotein), and Estriol (a hormone produced by both the placenta and fetus).
Amniocentesis: this invasive procedure is performed between weeks 16-20 into pregnancy. In this test, a small amount of amniotic fluid (usually less than one ounce, or 30 ml) is drawn from the amniotic sac using a thin needle. This fluid contains fetal cells shed by the fetus, that can be tested for various genetic mutations.
Chorionic villus sampling (also known as CVS): this procedure can be performed as early as week 10 into pregnancy. Since the genetic material in the chorionic villi is identical to the fetal genetic material, sampling the chorionic villi is sufficient for genetic testing, and it is not necessary to take samples from the fetus.
Cordocentesis: also known as percutaneous umbilical cord blood sampling, this procedure provides direct access to the fetal circulatory system, it is performed by drawing flood from the umbilical cord. This procedure allows testing for infections that were passed on to the fetus by the mother and provide treatment as necessary.
What is a fetal tissue biopsy?
While amniocentesis also uses samples of skin cells, fetal tissue sampling usually refers to a biopsy taken directly from the fetus. This sample is retrieved using forceps inserted through the mother’s abdomen under ultrasound guidance.
The sample retrieved is very small in size and does not usually exceed one millimeter. Analyzing this sample can help diagnose various severe skin diseases. The test is usually performed on rare occasions when other routine genetic tests cannot be performed, or in cases of a severe disorder in one of the parents.
It should be noted that according to certain researchers, fetal skin sampling is associated with a risk of 5% for loss of pregnancy. For this reason, this is not a routine procedure but is a test used in rare occasions only.
Which diseases can fetal skin sampling detect?
Epidermolysis Bullosa – this is an inherited skin disorder that causes the epidermis to become separated from other layers of the skin, which causes large blisters. People with Epidermolysis Bullosa usually suffer from absent nails and widespread peeling of the skin.
Ichthyosis – a severe skin disorder that causes the skin to be acutely dry and scaly. In severe cases, this disorder also causes intellectual disability and congenital bone defects.
Albinism – albinism is a genetic disorder with a recessive inheritance pattern. This condition causes the absence of pigments in the skin, hair, and eyes. People with albinism are extremely sensitive to light and are at an increased risk of developing skin cancer. In addition, they suffer from vision impairments. Fetal tissue sampling for albinism is only offered when other prenatal tests cannot be performed.
