Baylor Prenatal and Reproductive Genetics
Tests We Offer
Advanced testing, unparalleled expertise
At Texas Children’s, we offer the full range of prenatal and reproductive genetic tests, including carrier screening for chromosomal conditions, such as Down syndrome. Our team of geneticists and genetic counselors will work with you to recommend the most appropriate screening and testing before and during your pregnancy and will empower you to understand your genetic risk factors. Below are some of the most common tests and screenings we offer.
Tests We Offer
Doctors can often detect birth defects early on in a pregnancy through noninvasive imaging studies. We offer the following imaging options:
- Basic ultrasound
- Comprehensive scan
- 3-D/4-D ultrasound
- Fetal echocardiogram
- Fetal MRI
While many families recognize their risk to pass down a genetic condition based on a personal or family history, some genetic conditions are inherited from healthy parents who are “carriers” of the genetic condition. For most conditions, both parents must be carriers of the same genetic condition for their children to be at risk.
Carrier screening is a genetic test that can be performed on a blood or saliva sample. There are many different carrier screening panels available that vary in the number of conditions screened for. Your genetic counselor can help you decide which one is best for you.
CVS is an ultrasound-guided procedure that samples tissue (chorionic villi) in the placenta outside the amniotic sac. CVS is typically performed in the first trimester between 11 and 13 weeks gestation by a trained specialist and can provide earlier results than those provided by amniocentesis which is typically performed in the second trimester starting at 16 weeks gestation.
CVS allows for diagnostic genetic testing to be done on placental cells, which are typically genetically identical to the fetal cells. The type of testing done after a CVS varies in each case, but it can provide information on fetal karyotype, such as detecting Down syndrome, and certain genetic syndromes such as sickle cell disease or Tay Sachs disease.
The procedure can be performed via the abdominal wall or via the cervix, depending on the location of the placenta. There is a small risk of bleeding, infection and miscarriage. Your doctor will discuss the potential risks and benefits of the procedure.
Chromosomes are the structures in our cells that contain our genetic information. Routine chromosome analysis involves looking at the chromosomes of a baby by analyzing cells from the amniotic fluid (obtained from amniocentesis), placenta (obtained from CVS) or other fetal tissue. This analysis evaluates for missing or extra genetic information, which can lead to genetic syndromes, such as trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome), caused by an extra copy of either chromosome 21, 18 or 13, respectively. The risk for having a baby with a chromosomal trisomy increases as women age, but it can occur at any time. For example, at age 28 a woman has about a 1 in 1,000 risk for Down syndrome compared to a 1 in 100 risk at age 40.
CMA a comprehensive prenatal genetic testing option and is performed in conjunction with chromosome analysis. CMA has the ability to detect small missing or extra pieces of chromosome material (microdeletions and microduplications) that are associated with more than 180 genetic conditions, including most of the conditions that can be found on a routine chromosome analysis.
Percutaneous umbilical cord blood sampling (PUBS) allows doctors to sample fetal blood under ultrasound guidance. The test is usually performed after 18 weeks gestation. PUBS provides a means for rapid and accurate genetic testing, analysis of blood disorders (e.g. anemia, hemophilia, alloimmune thrombocytopenia, identification of congenital infection), or early detection of metabolic diseases that might possibly not be detected by amniocentesis or chorionic villus sampling in certain cases. This procedure is also used to perform blood transfusion and to directly administer medication to the fetus.
The procedure itself is similar to an amniocentesis procedure and involves placement of a small needle into the uterus for a fetal blood sample from the umbilical cord. Potential risks include spontaneous miscarriage, infection, hemorrhage, preterm labor and premature delivery.
Fluorescence in situ hybridization (FISH) is a more rapid way to test for common chromosome problems such as Down syndrome, trisomy 18, trisomy 13 and Turner syndrome.
Genetic amniocentesis is an ultrasound-guided procedure that samples a small amount of amniotic fluid (20–30 mL; 4–6 teaspoons) from the sac around the baby. An amniocentesis is typically performed starting at 16 weeks gestation by a trained specialist. An amniocentesis allows diagnostic testing to be done on fetal cells, compared to the CVS where diagnostic testing is done on the placental cells.
Diagnostic tests can be done on the sample to identify fetal chromosomal abnormalities (such as Down syndrome), prenatally diagnosable genetic diseases, and most neural tube defects (spina bifida). With amniocentesis, there is a small risk of bleeding, infection and miscarriage.
A genetic counseling appointment is scheduled for any person considering a diagnostic prenatal procedure, such as chorionic villus sampling or amniocentesis, in order to review the benefits, risks and limitations of the procedure. Available genetic testing options are also reviewed during this session.
Inherited conditions are genetic conditions that are passed from biological parents to their children. While many families recognize their risk to pass down a genetic condition based on a personal or family history, some genetic conditions are inherited from healthy parents who are “carriers” of the genetic condition. While it is common to be a carrier of a genetic condition, it is rare for reproductive partners to both be carriers of the same condition. For most conditions, both parents must be carriers of the same genetic condition for their children to be at risk.
Making the right decision for your family
Other testing for a specific genetic condition may be recommended depending on your family or pregnancy history and may include testing for a single gene, a panel of genes or whole exome/genome sequencing (WES/WGS). WES/WGS is the broadest test for diagnosing single gene disorders.
If you’re concerned about prenatal testing, our genetic counselors can help you understand and weigh the risks and benefits. Taking the time to evaluate all of your options will enable you to make the best decision for you and your baby.