Screening and Testing for Genetic Abnormalities in Multiple Gestations
Genetic abnormalities in pregnancy occur when a problem exists in one or more of the baby's chromosomes. Chromosomes are the individual instructions in each one of our cells that make us unique. Ochsner's Multifetal Pregnancy Center offers a variety of screening and invasive testing to identify genetic abnormalities in the multifetal pregnancy.
Prenatal screening tests can estimate a baby's risk of having a chromosomal abnormality, such as Down syndrome, without risk to the pregnancy. In the early part of pregnancy, between 11 to 13 weeks, you can choose to undergo first trimester screening (also known as nuchal translucency (NT) testing). This screening test includes an ultrasound of the back portion of the baby's neck and a simple blood draw. The ultrasound determines if your baby has increased fluid in the back of the neck, a potential sign an underlying chromosomal abnormality. Overall, NT screening in twins has a very high detection rate (>85%) for Down syndrome and is becoming the preferred method for screening in pregnancy. If you present for consultation after 15 weeks of pregnancy you have the option of "quad screening". This is another simple blood test that can be useful for the detection of chromosomal abnormalities between 15 to 21 weeks of pregnancy.
Invasive genetic tests, including chorionic villus sampling (CVS) and amniocentesis, are used to definitively diagnose chromosomal abnormalities in pregnancy. CVS is a procedure in which a small portion of the placenta (chorion) is sampled between 11 to 14 weeks of pregnancy versus amniocentesis which is a procedure in which a small amount of fluid around the baby (amniotic fluid) is sampled after 15 weeks of pregnancy. These tests can be also be used to definitively diagnose other familial genetic conditions such as cystic fibrosis or sickle cell disease.
Also your specialized prenatal care will include a detailed high definition ultrasound examination of your babies, usually performed between 18-20 weeks gestation. This evaluation is designed to look for structural defects that tend to occur more often in multiple than singleton pregnancies. Though not as sensitive for detecting the more common genetic diseases, on occasion ultrasound will find rare disorders that are not screened for using the tests.
Ochsner's Multifetal Pregnancy Center of New Orleans has nationally certified Maternal-Fetal Medicine doctors and sonographers who have extensive training in the performance of the above tests. We are proud to offer our patients the most innovative genetic tests that are available anywhere in the nation.