V. Genetic screening and testing options during pregnancy

But, first let’s explain WHY and WHAT we screen + test for in the first place.

Carrier Screening

Carrier Screening is a blood test that is performed to see if you, the biological parent, carry a gene for certain genetic disorders. Most of these conditions are autosomal recessive, which means that you and your partner would both need to carry the same genetic mutation to have a 25% chance of having an offspring with the said condition. Anyone who is considering pregnancy or is pregnant should be offered genetic carrier screening. It is designed to identify an individual who may be at higher risk for carrying a particular disorder/gene. In other words, genetic and family history should be evaluated. The most common conditions tested include cystic fibrosis, Tay-Sachs disease, sickle cell anemia, hemophilia and Fragile X syndrome. 

Chromosomes Testing

Aneuploidy screening checks the chromosomes of the baby, so it is offered with each pregnancy because the results are specific to the incident fetus. Aneuploidy screening typically entails an ultrasound, blood work and/or invasive testing of the placenta (chorionic villus sampling-CVS) or amniotic fluid (amniocentesis). Benefits of early screening include the potential for an earlier diagnosis and thereby improving reproductive choices based upon the results of testing.

i.  Non-invasive prenatal testing (NIPT)

NIPT is a screening test that can be performed after the 10th week of pregnancy. It is a maternal blood draw and therefore has no risk to the pregnancy. It screens for the more common trisomies: 21 (Down’s syndrome), 18 and 13 as well as certain sex chromosome conditions. This test is often accompanied by an ultrasound between 12-14 weeks to assess the nuchal translucency or area at the fetal neck which can be a sensitive genetic indicator.

ii.  Chorionic Villus Sampling (CVS)

A CVS is an invasive diagnostic test that is typically performed in the first trimester, from the 10th week of pregnancy to the end of the 13th week. Under ultrasound guidance (either transabdominal or sometimes transcervical) a needle biopsy of the placenta is obtained. This tissue sample can then assess the chromosomal make-up of the fetus with accuracy. There is however a small risk of miscarriage.

iii.  Amniocentesis

An amniocentesis (also called an amnio) is typically done 16-20 weeks of pregnancy where a small needle is inserted into the fluid filled sac around the baby and under ultrasound guidance. Fetal cells are floating in this fluid and are retrieved and undergo chromosomal analysis. This test is highly accurate but there is a small risk of miscarriage from the procedure.

iv.  Serum markers

Certain proteins and hormones can be analyzed through maternal blood to assess fetal chromosomes. The testing can be done in the first and second trimesters, first screen and sequential screen. This test is slightly less accurate than the NIPT and invasive diagnostic tests. It is less expensive than the other available tests.

v.  Ultrasound

Between 11-14 weeks gestation a space behind the fetal neck, nuchal translucency (NT) can be measured by ultrasound. When the NT is increased it can suggest a chromosomal or anatomical issue and additional testing can be offered. Also, the fetal nasal bone presence can be assessed at this early ultrasound and its presence can be reassuring for a fetus with a normal chromosomal make-up. A second trimester anatomical survey at approximately 20 weeks should be offered to all pregnant woman as part of routine prenatal care.

 Verbena does not provide medical advice, diagnosis, or treatment and is not a medical provider. Discuss potential pregnancy genetic testing and screening options with your personal OBGYN/provider.

If you think you may have a medical emergency, call your doctor or 911 immediately.