During pregnancy, you will have the option of testing for genetic diseases. Your provider may recommend additional testing based on your age, ethnicity, and reported personal or family history. Examples of these special tests are:
Chromosomal Screening Tests (for the fetus)
- Non-Invasive Prenatal Testing (NIPT): NIPT is a non-invasive blood draw that can detect common fetal chromosomal abnormalities, rare sex aneuploidies (only if done directly through the lab – ask your provider for information on sex aneuploidies), and select microdeletions. This test provides a high degree of accuracy without the risks associated with more invasive procedures and can be done any time after 10 weeks.
- Maternal-Serum AFP (MSAFP) – California Prenatal Screening Program (CPSP) offers a second trimester blood draw that screens for Abdominal Wall Defects and Open Neural Tube Defects (ONTD). This blood draw should be done between 15 – 20 weeks of gestation.
Nuchal Translucency Ultrasound is an ultrasound that allows for early fetal anatomy to be seen. This assesses the baby’s heart, placental site, and other anatomical structures. This ultrasound is performed between 12 – 14 weeks gestation and should be performed by UCSF, conveniently located across the hall from us. You may make this appointment in person, or by calling directly to 415.502.1330.
Chromosomal Diagnostic Tests (for the fetus)
- Chorionic Villus Sampling: 10 – 14 weeks
- Amniocentesis: 16 – 20 weeks
Carrier Testing for Cystic Fibrosis
Cystic Fibrosis (CF) is one of the most common inherited diseases. About 1 in 3200 Caucasians in the United States have cystic fibrosis, which means 1 in 29 Caucasians are carriers of this condition. Although it is less common in people of other ethnic or racial backgrounds, you may still wish to consider carrier testing even if you are only part Caucasian or if your partner is not Caucasian.
Cystic Fibrosis affects the lungs and pancreas, requiring lifelong treatment or lung transplantation. Cystic Fibrosis does not affect intelligence. It is a genetic disease that is inherited from both parents as an autosomal recessive condition. This means a child has a chance of being afflicted if both parents are carriers. A carrier is someone who has only one gene with the CF mutation and one gene that is normal. Carriers are typically symptom-free and do not know that they carry the mutation.
If no one in your family has cystic fibrosis, the chance that you are a carrier is based on your ethnic group:
- Caucasian: 1 in 29
- Hispanic: 1 in 46
- African-American: 1 in 65
- Asian-American: 1 in 90
If you and your partner are both carriers of a cystic fibrosis gene mutation, there are tests available to determine whether the baby has the disease. This testing can be performed using cells from chorionic villus sampling (CVS) or amniocentesis. If both members of a couple are carriers of a cystic fibrosis gene, in each pregnancy there is a 25% chance of having a child with the disease and a 75% chance of having a child without the disease.
Carrier testing for cystic fibrosis involves either a blood or saliva sample. Because the laboratory isolates DNA and tests for specific genetic mutations connected with specific diseases, the result is highly accurate.
Expanded Carrier Testing
It is possible to test you and your partner for other diseases for which you could be carriers. Some of these diseases cause birth defects and/or shortened lifespan. Some can be treated if detected early. As a carrier, you are likely healthy and have no idea that you have an abnormality in your genes. However, if both you and your partner are a carrier of the same disease, there is a 25% risk with every pregnancy that the baby could inherit both parental gene mutations and possibly be affected.
Thankfully there is only a 1% chance that both you and your partner are a carrier of the same disease but now is an opportunity to do carrier screening with a simple blood test to test for the possibility. If both you and your partner are carriers of the same disease, then there is genetic counseling and the option of diagnostic testing for the fetus.
