Screening for Chromosomal Abnormalities & Birth Defects
After the first OB visit to confirm the pregnancy, we offer screenings and exams during each trimester to provide the mother with information regarding the baby's development.
Each trimester has its own specific evaluations, and all are important to your prenatal care. Among these are tests for chromosomal abnormalities such as Down syndrome.
If desired, ask your care provider to discuss all available options with you.
Who Should be Screened?
Any expectant mother may choose to obtain screening. While these tests are optional, there are certain risk factors may prompt your provider to consider these tests especially important for you.
Risk factors that may increase your risk of having a child with a chromosomal defect include:
- being over 35 years of age.
- having a family history of a specific genetic condition.
- being a known carrier of a genetic condition.
- having a prior child with a genetic abnormality or birth defects.
Available Screening Tests
Genetic Carrier Screening
Recommended by The American College of Obstetricians and Gynecologists, this screening identifies carrier genes for Spinal Muscular Atrophy, Cystic Fibrosis and Fragile X syndrome. These are genes that parents carry that could be passed on to their baby. This testing is recommended for all patients.
Cell Free DNA in maternal serum testing (Non-Invasive Prenatal Testing)
This is a blood test that detects fragments of fetal DNA in maternal blood to screen Down syndrome and other chromosomal abnormalities. It can be done as early as 10 weeks and can also determine the gender. This test is usually recommended for women over age 35.
First Trimester Screen (Nuchal Translucency Test)
This screen uses an ultrasound to measure the fluid filled space at the back of the baby's growing neck called the nuchal translucency. If the nuchal translucency value is abnormal (greater than 3mm), this can indicate an increased risk of cardiac defects or other structural abnormalities. It is typically done between 11 and 13 weeks. This test is recommended for all patients.
This test uses ultrasound imaging to look for the presence of open neural tube defects which includes spina bifida. It is done between 15 and 18 weeks and is recommended for all.
This screen uses ultrasound to obtain information regarding size, weight, growth, gender, and possible birth defects or other abnormalities that might complicate the pregnancy. It is performed around 20 weeks of pregnancy.
Have My Results. Now What?
Once the results of your screening tests have been obtained by your provider, it will be determined whether your pregnancy is in a high risk or low risk category for having a chromosomal abnormality.
These results will be reviewed with you. Results demonstrating a decreased risk mean chances are very low that your developing baby will be born with one or more chromosomal abnormalities.
If the results suggest an increased risk, you and your doctor may discuss options that could include proceeding to diagnostic testing such as CVS or amniocentesis. These options will be discussed at length with you, and your care provider will help you understand each procedure and its risks. Together, you and your provider can come up with a care plan that best fits you and your baby.