Screening for Chromosomal Abnormalities & Birth Defects
A visit to the doctor has confirmed your pregnancy. This is an exciting time in the life of an expecting family. Preparation for your new arrival should begin immediately. The health of your new baby is paramount. Prenatal care is important to the health of both the mother and the baby. Proper screenings and exams during each trimester provide the mother with invaluable information regarding the baby's development. Each trimester has its own evaluations and all are important components in comprehensive prenatal care. Various screening and diagnostic options are available to assess specific risks and evaluate the development of your baby. If desired, you may partner with your physician to discuss the available options. Among these are tests for chromosomal abnormalities called aneuploidy. Examples include Down syndrome, Edward's syndrome, and Patau syndrome.
As early as 9-10 weeks | Non-Invasive Prenatal Testing:
Non-invasive prenatal testing uses cell free DNA collected from the expectant mother's blood. This screening test offers tremendous information regarding the potential for chromosomal abnormalities with a 99% detection rate for Down syndrome. This test can also detect gender as early as 9-10 weeks gestation. According to the American Congress of Obstetrics and Gynecology, this test is recommended for patients at high risk for aneuploidy.
10 - 13 weeks | Chorionic Villus Sampling (CVS):
A simple diagnostic procedure in which a sample of chorionic villi is removed from the developing placenta. This test can reveal if the growing fetus has evidence of aneuploidy by analyzing actual fetal tissue and cells.
11 1/7 - 13 6/7 weeks | Nuchal Translucency:
A minimally invasive screening test performed as early as the 11th week of pregnancy in which a hormonal assessment is performed in combination with an ultrasound designed to look at the clear space in the tissue at the back of the baby's growing neck called the nuchal translucency. In certain instances fluid can accumulate in this space making it appear larger and /or the laboratory tests may demonstrate abnormal values suggesting an increased risk for aneuploidy, cardiac defects, or other genetic syndromes.
15 - 20+ weeks | Quad Screen:
A screening test generally performed between 15 and 20 weeks of pregnancy that measures the levels of alpha-fetoprotein, hCG, estriol, and inhibin A in the mother's blood stream. Abnormal values are associated with increased risk for chromosomal abnormalities and other complications such as neural tube defects (Spina Bifida).
This is another diagnostic test typically performed after 15 weeks of pregnancy by inserting a small needle through the mother's abdomen into the amniotic sac. A small amount of fluid is collected. Analysis of this fluid contains actual cells from the baby and can offer information regarding potential chromosomal abnormalities, birth defects, and gender.
This noninvasive screening procedure is completed at approximately 20 weeks of pregnancy. This uses sound waves on the mother's abdomen directed toward the baby to obtain information regarding size, weight, growth, gender, and possible birth defects or other abnormalities that might complicate the pregnancy.
Who Should Be Screened?
Any expectant mother may choose to obtain screening, but certain risk factors may prompt your doctor to consider you as having a higher risk than other patients. Risk factors that may increase your risk of having a child with a chromosomal defect include, but are not limited to, age > 35 years, having a family history of a specific genetic condition, you or your partner is a known carrier of a genetic condition, and having a prior child with a genetic abnormality or birth defects.
The Results Are In. Now What?
Once the results of your screening tests have been obtained by your physician, 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 for aneuploidy (chromosomal abnormality) mean that the chances are very low that your developing baby will be born with one of the aforementioned abnormalities. Unfortunately, this does not eliminate the risk of an abnormality. 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.