Today, the standard of medical care requires that all women must be offered certain screening tests during pregnancy. Since many genetic disorders and birth defects are more common in certain ethnic groups and are linked through family history, the first prenatal screening tests typically come via history, pedigree analysis and carrier screening. A thorough history should identify risk factors for genetic disorders and must include the race, religion and ethnicity of both parents as well as the presence of genetic disorders or carrier status of the parents and relatives. Specialists in genetic screening through family history and pedigree analysis are called genetic counselors.
Carrier blood screening tests for genetic defects that are more common in different ethnic groups. Ideally, carrier screening should be performed even before conception, however, if it was not tested before pregnancy, then as soon as an expectant mother learns she is pregnant her blood should be tested to determine if she is a carrier of certain genetic conditions. If the mother’s test is positive, then the father’s blood must be tested, and further diagnostic studies, such as amniocentesis or chorionic villi sampling can then determine whether that pregnancy is afflicted with a genetic defect.
To view a chart that shows the carrier frequency of some genetic diseases among certain ethnic groups, access carrier frequency chart.
In addition to taking a family history, a pedigree analysis, genetic counseling and carrier screening, there is a two part prenatal screening test that is performed during the first trimester between 10-14 weeks of pregnancy. The first part of this test, called a nuchal translucency test, is an ultrasound examination which measures the translucent space at the back of the neck (nuchal) of the fetus and can be helpful in detecting Down syndrome. The second part of the first trimester screen measures the mother’s blood for two substances, PAPP-A (pregnancy-associated plasma protein-A) and hCG (human chorionic gonadotropin). The combined results of the nuchal translucency and first trimester blood test help identify fetuses at an increased risk of chromosomal disorders including Down syndrome and fetuses at an increased risk for cardiac defects.
When the nuchal translucency is increased but the blood test is normal, the test also helps to detect fetuses that may have a cardiac defect and require a targeted ultrasound.
A “Quad Screen” is a maternal blood test done between 16 and 18 weeks. The timing of the test is extremely important as some of the substances measured only provide accurate information at certain points in the pregnancy. As such, the dating of the pregnancy must be correct or the results may be misleading. The mother’s blood is analyzed for the presence of four substances: hCG (human chorionic gonadotropin), AFP (alpha-fetoprotein), inhibin A and UE3 (estriol). Quad Screen results show whether a fetus is at increased risk for neural tube defects like spina bifida, chromosomal disorders like trisomy 18 and 21 (Down syndrome) and even abdominal wall defects. Patients who have abnormal Quad Screen results must be offered further testing, such as a targeted ultrasound or amniocentesis, so that a diagnosis can be made with certainty.
It should be noted that although Quad Screen tests are highly accurate in identifying neural tube defects they often provide a false sense of security to parents regarding Down syndrome since they are only approximately 70% accurate in identifying fetuses with Down syndrome.
Ultrasound is a technique that uses sound waves to visualize organs within the human body. When performed and interpreted correctly, ultrasounds allow medical care providers to gain important health information about the fetus without any risk to the mother or the fetus. Between 16 to 22 weeks gestation, an ultrasound examination is performed to assess the fetal anatomy. This ultrasound is typically called a “Fetal Anatomical Survey.” During this ultrasound the interpreting physician checks whether the fetus is growing properly, the anatomy of the baby is normal and not discordant or disproportionate in size, the dating of the pregnancy is correct and there are no abnormalities. The measurements of the anatomy and cardiac views taken during this ultrasound are used to calculate risk and a thorough examination can help identify fetuses at increased risk for spina bifida and other neural tube defects, brain defects, cardiac defects, Down syndrome, and missing organs and bones.
A Targeted Ultrasound must be offered to women who may be at an increased risk of having a baby with a genetic disorder, birth defect or complication. If there is a family history of any genetic disorder or birth defect, or if the mother is considered to be of advanced maternal age, had an abnormal blood test, had a prior ultrasound that may have been abnormal or if any of the prior screening tests are inconclusive or indicate the mother is at an increased risk of carrying a fetus with a genetic disorder or birth defect, the mother must be offered a Targeted Ultrasound.
Targeted Ultrasounds assess the overall growth and development of a baby and screen for birth defects and genetic conditions. For this reason, Targeted Ultrasounds are often called Genetic Sonograms. Since the mid-1980s physicians have identified fetal anatomical signs or “markers” which are associated with Down syndrome, trisomy 18 and trisomy 13 and other genetic disorders. Targeted ultrasounds must be carefully performed and interpreted because the presence of any of these markers means there is a substantial risk the fetus has a genetic disorder or birth defect. Additionally, Targeted Ultrasounds can detect birth defects such as cleft lip, open neural tube defects such as spina bifida, heart defects and hydrocephaly.
New Jersey medical malpractice lawyers at Eichen Crutchlow Zaslow & McElroy, LLP regularly handle wrongful birth cases and cases involving negligent prenatal screening. If your child was born with a genetic disorder or birth defect, please contact us by phone at 732-777-0100 or online to schedule a consultation with a qualified NJ medical malpractice lawyer.