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Maternal Screening for Birth Defects

Prenatal screening helps identify genetic disorders that can be passed on to a child. Some parents may elect not to pursue further testing for various reasons. Your clinician will discuss options as well as the risks and benefits. Depending on ethnicity and family history your clinician may suggest these screenings.

Chorionic Villus Sampling
First Trimester Screen
Maternal Serum Alpha-fetoprotein (MSAFP) or Quad Screen
Down Syndrome
Neural Tube Defects - Spinal Bifida
Trisomy 18 and 13

Reasons to consider screening vary from person to person and couple to couple. Screening allows parents to consider options and pursue possible medical interventions, and/or begin planning for a child with special needs and addressing anticipated lifestyle changes.  For some it allows time to make a decision about carrying the fetus to term.

If you need additional support in making these decisions, you may be referred to a genetic counselor.  These health care professionals are experienced in helping families understand birth defects and how heredity works. They provide information to help families in making decisions about pregnancy, child care, genetic testing and chances of having children affected with genetically inherited conditions. 

Maternal Screenings are routinely offered to pregnant women to screen for neural tube defects, Down syndrome, and trisomy 18 & 13.

  • Down Syndrome

    Down Syndrome is a chromosomal disorder that includes a combination of birth defects. Affected individuals have some degree of intellectual disability, characteristic facial features and often, heart defects and other health problems. The severity of these problems varies greatly among affected individuals.  Down syndrome is one of the most common genetic birth defects. It affects about 1 in 800 babies each year in the United States.

  • First Trimester Screen

    The First Trimester screen is a combination of a blood sample and fetal ultrasound tests to determine risk for having a baby with Down syndrome and/or trisomy 18 & 13. This testing is performed between 11 and 13 weeks in pregnancy and identifies women who would benefit from further testing.  Blood is drawn to measure levels of free human chorionic gonadotropin (hCG) and pregnancy associated protein-A in plasma (PAPP-A) normally found in pregnant women.  Combined with an ultrasound measurement of the fluid surrounding the neck of the fetus, test results received at the earliest point during the pregnancy allows clinicians and patients’ time to make plans for additional testing and/or genetic counseling.  Your clinician may perform testing in her/his office or may refer you to a maternal fetal medicine physician for this screening.

  • Trisomy 18 and 13

    Trisomy 18 is a chromosomal condition linked to severe intellectual disability and abnormalities in many parts of the body. Individuals with trisomy 18 often have low birth weight, a small, abnormally shaped head, a small jaw and mouth, clenched fists with overlapping fingers, heart defects, as well as abnormalities of other organs. Only 5 to 10% of children with this condition live past their first year of life. Trisomy 18 occurs in about 1 in 5,000 newborns and approximately 80% of newborns affected by this disorder are female. Although women of all ages could have a baby with trisomy 18, the chance of having a baby with this condition increases as a woman gets older.

    Trisomy 13 is a chromosomal condition associated with severe intellectual disability and physical abnormalities in many parts of the body. Individuals with trisomy 13 often have heart defects, brain or spinal cord abnormalities, very small or poorly developed eyes, extra fingers and/or toes, an opening in the lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate), and weak muscle tone (hypotonia). Due to the presence of several life-threatening medical problems, many infants with trisomy 13 die within their first days or weeks of life. Only 5 to 10% of children with this condition live past their first year. Trisomy 13 occurs in about 1 in 16,000 newborns. Although women of any age can have a baby with trisomy 13, the chance of having a baby with this condition increases as a woman gets older.

    Most cases of trisomy 18 and 13 are not inherited, but occur as random events during cell division in early embryonic development. Some of the body's cells have the usual two copies of chromosome 18 or 13, and other cells have three copies of one of these chromosomes that may come from either the egg or the sperm.

    The inherited form of trisomy 18 and 13 occurs when an unaffected person carries a rearrangement of genetic material between chromosome 18 and other chromosomes. There is no “extra copy” of chromosome 18, only a rearrangement or translocation of the chromosome.  People who carry this type of translocation are at an increased risk of having children with the condition.  The physical features of these types of abnormalities may be different than those with full trisomy 18 or 13.

  • Neural Tube Defects - Spina Bifida

    Spina Bifida is a neural tube defect affecting approximately 1 in 1,000 pregnancies each year. The neural tube that includes the spinal cord and brain develops during the first month of pregnancy.  In a neural tube defect, a portion of the spinal column fails to close completely. The effects of spina bifida are different for every person and dependent on location of the defect. Conditions related to spina bifida include full or partial paralysis, difficulties with bladder and bowel control, learning disabilities, depression, as well as social and sexual issues.

    All pregnant woman are at risk for this birth defect. In fact, 95% of neural tube defects (NTDs) occur in women with no personal or family history of NTDs. Risk factors known to increase risk of an NTD include prior pregnancy with NTD, maternal insulin-dependent diabetes, anti-seizure medication (Valproic acid/Depakene, and Carbamazapine/Tegretol), exposure to high temperatures in early pregnancy (i.e., prolonged fevers, hot tub use) and race/ethnicity (NTDs are more common among white and Hispanic women).

  • Maternal Serum Alpha-fetoprotein (MSAFP) or Quad Screen

    Similar to the first trimester screen, this test also is used to identify pregnancies at a higher risk for certain birth defects such as neural tube defects and Down syndrome. It is offered between 15 and 18 weeks of pregnancy.  MSAFP measures three specific substances in blood, Alpha-fetoprotein (AFP), unconjugated estriol (uEST) and human chorionic Gonadotropin (hCG), found in pregnant women. Blood levels are compared to expected laboratory values and results are interpreted as normal, low or high. Both high and low levels indicate a need to follow up with further diagnostic studies such as amniocentesis and ultrasound.

    An “abnormal” test result may cause fear and concern, but at least one out of every ten women has an abnormal triple screen test result. Most of these women go on to have healthy babies. A normal MSAFP indicates there is low risk for certain abnormalities, but does not guarantee a perfect, normal baby.

  • Chorionic Villus Sampling

    Chorionic Villus Sampling (CVS) is a diagnostic test usually performed at 9-12 weeks gestation. It involves using ultrasound for needle guidance to obtain a sample of the placenta; cultures are taken to determine if there are any genetic, chromosomal or biochemical abnormalities present in the cells.

    Women over age 35 and women with previous children with birth defects most commonly undergo CVS.  It carries a 1% chance of miscarriage, though cramping and bleeding can be expected after the procedure. CVS takes about 30-45 minutes to perform; and can take up to two weeks for enough cells to grow and results to be finalized.

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