Christiana Care Maternity

First-Trimester Screening for Down Syndrome, Trisomy 18 and Trisomy 13 Chromosomal Disorders

Down syndrome and trisomies 13 and 18 are chromosomal disorders that cause mental retardation and birth defects. Babies with Down syndrome have an extra chromosome No. 21 (trisomy 21) which causes mental retardation and various medical problems involving the heart, digestive tract, or other organ systems.

Trisomy 18 (having an extra chromosome No. 18) and trisomy 13 (having an extra chromosome No. 13) are more severe disorders that cause profound mental retardation and severe birth defects in many organ systems.

Few babies born with trisomies 13 or 18 survive more than a few months. Anyone can have a baby with these chromosome abnormalities; however, the chance increases with the mother's age.

Christiana Care is the only health system in Delaware that offers first-trimester screening and the ability for immediate prenatal diagnostic testing for trisomy 21 (Down syndrome), trisomy 18 (Edwards' syndrome) and trisomy 13 (Patau syndrome) chromosomal disorders. The screening is noninvasive and poses no risk to the mother or baby. In fact, the American College of Obstetricians and Gynecologists has endorsed first-trimester screening for chromosomal disorders.

Facts about first-trimester screening:

• Screening for chromosomal disorders is performed between weeks 11 and 14 of pregnancy.
• The screening combines a maternal blood test and an ultrasound.
• The blood screen measures hormones and proteins found in the blood of all pregnant women. Unusually high or low levels of these hormones and proteins could indicate an increased risk for chromosomal abnormalities or other problems with the pregnancy.
• The ultrasound measures the amount of fluid at the back of a baby's neck and determines if a baby's nasal bone is present. Babies with chromosomal disorders may accumulate more fluid at the back of their neck during the first trimester. The ultrasound is non-invasive and does not cause the baby any pain or discomfort.
• Babies with no visible nasal bone at the time of the screening are at a higher risk for chromosomal disorders.
• First-trimester screening is not a diagnostic test and cannot determine whether a baby has Down syndrome or trisomy 18 and trisomy 13. However, screening does provide the patient with a personalized risk estimate for these conditions and gives the parents the ability to decide if they would like further testing. Most patients' risk decreases for these chromosome abnormalities after screening.
• First-trimester screening can identify up to 91 percent of pregnancies with Down syndrome and up to 95 percent of pregnancies with trisomy 18 and trisomy 13.
• According to the American Pregnancy Association, a positive diagnosis in the first trimester gives women more time to:
  • Seek potential interventions that might exist.
  • Begin planning for a child with special needs.
  • Identify support groups and resources.

• If experiencing an emergency, dial 911
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