All pregnant patients in our office are offered the Quadruple Screen between 15 and 20 weeks. This is a blood test drawn on the mother that tests for substances made by the baby and the placenta. The levels of these substances are used along with other factors to calculate the risk of certain birth defects including Trisomy 21 (Downs-Syndrome), Trisomy 18 (Edward’s Syndrome), and open neural tube defects (spina bifida).
This is a screening test only. It does not provide a diagnosis; rather, it predicts the likelihood of a problem occurring. Maternal serum screening tests for an increased risk of a baby with certain birth defects such as open neural tube defects, Downs-syndrome, Trisomy 18 and other related birth defects.
The maternal serum screen is not 100% accurate and can be abnormal when, in fact, the developing baby does not have one of these defects. If your test returns with a low chance of these abnormalities, nothing further is done. The test will detect above 80% of infants with spina bifida, about 76% of infants with Downs-Syndrome, and about 60% of infants with Trisomy 18.
Open neural tube defects (spina bifida) are abnormalities of the spinal cord or brain and occur in one or two out of every thousand births. Overall, if there is an abnormal result on the maternal serum screen the baby has a 4 to 7% risk of open tube defects.
Babies with Down syndrome have a distinct physical appearance, mental retardation and are at risk for other birth defects. About 1 in 800 babies are born with Down Syndrome and the risk increases with the age of the mother. Overall, in women with an abnormal test result, the baby has less than 3% risk of having Downs-Syndrome.
Babies with Trisomy 18 have serious mental and physical disabilities. Only one out of 10 affected babies live past their first year. Only one in 8000 babies are born with Trisomy 18 and the risk increases with the age of the mother.
Maternal serum screening is entirely voluntary and is the decision of the parents.
As indicated above, this test is not perfect. Some defects are missed and there are many abnormal serum screens that turn out to have no association with birth defects. If there are abnormal results, further testing will be offered to determine if anything is in fact wrong with the baby.