At Women’s Health of Mansfield we now offer a new screening option for Down
syndrome, trisomy 18 and open neural tube defects.
This test is called Sequential Screen which is a two-part screen and the only screen that
can provide you with two answers – an early, preliminary result in the first trimester and a
final result in the second trimester.
How does Sequential Screen work?
Between your 10th and 14th week of pregnancy, a small amount of blood and a special
ultrasound measurement will be taken. Sequential Screen will use information from your
blood and ultrasound measurement to provide you with your risk of having a baby with
Down syndrome or trisomy 18.
Between your 15th and 22nd week of pregnancy you will come back for a second blood
test. The second part of this screen will use the information collected at both times in
your pregnancy and provide you with a final screening result. The screen will tell you what
your risk is of having a baby with Down syndrome, trisomy 18 or an open neural tube defect.
Sequential Screen detects approximately:
· 70% of the babies with Down syndrome
· 80% of the babies with trisomy 18
· 90% of babies with Down syndrome
· 90% of babies with trisomy 18
· 80% of babies with open neural tube defects
Down syndrome is caused by an extra chromosome #21. This extra chromosome causes
mental and physical abnormalities. About 1 in 800 babies born with Down syndrome. The
risk of Down syndrome gradually increases with age of the mother, but can occur at any
Trisomy 18 is caused by an extra chromosome #18. This extra chromosome causes
severe mental and physical problems. About 1 in 6,500 babies is born with trisomy 18.
Only 1 out of 10 babies with trisomy 18 lives past the age of one year. As with Down
syndrome, the risk of trisomy 18 gradually increases with the age of the mother.
Open Neural Tube Defects
The neural tube, which forms very early in pregnancy eventually develops into the baby’s
brain and spinal cord. If this tube does not close completely, an opening remains along
part of the baby’s spine or head. This can lead to paralysis and other physical and/or
mental problems. Open neural tube defects occur in 1 out of 1,000 live births. The risk of
having a child with an open neural tube does not increase with the age of the mother.