A genetic counselor or clinician who can explain the meaning of the results and offer choices about follow up should interpret the screening results.
A mathematical calculation using the results obtained from the PAPP-A, hCG, and nuchal translucency ultrasound is used to determine a numeric risk of a chromosomal defect in the fetus. This risk is compared with an established cut-off. If the risk is higher than the cut-off value (e.g., probability of 1 in 230 or higher), then it is considered a positive screen and the woman may be at increased risk for having a baby with a chromosomal abnormality.
It is important to remember that positive screening tests are not diagnostic of fetal abnormalities. While they do indicate an increased risk, only a very small number of women with a positive first trimester screen have babies who actually have a chromosome disorder.
In pregnancies where the fetus is carrying a chromosomal defect, such as the extra chromosome material that results in Down syndrome or Edwards syndrome, the levels of PAPP-A tend to be decreased, the levels of hCG are significantly increased, and the space at the fetus's neck is larger than normal.
While the first trimester screen can correctly identify approximately 85% of women carrying a fetus with Down syndrome and up to 75% of those with Edwards syndrome, about 5% to 10% of normal pregnancies will have a false-positive result.
If a screening test is positive, more definitive tests are needed to determine and confirm a diagnosis. These may include a diagnostic test such as chorionic villus sampling (CVS) in the first trimester or amniocentesis in the second trimester. While these two procedures are more accurate than screening tests, they are also invasive and carry a small risk of miscarriage and a rare risk of injury to the fetus.
Screening will not detect all cases of fetal abnormalities.
Doctors look for specific problems at various ages, such as cataracts and other eye conditions during a baby's first year. These checkups are also a good time for you and the doctor to talk about any concerns you have. Many parents have similar concerns as their children grow, including: Newborn concerns, such as where to get emotional support and learn about Down syndrome. Infant concerns, such as what therapies your child may need and how to prevent colds. Early childhood concerns, such as how to teach healthy behaviors, social skills, and diet and exercise. Middle and late childhood concerns, such as how to support independence and education, and what team sports your child can play. Adolescent and young adult concerns, such as what to expect during puberty and adulthood.
If your child has Down syndrome, you'll likely rely on a team of specialists that can provide medical care and help him or her develop skills as fully as possible. Depending on your child's particular needs, your team may include some of these experts:
Primary care pediatrician to coordinate and provide routine childhood care
Test Method 1 : This is a screening or a blood test done during the first trimester between the 11th and 13th week of your pregnancy. A dual marker test is done along with a Nuchal translucency scan or NT scan. The blood test measures two markers namely hCG (human chorionic gonadotrophin), and PAPP-A (pregnancy-associated plasma protein) whereas the NT scan measures the fluid under the skin at the back of the baby's neck. The scores of both these tests are considered to check if a child suffers from Down's syndrome. In case, of a risk of Down's syndrome, the reports would show abnormal levels of hCG and PAPP-A and a higher NT scan value. Depending on the results, the expectant mother either falls in ïscreen positive or high risk' or ïscreen negative or low risk' category. In India, the chance of a mother carrying a Down's syndrome baby is 1 in 350. If the risk is less, the mother falls in ïscreen negative' category. Depending on the result, the expectant mother will be advised to go for a more invasive test like amniocentesis or CVS sampling.