Everything You Need to Know About Double Test Screening

In every pregnancy, tests and examinations are part of the routine. One of these is the Double Test Screening. Tests can check if everything is ok with the pregnancy.

Tests in all three trimesters of pregnancy
In the first trimester, one of the tests routinely performed is the double test screening. This checks the possibility of having a baby with a chromosomal abnormality.

Double test screening consists of measuring the nuchal translucency of the fetus. The levels of two hormones produced by the fetus from the mother’s blood, the hCG, and PAPP-A.

Nuchal translucency screening is a routine ultrasound done between the 11th and 13th week of pregnancy. After this period, the tissue on the fetus’s neck gets thicker. Thus, it is no longer translucent, making the test results inconclusive.
This screening measures the fluid on the base of the fetus's neck. Thus, it is possible to detect any chromosomal problem such as Down’s syndrome, trisomy 13, and trisomy 18.

However, it is good to know that nuchal translucency screening will not tell you for sure if your child will have a chromosomal problem. Instead, it will only show the likelihood of your child being born with a chromosomal problem.

Nuchal Translucency Screening
Nuchal translucency screening uses a special type of ultrasound with a high sensitive ultrasound. First, the fetus is measured from crown to rump. The size of the fetus must correspond with the baby's gestational age. Your own age is entered into the equation to calculate the probability for a chromosomal problem.

In babies with a chromosomal abnormality, such as in cases of Down’s syndrome, trisomy 13 or trisomy 18, the nuchal fold expands in size. It is due to a fluid build-up.

Due to a relatively high rate of errors which accompany the nuchal translucency screening. Your doctor often recommends a combined screening. This will include measuring two blood tests. The levels of hCG (human chorionic gonadotropin) and the levels of PAPP-A (pregnancy-associated plasma protein A) for a better and more accurate result.

This screening is called the double screening. It is a routine screening performed in every pregnant woman during the first trimester of pregnancy.

Double Test Screening
hCG and PAPP-A are two hormones produced by the fetus which passes into the mother’s bloodstream. In cases of a chromosomal abnormality, besides an increased size of the nuchal folds, the levels of these two hormones will be higher than normally.

As mentioned, the double test screening is not 100% accurate. It will only show the likelihood of having a child with a chromosomal abnormality. In some tests, a false positive result is noticed. Down’s syndrome is the most common type of the three chromosomal disorders mentioned above.

In general, the test results of double test screening are positive or negative. If the risk is less than 1 in 350, the screening is negative. If the risk is higher than 1 in 350, the screening is positive.

A double test screening is recommended worldwide. Once the results are negative there is no other reason to suspect Down’s syndrome. Thus, there is no need for additional tests and examinations.

A triple test screening can also be done. This is regardless of the results of double test screening. This screening is routine if there is a high risk of giving birth to a child with a chromosomal abnormality. Including mother is over the age of 35.

If the second-trimester screening also shows a higher risk for chromosomal abnormalities. Your health care provider will order some other tests, known as diagnostic tests such as sonograms, chorionic villus sampling, and amniocentesis.
Unfortunately, these diagnostic tests have a risk of complications, including miscarriage.

It is good to know that even though your first-trimester screening resulted positive, these tests are not diagnostic. They will only show an increased risk of having a baby with a genetic abnormality.

Only a very small number of pregnant women who test positive on their double test screening end up giving birth to a child with a chromosomal abnormality.

In multiple pregnancies, the calculation of the risk for a chromosomal abnormality can be quite difficult. This is due to higher levels of hCG and PAPP-A, normally noticed in these pregnancies.

Pregnancy stress can also cause issues. Consult your gynecologist to find out more. There are multiple methods to avoid stress and have a healthy pregnancy.