What are the results of prenatal screening Double test?

The article was professionally consulted by Specialist Doctor II Huynh Thi Hien - Obstetrician and Gynecologist - Department of Obstetrics and Gynecology - Vinmec Nha Trang International General Hospital

Double test prenatal screening helps to assess the risk of a baby having birth defects. So what is the normal result of the Double test prenatal screening test?

Screening test Double test performed on venous blood samples of pregnant women, usually from about the first trimester of pregnancy, through quantification of the following indicators:
Free beta-hCG (free beta-human chorionic gonadotropin) levels ). PAPP-A (pregnancy associated plasma protein A) is present in the blood of pregnant women. The results of prenatal screening Double test combined with ultrasound measuring nuchal translucency (NT), head-buttock length (CRL) of the fetus and some other information helps to assess the risk of the baby being born with abnormality. chromosomal abnormalities such as Down syndrome, Edwards (Trisomy 18) and Patau (Trisomy 13) are high or low.
The accuracy of Double test combined with ultrasound results has the ability to detect fetal malformations in the range of 85 - 90% for Down syndrome, 5% false positive and 95% of fetuses with Edwards syndrome. Patau control with 0.3% false positives.

Normal values ​​of parameters of free β-hCG and PAPP-A of pregnant women's blood after correction are equal to 1 MoM.
The low and high cutoff values ​​of the parameters to assess the risk of birth defects are as follows:
Free β-hCG in the blood < 0.4 or > 2.5 MoM PAPP-A < 0.4 MoM Measurement Nuchal translucency Nuchal translucency is of great value in assessing the risk of chromosomal abnormalities. If the fetus has a nuchal translucency < 3 mm, the fetus has a low risk of birth defects (lower risk of Down syndrome). When the fetus has a nuchal translucency greater than 3.5 mm, the fetus is at risk of chromosomal abnormalities. Safety threshold for fetal malformations The fetal risk threshold for the risk of Down syndrome and Down syndrome according to maternal gestational age is 1/250. That is, the screening result gives the denominator > 250, the fetus is at low risk, < 250, the fetus is at high risk. The risk threshold for Edwards, Patau syndrome is about 1/100. If the screening result has a denominator > 100, the fetus is at low risk, and if the denominator is > 100, the fetus is at high risk with two syndromes.

Double test is a routine screening method, with an accuracy of about 75%, the screening results of Double test aim to assess the risk of fetal malformations with common syndromes such as Down, Trisomy 18, Trisomy 13
When the results of antenatal screening Double test are high risk, additional screening methods and diagnostic tests should be performed to accurately diagnose the condition of the fetus.

Triple test after high-risk Double test results
Triple Test is also a biochemical screening test to help answer high-risk or low-risk pregnancies for the above diseases. If the results of the Triple test pregnancy test are high-risk, then diagnostic tests should be done to make a final conclusion.
Noninvasive prenatal screening NIPT
During pregnancy, the mother's blood also contains free fetal DNA. Instead of amniocentesis and placental biopsy, the non-invasive prenatal screening method (NIPT) is much safer because only 20ml of blood is taken from the mother's veins from the 9th week of pregnancy on to progress. DNA sequence.
This result will help experts detect fetal chromosomal abnormalities of some common diseases such as Down syndrome, Patau, Edward, Turner, Klinerfelter, ...
Based on diagnostic tests and With prenatal screening, pregnant mothers will be more reassured about their baby's health status as well as have time to prepare for necessary measures if the fetus has severe birth defects.
Currently, Vinmec International General Hospital has a team of qualified genetic consultants for customers before making a decision to do NIPT. Besides, Vinmec Gen Technology Center is equipped with modern machinery system, combining technology with Gene Technology research centers in the US for fast, accurate and outstanding safety results.
For more information about birth defects screening services and maternity packages at Vinmec, you can go directly to the hospital and call hotline 0243 9743 556 for support.