Скачать или смотреть Maternal Markers | Tests for birth defects | Pregnancy Health

Maternal markers are widely used for Prenatal screening as a part of routine antenatal care. The common disorders being screened for include, chromosomal abnormalities such as the common trisomies, including Downs syndrome, Edwards syndrome, Patau syndromes, and fetal neural tube defects (NTDs) such as anencephaly and spina bifida.



There is a fundamental difference between a screening and a diagnostic test. As the term itself implies, Maternal Markers or prenatal screening are a type of screening tests. The aim is not to give us a definitive diagnosis in “yes or no” but it is to identify those pregnancies that are at high risk of a given outcome, from among apparently healthy pregnancies. This will help us decide the next step, that may be a secondary screening test or an expensive and invasive diagnostic test. For example, screening for Down syndrome does not aim to make a diagnosis per se, but it helps in judicious use of invasive diagnostic procedures such as chorionic villus sampling (CVS) or amniocentesis, that would be risky and expensive, to offer without prior selection by screening.



Maternal screening includes measurement of certain biomarkers in maternal blood sample which are proteins produced by the fetus or placenta. Also, a number of maternal and fetal biophysical factors are considered for a comprehensive risk calculation. To obtain a complete report, various details required are- mothers’ date of birth, sample collection date, gestational age based on USG, mother’s weight, ethnic race, insulin dependent diabetes status prior to pregnancy, number of fetuses and if it’s an IVF case. Finally, the risk is calculated in relation to population standards.

There are mainly two different versions of Maternal screening: first trimester screening and second trimester screening.

First trimester screening is performed in between 9 weeks to 13 weeks plus 6 days of gestation. It is also called Dual Marker as it tests for two biomarkers in the mother’s blood sample- PAPP A, Free Beta HCG. It also requires a specific ultrasound measurement for Nuchal Translucency, CRL and status of nasal bone. NT/ Nuchal Translucency is collection of fluid under the skin at the back of the baby’s neck. Dual Marker provides information regarding the risk of Down’s syndrome, Edwards syndrome, Patau’s syndrome.

Second trimester screening is performed in between 14 weeks to 22 weeks of gestation. It is called a Triple screening when the mother's blood sample is tested for three biomarkers- beta HCG, alpha fetoprotein, and Unconjugated estriol. It is called a Quadruple screening when Inhibin A is also tested in addition to these three biomarkers. Second trimester screening also provides information regarding the risk of neural tube defects in addition to Down’s syndrome and Edwards syndrome.


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