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Biochemical screening

Biochemical serum screening is a laboratory test (blood sample) which is used to assess the risk for having a baby with Down syndrome and two other chromosomal abnormalities. It is usually performed in the first (between 12+0-13+6 w.g.) or second trimester (15-19 w.g.) of pregnancy.


Biochemical serum screening at 12+0-13+6 w.g. is based on the evaluations of two hormones - the beta-fraction of the human chorionic gonadotropin hormone (β-cHG) and the pregnancy-related plasma protein A (PAPP-A).


This type of screening can be performed as a standalone test or it can be combined with additional ultrasound markers assessed during the first trimester scan at 12+0-13+6 w.g. The combined test has a higher sensitivity and should be the test of choice.


In the combined screening in the first trimester, the blood sample is combined with the evaluation of some ultrasound markers for chromosomal (genetic) abnormalities of the fetus after a preliminary examination of the fetal morphology. The most commonly used ultrasound markers in practice are - the measurement of the thickness of the nuchal translucency, the assessment of the nasal bone, the blood flow in the Ductus venosus and in the tricuspid valve, the course of the right subclavian artery, etc. In this way, the sensitivity of the screening increases significantly.


The combined (ultrasound and biochemical) screening between 12+0-13+6 years. is significantly more accurate than self-performed BHS in the first or second trimester.

In order to plan and perform combined (ultrasound and biochemical) first trimester screening at MC MARKOVS between 12-13+6 w. g. (optimally 12+0-13+6 w.g.) the following conditions should be observed:

  • The patient should get acquainted with the aim, possibilities and limitations of the test - information can be obtained from your doctor and/or the fetal medicine specialist at MC MARKOVS;
  • The pregnancy should be between 12+0-13+6 w.g.;
  • The first trimester scan should be performed prior to the blood sample;
  • Accurate determination of the gestational age is required (the sonographic determination of the gestational age increases the sensitivity of the biochemical screening by about 10%);
  • The evaluation of some important ultrasound markers during the first trimester scan (nuchal translucency thickness, nasal bone, Ductus venosus blood flow, etc.) significantly increases the sensitivity of the first trimester combined screening;
  • A written consent is taken prior to the blood sample collection.

After the fetal anomaly scan and the collection of the blood sample an individual assessment of the risk for having a baby with Down syndrome and/or some of the most common fetal chromosomal abnormalities is performed.


The result is usually done in a few working days and after that it is consulted by your doctor.


If the calculated risk is higher than 1 in 100 (e.g. risk of 1:50 is higher than 1 in 100) additional diagnostic testing (chorion villous sampling or amniocentesis) is discussed. In intermediate cases (calculated risk between 1:100 and 1:1000), non-invasive prenatal testing (NIPT) may be considered. If the estimated risk is less than 1:1000, no further tests are usually recommended.


For more information about the possibilities of performing combined first trimester screening at MC MARKOVS you can contact your doctor or call at the registration desk.


Attention: In order to perform a combined (ultrasound and biochemical) screening for chromosomal fetal abnormalities you must plan your visit to MC MARKOVS between 08.00 and 16.00h.


The laboratory at MC MARKOVS has limited working hours from 08:00 to 16:00h every working day.