First Trimester Combined Screening — Basic

The basic first-trimester combined screening at G-CENTRUM Olomouc combines a blood test and a nuchal translucency ultrasound to calculate each individual woman's risk of fetal chromosomal conditions including Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13). The blood draw (measuring PAPP-A and free β-hCG hormones) is taken at 9–10 weeks of pregnancy; the ultrasound measurement of nuchal translucency — the fluid-filled space at the back of the fetal neck — follows at 11–14 weeks. Both results are combined with maternal age and pregnancy data to produce a personalised risk figure.

First-trimester combined screening is the internationally recommended standard for early chromosomal risk assessment in pregnancy, offering substantially higher detection rates than blood testing or ultrasound alone. At G-CENTRUM Olomouc, the screening is conducted in two coordinated steps integrated into the clinic's prenatal care pathway. Step one (9–10 weeks): A venous blood draw measures two serum biomarkers — PAPP-A (pregnancy-associated plasma protein A) and free β-hCG (free beta human chorionic gonadotrophin). These hormones are produced by the placenta, and their levels deviate from the expected range in pregnancies affected by Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome), and Trisomy 13 (Patau syndrome). Step two (11–14 weeks): A specialist at G-CENTRUM performs the nuchal translucency (NT) ultrasound, measuring the fluid accumulation at the back of the fetal neck. Increased NT thickness is associated with chromosomal abnormalities and certain structural conditions. The measurement requires a precisely dated pregnancy and a technically proficient operator — G-CENTRUM's perinatology team has extensive experience in first-trimester fetal ultrasound. The two results are combined with maternal age, gestational age, and fetal crown-rump length using validated risk algorithms to produce a personalised risk ratio for each condition. This combined approach achieves detection rates of approximately 85–90% for Trisomy 21 at a 5% screen-positive rate — substantially better than either test alone. The basic screening does not include preeclampsia markers; women who also want preeclampsia risk screening should choose the extended version. Women who receive a screen-positive result are offered referral for confirmatory testing including NIPT or amniocentesis.