First trimester screening for aneuploidy: serum biochemical markers

Area of Science:

• Maternal-fetal medicine
• Biochemistry
• Genetics

Background:

• First-trimester screening for Down syndrome is crucial for early detection.
• Maternal serum analytes are key biomarkers in prenatal screening.
• Pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (beta-hCG) are significant first-trimester markers.

Purpose of the Study:

• To review first-trimester Down syndrome screening using maternal serum analytes.
• To evaluate the effectiveness of PAPP-A and free beta-hCG in early pregnancy.
• To compare first-trimester screening performance with second-trimester methods.

Main Methods:

• Review of existing data on first-trimester screening markers.
• Analysis of maternal serum levels of PAPP-A and free beta-hCG in Down syndrome pregnancies.
• Assessment of screening performance metrics (detection rate and false positive rate).

Main Results:

• Maternal serum PAPP-A levels are low (0.4 MoM) and free beta-hCG levels are high (1.8 MoM) in Down syndrome pregnancies.
• Combined screening with PAPP-A, free beta-hCG, and maternal age yields a 60% detection rate at a 5% false positive rate.
• First-trimester screening performance is comparable to second-trimester double markers but inferior to triple or quad marker screening.

Conclusions:

• First-trimester screening with PAPP-A and free beta-hCG offers a valuable option for Down syndrome detection.
• This screening method is less sensitive than established second-trimester protocols.
• First-trimester serum marker screening is not recommended unless second-trimester screening is not feasible.