Second trimester screening for Down's syndrome: 7 years experience

Area of Science:

• * Prenatal diagnostics and screening
• * Maternal serum marker analysis
• * Genomic and chromosomal abnormality detection

Background:

• * Second-trimester antenatal screening for Down syndrome is crucial for early detection and management.
• * Maternal serum markers like alpha-fetoprotein (alphaFP) and human chorionic gonadotropin (hCG) are utilized in screening protocols.
• * Evaluating the long-term effectiveness and community acceptance of established screening programs is essential.

Purpose of the Study:

• * To assess the efficacy of a 7-year Down syndrome screening program utilizing alphaFP and total hCG.
• * To determine the detection rates and false positive rates associated with this two-marker screening approach.
• * To evaluate the uptake and acceptance of the screening program within the local obstetric population.

Main Methods:

• * Analysis of maternal serum samples from 66,631 women between 15-20 weeks gestation over a 7-year period.
• * Calculation of Down syndrome risk using maternal age, alphaFP, and total hCG levels.
• * Correlation of screening results with cytogenetic data for outcome determination.

Main Results:

• * 108 Down syndrome pregnancies were identified out of 66,631 screened women.
• * A cutoff of 1:250 identified 66.7% of affected pregnancies with a 5.8% false positive rate.
• * Screening uptake declined from 84% to 59.5% over the study period, with higher detection rates when performed before 17 weeks gestation.

Conclusions:

• * Two-marker screening with alphaFP and total hCG is an effective method for Down syndrome detection in the second trimester.
• * The screening program demonstrated wide acceptance within the community during the initial 7 years.
• * Detection rates are comparable to other second-trimester studies employing similar two-marker strategies.