First-trimester maternal serum alpha-fetoprotein screening for chromosome defects

Area of Science:

• Prenatal diagnostics
• Biochemistry
• Genetics

Background:

• Low maternal serum alpha-fetoprotein (AFP) in the second trimester is linked to an increased risk of fetal Down syndrome.
• The utility of first-trimester AFP screening for chromosomal abnormalities remains less understood.

Purpose of the Study:

• To investigate the association between first-trimester maternal serum AFP levels and fetal chromosome defects.
• To assess the feasibility of first-trimester AFP screening for detecting trisomies and other chromosomal disorders.

Main Methods:

• Prospective collection of maternal serum samples from 540 women before chorionic villus sampling (8-12 weeks' gestation).
• Sensitive monoclonal-based radioimmunoassay used to measure AFP levels, blinded to cytogenetic results.
• Analysis of AFP values in relation to fetal chromosome defect diagnoses.

Main Results:

• Low maternal serum AFP (≤0.6 multiples of the median) was associated with 29.6% of serious chromosome defects.
• Overall, 10.9% of women had low AFP levels, with 8 of these cases involving fetuses with serious chromosome defects.
• Women with low first-trimester AFP had a 1 in 8 risk of fetal trisomy and a 1 in 7 risk of any serious chromosome defect.

Conclusions:

• First-trimester maternal serum AFP screening is a feasible method for identifying pregnancies at increased risk of fetal chromosome defects.
• Further prospective studies in routine pregnancy populations are needed to determine the detection efficiency of this screening method.