alpha-Fetoprotein: relationship between maternal serum and amniotic fluid levels

Area of Science:

• Prenatal diagnostics
• Biochemistry
• Maternal-fetal medicine

Background:

• Alpha-fetoprotein (AFP) is a biomarker used in prenatal screening.
• Understanding AFP levels in maternal serum and amniotic fluid is crucial for accurate screening.
• Previous assumptions about AFP transfer mechanisms require investigation.

Purpose of the Study:

• To determine the relationship between maternal serum AFP and amniotic fluid AFP levels.
• To assess the predictability of amniotic fluid AFP from maternal serum AFP concentrations.
• To evaluate the mechanism of AFP transfer between these compartments.

Main Methods:

• Analysis of 297 paired maternal serum and amniotic fluid samples.
• Samples from normal pregnancies at 16-17 weeks gestation.
• AFP assays performed by a single reference laboratory; gestational age confirmed by ultrasonography.

Main Results:

• No statistical relationship was found between maternal serum AFP and amniotic fluid AFP (r = 0.006).
• Individual analysis for 16 and 17 weeks confirmed the lack of correlation.
• Amniotic fluid AFP levels cannot be predicted by maternal serum AFP levels.

Conclusions:

• Simple diffusion is an inadequate explanation for AFP transfer from amniotic fluid to maternal serum.
• The findings highlight the need for population-based studies for accurate AFP screening.
• Reference laboratory determination of "normal" values remains essential for neural tube defect screening.