In this study we examined alpha-fetoprotein (AFP) mRNA expression in fetal liver at 12-15 weeks of gestation in trisomy 21 (n = 13), trisomy 18 (n = 5) and control fetuses (n = 24). No significant difference was found in the steady-state level of fetal liver AFP mRNA levels in either of the two trisomy groups studied. These findings suggest that the decrease in maternal serum AFP concentration found in trisomic pregnancies is unlikely to be the consequence of impaired transcription of the AFP gene by the fetal liver.