Maternal homocysteine level and markers used in first-trimester screening for fetal Down syndrome.

This study examined possible relationships between homocysteine and markers used in first-trimester screening for Down syndrome. Pregnancies were categorized into 4 groups according to quartile ranking of maternal plasma homocysteine concentration. Of the 595 pregnancies, 147 were assigned to group 1 (homocysteine level 0.6-3.5 μmol/L), 156 to group 2 (homocysteine level 3.6-4.5 μmol/L), 142 to group 3 (homocysteine level 4.6-5.6 μmol/L), and 150 pregnancies to group 4 (homocysteine level 5.7-12.6 μmol/L). No significant difference in mean nuchal translucency and mean free β-human chorionic gonadotropin (free-βhCG) multiples of the median (MoM) levels were observed. However, the mean pregnancy-associated plasma protein A (PAPP-A) MoM levels were significantly decreased in inverse relationship with homocysteine level among all 4 groups (F = 31.127, P < .001). If homocysteine is assayed as part of the first-trimester maternal serum testing, it is important to adjust for homocysteine concentration when using PAPP-A serum level for calculating the risk of fetal aneuploidy.