Periodic acid Schiff (PAS) positivity in fetal erythroblasts.

The smears of 26 fetal blood samples taken for prenatal diagnosis were stained for the PAS reaction. Twelve out of 26 cases were subsequently found to be normal and 14 were found to be affected by different abnormalities; 83.4% of normal cases and 92.8% of abnormal cases showed moderate positivity to the PAS reaction. A higher percentage of PAS positive erythroblasts was found in the abnormal cases (p less than 0.01). Five cases with a percentage greater than 10% also showed a very high percentage of erythroblasts. No linear correlation was found between PAS positivity and erythroblastosis either in the normal or the abnormal cases, but pooling them resulted in a correlation between PAS positivity and erythroblastosis (r = 0.536; p less than 0.005). PAS positivity was most often diffuse and scored 1+. Since erythroblastosis is considered an indirect sign of fetal liver erythropoiesis, the hepatic environment and its peculiar hemopoiesis could play a role in producing a cohort of PAS positive erythroblasts.