Transfer of folate to the fetus.

The accumulation of tritium-labelled folate in the product of conception was examined in eight women undergoing hysterotomy for termination of pregnancy. Folic acid containing a small quantity of tracer material (50n Ci/mug.) was injected intravenously 20 minutes before operation in 4 patients but 24 hours beforehand in the remainder. After operation, maternal blood, placenta, fetal blood, and fetal liver were examined for radioactivity as was the daily urine output during the patient's postoperative hospital stay. The results indicated that only 1/2 per cent of the injected material accumulated in the product of conception--uptake was primarily by fetal liver and no large placental pool of folate was involved. Approximately half of the injected load was excreted in the urine--the majority in the first 24 hours--and the remainder was presumed to have been retained by maternal tissues. Bioassay with L. casei and chromatography on TEAE cellulose suggested that extensive metabolism of the injected material had taken place and that fetal uptake might be more efficient than indicated by counting radioactivity alone.