Objective: To measure levels of folate and vitamin B12 in matched samples of amniotic fluid and extra-embryonic coelomic fluid from 9 to 12 weeks' gestation.
Design: Prospective observational study.
Setting: Homerton Hospital, London.
Subjects: Twenty-two women with ultrasonographically normal pregnancies before surgical termination.
Methods: Transvaginal ultrasound-guided needle aspiration of amniotic fluid and extra-embryonic coelomic fluid was performed. Pure samples of amniotic fluid and extra-embryonic coelomic fluid were obtained from each pregnancy, and folate and vitamin B12 were measured using microbiological assays.
Results: Levels of folate and vitamin B12 were higher in extra-embryonic coelomic fluid than in amniotic fluid and maternal serum. Amniotic fluid folate levels were lower than in maternal serum whereas vitamin B12 levels in amniotic fluid were higher than in maternal serum. All differences in concentration were significant (P < 0.0005; paired t-test). Positive correlations were found between the concentrations of folate and vitamin B12 in each fluid. There was a linear correlation between gestational age and amniotic fluid folate levels (r = 0.648; P = 0.001).
Conclusions: High concentrations of folate and vitamin B12 in coelomic fluid suggest that the coelomic cavity plays an important role in the materno-fetal exchange of these nutrients.