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ABSTRACT

Objective To measure levels of folate and vitamin B12 in matched samples of amniotic fluid and extraembryonic 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-embyronic 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-embyronic 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.