The coelomic cavity: an important site of materno-fetal nutrient exchange in the first trimester of pregnancy.

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.