Biochemical composition of amniotic fluid and extraembryonic coelomic fluid in the first trimester of pregnancy.

OBJECTIVE

To determine the biochemical composition of amniotic fluid and extraembryonic coelomic fluid between 8 and 12 weeks gestation.

DESIGN

Prospective observational study.

SUBJECTS

40 women with a normal pregnancy between 7 and 12 weeks gestation having termination of pregnancy.

INTERVENTIONS

Before termination the women had a transvaginal ultrasound guided amniocentesis. Pure samples of amniotic fluid and extraembryonic coelomic fluid were obtained from each woman and standard biochemical variables were measured in each fluid sample immediately after collection.

RESULTS

Levels of sodium, potassium and bicarbonate were significantly higher in amniotic fluid whilst chloride, urea, bilirubin, protein, albumin, glucose, creatinine, calcium and phosphate were present in higher concentrations in extraembryonic coelomic fluid. All differences in concentration were significant (P less than 0.05; unpaired t-test). No relation was demonstrated between electrolyte concentrations in amniotic fluid or coelomic fluid and stage of gestation.

CONCLUSIONS

Amniotic fluid and extraembryonic coelomic fluid have a widely differing biochemical composition. The biological significance of these differences remains unexplained.