Solutes in maternal circulation and gestational sac compartments during early human development

The aim of this study was to review previous work reporting the concentration of solutes measured in maternal circulation, extra-embryonic celomic fluid, and amniotic fluid, to gain insights into the mechanism that could lead to compartmentalization of fluid and solutes within the gestational sac prior to the 12th week of pregnancy.

We conducted a Medline and PubMed literature search from January 1990 through March 2004 using the key words amniotic fluid, celomic fluid, coelomic fluid, celocentesis, coelocentesis, amniocentesis, yolk sac and embryonic cavities. We selected those articles describing solutes that had been measured in the same patient in samples obtained prior to 12 weeks' gestation from maternal circulation, celomic fluid and amniotic fluid. Information extracted from these publications included: gestational age at sampling, number of samples evaluated, mean concentration of the solutes in each of the three fluids and bibliographic citation.

We found 73 publications with the key words and selected 13 that met the inclusion criteria. The concentration of 31 solutes reported in each of the three compartments was documented and gradients among compartmental interfaces calculated.

This study describes the concentration of solutes measured in maternal circulation, extracelomic fluid and amniotic fluid early in human development. Analysis of calculated gradients across the compartmental interfaces suggests that the shift of fluid may depend on the biophysical properties of the placenta and yolk sac and on graded changes in hydrostatic pressures across compartments.