Coelomic fluid chorionic gonadotrophin and protein concentrations in normal and complicated first trimester human pregnancies

Coelomic fluid and maternal serum samples were collected from43 normal pregnancies and 18 missed abortions between 7 and12 weeks of gestation. The samples were analysed for the concentrationsof intact human chorionic gonadotrophin (HCG), free HCG, freeHCG and total protein. The relationships between the biologicalfindings and the ultrasound and pathological features were assessedby regression analysis. In normal pregnancies, intact HCG, freeHCG and free HCG concentrations were respectively 1.3, 185 and33 times higher in coelomic fluid than in maternal serum. Thecoelomic concentrations of intact HCG and free HCG decreasedsignificantly with advancing gestation. No relationship wasfound between coelomic fluid and maternal serum concentrationsof the different variables. These findings suggest that in normalpregnancies, the concentration of HCG in the coelomic fluid,as in maternal serum, is mainly influenced by cytotrophoblasticdifferentiation and that the metabolic clearance of HCG moleculesis slower in the coelomic cavity than in maternal serum. Inmissed abortions, the serum concentrations of intact HCG, HCGand free HCG and the coelomic concentration of total proteinwere significantly lower than in normal pregnancies. In threeout of nine anembryonic pregnancies diagnosed by ultrasound,embryonic remnants were present at histological examination.The coelomic concentration of total protein was extremely lowin all missed abortions with advanced trophoblastic necrosis,whereas the HCG concentration was low when embryonic remnantswere absent. These findings support the concept that embryonicand placental development are closely related in the first trimesterof human pregnancy, placental biological functions persistingonly for a limited period of time after embryonic demise.