HUMAN CHORIONIC-GONADOTROPIN PATTERN IN MATERNAL CIRCULATION - AMNIOTIC-FLUID AND FETAL CIRCULATION IN LATE PREGNANCY

This study had two purposes. One was to investigate the placental gradients and the relationship of human chorionic gonadotropin (hCG) concentrations in maternal serum (MS), amniotic fluid (AF) and fetal serum (FS). The other was to study the fetal sex effect. This study included 93 patients with normal singleton term pregnancies. AF samples contaminated with blood were excluded. Fetuses did not have any abnormalities. We measured hCG by double antibody betahCG radioimmunoassay. We found that there were conspicuous hCG slopes in MS, AF and FS levels. The hCG level in MS was 12.9 +/- 1.3 IU/mL (mean +/- SE, n = 93). It was much higher than levels in AF or FS. AF (0.461 +/- 0.053 IU/mL, n = 25) also had higher hCG level than FS (0.038 +/- 0.0056 IU/mL, n = 93). The hCG concentrations in AF and FS were highly correlated with those in corresponding MS (P < .001 and P < .05, respectively). The concentrations in AF were also positively correlated with those in corresponding FS (P < .05). The mean of MS/AF ratios for hCG was 413.6 +/- 23.4 (+/- SE); of MS/FS, it was 37.8 +/- 9.2; of AF/FS, it was 15.3 +/- 2.6. At late pregnancy, higher hCG levels of MS, AF or FS may result in female fetuses than in male fetuses. The results revealed that there were hCG concentration gradients on both placental and fetal membranes. It also implied that hCG levels in AF may decline as gestation ages advance. For biochemical studies in FS, using pure cord venous blood may have more consistent results than using mixed blood. In addition, the results also supported the hypothesis that the presence of hCG in AF or FS represents secretion from the trophoblastic tissue into the two compartments. In late pregnancy, the trophoblastic tissue in women bearing a female fetus may secrete more hCG to MS, AF and to FS than in women bearing a male fetus.