[Sialic acid, steroids and proteohormones in maternal, cord and retroplacental blood].

BACKGROUND

To study the storage of sialic acid in newborns reference concentrations for sialic acid were measured in maternal, retroplacental and cord blood and compared with the concentration of human placental lactogen (hPL) and estriol (E3). High serum concentrations of hPL and E3 in retroplacental blood indicate the synthesis of these products in the fetoplacental unit. The comparison of the serum concentrations give first informations for a possible role of the placenta as a place of production and storage of the investigated products.

METHODS

The concentrations of sialic acid, hPL and unconjugated E3 were determined in maternal and retroplacental blood samples of 126 pregnant women (16-42 years old) between 28 and 42 weeks of gestation. 84 of these pregnant women had uncomplicated pregnancy with birth after 37 gestational weeks. Measurements of E3 and hPL were performed by solid phase radioimmunoassays. Concentrations of sialic acid were determined by HPLC (high performance liquid chromatography).

RESULTS

Means and medians of the three parameters for both groups differentiate hardly. The retroplacental serum concentrations of hPL and E3 are increased significantly compared with maternal blood. The same trend was found for sialic acid without significance. The highest concentrations of E3 were found in the cord blood (298.2 +/- 138.0 ng/ml) (p < 0.01). On the other hand the lowest concentrations of sialic acid (36.1 +/- 19.6 mg/l) (p < 0.01) were estimated in cord blood samples. It was estimated a significant correlation between fetal and retroplacental concentrations of E3. Significant correlations (p < 0.01) were found for sialic acid between maternal and retroplacental blood on the one side and maternal and the cord blood on the other side. Significant increased mean sialic acid concentrations in retroplacental blood (x = 102.67 mg/l) were found in female newborns in comparison with male newborns (x = 80.58 mg/l). There were not significant differences between prematurity and term delivery.

CONCLUSION

Increased sialic acid concentrations in retroplacental blood samples are a sign of sialic acid accumulation in the fetomaternal area aiming to induce the tolerance of fetal allotransplantat. There are no evidence for a take up of free sialic acid by fetus.