Relation between maternal angiogenic factors and utero-placental resistance in normal first- and second-trimester pregnancies.

Objective: Soluble endoglin (sEng) is a novel antiangiogenic protein and elevated sEng concentrations in maternal circulation are closely related to preeclampsia and HELLP syndrome. As the perfusion of the uterine arteries as well as the dynamics of angiogenic factors between first and second trimester have prognostic value regarding pregnancy outcome, it was the aim of this study to investigate the relation between maternal angiogenic factors and uterine Doppler parameters.

Study Design: The longitudinal study includes 50 normal pregnancies. Pulsatility index (PI) of the uterine arteries was detected by Doppler ultrasound in first and second trimester. In parallel, maternal sEng and soluble fms-like tyrosine kinase 1 (sFlt1) concentration was measured using ELISA.

Results: In the first trimester, the sEng concentrations were 4.92 ± 1.36 ng/mL and the uterine PI was 1.14 ± 0.28. In the second trimester, the maternal sEng concentration decreased significantly to 3.99 ± 0.63 ng/mL (p < 0.05) which was associated by a decrease of the uterine PI to 0.78 ± 0.15 (p < 0.001). Soluble fms-like tyrosine kinase 1 concentrations did not differ significantly between first and second trimester (423 ± 333 vs. 444 ± 291 pg/mL). There was a significant negative correlation between sEng and uterine resistance in the second trimester (r = -0.416; p < 0.001).

Conclusions: In normal pregnancy, parallel to the fall of utero-placental resistance, there is a physiological decline of the maternal sEng concentration between first and second trimester. In second trimester, there is a negative correlation between sEng and uterine Doppler parameters.