E. Jauniaux et al., THE ROLE OF RELAXIN IN THE DEVELOPMENT OF THE UTEROPLACENTAL CIRCULATION IN EARLY-PREGNANCY, Obstetrics and gynecology, 84(3), 1994, pp. 338-342
Objective: To evaluate the relation between the development of the ute
roplacental circulation as assessed by Doppler velocimetry and the mat
ernal blood relaxin concentration. Methods: Transvaginal color Doppler
investigation of the uteroplacental circulation was performed in 42 h
ealthy women at 6-15 weeks' gestation before termination of pregnancy
for psychosocial reasons. The resistance index (RI), pulsatility index
(PI) and maximum peak velocity were recorded at the level of the main
uterine artery, and the presence of intervillous now was noted. Relax
in, hCG, 17 beta-estradiol (E2), and progesterone levels were measured
in maternal venous blood. Results: Limited intervillous flow was note
d from 10 weeks' gestation and continuous intervillous now from 12 wee
ks. An inverse relation was observed between the circulating levels of
both E2 and progesterone and uterine artery RI and PI, whereas the re
laxin level correlated positively with uterine RI and PI. Estradiol an
d progesterone levels also correlated positively with uterine peak sys
tolic velocity and intervillous blood now. Multiple linear regression
analysis indicated that both hormones contributed to the decrease in d
ownstream resistance to uterine blood now with advancing gestational a
ge, as assessed by uterine RI. In addition, relaxin contributed to the
uterine RI and PI and to the intervillous blood now. Conclusion: Thes
e data suggest that relaxin, E2, and progesterone may influence the ch
anges in uterine blood now that occur in early pregnancy. The role pla
yed by E2 and progesterone in the development of the uteroplacental ci
rculation may be modulated by relaxin, constituting a novel function f
or this ovarian peptide.