An orthostatic uterovascular syndrome--a prospective, longitudinal study.

OBJECTIVE

The interaction between maternal hemodynamics and uterine activity in the upright position was investigated longitudinally (358 measurements) in 40 healthy pregnant women from 20 gestational weeks to term.

STUDY DESIGN

Maternal-fetal hemodynamic parameters and uterine contractions were measured noninvasively in four different postures.

RESULTS

Hemodynamic disturbances caused by compression of pelvic vessels by the gravid uterus in the upright position were detected in two of 40 (5%) women as early as 24 weeks' gestation; a peak was reached at 38 weeks (71%). With a decrease in the stroke volume (22%, p < 0.001) neither the cardiac output (-11%, p < 0.05) nor the systolic blood pressure (-1.4%, p < 0.05) remained constant, although there was a compensatory heart rate increase.

CONCLUSION

A significantly increased number of spontaneous uterine contractions in the upright position is associated with release of the blocked venous return flow and restoration of normal maternal hemodynamics.