Pregnancy, vascular tone, and maternal hemodynamics: A crucial adaptation

The adaptation of vascular tone in early pregnancy precedes and probably tr iggers blood volume and cardiac output increase. Because the endothelium is known to regulate vascular smooth muscle action, the role of nitric oxide (NO) in the setting up of adequate uteroplacental and renal blood flow duri ng normal pregnancy was investigated, The persistence of abnormally high ut eroplacental resistance is a strong predisposing factor for intrauterine gr owth retardation and preeclampsia and can be screened by second trimester D oppler assessment of the uterine arteries, Current hypotheses suggested by experimental end clinical data concerning preeclampsia confirm the crucial role played by the endothelium and vascular tone adaptation. The analysis o f these data leads to consider apart early-onset preeclampsia effecting pre gnancies with growth retarded fetuses and associated with high vascular res istance, Lastly, NO donors seem to significantly decrease the impedance in the uteroplacental circulation and to improve fetoplacental hemodynamics as sessed by Doppler measurements, and their therapeutic use in some forms of preeclampsia might be promising.