ALTERATIONS IN UTEROPLACENTAL BLOOD-FLOW PRECEDE HYPERTENSION IN PREECLAMPSIA AT HIGH-ALTITUDE

High-altitude residence during pregnancy is associated with an increas ed incidence of preeclampsia. To determine whether uteroplacental bloo d flow was reduced and pelvic blood flow distribution altered before t he onset of hypertension, we measured common iliac (CI), uterine (UA), and external iliac (EI) artery flow velocities (FV), indexes of flow distribution, and blood volume (BV) at week 12, 24, and 36 of pregnanc y and 6 mo postpartum in 23 normotensive, 7 preeclamptic, 5 transientl y hypertensive, and 3 chronically hypertensive residents of 3,100 m. N ormotensive women had a progressive increase in CIFV and UAFV, decreas e in EIFV, redistribution of CIFV from the EI to the UA, and increase in BV with advancing pregnancy. Preeclamptic women attained maximal UA FV and redistribution of CIFV from the EI to the UA well before the on set of hypertension and, unlike normotensive women, showed no further increases near term. Plasma volume increment with pregnancy related to the fall in the EIFV/CIFV ratio. Transiently hypertensive women resem bled normotensive subjects in the parameters measured, whereas chronic ally hypertensive subjects resembled preeclamptic subjects. We conclud ed that preeclamptic vs. normotensive pregnant residents of high altit ude had less redistribution of CI flow to the UA and no increase in UA blood flow near term. That these differences were present before the onset of hypertension supports the concept that preeclampsia is charac terized by an incomplete vascular adjustment to pregnancy.