THE ASSOCIATION BETWEEN INCREASED MEAN ARTERIAL-PRESSURE AND ABNORMALUTERINE ARTERY RESISTANCE TO BLOOD-FLOW DURING PREGNANCY

Objective: To examine the relation between increased mean arterial pre ssure (MAP) and the uterine artery resistance index (RI) to blood flow in the third trimester of pregnancy. Methods: One hundred consecutive patients in the third trimester whose pregnancies were complicated by hypertensive disorders, with or without proteinuria, had uterine arte ry resistance to blood flow measured using continuous-wave Doppler. Re sults: The RI was in the normal range in 20 patients. Unilaterally abn ormal RI was found in 32 and bilaterally abnormal RI in 46 (two subjec ts were excluded from this categorization because measurements were ob tained from only one side of the uterus). A MAP below 100 mmHg was ass ociated with a normal RI. All six subjects with MAP of 140 mmHg or gre ater had bilaterally abnormal RI. Mean arterial pressure values of 100 -139 mmHg included 90% of the women with normal RI, 100% of those with unilaterally abnormal RI, and 87% of those with bilaterally abnormal RI. Proteinuric and nonproteinuric groups differed with respect to bot h MAP (P = .04) and RI (P = .01). Pregnancy outcome was less favorable in the unilaterally abnormal RI subgroup than in the normal RI subgro up. The bilaterally abnormal subgroup of patients had the most adverse pregnancy outcomes. Conclusions: Pregnant patients in the third trime ster who have increased MAP but a normal uterine artery RI can expect a good pregnancy outcome. Increased MA.P associated with abnormal uter ine artery RI may result in an unfavorable pregnancy outcome, particul arly in those with bilaterally increased RI to blood flow. Doppler mea surement of uterine artery impedance is recommended in pregnancies com plicated by hypertensive disorders.