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Twenty-four-hour ambulatory blood pressure monitoring can detect some pregnant women who will develop a serious complication of pregnancy called preeclampsia. In a study of 286 pregnant women, those who eventually developed preeclampsia were more likely to have high blood pressure between 18 and 30 weeks gestation.

Blood vessel contraction and relaxation is different in women and men, according to a study of 29 women and 15 men. Oral contraceptives can change blood vessel contraction and relaxation in women.

Ambulatory blood pressure monitoring may be beneficial in pregnant women who have hypertension and are at risk for preeclampsia. Researchers used a Holter monitor to analyze the normal variations in blood pressure in 259 women at various times during pregnancy. The highest systolic values tended to increase slightly throughout pregnancy. Blood pressure during waking hours tended to be higher than blood pressure measured in the doctor's office. Both systolic and diastolic blood pressure fell during sleep, just as it does in most people.

Byline: Mark A. Brown, Arlene Robinson, Lucy Bowyer, Megan L. Buddle, Allison Martin, Jane L. Hargood, Greg M. Cario Keywords: Ambulatory blood pressure monitoring; preeclampsia; hypertension; pregnancy Abstract: OBJECTIVE: Noninvasive 24-hour ambulatory blood pressure monitoring holds great promise as a useful tool in the management of hypertensive pregnancies and pregnancies considered 'at risk' for development of preeclampsia. The purpose of this study was to define ambulatory blood pressure monitoring parameters throughout normal pregnancy, including women considered at risk for development of hypertension who continued to have a completely normal pregnancy. STUDY DESIGN: Two hundred seventy-six 24-hour ambulatory blood pressure monitoring studies were made cross-sectionally with use of a Spacelabs 90207 device (validated for use in pregnancy), at one or more of 9 to 17, 18 to 22, 26 to 30, and >30 weeks' gestation. Upper limits of normal were defined as the mean plus 2 SDs for awake and sleep ambulatory blood pressure monitoring results at each stage. RESULTS: Average awake upper limits of normal were 130/77, 132/79, 133/81, and 135/86 mm Hg at the four stages of pregnancy, respectively. Systolic blood pressure fell significantly by 12% to 14% (p < 0.0001) and diastolic blood pressure by 18% to 19% (p < 0.0001) during sleep at all stages of pregnancy. Awake ambulatory blood pressure monitoring systolic measurements were 11 to 12 mm Hg higher than 'clinic' measurements (p < 0.001) and diastolic measurements were 5 to 11 mm Hg higher (p < 0.0001) throughout pregnancy. Maximum blood pressure variability ranged from 8 to 13 mm Hg. CONCLUSIONS: The upper limits of normal ambulatory blood pressure monitoring-derived measurements rise slightly as pregnancy progresses. Awake measurements are higher than 'clinic' measurements recorded under relaxed conditions by a clinical researcher. The diurnal blood pressure fall and variabilities are similar during pregnancy to those seen in nonpregnant subjects. These data should provide valuable references for further studies of ambulatory blood pressure monitoring in high risk pregnancies. (Am J Obstet Gynecol 1998;178:836-42.) Author Affiliation: Kogarah, Australia Article History: Received 13 May 1997; Revised 2 October 1997; Accepted 3 October 1997 Article Note: (footnote) [star] From the Departments of Renal Medicine,a Medicine,b and Obstetrics,c St. George Hospital and University of New South Wales., [star][star] Supported by National Heart Foundation of Australia project grant No. G96S 4561., a Reprints not available from the authors., aa 6/1/86646