Evaluation of different blood pressure assessment strategies and cutoff values to predict postpartum hypertension-related readmissions: a retrospective cohort study.

BACKGROUND: The American College of Obstetricians and Gynecologists suggests the initiation of postpartum antihypertensive treatment for women with hypertension in the postpartum period, a systolic blood pressure of ≥150 mm Hg or diastolic blood pressure of ≥100 mm Hg on 2 occasions at least 4 to 6 hours apart; however, the utility and validity of this strategy for preventing postpartum hypertension-related readmission remain unknown. OBJECTIVE: The primary objective was to evaluate the accuracy of different blood pressure assessment strategies for predicting postpartum hypertension-related readmissions. The secondary objective was to consider the impact of using different blood pressure thresholds for initiating postpartum antihypertensive treatment vs the impact of using the current blood pressure threshold recommended by the American College of Obstetricians and Gynecologists. STUDY DESIGN: A retrospective cohort study of 24,917 women who delivered at a single midwestern academic hospital between January 1, 2009, and June 30, 2015. Of those women, 3830 were identified as hypertensive, and 112 of 3830 women (2.92%) were readmitted for hypertension management. Blood pressures measured between delivery and 72 hours after delivery were used to evaluate 3 different blood pressure assessment strategies: average systolic or diastolic blood pressure exceeding the predetermined threshold (strategy 1), maximum systolic or diastolic blood pressure exceeding the predetermined threshold on 1 occasion (strategy 2), and maximum systolic or diastolic blood pressure exceeding the predetermined threshold on 2 occasions at least 4 hours apart (strategy 3). Analyzed blood pressure thresholds included all the integer blood pressure values between 100/50 mm Hg to 160/110 mm Hg for strategy 1 and 120/70 mm Hg to 190/140 mm Hg for strategies 2 and 3. The primary outcome was hypertension-related postpartum readmission. Receiver operating characteristic curves and the area under the curve were used to measure the predictive value of these strategies. RESULTS: The American College of Obstetricians and Gynecologists' recommendation of using blood pressure ≥150/100 mm Hg as a threshold had a sensitivity of 38% and specificity of 95%, whereas following strategy 3 and reducing the threshold to 140/90 mm Hg demonstrated a sensitivity of 71% and specificity of 84%. The area under the curve for the 3 strategies were as follows: strategy 1 (area under the curve, 0.81; 95% confidence interval, 76.95-85.08), strategy 2 (area under the curve, 0.79; 95% confidence interval, 74.70-82.81), and strategy 3 (area under the curve, 0.83; 95% confidence interval, 79.83-87.24). The difference between the areas under the curve of strategies 2 and 3 was statistically significant (P<.0001). CONCLUSION: The strategy of using the maximum systolic or diastolic blood pressure exceeding the blood pressure threshold on 2 occasions at least 4 hours apart at lower blood pressure thresholds can predict readmissions with higher sensitivity or specificity. Compared with the threshold of the American College of Obstetricians and Gynecologists' recommended blood pressure of ≥150/100 mm Hg, if the threshold for the postpartum antihypertensive treatment initiation was lowered to a blood pressure of ≥140/90 mm Hg, it would significantly reduce postpartum readmissions.