634: Physiologic blood pressure patterns in hypertensive pregnancies

Abstract

Little is understood about the pattern of blood pressure (BP) alterations in women with chronic hypertension (HTN) during pregnancy, making distinctions between preeclampsia and normal return to elevated prepregnancy BP difficult. We aimed to assess physiologic BP changes throughout pregnancy in women with HTN who do and do not develop preeclampsia (PEC), as compared to women with no history of hypertension. STUDY DESIGN: Retrospective cohort of all singleton gestations with HTN 2000-2014 in a single tertiary care center and a randomly selected cohort of women with no history of HTN and normal pregnancy outcomes (NML) in the same time period with blood pressure measurements available <12 weeks. Subjects were excluded for major medical problems other than HTN, fetal anomalies, and initiation or increases in antihypertensives after 20 weeks. Diagnosis of PEC required both BP140/90 mm Hg and a laboratory abnormality (proteinuria, creatinine, AST, or platelets) per ACOG definitions. Comparisons were made between NML, HTN without PEC who delivered at term, and HTN with PEC. Generalized linear models were used to define and compare the nadir of systolic and diastolic BP between groups. RESULTS: Of 169 pregnancies with HTN meeting inclusion critier, 113 (67%) were included in HTN without PEC and 56 (33%) were included in HTN with PEC. 141 NML pregnancies were used as comparison group. As expected, NML subjects had lower BP throughout gestation. The nadir of systolic and diastolic BP was earliest in NML (SBP 21 (19-23 wks), DBP 23 (22-24 wks)) and HTN with PEC (SBP 21 (18-24 wks), DBP 23 (21-24 wks), Figure). In HTN without PEC, BP did not return to prepregnancy values until after 25 weeks (24-26), and remained below 140/90. CONCLUSION: Women with HTN and PEC have higher BP throughout pregnancy and earlier BP nadirs than HTN without PEC and NML. BP elevations in HTN without PEC can be expected after 25 weeks, although in this cohort blood pressures remained <140/90 mm Hg without medication adjustments.

Maternal preconception blood pressure and the association with preterm birth

“…Maternal BP decreases physiologically from early to mid-pregnancy. Women with chronic hypertension who have experienced preeclampsia appear to reach the nadir earlier than women who do not experience preeclampsia [8,9]. Many guidelines define chronic hypertension as that diagnosed before pregnancy or before 20 weeks of gestation [10][11][12]; however, a physiological decrease in BP can obscure the diagnosis of chronic hypertension at <20 weeks of gestation.…”