Challenging the definition of hypertension in pregnancy: a retrospective cohort study

Abstract

BACKGROUND: In routine antenatal care, blood pressure is used as a screening tool for preeclampsia and its associated adverse outcomes. As such women with a blood pressure greater than 140/90 mm Hg undergo further investigation and closer follow-up, whereas those with lower blood pressures receive no additional care. In the nonpregnant setting, the American College of Cardiology now endorses lower hypertensive thresholds and it remains unclear whether these lower thresholds should also be considered in pregnancy. OBJECTIVE: (1) To examine the association between lower blood pressure thresholds (as per the American College of Cardiology guidelines) and pregnancy outcomes and (2) to determine whether there is a continuous relationship between blood pressure and pregnancy outcomes and identify the point of a change at which blood pressure is associated with an increased risk of such outcomes. STUDY DESIGN: This was a retrospective study of singleton pregnancies at Monash Health, Australia. Data were obtained with regards to maternal characteristics and blood pressure measurements at varying gestational ages. Blood pressures were then categorized as (1) mean arterial pressure and (2) normal, elevated, stage 1 and stage 2 hypertension, as per the American College of Cardiology guidelines.Multivariable regression analysis was performed to identify associations between blood pressure categories and pregnancy outcomes. RESULTS: This study included 18,243 singleton pregnancies. We demonstrated a positive doseeresponse relationship between mean arterial pressure and the development of preeclampsia in later pregnancy. Across all gestational ages, the risk of preeclampsia was greater in those with "elevated blood pressure" and "stage 1 hypertension" in comparison with the normotensive group (adjusted risk ratio; 2.45, 95% confidence interval, 1.74e3.44 and adjusted risk ratio, 6.60; 95% confidence interval, 4.98e8.73 respectively, at 34e36 weeks' gestation). There was also an association between stage 1 hypertension, preterm birth, and adverse perinatal outcomes. CONCLUSION: This study demonstrated that preeclampsia and the associated adverse outcomes are not exclusive to those with blood pressures greater than 140/90 mm Hg. As such, those with prehypertensive blood pressures may also benefit from closer monitoring. Further research is essential to determine whether lowering the blood pressure threshold in pregnancy would improve detection and outcomes.

Prevalence of Hypertension Among Pregnant Women When Using the 2017 American College of Cardiology/American Heart Association Blood Pressure Guidelines and Association With Maternal and Fetal Outcomes

“…6 Several groups have examined the application of the 2017 ACC/AHA diagnostic thresholds early in pregnancy and found that stage 1 hypertension was associated with an increased risk of hypertensive disorders of pregnancy including preeclampsia and gestational hypertension and adverse perinatal outcomes compared with normotension. [15][16][17][18] Our findings confirm and extend this prior work to examine the impact of reclassifying women using not only early pregnancy BP but also outpatient BP measurements prior to pregnancy and throughout gestation up until delivery. Our approach thus mimics clinical practice.…”

Blood pressure thresholds in pregnancy for identifying maternal and infant risk: a secondary analysis of Community-Level Interventions for Pre-eclampsia (CLIP) trial data

“…In 2017, the American College of Cardiology and American Heart Association recommended lowering See Online for appendix the blood pressure thresholds for diagnosing hypertension outside of pregnancy, classified as: elevated blood pressure (or elevated sBP; defined as sBP 120-129 mm Hg and dBP <80 mm Hg), stage 1 hypertension (sBP 130-139 mm Hg or dBP 80-89 mm Hg, or both), and stage 2 hypertension (sBP ≥140 mm Hg or dBP ≥90 mm Hg, or both). 2 Although the American College of Obstetricians and Gynecologists and WHO have retained a definition of blood pressure greater than or equal to 140/90 mm Hg for hypertension in pregnancy, several studies have reported a doseresponse relationship between increasing blood pressure and adverse pregnancy outcomes, across gestational ages; 3,4 these findings provide potential support for the redefinition of hypertension in pregnancy. However, despite use of blood pressure as an essential screening test in pregnancy, no studies have yet reported the diagnostic test properties (such as sensitivity and specificity) of various blood pressure thresholds for hypertension diagnosis.…”

Adverse pregnancy outcomes associated with moderate elevations in blood pressure or blood glucose in Ugandan women; a prospective cohort study

“… 31 Many previous studies reported an interaction between stage 1 hypertension and the development of preeclampsia. 7 , 8 , 9 , 10 , 11 , 32 These were performed in high-income settings and at various stages of gestation. In our study, we did not consider hypertensive disorders as a primary or secondary outcome because of the difficulties in the standardization of the diagnosis across the sites.…”

“…Other studies have demonstrated associations between stage 1 hypertension and preterm birth. 7 , 8 , 9 , 11 , 32 Many of these include “indicated preterm birth,” which we presume includes induction of labor or cesarean delivery owing to preeclampsia. These interventions may be less readily available in our own setting, which may in turn contribute to the high perinatal mortality rates in line with previous reports.…”

“… 3 Although publications by the World Health Organization (WHO) (2017), 4 American College of Obstetricians and Gynecologists (2019), 5 and National Institute for Health and Clinical Excellence (2019) 6 still recognize a cutoff of ≥140/90 mm Hg in pregnancy, they acknowledge an accumulating body of evidence suggesting a graded association between more moderate elevations in blood pressure and adverse pregnancy outcomes. 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 Similarly, the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study showed hyperglycemia within the GDM-range was linearly associated with adverse pregnancy outcomes, notably large birthweight (>90th centile). 15 This has led to the recent tightening of international diagnostic criteria for GDM to capture women with milder derangements in glucose control 16 and implementation of interventions to manage even mild GDM.…”