The Active Implementation of Pregnancy Hypertension Guidelines in British Columbia

von Dadelszen, Peter MBChB, DPhil; Sawchuck, Diane RN, RM, PhD; McMaster, Romy MSc; Douglas, M. Joanne MD; Lee, Shoo K. MBBS, PhD; Saunders, Sarah BSc; Liston, Robert M. MBChB; Magee, Laura A. MD, MSc; for the Translating Evidence-Based Surveillance and Treatment Strategies (TESS) Group

Obstetrics & Gynecology:
doi: 10.1097/AOG.0b013e3181eb669d
Original Research

OBJECTIVE: To reduce maternal and perinatal morbidity and mortality associated with the hypertensive disorders of pregnancy by using an active model of guideline implementation.

METHODS: This study used a preintervention and postintervention cohort comparison design. We interrogated the British Columbia Perinatal Database Registry for 6 years of existing prospectively gathered data (fiscal years 2000–2001 to 2005–2006), introduced the hypertensive disorders of pregnancy guidelines, and assessed the incidence of the combined adverse maternal and perinatal outcomes for the next 2 years (fiscal years 2006–2007 and 2007–2008). The combined adverse maternal outcome was maternal death, life-threatening, or life-altering complications. The combined perinatal outcome included the severe complications of prematurity and hypoxic–ischemic encephalopathy.

RESULTS: Eighteen thousand seventy-six women were diagnosed with hypertensive disorder of pregnancy in British Columbia from 2000–2001 to 2007–2008. Outcomes were compared preguideline (n=13,150 deliveries) and postguideline (n=4,926 deliveries) implementation. The incidence of the combined adverse maternal outcome decreased from 3.1% to 1.9% (relative risk 0.60, 95% confidence interval 0.48–0.75). There was a concomitant fall in the incidence of the combined adverse perinatal outcome.

CONCLUSION: The active introduction of standardized management of women with a hypertensive disorder of pregnancy is associated with reduced maternal and perinatal risk.


In Brief

The active management of hypertensive disorders of pregnancy-guideline implementation is associated with improved maternal outcomes in British Columbia, Canada.

Author Information

From the Departments of Obstetrics and Gynaecology, Anesthesiology, Pharmacology and Therapeutics, and Medicine, School of Public and Population Health, Child and Family Research Institute, and Faculty of Medicine, University of British Columbia, and the BC Perinatal Health Program, Vancouver, British Columbia, Canada; and the Department of Paediatrics, University of Toronto, Ontario, Canada.

*For a list of other members of the TESS Group, see the Appendix online at

Corresponding author: Peter von Dadelszen, 2H30-4500 Oak Street, Vancouver, BC V6H 3N1, Canada; e-mail:

Supported by the Michael Smith Foundation for Health Research (Health Services Research Operating Grant and salary awards to Dr. Magee and Dr. von Dadelszen), the Canadian Institutes for Health Research (salary award to Dr. von Dadelszen), and the Child and Family Research Institute (salary award to Dr. von Dadelszen).

Financial Disclosure The authors did not report any potential conflicts of interest.

Article Outline

Globally, the hypertensive disorders of pregnancy are leading causes of maternal mortality.1 Although the mainstays of management include “full assessment of the mother and her baby, and delivery on the best day in the best way,”2 the assessment, surveillance, and management of women with suspected or confirmed preeclampsia vary among practitioners.3,4 Standardizing care is associated with reduced adverse health outcomes across disciplines and medical conditions.5–8

We have previously undertaken a preintevention and postintervention cohort comparison of women admitted with preeclampsia to a single tertiary perinatal unit.9 The introduction of standardized assessment and surveillance for women with preeclampsia was associated with fewer adverse maternal outcomes. To be effective in enhancing practice patterns to improve outcomes, a proactive and evidence-based strategy of knowledge translation is crucial. Both audit and interactive large group educational sessions can effectively improve clinical practice.10–12

Tuffnell et al13 demonstrated that active guideline implementation, including local audit and regional staff education sessions, was associated with fewer maternal transfers and intensive care unit admissions for women admitted with severe preeclampsia. However, Foy et al14 found that passive guideline dissemination failed to influence adverse maternal and perinatal outcomes.

We describe a strategy of active implementation of hypertensive disorders of pregnancy guidelines within community, regional, and tertiary maternity hospitals in five health authorities in British Columbia and the incidence and pattern of adverse maternal and perinatal outcomes before and after active guideline implementation stratified by facility size and by health authority.

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Data were obtained from the British Columbia Perinatal Database Registry for births in British Columbia for the 5-year period of April 1, 2000, to March 31, 2006 (preintervention) and April 1, 2006, to March 31, 2008 (postintervention). The British Columbia Perinatal Database Registry is a database designed for the collection of specific maternal and newborn data elements for the purpose of summarizing, interpreting, and reporting on perinatal outcomes at community, regional, and provincial levels. Throughout the study period, data were abstracted into the database by trained abstractors using chart review and clinician diagnoses. Data are collected on all births in British Columbia 20 weeks or greater of gestation, delivering a fetus 500 g or greater, or both as well as newborn and postpartum readmissions. Complete provincial data, including all hospital births and births at home by registered midwives, have been available since the 2000–2001 fiscal year with close to 500,000 records currently available in the database. Data from the Canadian Institute for Health Information and matched files from the British Columbia Vital Statistics Agency complement the data elements. Beginning with fiscal year 2004–2005 discharges, data elements from the Canadian Institute for Health Information are coded using the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10); before this, the International Classification of Diseases, Ninth Revision (ICD-9) was used. Numerous and ongoing data quality checks, conducted at the time of abstraction and systematically as data were merged into the centralized database, ensured highly accurate data. This project was approved by the University of British Columbia Clinical Research Ethics Board and the British Columbia Perinatal Health Program Research Review Committee.

The study inclusion criteria were women diagnosed as having a hypertensive disorder of pregnancy, defined as blood pressure readings of 140/90 mm Hg or greater on two consecutive readings during the pregnancy, before labor. The hypertensive disorders of pregnancy were defined using ICD-10 codes as preexisting hypertension (O10), gestational hypertension without proteinuria (O13), gestational hypertension with proteinuria (preeclampsia, O14), eclampsia (O15), and preexisting hypertension with superimposed preeclampsia (O11). Women with unspecified hypertension (ICD-10 O16) were excluded. The ICD-10 codes were entered into the database by trained abstractors using clinician diagnoses and chart review.

The components of the combined adverse maternal outcome were maternal death (coded directly as death occurring during the delivery admission or within 6 weeks); eclampsia (ICD-9 642.6, 642.7 and ICD-10 O15); stroke (ICD-9 674.0 and ICD-10 I64); transient ischemic attack (ICD-9 435 and ICD-10 G45.8, G45.9); retinal detachment (ICD-9 361.0, 361.2, 361.8 and ICD-10 H33.0, H33.4, H33.5); hepatic failure, hematoma or rupture (ICD-9 570, 864.0, 864.1 and ICD-10 S36.10, S36.15, K72); myocardial infarction (ICD-9 410 and ICD-10 121); acute renal failure (ICD-9 669.3, 584 and ICD-10 N17, N18, O90.4); pulmonary edema (ICD-9 514, 518.4 and ICD-10 J81); and transfusion of any blood products (coded directly). Women were deemed to have achieved the outcome if one or more components complicated their care.

The combined adverse perinatal outcome comprised perinatal mortality (coded directly; defined as stillbirth [lower limit: 20 weeks of gestation or 500 g], neonatal death [0–7 days of postnatal life], and late neonatal death [8–28 days]), bronchopulmonary dysplasia (ICD-9 770.7 and ICD-10 P27.1); grade III or IV intraventricular hemorrhage (ICD-9 772.1 and ICD-10 P52.2); cystic periventricular leukomalacia (ICD-10 P91.2); stage 3 or 4 retinopathy of prematurity (ICD-9 362.2 and ICD-10 H35.1); necrotizing enterocolitis (ICD-9 777.5 and ICD-10 P77); and hypoxic–ischemic encephalopathy (ICD-9 768.9 and ICD-10 P96.1). Fetuses and neonates were deemed to have achieved the outcome if one or more components complicated their care.

In 2006, provincial hypertensive disorders of pregnancy guidelines focusing on the recommended surveillance and management of hypertensive disorders of pregnancy were developed and implemented with the specific objective of actively engaging medical opinion leaders and early majority adaptors. After circulation of a draft document, a representative selection of obstetrician, family practitioner, midwifery, obstetric internal medicine, obstetric anesthesiology, obstetric nursing, laboratory leaders, and perinatal pharmacy leader representatives from all provincial health authorities participated in a 1-day stakeholders' meeting for input and consensus before guideline publication.15 Medical, nursing, and midwifery opinion leaders were identified jointly by the medical director and nursing consultants at the British Columbia Perinatal Health Program in conjunction with the medical and perinatal leaders in the respective health authorities.

In addition to routine measurement of blood pressure, standardized antepartum and postpartum assessment and surveillance guidelines were included in the provincial hypertensive disorders of pregnancy guidelines that outlined a minimum standard of investigations as previously described9 and summarized in Table 1. Additional clinical, laboratory, and ultrasound evaluations were performed whenever considered necessary or prudent by providers. There was no policy of mandatory subspecialty consultation. In addition to routine measurement of blood pressure, preprinted assessment, and surveillance guidelines, the provincial guidelines admitted uncertainty about blood pressure targets for nonsevere pregnancy hypertension,16 supported the concomitant use of magnesium sulfate and nifedipine,17 and recommended restriction of fluid in severe preeclampsia to 80 mL/hour.13

The provincial hypertensive disorders of pregnancy guidelines were published (print and open access online) and distributed in September 2006 and sent to all maternity hospitals in British Columbia along with all physicians (obstetricians, anesthesiologists, internists, general practitioners) and midwives individually who provide antenatal and intrapartum care15; a national guideline based on these guidelines was subsequently published in 2008.18 In the Fall of 2006, 1- to 2-hour interactive educational sessions and medical rounds were conducted in all regional referral centers in each of the health authorities with videoconferencing capability to satellite maternity units. The first half of the sessions focused on the evidence supporting the recommendations for assessment, surveillance, expectant management, antihypertensive and anticonvulsant therapies (including the combined use of nifedipine and magnesium sulfate), thromboprophylaxis, and new fluid management protocols of 80 mL/h maximum total intake in severe preeclampsia with a tolerance of 10 mL/h urine output. The second half of the sessions encouraged questions and discussion around facilitators and barriers to uptake of the hypertensive disorders of pregnancy recommendations within their local institutions and practice environments. In addition, a series of six provincial and regional telehealth rounds were given to reinforce the primary messages that focused on the major practice changes that were anticipated to be most difficult to implement.

The combined adverse maternal and perinatal outcomes were compared between the pre- and postintervention epochs. Because adverse outcome were uncommon (particularly in the postintervention period), statistical analysis of rates and ratios were carried out by assessing Fisher's exact test and risk ratio (95% confidence intervals [CIs]). A χ2 test for heterogeneity between odds ratios (ORs) was performed to compare the changes in incidence of adverse outcomes between epochs between hypertensive disorders of pregnancy and nonhypertensive disorders of pregnancy pregnancies.19 Significance was set P<.05 using Prism 4.0 (GraphPad, San Diego, CA).

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For the 5-year preintervention period from fiscal year 2000–2001 to 2005–2006, 13,150 cases of hypertensive disorders of pregnancy were identified (5.49% of deliveries), and of those, 12.1% had chronic hypertension, 63.4% had gestational hypertension, 20.9% had preeclampsia, 1.9% had preeclampsia superimposed on preexisting hypertension, and 1.6% had eclampsia. For the 2-year postintervention period from fiscal year 2006–2007 to 2007–2008, 4,926 cases of hypertensive disorders of pregnancy were identified (5.75% of deliveries), of whom 12.0% had chronic hypertension, 65.4% had gestational hypertension, 19.7% had preeclampsia, 2.1% had superimposed preeclampsia, and 0.8% had eclampsia.

In Table 2 we present the demographics of women with hypertensive disorders of pregnancy in the preintervention and postintervention cohorts and comparisons with other women with normal pregnancy outcomes in British Columbia during the same two epochs. Women with hypertensive disorders of pregnancy were more frequently obese, carrying a multiple pregnancy, nulliparous, and delivered preterm.

In Tables 3 and 4, we present the adverse maternal and perinatal outcomes, respectively, by epoch. Again, the data from the nonhypertensive disorders of pregnancy population are presented for comparison. We observed a significant fall in both maternal and perinatal outcomes associated with the introduction of the guidelines. For adverse maternal outcomes, these were of greater magnitude than the general increase in the incidence of events seen for nonhypertensive disorders of pregnancy pregnancies. However, the incidence of adverse perinatal outcomes for nonhypertensive disorders of pregnancy pregnancies also fell between epochs (Table 3), and a χ2 test did not identify heterogeneity between ORs between hypertensive disorders of pregnancy and nonhypertensive disorders of pregnancy populations (P<.15).19

Figure 1 presents the incidence of combined adverse maternal and perinatal outcomes, respectively, by health authority (the health authority to which each letter in A and B differs between the figures). In Figure 2, we present the data by size of maternity facility (categorized by number of births per annum).

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In this study, we have observed an association between the introduction of evidence-based guidelines and improved maternal and perinatal outcomes across the Province of British Columbia. These findings complement our previous observation at British Columbia Women's, whereby the introduction of assessment and surveillance guidelines for women admitted with preeclampsia were associated with improved maternal, but not perinatal, outcomes.9 That we have observed improved outcomes on both occasions increases our confidence that the changes are more likely to reflect a cause-and-effect relationship between the intervention and outcome rate.

The principal component of the combined adverse maternal outcome to fall was the incidence of eclampsia. Although the guidelines were largely facility-focused, the assessment and surveillance component has been used to triage women for either admission or continued outpatient management and a clear emphasis was placed on the use magnesium sulfate prophylaxis against eclampsia with “severe” disease. Unfortunately, we were unable to determine whether the reduction in eclampsia related primarily to outpatient or inpatient seizures or whether the timing of seizures (antepartum, intrapartum, postpartum) was influenced.

It is possible that these improvements came at the cost of transient acute renal failure (OR 2.08, 95% CI 0.80–5.37). If so, this might reflect the emphasis placed on restricted fluid management in the guideline and associated presentations. There was no increase in need for transient dialysis between the preintervention and postintervention phases, and no women experienced irreversible renal compromise. However, a similar trend, and magnitude of effect, toward increased renal failure was observed in the nonhypertensive disorders of pregnancy population (OR 1.94, 95% CI 0.85–1.75). Therefore, the change in coding classification system that was used to identify hypertensive disorders of pregnancy and many of the maternal and newborn outcomes (from ICD-9 to ICD-10) in 2004–2005 may partially explain the observed effect. Acute pulmonary edema, for which there was a trend toward a decline in incidence, is more dangerous to women than transient renal failure17 and appears largely iatrogenic.18

For the change in ICD coding between epochs to have altered the observed change in adverse maternal outcomes, the underreporting error in the postintervention period would have had to be 35% (incidence of adverse outcomes in postintervention period=126 of 4,926 hypertensive disorders of pregnancy pregnancies; ie, 1.35×observed incidence with ICD-10 coding). It is possible that the improvements in adverse perinatal outcomes observed across the province related to coding changes between epochs for both hypertensive disorders of pregnancy and nonhypertensive disorders of pregnancy pregnancies. Because the χ2 test for heterogeneity is conservative, the apparently greater fall in adverse perinatal outcomes for hypertensive disorders of pregnancies may represent a differential benefit for those pregnancies compared with nonhypertensive disorders of pregnancies.

We noted that degrees of improvement varied between health authorities, but improvements were consistently observed. For adverse maternal outcomes, improvements differed between home health authorities, and the greatest benefits were observed for the health authorities with the highest preintervention rates of adverse events and for smaller units.

It is our belief that these improvements relate to four principal factors. First, we used a model of interactive and iterative guideline development that caused the participants (local change leaders in their own communities) to be become invested in the resultant document.

Second, we published the guidelines in hard and electronic copy and made them readily available to individual practitioners and on delivery suites across the province.

Third, we presented the guidelines through provincial telehealth rounds on three occasions during the implementation phase and undertook a road trip to most regional centers, where local rounds (sometimes with regional telehealth) were presented and an opportunity given for dialog. These presentations were focused on what we recognized would be the contentious issues in the guidelines such as fluid restriction (total hourly intake of 80 mL/h) in women with severe preeclampsia.

Fourth, the guidelines were perceived to be evidence-based by the medical, midwifery, and nursing practitioners who were being asked to implement them.

This process of active guideline implementation is similar that adopted for the guidelines relating to the management of severe preeclampsia in West Yorkshire.13 In that implementation study, the centers noted improved outcomes that were associated with fewer maternal transfers and intensive care unit admissions. The Tufnell study and our own findings differ from those of Foy,14 in which clearly evidence-based guidelines were introduced through the usual, passive, mechanism without noticeable improvements in outcome in Scotland.

The principal limitation of the study was the preintervention and postintervention design. However, these findings reinforce our previous observations in a single unit,9 that active implementation of an evidence-based intervention, such as assessment and surveillance guidelines (our previous study) or more global guidelines (this study), are associated with improved outcomes in communities of care. These communities of care can be single institutions or wider jurisdictions. In the future, a formal stepped-wedge design might better be used to monitor guideline implementation across a range of sites and regions.

In summary, consistent with our single-site experience,9 we have observed that the active management of hypertensive disorders of pregnancy guideline implementation was associated with improved maternal, and possibly perinatal, outcomes in British Columbia.

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