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Chronic hypertension and pregnancy outcomes: systematic review and meta-analysis

BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2301 (Published 15 April 2014) Cite this as: BMJ 2014;348:g2301
  1. Kate Bramham, clinical research fellow,
  2. Bethany Parnell, medical student,
  3. Catherine Nelson-Piercy, professor of obstetric medicine,
  4. Paul T Seed, senior lecturer in medical statistics,
  5. Lucilla Poston, professor of Women’s Health,
  6. Lucy C Chappell, clinical senior lecturer in maternal and fetal medicine
  1. 1Division of Women’s Health, Women’s Health Academic Centre, King’s College London and King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom
  1. Correspondence to: L Chappell lucy.chappell{at}kcl.ac.uk
  • Accepted 12 March 2014

Abstract

Objective To provide an accurate assessment of complications of pregnancy in women with chronic hypertension, including comparison with population pregnancy data (US) to inform pre-pregnancy and antenatal management strategies.

Design Systematic review and meta-analysis.

Data sources Embase, Medline, and Web of Science were searched without language restrictions, from first publication until June 2013; the bibliographies of relevant articles and reviews were hand searched for additional reports.

Study selection Studies involving pregnant women with chronic hypertension, including retrospective and prospective cohorts, population studies, and appropriate arms of randomised controlled trials, were included.

Data extraction Pooled incidence for each pregnancy outcome was reported and, for US studies, compared with US general population incidence from the National Vital Statistics Report (2006).

Results 55 eligible studies were identified, encompassing 795 221 pregnancies. Women with chronic hypertension had high pooled incidences of superimposed pre-eclampsia (25.9%, 95% confidence interval 21.0% to 31.5 %), caesarean section (41.4%, 35.5% to 47.7%), preterm delivery <37 weeks’ gestation (28.1% (22.6 to 34.4%), birth weight <2500 g (16.9%, 13.1% to 21.5%), neonatal unit admission (20.5%, 15.7% to 26.4%), and perinatal death (4.0%, 2.9% to 5.4%). However, considerable heterogeneity existed in the reported incidence of all outcomes (τ2=0.286-0.766), with a substantial range of incidences in individual studies around these averages; additional meta-regression did not identify any influential demographic factors. The incidences (the meta-analysis average from US studies) of adverse outcomes in women with chronic hypertension were compared with women from the US national population dataset and showed higher risks in those with chronic hypertension: relative risks were 7.7 (95% confidence interval 5.7 to 10.1) for superimposed pre-eclampsia compared with pre-eclampsia, 1.3 (1.1 to 1.5) for caesarean section, 2.7 (1.9 to 3.6) for preterm delivery <37 weeks’ gestation, 2.7 (1.9 to 3.8) for birth weight <2500 g, 3.2 (2.2 to 4.4) for neonatal unit admission, and 4.2 (2.7 to 6.5) for perinatal death.

Conclusions This systematic review, reporting meta-analysed data from studies of pregnant women with chronic hypertension, shows that adverse outcomes of pregnancy are common and emphasises a need for heightened antenatal surveillance. A consistent strategy to study women with chronic hypertension is needed, as previous study designs have been diverse. These findings should inform counselling and contribute to optimisation of maternal health, drug treatment, and pre-pregnancy management in women affected by chronic hypertension.

Footnotes

  • Contributors: KB, BP, and LCC contributed to study conception and design, analysis and interpretation of the data, and drafting and revising of the article and were involved in the final approval of the version to be published. PTS contributed to the analysis and interpretation of the data and revision of the article. CN-P and LP contributed to the interpretation of the data, drafting and revising of the article, and approval of the final paper. LCC is the guarantor.

  • Funding: This work is produced by KB under the terms of a doctoral research training fellowship issued by the National Institute for Health Research.  The views expressed in this publication are those of the author and not necessarily those of the NHS, the National Institute for Health Research, or the Department of Health. PTS’s salary is funded by Tommy’s Charity.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could have influenced the submitted work.

  • Ethical approval: Not needed

  • Transparency declaration: LCC affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

  • Data sharing: The dataset is available to interested academic parties from the corresponding author.

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