Cardiovascular mortality after pre-eclampsia in one child mothers: prospective, population based cohort study
BMJ 2012; 345 doi: https://doi.org/10.1136/bmj.e7677 (Published 27 November 2012) Cite this as: BMJ 2012;345:e7677
- Rolv Skjaerven, professor12,
- Allen J Wilcox, senior investigator3,
- Kari Klungsøyr, associate professor12,
- Lorentz M Irgens, professor12,
- Bjørn Egil Vikse, associate professor45,
- Lars J Vatten, professor6,
- Rolv Terje Lie, professor12
- 1Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway
- 2Medical Birth Registry of Norway, National Institute of Public Health, Bergen
- 3National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, North Carolina, USA
- 4Institute of Medicine, University of Bergen
- 5Department of Medicine, Haukeland University Hospital, Bergen
- 6Department of Public Health, Norwegian University of Science and Technology, Trondheim, Norway
- Correspondence to: R Skjaerven rolv.skjaerven{at}smis.uib.no
- Accepted 2 November 2012
Abstract
Objective To assess the association of pre-eclampsia with later cardiovascular death in mothers according to their lifetime number of pregnancies, and particularly after only one child.
Design Prospective, population based cohort study.
Setting Medical Birth Registry of Norway.
Participants We followed 836 147 Norwegian women with a first singleton birth between 1967 and 2002 for cardiovascular mortality through linkage to the national Cause of Death Registry. About 23 000 women died by 2009, of whom 3891 died from cardiovascular causes. Associations between pre-eclampsia and cardiovascular death were assessed by hazard ratios, estimated by Cox regression analyses. Hazard ratios were adjusted for maternal education (three categories), maternal age at first birth, and year of first birth
Results The rate of cardiovascular mortality among women with preterm pre-eclampsia was 9.2% after having only one child, falling to 1.1% for those with two or more children. With term pre-eclampsia, the rates were 2.8% and 1.1%, respectively. Women with pre-eclampsia in their first pregnancy had higher rates of cardiovascular death than those who did not have the condition at first birth (adjusted hazard ratio 1.6 (95% confidence interval 1.4 to 2.0) after term pre-eclampsia; 3.7 (2.7 to 4.8) after preterm pre-eclampsia). Among women with only one lifetime pregnancy, the increase in risk of cardiovascular death was higher than for those with two or more children (3.4 (2.6 to 4.6) after term pre-eclampsia; 9.4 (6.5 to 13.7) after preterm pre-eclampsia). The risk of cardiovascular death was only moderately elevated among women with pre-eclamptic first pregnancies who went on to have additional children (1.5 (1.2 to 2.0) after term pre-eclampsia; 2.4 (1.5 to 3.9) after preterm pre-eclampsia). There was little evidence of additional risk after recurrent pre-eclampsia. All cause mortality for women with two or more lifetime births, who had pre-eclampsia in first pregnancy, was not elevated, even with preterm pre-eclampsia in first pregnancy (1.1 (0.87 to 1.14)).
Conclusions Cardiovascular death in women with pre-eclampsia in their first pregnancy is concentrated mainly in women with no additional births. This association might be due to health problems that discourage or prevent further pregnancies rather than to pre-eclampsia itself. As a screening criterion for cardiovascular disease risk, pre-eclampsia is a strong predictor primarily among women with only one child—particularly with preterm pre-eclampsia.
Footnotes
We thank reviewers and colleagues for their advice and help on previous versions of this paper, in particular Jørn Olsen, Tine B Henriksen, Matt Gilman, Janet Rich-Edwards, and James Roberts.
Contributors: RS proposed the study, did the data analysis and the graphs, and drafted the manuscript. AJW, KK, LMI, BEV, LJV, and RTL reviewed the preliminary analyses and initial draft of the manuscript and provided critical comments. All the authors reviewed the final version of the manuscript. RS is the guarantor, has full access to all of the data in the study, and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Funding: The study has been supported by grants from the Norwegian Research Council and by the Intramural Research Program of the National Institute of Environmental Health Sciences, National Institute of Health. The authors’ institutions had no role in the design and conduct of the study; the collection, management, analysis, and interpretation of the data; or the preparation, review, or approval of the manuscript.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: support from the Norwegian Research Council and the National Institute of Environmental Health Sciences; 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 appear to have influenced the submitted work .
Ethical approval: The study was approved by the internal review board of the Medical Birth Registry of Norway and by the regional ethics committee, REK Vest, Norway (2009/1868).
Data sharing: No additional data available.
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