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Cohort study
Hypertension during pregnancy is associated with increased risk of chronic and end-stage kidney disease
  1. Reem A Asad,
  2. Vesna D Garovic
  1. Department of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA
  1. Correspondence to: Dr Vesna D Garovic
    Department of Nephrology and Hypertension, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA, garovic.vesna{at}mayo.edu

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Implications for practice and research

  • Women with a history of hypertensive pregnancy disorders may have an elevated risk of future chronic kidney disease (CKD) and end-stage renal disease (ESRD).

  • Follow-up of renal function and proteinuria after pre-eclamptic pregnancies could facilitate early detection and intervention of renal disease.

Context

To date, case–control and registry-based cohort studies have suggested that women with histories of hypertensive pregnancy disorders and pre-eclampsia in particular, are at risk for future cardiovascular disease (CVD).1 ,2 Limited data have suggested that women with pre-eclampsia are at risk for microalbuminuria,3 CKD and ESRD years after their affected pregnancies.4 The limitations of the available evidence do not allow for the establishment of more specific renal follow-up guidelines after pre-eclamptic pregnancies. Most importantly, these studies were not fully adjusted for traditional CKD risk factors, the reports of essential hypertension and renal disease were not validated and the results were not adjusted for pre-pregnancy blood pressure.3 ,4

Methods

This cohort study was conducted using the healthcare reimbursement claims from the National Health Research Institutes for Taiwan's National Health Insurance Programme for 1996–2009. The Taiwan National Health Insurance Programme had a coverage rate of 93.1% for the 23 million residents in 1996; the coverage rate was 99% in 2009. The study cohort included 26 651 women with hypertensive pregnancy disorders, as identified by using the International Classification of Diseases, ninth revision (ICD-9) codes; this excluded women with a history of hypertension, diabetes, renal disease and systemic lupus erythematosus that predated their index pregnancies. For each case, eight normotensive controls were randomly selected and matched for age and year of index pregnancy, for a total of 213 397 controls. The analysis included calculations of HR adjusted for demographic and clinical factors for the outcomes of CKD and ESRD (identified through ICD-9 codes) in women with, versus those without, hypertensive pregnancy disorders.

Findings

The risk of CKD and ESRD was greater for women with hypertensive pregnancy disorders compared with those without, HR 9.38 (95% CI 7.09 to 12.4) and 12.4 (95% CI 8.54 to 18.0), respectively. The risk was greater in women with pre-eclampsia or eclampsia (HR 14.0, 95% CI 9.43 to 20.7) compared with those with gestational hypertension only (HR 9.03, 95 CI 5.20 to 15.7). The Kaplan-Meier analysis showed that the ESRD-free survival was greater in women without, compared with those with, hypertensive pregnancy disorders (p<0.001).

Commentary

This is the first study to explore the association between hypertension in pregnancy and future renal disease in an Asian (Taiwanese) population, and to report that the estimated risk for ESRD was higher than among white, Norwegian women with pre-eclampsia.4 Future studies should assess for these associations in other racial groups. African-American women are known to be at a particularly high risk for pre-eclampsia and related complications; whether this may translate into an elevated risk for renal disease later in life, remains to be determined.

This study further adds to the literature by studying the association between hypertensive pregnancy disorders and ESRD while adjusting for hypertension and diabetes (two major risk factors for renal disease) that these women developed later in life. Among these women, a history of hypertensive pregnancy disorders conferred a greater risk for ESRD. However, the HR for ESRD, adjusted for urban status, coronary artery disease, congestive heart failure, hyperlipidaemia and placental abruption (HR 12.4, 95% CI 8.54 to 18.0), significantly decreased after including postpartum hypertension and diabetes in the model (HR 2.72, 95% CI 1.76 to 4.22). The results suggest that hypertension and diabetes may be contributing significantly to ESRD risk, which has been attributed to hypertensive pregnancy disorders. Close monitoring and early treatment of hypertension and diabetes may improve renal outcomes in women with a history of hypertensive pregnancy disorders.

Future population-based studies evaluating this association are needed, in which both hypertensive pregnancy disorders and outcomes will be confirmed based on accepted clinical criteria (not on diagnostic codes only), while taking into account known risk factors for renal disease before, during and after hypertensive pregnancies.

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Footnotes

  • Competing interests None.

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