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The Effect of Pregnancy on the Long-term Risk of Graft Loss, Cardiovascular Disease, and Death in Kidney Transplanted Women in Norway: A Retrospective Cohort Study

Majak, Guri B., MD1,2; Reisæter, Anna Varberg, MD, PhD3; Weedon-Fekjær, Harald, PhD4; Henriksen, Tore, MD, PhD1,5; Michelsen, Trond M., MD, PhD1,2,6

doi: 10.1097/TP.0000000000002167
Original Clinical Science—General

Background Kidney transplant recipients have now conceived for almost 50 years. Nevertheless, few studies have evaluated long-term health outcomes for kidney transplanted women after pregnancies.

Methods We conducted a retrospective cohort study of all Norwegian women receiving a kidney transplant before the age of 50 years between 1969 and 2013, with graft loss, cardiovascular disease, and death as outcomes. Baseline characteristics for all women were ascertained at first transplantation, with information about exposure, outcomes, and potential confounders collected from medical records. To account for changes in pregnancy status, data were analyzed using proportional hazard Cox regression with pregnancy status as a time-dependent covariate changing at the time of pregnancy.

Results Of 650 women studied, 124 had a pregnancy after kidney transplantation. During the study period, graft loss, cardiovascular disease, and death occurred in 237, 73, and 274 women, respectively. Pregnancy was associated with 54% lower risk of graft loss (95% confidence interval [CI]: 25% to 71%) and 72% lower risk of death (95% CI, 53%-84%). Adjusting for possible confounders had a minimal impact on estimated values. There were considerable uncertainties and no statistically significant results regarding the estimated risk of cardiovascular disease after pregnancy (univariate hazard ratio, 0.91; 95% CI, 0.43-1.92; multivariate hazard ratio, 0.71; 95% CI, 0.32-1.60).

Conclusions Kidney transplanted women with pregnancies have a low risk of subsequent graft loss or death. These results are reassuring for the current clinical practice.

The authors have evaluated the impact of pregnancy on long-term kidney transplant outcome and found kidney transplanted women with pregnancies have a low risk of subsequent graft loss or death.

1 Division of Obstetrics and Gynecology, Department of Obstetrics, Oslo University Hospital, Oslo, Norway.

2 Norwegian National Advisory Unit on Women's Health, Oslo University Hospital, Rikshospitalet, Oslo, Norway.

3 Department of Transplantation Medicine, Oslo University Hospital, Rikshospitalet, Oslo Norway.

4 Oslo Centre for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway.

5 University of Oslo, Oslo, Norway.

6 Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO.

Received 26 August 2017. Revision received 1 January 2018.

Accepted 3 January 2018.

This research was funded by grants from the South-Eastern Norway Regional Health Authority.

The authors declare no conflicts of interest.

G.B.M. conceived and contributed to the design of the study, recruitment of patients, data collection, the analysis and interpretation of the data, and drafted the first version of the article. A.V.R., H.W.F., and T.H. made substantial contributions to the design of the study and the analysis and interpretation of the data, provided intellectual input and supervision throughout the study, and contributed substantially to drafting of the article. T.M.M. was the principal investigator. He made substantial contributions to the design of the study, contributed to the analysis and interpretation of the data, provided intellectual input and supervision throughout the study, and contributed substantially to drafting the article. All of the authors revised the article, commented on draft versions, and provided final approval of the version to be published, and agreed to be accountable for all aspects of the work in terms of ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Details of Ethics Approval: This study was approved by the Regional Committee for Medical Research Ethics in South East Norway (reference number 2012/1139).

Correspondence: Guri B. Majak, MD, Women and Children's Division, Oslo University Hospital Rikshospitalet, Postbox 4950, Nydalen, 0424 Oslo, Norway. (gurifb@hotmail.com).

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