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

ABSTRACTBackgroundKidney transplant recipients have now conceived for almost 50 years. Nevertheless, few studies have evaluated long-term health outcomes for kidney transplanted women following pregnancies.MethodsWe 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.ResultsOf 650 women studied, 124 had a pregnancy following 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% to 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 following pregnancy (univariate hazard ratio; 0.91, 95% CI: 0.43 to 1.92, multivariate hazard ratio; 0.71, 95% CI: 0.32 to 1.60).ConclusionsKidney transplanted women with pregnancies have a low risk of subsequent graft loss or death. These results are reassuring for the current clinical practice. Background Kidney transplant recipients have now conceived for almost 50 years. Nevertheless, few studies have evaluated long-term health outcomes for kidney transplanted women following 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 following 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% to 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 following pregnancy (univariate hazard ratio; 0.91, 95% CI: 0.43 to 1.92, multivariate hazard ratio; 0.71, 95% CI: 0.32 to 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. Corresponding author: Dr Guri B. Majak, Women and Children´s Division, Oslo University Hospital Rikshospitalet, Postbox 4950 Nydalen, 0424 Oslo, Norway. Email: gurifb@hotmail.com Authorship Contribution GBM 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 manuscript. AVR, HWF and TH 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 manuscript. TMM 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 manuscript. 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. Disclosure The authors declare no conflicts of interest Funding This research was funded by grants from the South-Eastern Norway Regional Health Authority. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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