TL;DR
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A Canadian matched cohort study found that pregnancies after living kidney donation were associated with higher rates of hospitalization for gestational hypertension, preeclampsia or eclampsia, and small-for-gestational-age births. The researchers said most pregnancies after donation proceeded without major issues, and the birth-size finding needs confirmation.
A Canadian matched cohort study found that pregnancies after living kidney donation were associated with higher rates of hospitalization for gestational hypertension, preeclampsia or eclampsia, and small-for-gestational-age births. The researchers stressed that these complications remained uncommon overall and that most post-donation pregnancies proceeded without major issues. The findings were presented at the American Society of Nephrology Kidney Week meeting and published in JAMA on October 22, 2026.
Among singleton pregnancies reaching at least 20 weeks, the study’s primary outcome—a hospitalization with a diagnosis of gestational hypertension, preeclampsia or eclampsia—was recorded in 11.9% of pregnancies among kidney donors, compared with 8.3% among matched nondonors. The reported risk ratio was 1.51, with a 95% confidence interval of 1.10 to 2.08. The result indicates a higher relative risk in the donor group, while the absolute difference between the groups was 3.6 percentage points.
Small-for-gestational-age births, defined as birth weight below the 10th percentile, occurred in 13.8% of donor pregnancies and 7.9% of nondonor pregnancies. The reported risk ratio was 1.86 (95% CI 1.37-2.52). Lead researcher Amit X. Garg, MD, PhD, of London Health Sciences Centre in Ontario, said this association was less anticipated and needs confirmation because it was one of several secondary outcomes assessed.
The population-based analysis used administrative health data from three Canadian provinces. It included 385 pregnancies among 252 donors, matched with 1,540 pregnancies among 1,535 nondonors. Matching accounted for factors including maternal age, delivery date, parity, time between study entry and delivery, and income quintile. Eleven other secondary outcomes showed no clear difference between groups, including preterm birth or low birth weight, severe maternal morbidity, cesarean delivery, gestational diabetes, stillbirth and neonatal death.
Pregnancy Counseling After Donation
The findings add evidence for discussions with people considering living kidney donation who may want children later. Living donation can provide a kidney to someone with kidney failure, but the results suggest a modestly higher chance of certain pregnancy complications after donation. The study does not establish that donation itself caused the observed differences, and its findings do not mean that a future pregnancy is generally unsafe.
Garg said prospective donors should be counseled about the possible association and that donors who become pregnant should have access to appropriate prenatal care, including attention to blood pressure and other signs of hypertensive disorders. He also said that wanting to become pregnant in the future should not, by itself, rule someone out as a living donor. The balance of recipient benefit and donor health remains part of an individualized decision with a clinical team.
The issue affects a substantial share of potential donors: the report notes that approximately 65% of living kidney donors are women, and about 75% are of childbearing age when they donate. Those figures make clear counseling relevant to donation decisions and later pregnancy care.
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How the Study Compared Pregnancies
The research builds on earlier evidence that informed 2017 international guidelines advising clinical teams to discuss the potential risk of gestational hypertensive disorders with donor candidates. Pregnancy places added demands on the kidneys, including increases in renal blood flow and filtration, offering a possible biological explanation for the association. The study authors also cited experimental work in mice after removal of one kidney, but animal findings do not establish the mechanism in human pregnancies.
In subgroup analyses, the primary-outcome risk ratios were consistent across parity and the time elapsed since study entry. The association appeared larger among donors aged 35 or older at delivery: the outcome occurred in 14.3% of their pregnancies, compared with 7.6% among matched nondonors (RR 1.99, 95% CI 1.18-3.33). Among women under 35, rates were 10.7% and 8.7%, respectively (RR 1.41, 95% CI 0.93-2.15). These subgroup estimates do not show that age explains the overall association.
“Donor candidates who may become pregnant should be counseled that donation may be associated with a modestly higher chance of developing gestational hypertension or preeclampsia.”
— Amit X. Garg, MD, PhD, lead researcher, speaking to MedPage Today
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Limits on Causation and Risk
The study found an association; it cannot show that kidney donation caused the complications. The authors identified possible residual genetic confounding, since donors may be related to recipients and could share genetic susceptibility to kidney dysfunction. Administrative records also lacked information on maternal body mass index, blood pressure measurements and medication use during pregnancy, factors that could affect comparisons.
The small-for-gestational-age result is a secondary finding and, the researchers said, requires confirmation in other studies. Although the age-35-and-older subgroup had a larger reported risk ratio, the study does not settle how age, other health characteristics or donation-related changes contribute to outcomes. The data also do not establish an individual donor’s future pregnancy risk.
Most pregnancies in both groups did not have the primary outcome, and the report says most pregnancies after donation proceeded without major issues. The study’s reported figures apply to the population and outcomes it measured; they should not be read as a prediction for every person considering donation.
small for gestational age baby growth chart
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Further Evidence and Prenatal Care
The authors said the small-for-gestational-age finding needs testing in other studies. Further research could help clarify whether the association persists in different populations and how donor health factors influence pregnancy outcomes. The report does not identify a scheduled follow-up study or a new clinical guideline prompted by these results.
For now, the researchers’ stated implication is to include possible pregnancy-related blood pressure risks in donor counseling and to support appropriate prenatal care for donors who later become pregnant. People weighing donation and future pregnancy can discuss their personal health history and the study’s limits with qualified clinicians before making decisions.
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Key Questions
What pregnancy risk was higher after kidney donation?
The study found the primary outcome—hospitalization with a diagnosis of gestational hypertension, preeclampsia or eclampsia—in 11.9% of donor pregnancies and 8.3% of matched nondonor pregnancies. It also reported more small-for-gestational-age births in the donor group.
Does the study prove kidney donation causes these complications?
No. It was an observational matched cohort study and found an association, not proof of causation. The authors noted possible genetic confounding and missing information on factors such as body mass index, blood pressure and medication use.
Were complications common among donors who became pregnant?
The complications were uncommon overall. The report says the vast majority of pregnancies after donation proceeded without major issues, and fewer than 2% of pregnancies in either group had the primary outcome first recorded before 34 weeks.
Does wanting a future pregnancy rule someone out as a donor?
Garg said a desire for future pregnancy should not, by itself, exclude someone from living donation. Prospective donors should discuss their circumstances and the potential risks with their clinical team.
What should donors know if they become pregnant?
Garg said donors who become pregnant should have access to appropriate prenatal care, with attention to blood pressure and features of hypertensive disorders. The study does not provide individualized medical advice or predict one person’s outcome.
Source: rss
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