A Canadian matched cohort study published on October 22, 2026, reveals that women who become pregnant after living kidney donation face a modestly higher risk of gestational hypertension and preeclampsia compared with nondonors, alongside an elevated rate of small-for-gestational-age births.
Living kidney donation offers extraordinary medical benefits to individuals experiencing kidney failure. Yet the long-term health implications for donors of childbearing age have long remained a subject of clinical study.
Now, new population-based findings published in JAMA provide clearer data on subsequent pregnancies. The research team evaluated administrative health databases across Ontario, British Columbia, and Alberta to track maternal and neonatal outcomes among donors and matched nondonors.
📣 Presented at #KidneyWk: Among women with postdonation #Pregnancy after living #KidneyDonation, hospitalization with gestational #hypertension, #preeclampsia, or #eclampsia was more common than in matched pregnancies among nondonors. Most postdonation pregnancies remained… pic.twitter.com/dq7Nuji7Gx
How the Canadian Matched Cohort Study Compared Donors and Nondonors
Investigators identified female kidney donors aged 18 to 42 who underwent nephrectomy between July 1992 and August 2021, following their health trajectories through March 2023. To establish a rigorous comparison group, researchers assigned nondonors a simulated donation date and systematically excluded anyone with any of 35 pre-existing conditions that would disqualify someone from donating a kidney, such as chronic hypertension, diabetes, established kidney disease, and lupus.
Each donor pregnancy was matched against four nondonor pregnancies. The matching criteria accounted for delivery date, maternal age at delivery, time elapsed from cohort entry to delivery, parity, and income quintile.
Pregnancy Complication Rates and Findings Revealed in JAMA
The analysis captured 385 pregnancies among 252 living donors and compared them with 1,540 pregnancies among 1,535 matched nondonors. The primary composite outcome—hospitalization carrying a diagnosis of gestational hypertension, preeclampsia, or eclampsia between 20 weeks of gestation and six weeks postpartum—occurred in 11.9% of donor pregnancies compared with 8.3% of nondonor pregnancies.
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, London Health Sciences Centre
That primary composite outcome yielded a risk ratio of 1.51, accompanied by a 95% confidence interval spanning 1.10 to 2.08. Researchers calculated a model-based absolute risk difference of 2.7 percentage points. Furthermore, investigators observed that more than 88% of donor pregnancies proceeded without these hypertensive complications, and fewer than 2% of events in either group were recorded before 34 weeks of gestation.
Secondary outcomes yielded a separate signal regarding birth weights. Small-for-gestational-age births—defined as a birth weight falling below the 10th percentile—appeared in 13.8% of donor pregnancies versus 7.9% of matched nondonor controls. Post hoc evaluations showed this pattern persisted at stricter statistical thresholds, including birth weights beneath the fifth percentile and the third percentile.
Clinical Counsel and Biological Mechanisms Behind the Data
The observed link aligns with prior literature that prompted international clinical guidance. The 2017 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guidelines already advise medical teams to inform prospective donors about potential gestational hypertensive risks.
Biologically, pregnancy places heavy physiological demands on the renal system, requiring marked increases in renal blood flow and glomerular filtration rate. Researchers cited an experimental model showing that unilaterally nephrectomized mice exhibit impaired renal adaptation during pregnancy, accompanied by abnormal placental development, placental hypoperfusion, and an antiangiogenic state.
Living kidney donation provides an extraordinary benefit to people with kidney failure, and the decision to donate requires thoughtful consideration of both the benefits to the recipient and the long-term health of the donor.
Amit X. Garg, MD, PhD, London Health Sciences Centre
Subgroup analyses also highlighted maternal age as a factor. The risk ratio for gestational hypertensive disorders was larger among women aged 35 or older at delivery, while younger cohorts showed smaller relative risk margins.
Limitations and Unresolved Questions in Kidney Donor Research
Study authors noted several limitations within their administrative healthcare dataset. The records lacked direct measurements of maternal body mass index, serial blood pressure readings, and outpatient medication use during pregnancy. Diagnostic administrative codes could not differentiate disease severity.
Residual genetic confounding also remains difficult to rule out entirely. In Ontario, where data on donor-recipient relationships were accessible, 63.9% of donors were first-degree relatives of the transplant recipients. Because nondonors are unlikely to share that exact familial predisposition to kidney dysfunction, inherited factors could theoretically contribute to the observed outcomes.
Investigators emphasized that the findings should not discourage capable individuals from becoming living donors. Future studies are expected to confirm whether the elevated rate of small-for-gestational-age births stems from biological adaptation or random variation, and to expand research across diverse patient demographics.
