Amit X. Garg, MD, PhD, is a professor of medicine, epidemiology and biostatistics at Western University, nephrologist at London Health Sciences Centre.

Amit X. Garg, MD, PhD

Small for gestational age births and shared donor-recipient genetics complicate the picture of pregnancy after

Investigators behind a new Canadian study of pregnancy after living kidney donation are weighing why donors had more small for gestational age (SGA) births than matched nondonors, and whether shared genetics with recipients could play a role.¹

American Society of Nephrology (ASN) Kidney Week 2026

 by Amit X. Garg, MD, PhD, and published simultaneously in 

, spanned 3 provinces and also found a modest increase in hypertensive disorders of pregnancy among donors.¹

Interpreting Kidney Donor Pregnancy Signals, With Amit Garg, MD, PhD

How Did the Study Compare Donors and Nondonors?

Using linked administrative health databases from Ontario, British Columbia, and Alberta, investigators compared 385 pregnancies in 252 living kidney donors with 1,540 matched pregnancies in 1,535 nondonors.¹ To reflect donors’ healthier baseline profile, nondonors with any of 35 conditions that would preclude donation were excluded. Pregnancies were matched 1:4 on delivery date, maternal age, time from cohort entry to delivery, parity, and income.¹

The primary outcome, hospitalization with gestational hypertension, preeclampsia, or eclampsia, occurred in 11.9% of donor pregnancies vs 8.3% of nondonor pregnancies (risk ratio [RR], 1.51; 95% CI, 1.10-2.08).¹ More than 88% of donor pregnancies were unaffected, and rates of other outcomes, including severe maternal morbidity, preterm birth or low birth weight, and neonatal intensive care admission, were similar between groups.¹

Why Might Small for Gestational Age Births Have Been More Common in Donor Pregnancies?

Among 12 secondary outcomes, SGA birth, defined as birth weight below the 10th percentile, occurred in 13.8% of donor pregnancies vs 7.9% of nondonor pregnancies (RR, 1.86; 95% CI, 1.37-2.52).¹ In post hoc analyses, the association persisted at stricter thresholds, including birth weight below the fifth percentile (6.5% vs 3.6%) and the third percentile (4.7% vs 1.9%).¹

“One possibility is chance, particularly given the number of secondary outcomes we examined. At the same time, there is biological plausibility,” said Garg, professor of medicine, epidemiology and biostatistics at Western University, nephrologist at London Health Sciences Centre, and corresponding author of the study, in an interview with HCPLive.

Garg explained that reduced kidney function may impair normal renal adaptation to pregnancy and, in turn, may affect placental development and blood flow. In the paper, investigators cited an experimental model in which mice with 1 kidney removed showed impaired kidney adaptation to pregnancy, with abnormal placental development and placental hypoperfusion.¹ According to Garg, the finding warrants evaluation and confirmation in future studies.

Could Genetics Explain the Pregnancy Risks Seen in Kidney Donors?

Investigators flagged residual genetic confounding as a limitation. In Ontario, where donor-recipient relationship data were available, 63.9% of donors were first-degree relatives of their recipients.¹ Garg noted that few nondonors would be expected to have a first-degree relative with kidney failure, so inherited susceptibility could contribute to the observed association. Post hoc analyses, limited by small event counts, could neither confirm nor rule out a difference in risk by relatedness.¹

Garg pointed to several observations that reduce this concern. All donors had normal measures of kidney health at evaluation, and pregnancies occurred a mean of 5.6 years after donation.¹ By design, individuals with a recorded hypertensive disorder of pregnancy before cohort entry were excluded.¹ In Canada, individuals with these complications would generally not be accepted as donors while still of childbearing age, he added.

“So certainly, genetic confounding remains possible, but these observations make it less likely to fully explain the observed association,” Garg said.

Editor’s Note: Garg reported no relevant disclosures.

Wang C, Naylor KL, McArthur E, et al. Pregnancy outcomes after living kidney donation. 

. Published online October 22, 2026. doi:10.1001/jama.2026.21737

Garg AX. Pregnancy outcomes after living kidney donation. Presented at: American Society of Nephrology Kidney Week 2026; October 22, 2026; Denver, CO. Abstract TH-OR117.

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Chance, biology, and shared genetics may explain more small for gestational age births after living kidney donation.

Future pregnancy plans need not rule out living kidney donation, but candidates should be counseled on hypertensive risk.

New data on pregnancy after living kidney donation give transplant teams clearer numbers to share with donor candidates who may want children in the future.¹

In a matched cohort study from 3 Canadian provinces, presented at 

, most donor pregnancies were uncomplicated, with a modest increase in hypertensive disorders of pregnancy.¹

Counseling Kidney Donors on Future Pregnancy, With Amit Garg, MD, PhD

Will Donating a Kidney Affect Future Pregnancies?

In 2024, more than 40,000 living kidney donations were reported across 88 countries.¹ For donors who may become pregnant later, Garg said the central question is whether donation will affect those pregnancies.

In the cohort of 385 donor pregnancies and 1,540 pregnancies in matched nondonors of similar baseline health, hospitalization with gestational hypertension, preeclampsia, or eclampsia occurred in 11.9% vs 8.3% (risk ratio [RR], 1.51; 95% CI, 1.10-2.08), and more than 88% of donor pregnancies were unaffected.¹ Small for gestational age births were also more common (13.8% vs 7.9%; RR, 1.86; 95% CI, 1.37-2.52), a secondary finding Garg said could reflect chance or biology. Rates of severe maternal morbidity, cesarean delivery, postpartum hemorrhage, gestational diabetes, preterm birth or low birth weight, and neonatal intensive care admission were similar between groups.¹

What Do the Findings Mean for Living Kidney Donation?

“If someone is interested in having a pregnancy after donation, that doesn’t preclude them from being a donor,” said Garg, professor of medicine, epidemiology and biostatistics at Western University, nephrologist at London Health Sciences Centre, and corresponding author of the study, in an interview with HCPLive.

Garg also emphasized encouraging healthy lifestyle behaviors after donation, noting obesity is associated with greater preeclampsia risk, along with appropriate monitoring for these complications. With living kidney donation performed worldwide, he said transplant centers should be confident donors will have access to good maternal care should they become pregnant.

How Should Clinicians Counsel Kidney Donor Candidates About Pregnancy?

The 2017 Kidney Disease: Improving Global Outcomes (KDIGO) guideline on living kidney donors recommends counseling donor candidates about the potential for an increased risk of gestational hypertension or preeclampsia.² According to Garg, the findings support this guidance, including asking candidates about future pregnancy plans during evaluation.

Age may matter in these conversations. In subgroup analyses, the RR for the primary outcome was larger among pregnancies at a maternal age of 35 years or older (14.3% vs 7.6%; RR, 1.99; 95% CI, 1.18-3.33) than among younger mothers (RR, 1.41; 95% CI, 0.93-2.15).¹

“When we counsel donor candidates, we should discuss the possible effect of donation on future pregnancy, including a higher risk of gestational hypertension or preeclampsia,” Garg said.

Investigators noted that most Canadian donors are White and receive care in publicly funded health systems, which may limit generalizability, and called for additional study among donors of African ancestry, including those with apolipoprotein L1 high-risk genotypes.¹

Lentine KL, Kasiske BL, Levey AS, et al. KDIGO clinical practice guideline on the evaluation and care of living kidney donors. 

. 2017;101(8S suppl 1):S1-S109. doi:10.1097/TP.0000000000001769

Future pregnancy plans don’t preclude living kidney donation, but candidates should be counseled on gestational hypertension risk.

A Canadian matched cohort study weighs whether pregnancies after 

 carry added hypertensive risk. About 65% of living kidney donors are female, and roughly 75% are of childbearing age at donation, making the effect of donation on future pregnancies a central question during donor evaluation.¹

, a new matched cohort study offers more precise estimates than earlier, smaller studies. Most donor pregnancies were uncomplicated, though investigators observed a modest increase in hypertensive disorders of pregnancy.¹

Hypertensive Pregnancy Risk in Kidney Donors, With Amit Garg, MD, PhD

Why Evaluate Pregnancy in Living Kidney Donors?

For people with kidney failure, a living donor transplant improves both life expectancy and quality of life, but transplant teams also have a responsibility to understand long-term outcomes for donors. Garg noted that consensus guidance from 2004 was reassuring that donor nephrectomy would not adversely affect future pregnancies. Since then, 3 studies, including a 2015 Ontario analysis from his group, have linked donation to a greater risk of gestational hypertension and preeclampsia.¹,²

“Despite these studies, recent reviews still say there’s uncertainty, and current practice patterns vary. Some people are counseled in certain ways; some people aren’t,” said Garg, professor of medicine, epidemiology and biostatistics at Western University, nephrologist at London Health Sciences Centre, and corresponding author of the study, in an interview with HCPLive.

The new analysis adds British Columbia and Alberta to the earlier Ontario cohort and extends follow-up through 2023. Approximately one-third of donor pregnancies were also included in the 2015 study.¹

Using linked provincial administrative health databases, investigators identified living female kidney donors aged 18 to 42 years who donated a kidney between July 1992 and August 2021 and subsequently had singleton pregnancies of at least 20 weeks' gestation, with follow-up through March 2023.¹

Because donors tend to be healthier than the general population, nondonors were assigned a simulated donation date and excluded if they had any of 35 conditions that would preclude donation, including hypertension, diabetes, kidney disease, and lupus.¹ Each donor pregnancy was matched to 4 nondonor pregnancies on delivery date, maternal age at delivery, time from cohort entry to delivery, parity, and income quintile. Province-specific estimates were pooled using meta-analysis.¹

The primary outcome was a composite of hospitalization with a diagnosis of gestational hypertension, preeclampsia, or eclampsia from 20 weeks' gestation through 6 weeks postpartum. Investigators also assessed 12 maternal, fetal, and neonatal secondary outcomes.¹

What Were the Pregnancy Outcomes After Kidney Donation?

The analysis included 385 pregnancies in 252 donors and 1540 matched pregnancies in 1535 nondonors.¹ The primary outcome occurred in 11.9% of donor pregnancies vs 8.3% of nondonor pregnancies (risk ratio [RR], 1.51; 95% CI, 1.10–2.08).¹ The model-based absolute risk difference was 2.7 percentage points (95% CI, −0.8 to 6.1). Investigators presented results descriptively rather than with formal significance testing because of overlap with the earlier cohort.¹ More than 88% of donor pregnancies were unaffected, and fewer than 2% had events recorded before 34 weeks' gestation.¹

Among secondary outcomes, preeclampsia or eclampsia occurred in 7.8% vs 5.5% of pregnancies (RR, 1.52; 95% CI, 1.01–2.29).¹

Small for gestational age (SGA) births occurred in 13.8% of donor pregnancies vs 7.9% of nondonor pregnancies (RR, 1.86; 95% CI, 1.37–2.52). Investigators cautioned that the association could reflect chance given the number of secondary outcomes examined.¹

Rates of severe maternal morbidity, cesarean delivery, postpartum hemorrhage, gestational diabetes, preterm birth or low birth weight, and neonatal intensive care admission were similar between groups, and no stillbirths occurred in either.¹

“So overall, the study shows that people who become pregnant after donation generally have very healthy pregnancies and healthy children. There’s a modest increase in the risk of developing high blood pressure or preeclampsia during those pregnancies,” Garg said.

Investigators noted the administrative data did not include blood pressure, body mass index, or medication use during pregnancy, and outcomes relied on diagnostic codes that could not distinguish disease severity. Donors also received slightly more prenatal surveillance than nondonors, and residual genetic confounding remained possible because many donors were biologically related to their transplant recipients.¹

The findings support counseling prospective donors about pregnancy-related hypertensive risk and informing prenatal care for individuals who become pregnant after donation, according to the investigators.¹

Editor's Note: Garg reported no relevant disclosures.

. Published online October 22, 2026. doi:

Garg AX, Nevis IF, McArthur E, et al. Gestational hypertension and preeclampsia in living kidney donors. 

A Canadian cohort found modestly greater preeclampsia risk after donation, though most pregnancies were uncomplicated.

Amit X. Garg, MD, PhD

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