Pregnancy Outcomes After Living Kidney Donation.

People who become pregnant after living kidney donation may be at increased risk of pregnancy-related adverse outcomes, although the evidence is unclear. To determine whether pregnancies after living kidney donation are associated with a higher risk of adverse pregnancy outcomes than matched pregnancies among nondonors. This matched cohort study used provincial administrative health care databases from Ontario, British Columbia, and Alberta, Canada, and included 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. These pregnancies were matched 1:4 with singleton pregnancies of at least 20 weeks' gestation among female nondonors. Pregnancies in donors and nondonors were matched on delivery date, age at delivery, years between cohort entry and delivery, number of prior pregnancies, and income. Final follow-up occurred until March 2023. Outcome analysis occurred from August 2024 to September 2026. The primary outcome was a composite of hospitalization with a diagnosis of gestational hypertension, preeclampsia, or eclampsia. Secondary outcomes included 12 maternal, fetal and neonatal adverse outcomes, including the individual components of the primary outcome, the composite of low birth weight or preterm birth, and small for gestational age at birth. The sample included 385 pregnancies in 252 living kidney donors (mean [SD] age, 27.8 [5.0] years) matched to 1540 pregnancies in 1535 nondonors (mean [SD] age, 27.0 [4.8] years). The primary composite outcome of gestational hypertension, preeclampsia, or eclampsia occurred in 46 donor pregnancies (11.9%) and 128 nondonor pregnancies (8.3%; risk ratio, 1.51; 95% CI, 1.10-2.08). Among the 12 secondary outcomes, the 95% CI for the risk ratio excluded 1.00 for the outcome of small for gestational age, which occurred in 53 donor pregnancies (13.8%) and 121 nondonor pregnancies (7.9%) (risk ratio, 1.86; 95% CI, 1.37-2.52). In this study, pregnancy after living kidney donation was associated with a higher risk of the composite outcome of hospitalization with a diagnosis of gestational hypertension, preeclampsia, or eclampsia, when compared with matched pregnancies in nondonors. Most postdonation pregnancies were uncomplicated. These findings support counseling donor candidates who may become pregnant about this risk and informing the prenatal care of donors who become pregnant.