Pregnancies in living kidney donors

BACKGROUND AND HYPOTHESIS: Although the majority of kidney donors are women, data on pregnancy-related maternal and fetal outcomes remain scarce. Understanding these risks is essential for evidence-based counselling. Our aim was to assess whether pregnancies in living kidney donors were associated with adverse outcomes. We hypothesized that kidney donation increases the risk of pregnancy complications, particularly pre-eclampsia and related adverse outcomes. METHODS: In this nationwide registry-based cohort study, Swedish women ≤45 years with births before and/or after kidney donation between 1973 and 2022 were identified through linkage of the National Patient Register, Scandiatransplant Register, and Medical Birth Register. Using a dual study design, post-donation pregnancies were compared with a 1:10 matched control group (matched on age, year, parity and region), and pre-donation pregnancies served as within-donor controls. RESULTS: Among 679 donors, 1305 pre- and 139 post-donation pregnancies were identified. Compared to controls, post-donation pregnancies had higher proportions of low-birth-weight (<2500 g; 9.4 vs. 3.7%, OR 2.69, 95% CI 1.33-5.42) and small-for-gestational-age (SGA, defined as birth weight < -2 SD) infants (5.8 vs. 2.2%, OR 2.54, 95% CI 1.13-5.72). The combined outcome of pre-eclampsia and SGA was more frequent post-donation (OR 2.08, 95% CI 1.03-4.22). No significant difference was found for pre-eclampsia alone (4.3% vs. 2.4%, OR 1.91, 95% CI 0.78-4.72). Preterm birth (<37 weeks) was more frequent post-donation than in controls (9.4 vs. 5.0%, OR 1.95, 95% CI 0.99-3.84). CONCLUSIONS: Overall, no clear excess risk of pre-eclampsia was found in post-donation pregnancies. However, modestly increased risks of low-birth-weight and small-for-gestational-age infants were observed, although absolute risks remained low. A possible trend towards preterm birth compared with matched controls was observed. These findings support individualized pre-donation counselling and highlight the need for enhanced monitoring in pregnancies following kidney donation.