BACKGROUND: The effect of pregnancy on the course of estimated glomerular filtration rate (eGFR) is unknown in kidney transplant recipients (KTRs).
METHODS: We conducted a nationwide multicenter cohort study in KTRs with pregnancy (>20 weeks) after kidney transplantation (KT). Annual eGFR's after KT until death or graft loss and additional eGFR's before each pregnancy were collected according to protocol. Changes in eGFR slope before and after each pregnancy were analyzed by generalized estimating equations (GEE) multilevel analysis adjusted for transplant vintage.
RESULTS: We included 3194 eGFR measurements before and after pregnancy in 109 (55%) KTRs with 1, 78 (40%) with 2 and 10 (5%) with 3 pregnancies after KT. Median follow-up after first delivery post-KT was 14 years (IQR 18 years). Adjusted mean eGFR pre-pregnancy was 59 ml/min/1.73m2 (SEM 1.72; 95% CI 56-63), after first pregnancy 56 ml/min/1.73m2 (SEM 1.70; 95% CI 53-60), after second pregnancy 56 ml/min/1.73m2 (SEM 2.19; 95% CI 51-60) and after third pregnancy 55 ml/min/1.73m2 (SEM 8.63; 95% CI 38-72). Overall eGFR slope after first, second and third pregnancy was not significantly worse than pre-pregnancy (p = 0.28). However, adjusted mean eGFR after first pregnancy was 2.8 ml/min/1.73m (p = 0.08) lower than pre-pregnancy.
CONCLUSIONS: First pregnancy has a small, but no significant, effect on eGFR slope in KTR. Midterm hyperfiltration, a marker for renal reserve capacity, was associated with better eGFR and death-censored graft survival. In this KTR cohort with long-term follow-up, no significant effect of pregnancy on kidney function was detected.