#2403 Impact of pregnancy on kidney transplant recipients
Authors: González-García Celia , Hernández-Velasco Paúl , Sevillano Angel , Polanco Natalia , Ruiz Enrique Morales , Andrés Amado , Trujillo Hernando , Monte Esther González 
Published: May 2024

Abstract

Background and Aims
Kidney transplantation (KT) provides an opportunity to increase fertility in women with chronic kidney disease and gestational desire. Lack of knowledge about obstetric complications and implications for the graft may lead to discourage pregnancy for these women. Although the incidence of pregnancy is rising in women receiving KT, the impact that it may have on the graft function is unknown.

Method
We conducted an observational, retrospective, single-centre study of a cohort of kidney transplant recipients (KTR) who became pregnant between 2007 and 2022. Clinical and analytical parameters were evaluated before, during and after pregnancy. The main aim was to assess the long-term impact of pregnancy on the graft by analysing renal function 3 years after pregnancy.

Results
We included 25 women receiving a KT between 1990 and 2018, among which 72% (n = 18) were transplanted from a deceased donor. 2 women (8%) received a combined liver-kidney transplant and 2 women (8%) a simultaneous pancreas-kidney transplant. Maintenance immunosuppression before conception included teratogenic drugs in 68% of cases [12 of them (48%) received mycophenolate mofetil and 5 of them (20%), mTOR inhibitors]. Planned withdrawal was only applied in 50.0% of pregnancies (n = 15).
30 pregnancies were identified (5 patients had 2 post-transplant pregnancies). Median age at gestation was 35 years [interquartile range (IQR) 33-39]. 5 conceptions required assisted reproductive technology. The main complications were gestational hypertension in 4 KTR (13.3%) and preeclampsia in 7 pregnancies (23.3%). 60% of neonates (n = 18) were preterm births (36 [IQR 34-37] weeks of pregnancy at birth) and 44% (n = 12) had low birth weight (2530 [IQR 2283-2950] grams). No foetal malformations were described.
Due to physiological changes, a significant increase in estimated glomerular filtration rate (eGFR) was observed in the first and the second trimester of pregnancy (61 [IQR 50-91] ml/min and 70 [IQR 50-90] ml/min, respectively vs. baseline eGFR 59 [IQR 47-77] ml/min; p 0.001]. However, eGFR was equal to the previous one in the third trimester of pregnancy (60 [IQR 44-69] ml/min vs. 59 [IQR 47-77] ml/min; p 0.322). Median proteinuria remained below 0.5 g/day throughout pregnancy, without significant variation. Immunosuppression regimen during pregnancy was mainly based on a combined therapy of steroids, calcineurin inhibitors and azathioprine (21 KTR, 70%). Tacrolimus dose increase (median 63.6% [IQR 33.3-90.0%]) was necessary to maintain proper drug levels throughout gestation.
Kidney graft function showed a decline in the first and second year after pregnancy compared to baseline function (54 [IQR 35-77] ml/min and 55 [IQR 36-75] ml/min vs. 59 [IQR 47-77] ml/min; p 0.018 and p 0.021, respectively]. Nevertheless, by the third year post-pregnancy, eGFR was similar to the baseline function (62 [IQR 43-73] ml/min vs. 59 [IQR 47-77] ml/min; p 0.365]. Likewise, annual eGFR variation was comparable during 3 years before (+1.0 ml/min/year) and 3 years after pregnancy (−0.9 ml/min/year), hence no worsening was observed after gestation (p 0.78). No differences were observed in proteinuria either (baseline proteinuria 0.17 [IQR 0.13-0.3] g/day vs. third-year proteinuria 0.21 [IQR 0.15-0.34] g/day; p 0.938).
Only 5 women had a baseline serum creatinine above current recommendations for pregnancy (&gt;1.5 mg/dl) and only 3 women presented baseline proteinuria &gt; 0.5 g/day. In this group (n = 7), pregnancy occurred later after KT (96.0 [IQR 80.9-213.0] vs. 46.0 [IQR 16.0-67.5] months; p 0.024). The only 2 graft losses in the cohort were in this group. Both were attributed to transplant glomerulopathy, and they occurred at years 3 and 5 after pregnancy. On the other side, in this group there were no other baseline differences or obstetrical complications [Table 1].

Conclusion
Pregnancy does not normally affect graft function and it stabilises within 3 years after gestation. It is important to increase data on women with suboptimal graft function to determine the direct implications that pregnancy may have on these KTRs.