Pregnancy After Kidney Transplantation: Outcomes, Tacrolimus Doses, and Trough Levels

Although pregnancy after kidney transplantation has been considered as high risk for maternal and fetal complications, it can be successful in properly selected patients. It is well known that pregnancy can induce changes in the plasma concentrations of some drugs; however, there has been very limited information about tacrolimus pharmacokinetics during pregnancy. In this study, we evaluated the tacrolimus doses, blood levels, and the outcomes of pregnancies in kidney allograft recipients. From 2004 to 2014, we found 16 pregnancies in 12 kidney allograft recipients at our center. We reviewed the files and data reports including fetal outcomes, graft function, complications, tacrolimus trough levels, and doses. We analyzed the tacrolimus trough levels and doses before pregnancy, during pregnancy (monthly), and in the postpartum period. Throughout the pregnancy, we aimed to achieve tacrolimus trough levels between 4 and 7 ng/mL. All patients were on triple immunosuppression, including tacrolimus, azathioprine, and prednisolone. In total, 11 of 16 (68.7%) pregnancies were successful, with a mean weight gain of 12.5 ± 1.66 kg. One patient developed gestational diabetes mellitus and 2 had preeclampsia. Although 5 of 11 babies were found to have low birth weight, 4 of these were premature. Two patients lost their grafts, 1 due to acute rejection and the second due to progression of chronic allograft dysfunction. We have shown that tacrolimus doses need to be significantly increased to keep appropriate trough levels during pregnancy (the doses: before, 3.20 ± 0.9 mg/day; first trimester, 5.03 ± 1.5; second trimester, 6.50 ± 1.8; third trimester, 7.30 ± 2.3; post-partum, 3.5 ± 0.9). In conclusion, the dose of tacrolimus needs to be increased to provide safe and stable tacrolimus trough levels during pregnancy. Although pregnancy can be successful in most cases, it should be kept in mind that there is an increased risk of maternal and fetal complications, including allograft loss, low birth weight, spontaneous abortus, and preeclampsia.