Pregnancy outcomes following maternal kidney transplantation: a national cohort study

Internal design flaws in previous reports of pregnancies following kidney transplantation have been outlined, and the need for a validation has been stated. The aim of this study was to collect information about obstetrical and neonatal outcomes in all Norwegian pregnancies following maternal kidney transplantation, and to compare these data with the general Norwegian population.

A retrospective cohort study based on 1 272 000 deliveries in Norway between 1969 and 2013. All data were collected from medical records. From the source population, we compared 119 first deliveries in kidney transplanted women with 238 first deliveries in nontransplanted women. An explanatory strategy was used in the analysis.

The risk of preeclampsia was significantly increased in kidney-transplanted women compared with nontransplanted women (adjusted incidence rate ratio: 6.06, 95% confidence interval 3.18-11.55). Additionally, preeclampsia in kidney-transplanted women was early onset (diagnosed <34 gestational weeks) in half of the cases. There were also persistent risks of cesarean delivery (adjusted incidence rate ratio 4.14, 95% confidence interval 2.56-6.66), preterm delivery (adjusted incidence rate ratio 4.45, 95% confidence interval 2.13-9.30) and a birthweight below the 10th centile (22.7% vs. 9.7%) in the kidney-transplanted group. A high proportion (63%) of the kidney-transplanted women with chronic hypertension developed preeclampsia.

Using consistent diagnostic criteria, this study shows high rates of maternal and neonatal complications in pregnancies following kidney transplantation. In particular, we reveal a high rate of early-onset preeclampsia requiring operative preterm delivery, conferring long-term risks on both the mother and child.