Unintended Pregnancy After Kidney Transplantation: Risk Factors and Associated Obstetric and Allograft Outcomes

To define risk factors, obstetric morbidity, and allograft outcomes associated with an unintended pregnancy after kidney transplant.

This is a retrospective cohort study of pregnancies in women after kidney transplantation enrolled in the Transplant Pregnancy Registry International with births between 1967 and 2019, with cohorts categorized as intended pregnancies and unintended pregnancies. The primary outcome was acute kidney rejection during pregnancy or by 6 weeks postpartum. Secondary outcomes included allograft loss, severe maternal morbidity, and neonatal composite morbidity. Multivariable logistic regression, Kaplan-Meier curves, and Cox proportional hazards regression models were performed, with adjustment for covariates pertinent to allograft function.

Among 1,723 pregnancies of kidney transplant recipients, 1,081 (62.7%) were intended and 642 (37.3%) were unintended pregnancies. Risk factors for unintended pregnancy included younger age, Black race, nulliparity, chronic hypertension, and transplant from a deceased donor. Exposure to mycophenolate products (16.0% vs 5.7%) and termination (4.7% vs 0.4%) were more common in unintended pregnancies (P<.001). Unintended pregnancy was not associated with acute kidney rejection (2.3% vs 0.9%, adjusted odds ratio [AOR] 2.38, 95% CI, 0.91-6.30, P=.08). Unintended pregnancy was independently associated with allograft loss at 2 years from the end of pregnancy (8.1% vs 3.5%, AOR 2.27, 95% CI, 1.32-3.94, P=.003) but not allograft survival (adjusted hazard ratio 1.22, 95% CI, 1.00-1.49, P=.05). There were no differences in severe maternal morbidity (3.3% vs 3.6%) or neonatal composite morbidity (12.9% vs 14.3%) by pregnancy intention.

Unintended pregnancy was not associated with acute kidney allograft rejection in the peripartum period, but it was associated with mycophenolate exposure and allograft loss at 2 years from pregnancy. The same social vulnerabilities that underlie difficulty in accessing reproductive care may be similarly important for transplant health. We recommend prepregnancy counseling and longitudinal follow-up of transplant recipients to reduce rates of unintended pregnancy and to optimize transplantation success over time.