Racial disparities and factors associated with pregnancy in kidney transplant recipients in the United States

BACKGROUND: Although kidney transplant improves reproductive function in women with end-stage kidney disease (ESKD), pregnancy in kidney transplant recipients’ remains challenging due to the risk of adverse maternal and fetal outcomes. METHODS: We evaluated a retrospective cohort of 7,966 women who were aged 15–45 years and received a kidney transplant between January 1, 2005 and December 31, 2011 from the United States Renal Data System with Medicare as the primary payer for the entire three years after the date of transplantation. Unadjusted and adjusted rates of pregnancy in the first three post-transplant years were calculated, using Poisson regression for the adjustment. Factors associated with pregnancy, including race, were examined using logistic regression. RESULTS: Overall, 293 pregnancies were identified in 7966 women. The unadjusted pregnancy rate was 13.8 per thousand person-years (PTPY) (95% confidence interval (CI), 12.3–15.5). Pregnancy rates were roughly constant in the years 2005–2011 except in 2005 and 2010. The rate of pregnancy was highest in Hispanic women (21.4 PTPY; 95% CI, 17.2–26.4) and Hispanic women had a higher likelihood of pregnancy as compared to white women (OR, 1.56; CI, 1.12–2.16). Pregnancy rates were lowest in women aged 30–34 years and 35–45 years at transplant, and women aged 30–34 years and 35–45 years at transplant were less likely to ever become pregnant during the follow-up (odds ratio [OR], 0.69; CI, 0.49–0.98 and OR, 0.14; CI 0.09–0.21 respectively) as compared to women aged 25–29 years at time of transplant. Women had higher rates of pregnancy in the second and third-year post-transplant (16.0 PTPY, CI 13.2–19.2 and 16.9 PTPY, CI 14.0–20.4) than in the first-year post-transplant (9.0 PTPY, CI 7.0–11.4). In transplant recipients, pregnancy was more likely in women with ESKD due to cystic disease (OR, 2.42; CI, 1.02–5.74) or glomerulonephritis (OR, 2.14; CI, 1.07–4.31) as compared to women with ESKD due to diabetes. CONCLUSION: Hispanic race, younger age, and ESKD cause due to cystic disease or glomerulonephritis are significant factors associated with a higher likelihood of pregnancy. Pregnancy rates have been fairly constant over the last decade. This study improves our understanding of factors associated with pregnancy in kidney transplant recipients.