Factors influencing fertility rates in Australian women receiving kidney replacement therapy: analysis of linked Australia and New Zealand Dialysis and Transplant Registry and perinatal data over 22 years.

BACKGROUND: Pregnancy in women receiving kidney replacement therapy (KRT) is uncommon, and trends and factors influencing fertility rates remain poorly defined. METHODS: The Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) was linked to mandatory perinatal data sets (all births from 1991 to 2013, ≥20 weeks' gestation) in four Australian jurisdictions. Overall, age- and era-specific fertility rates were calculated based on general and KRT population denominators. RESULTS: From 2 948 084 births, 248 babies were born to 168 mothers receiving KRT (37 babies born to 31 dialysed mothers; 211 babies born to 137 transplanted mothers). Substantial agreement between ANZDATA and perinatal data sets was observed for birth events and outcomes. Transplanted women had higher fertility rates than dialysed women in all analyses, with 21.4 live births/1000 women/year [95% confidence interval (CI) 18.6-24.6] in transplanted women, 5.8 (95% CI 4.1-8.1) in dialysed women and 61.9 (95% CI 61.8-62.0) in the non-KRT cohort. Fertility rates for dialysed women rose in recent years. After adjusting for maternal age and treatment modality, Caucasian women had higher fertility rates, while women with pre-existing diabetes, or transplanted women with exposure to KRT for ≤3.0 years had lower rates. As expected, transplanted women with a pre-conception estimated glomerular filtration rate (eGFR) of <45 mL/min/1.73 m2 or transplant-to-pregnancy interval of <1.0 year had lower fertility rates. Geographical location, socioeconomic status and primary disease (glomerulonephritis versus other) did not affect fertility rates. CONCLUSIONS: Reporting of births to ANZDATA is sufficiently accurate to justify ongoing data collection. Rising fertility rates in dialysed women may indicate permissive attitudes towards pregnancy. Treatment modality, ethnicity, diabetes, pre-conception eGFR, transplant-to-pregnancy interval and duration of KRT exposure were associated with fertility rates. These factors should be considered when counselling women with kidney disease about parenthood.