The Spectrum of Adverse Pregnancy Outcomes Based on Kidney Disease Diagnoses: A 20-Year Population Study

Background and Objectives: Kidney disorders in pregnancy may be under-recognized and have variable impact on outcomes depending on diagnosis. Population-level data are limited, particularly for Australia, and comparison of impact of different kidney disorders on pregnancy has rarely been assessed. This study examined the prevalence and outcomes of varied kidney disorders using population-level perinatal data from a large cohort. Methods: Women with singleton pregnancies > 20 weeks’ gestation from the South Australian Pregnancy Outcomes Unit (1990–2012). Women with a kidney disorders diagnostic code were grouped into categories (immunological, cystic/genetic, urological, vesicoureteral reflux (VUR), pyelonephritis and “other”). Key pregnancy outcomes were assessed, with adjustment for demographic variables. Results: Kidney disorders were reported in 1,392 (0.3%) of 407,580 births. These pregnancies had increased risk of pregnancy-induced hypertension (OR 2.16, 95% CI 1.82–2.56), induction of labor (RRR vs. spontaneous birth 2.10, 95% CI 1.87–2.36), all Caesarean section (OR 1.31, 95% CI 1.17–1.47) as well as Caesarean section without labor (RRR 1.82, 95% CI 1.57–2.10), preterm birth (< 37 weeks; 2.76, 95% CI 2.40–3.18), low birth weight (< 2,500 g) infants (OR 2.43, 95% CI 2.07–2.84), and neonatal intensive care admission (OR 2.64, 95% CI 2.12–3.29). Diagnostic subgroups demonstrated differing patterns of adverse outcomes, enabling the development of a matrix of risk. Women with immunological renal conditions and VUR had greatest risk overall, and only women with immunological diseases had increased risk of small-for-gestational age < 10th centile (OR 2.36, 95% CI 1.26–4.42). Women with nonchronic urological conditions and pyelonephritis had increased risk of preterm birth, but not other adverse events. VUR conferred particularly increased risk of Caesarean section and induced labor. Conclusions: In a cohort of > 1,300 women with varied kidney disorders, increased adverse obstetric and perinatal events were observed, and the nature and magnitude of risk differed according to diagnosis. In particular, vesicoureteric reflux is not a benign condition in pregnancy. Women with nonchronic conditions still had increased risk of preterm birth. We confirm that women with kidney disorders warrant vigilant and tailored prepregnancy care and clinical care in pregnancy.