Background
Data regarding the effect of a solitary kidney during pregnancy have come from studies of living kidney donors. We evaluated the risk of adverse pregnancy outcomes in women with a single kidney from renal agenesis.
Study Design
Matched cohort study.
Setting and Participants
Using data from 7,079 childbirths from an integrated health care delivery system from 1996 through 2015, we identified births from women with renal agenesis. Only first pregnancies and singleton births were included. After excluding those with diabetes and kidney disease, a total of 200 women with renal agenesis were matched 1:4 by age (within 2 years), race, and history of hypertension to women with two kidneys.
Predictor
Renal agenesis defined by ICD-9 codes prior to pregnancy.
Outcomes
The primary outcome was adverse maternal outcomes including preterm delivery, delivery via cesarean section, preeclampsia/eclampsia, and length of stay at hospital. Adverse neonatal endpoints were considered as a secondary outcome and included low birth weight (<2,500 g) and infant death/transfer to acute inpatient facility.
Results
The mean gestational age at delivery was 37.9 ± 2.1 weeks for women with renal agenesis compared to 38.6 ± 1.8 weeks for women with two kidneys. Compared to women with two kidneys, those with renal agenesis had an increased risk of preterm delivery (OR, 2.88; 95% CI, 1.86-4.45), delivery via cesarean section (OR, 2.11; 95% CI, 1.49-2.99), preeclampsia/eclampsia (OR, 2.41; 95% CI, 1.23-4.72), and length of stay >3 days (OR, 1.81; 95% CI, 1.18-2.78). Renal agenesis was not significantly associated with an increased risk of infant death/transfer to acute facility (OR, 2.60; 95% CI, 0.57-11.89) or with low birth weight after accounting for preterm delivery (OR, 2.11; 95% CI, 0.76-5.88).
Limitations
Renal agenesis was identified by ICD-9 code not by abdominal imaging.
Conclusion
Women with unilateral renal agenesis have a higher risk of adverse outcomes in pregnancy.