Objectives: To determine the correlation between the spot albumin-to-creatinine (ACR) ratio and protein-to-creatinine ratio (PCR) in pregnancy and if either test is predictive of adverse pregnancy outcome., Study Design: Prospective consecutive cohort study in a single tertiary centre examining 181 patients undergoing proteinuria screening after 20weeks of pregnancy. A spot PCR and ACR was performed on the first void of the day. Comparison was with linear and logistic regression and ROC curve. Optimal values for the ACR were obtained and compared to a PCR value of 30mg/mmol with respect to adverse pregnancy outcomes., Main Outcome Measures: Birth weight <10th centile, preterm birth <32 and <37weeks, placental abruption, caesarean section, induction of labour, fetal death in utero or neonatal death, Apgar score <5 at 1min and/or 5min, pulmonary oedema, sustained blood pressure >170/110mmHg, magnesium infusion or labetalol infusion during labour., Results: 254 tests were performed. The ACR and PCR were highly correlated (r=0.95, p<0.001) and the area under ROC curve was 0.98. An ACR of 13.4mg/mmol corresponded to a PCR of 30mg/mmol. Neither was more predictive of adverse pregnancy outcome nor was the level of proteinuria., Conclusions: The ACR is not inferior to nor does it perform better than the PCR in screening for proteinuria in pregnancy. Clinicians should use the test with which they are more familiar and may wish to assess local laboratory costs and methods in their selection., (Copyright © 2015 International Society for the Study of Hypertension in Pregnancy. Published by Elsevier B.V. All rights reserved.)