Updated publication reference for PubMed record(s): 31772271. Polycystic ovary syndrome (PCOS) is the most common endocrinological disorder of fertile-aged women. PCOS has been associated with adverse pregnancy outcomes and abnormalities of the placenta. By taking a quantitative label-free quantitative proteomics approach we set out to investigate if changes in the plasma proteome of pregnant women with PCOS could elucidate the mechanisms behind the pathologies observed in PCOS pregnancies. We have performed label-free quantitative proteomics on plasma samples from pregnant women with PCOS at term (n=14) and plasma samples from pregnant control women (n = 23) matched for age, gestational length and BMI. The samples are derived from BASIC pregnancy cohort from Uppsala, Sweden. A total of 169 proteins with two or more unique peptides were identified.