The association of an opioid with a local anesthetic improves the quality of labor analgesia and reduces the risk of systemic toxicity of the local anesthetic. However, opioids are not devoid of side effects. The aim of this study was to compare the side effects of subarachnoid sufentanil associated with bupivacaine to those caused by epidural sufentanil associated with ropivacaine in the doses used in the Anesthesiology Department in pregnant women undergoing labor analgesia.Sixty pregnant women, ASA physical status I and II, ages between 15 and 42 years, at term and with healthy fetuses, undergoing labor analgesia were enrolled in this study. They were randomly divided in two groups: G1 - combined spinal epidural anesthesia - 0.5% bupivacaine (2.5 mg) and subarachnoid sufentanil (5 microg); G2 - Epidural Block - 0.2% ropivacaine (20 mg), and epidural sufentanil (10 microg). Complementary doses of 0.2% ropivacaine (12 mg) were administered whenever necessary, and 1% ropivacaine (50 mg) was administered for labor resolution. Patients were evaluated after analgesia (M1) regarding the presence of hypotension, maternal bradycardia, pruritus, nausea, vomiting, respiratory depression, and sedation. They were also evaluated postoperatively (M2) regarding the presence of nausea, vomiting, pruritus, sedation, urinary retention, and pain. Newborns were evaluated by the Apgar score. The test t Student, Mann-Whitney test, and Chi-Square test were used for the statistical analysis.Both groups were similar regarding age, weight, height, duration of labor after analgesia, Apgar score of the newborns, hypotension, maternal bradycardia, nausea, vomiting, pruritus, and urinary retention. Sedation was more frequent in patients in G2 at M1 (50%), which was statistically significant.Subarachnoid or epidural sufentanil, in the doses used in this study, associated with local anesthetics, had the same effect on the duration of labor after analgesia and in the Apgar score of newborns. Sedation was the most frequent side effect in patients receiving epidural sufentanil.