BACKGROUND: Studies of gastric volume and pH during various stages of pregnancy have not confirmed a consistently evaluated volume or acidity, but point out that these patients may be at risk. The aim of this study was to evaluate the volume and acidity of gastric contents in pregnant and non-pregnant patients. METHODS: Thirty pregnant patients scheduled for elective cesarean section under spinal anesthesia (pregnant group) and thirty non-pregnant female patients that underwent gynecologic surgery with general anesthesia (non-pregnant group) were enrolled. Preoperative fasting times and anxiety score, using a visual analogue scale from 0 to 10, were obtained from all patients. After the induction of anesthesia, gastric contents were aspirated gently using a 14-F multiorifice nasogastric tube and syringe. Gastric volume and acidity were measured. RESULTS: The gastric volume (ml) in the pregnant group was 42.8 +/- 35.0 (mean +/- SD, range: 5-130), and in the non-pregnant group 15.8 +/- 11.9 (range: 3-50). The gastric pH in the pregnant group was 2.1 +/- 0.9 (range: 1.3-5.4), and in the non-pregnant group 2.8 +/- 1.7 (range: 1.3-6.5). CONCLUSIONS: We confirm that pregnant women have more acidic and greater gastric volumes than non-pregnant women.