Ultrasonographic measurement of antral area for estimating gastric fluid volume in pregnant women

Study objective: To calculate the stomach volume according to the antral area in pregnant women. Design: Prospective observational study. Setting: One of the maternity units in our hospital. Patients: 24 singleton pregnancy women, over 18-year-old, non-laboring, gestational age >= 36 weeks, ASA physical status I to II were involved in our study. Interventions and measurements: An ultrasound assessment of the antrum was performed to the pregnant women after 8 hours fasting for the first time. Those lacking of visualization of any gastric contents in the antrum in both the supine and the right lateral decubitus positions were included in our study. Thereafter 50 ml of water was ingested, 4 times, 200 ml in total. The antrum area was examined 2mins after each 50 ml ingest of water. Main results: A high correlation between CSA and volume of liquid ingested (r = 0.90,P < 0.01) was found. We can construct a formula for the prediction of volume values based on the measured CSA values and demographic variables. The equation is: Volume(ml) = 270.76 + 13.68*CSA - 1.20*gestational age Conclusions: Bedside antrum area examination by ultrasonography can provide quantitative information for the assessment of the gastric content and volume in the pregnant women. We can calculate the actual stomach capacity according to the CSA of the gastric antrum.