HYPERVENTILATION IN OBSTETRICS

Hyperventilation is common in obstetrics and it is important to determine its effects, if any, on the fetus. Previous studies in the human subject have been limited to measurements made at birth. The present investigation was carried out on conscious patients in labor, with measurements on maternal and fetal capillary blood. In 86 patients, no relationship was found between maternal pCO2 and fetal pO2. Six patients deliberately overbreathed for up to 18 minutes. Although maternal and fetal pH increased and pCO2 fell, no change in pO2 or base excess was found during hyperventilation or recovery. Spontaneous hyperventilation neither harms nor benefits the fetus but hyperventilation and general anesthesia may cause fetal metabolic acidosis and lower oxygen tension. © 1969.