by Michele Brown
Prior to the mid-1940's, women were allowed to eat during labor. Then, a 1946 study showed that women who ate during labor had a higher chance of aspiration, (involuntary inhalation of stomach contents during anesthesia.) After the publication of the study by Curtis Mendelson, women were strongly advised that they should stop eating as soon as they felt contractions or thought that they were in labor.
Since this 1946 study, standard conventional obstetrical practice in the United States has adhered to the belief that women in labor should restrict the amount of oral and fluid intake. These concerns have been based on the presumption that potentially fatal aspiration of stomach contents, or asphyxiation, from large food particles could occur if an emergency cesarean section was warranted under general anesthesia. Recent studies in the obstetrical literature have re-evaluated this position and questioned the evidence to support this practice.
The actual incidence of aspiration during birth is 7 per 10 million births in cases accumulated between 1979 and 1990 in the United States. A study in which 11,814 women were allowed to eat and drink during labor reported no maternal damage or death occurring from aspiration. There have been no maternal mortalities due to aspiration in Australia since 1987 and only one death in the UK in the 1990's despite a recent liberalization of oral intake policy.
Pregnancy causes slowed gastric motility or action. Gastric emptying is further delayed in labor due to the use of narcotic analgesics that can predispose women to aspirate abdominal contents. In addition, the acidic nature of the stomach content can cause bronchospasm and congestion which can result in pulmonary edema and death. Certain high-risk conditions make a person more prone to aspiration, such as obesity, small airways and patients with a history of gastroesophageal reflux. Also, poor anesthesia technique can contribute to aspiration, such as blowing air into the stomach and anesthesia that is too light which may cause bucking and coughing with a full stomach and then, essentially, aspiration of the regurgitated stomach content.
Intravenous hydration with Ringers lactate has been the mainstay of fluid and nutritional replacement during labor, with the occasional use of ice chips.
Energy requirements are increased during labor, similar to an athlete doing strenuous exercise requiring increased caloric expenditure. Exclusive intravenous therapy may not be sufficient to meet these requirements. Long labors without eating can cause a woman to metabolize fats instead of carbohydrates, which can lead to a buildup of ketones which has been associated with prolonged labors.
Large infusions of glucose solutions can lead to elevated blood sugar levels in the infant, while after birth this is followed by low glucose levels, jaundice, low ph, electrolyte problems and rapid breathing. Lower dose 5% glucose solutions have been associated with greater weight loss in the infant after the first 2 days of birth. In addition, women may be more prone to fluid overload, immobilization, and increased stress when only IV fluids are used.
The restriction of oral intake and reduction of the volume of contents in the stomach prior to Cesarean section has not eliminated the reported very rare risk of aspiration. Fasting women in labor have been found to have gastric contents with more concentrated acidic content which may increase the maternal morbidity and mortality.