The advice to avoid eating during labor, known as “nil per os” (NPO), is a long-standing medical policy rooted in patient safety. This restriction primarily concerns the potential need for an emergency procedure. Understanding the medical rationale helps explain why healthcare providers are cautious about allowing solid food intake once labor begins.
The Primary Safety Concern
The main reason for limiting oral intake during labor is the risk of pulmonary aspiration, which occurs when stomach contents are accidentally inhaled into the lungs. Labor significantly slows down the stomach’s ability to empty, sometimes by as much as 90% compared to a non-pregnant state, leading to a larger volume of contents remaining for longer periods.
The physical stress of contractions and increased intra-abdominal pressure can also make regurgitation more likely. If a patient requires general anesthesia for an emergency surgery, the protective airway reflexes are temporarily suppressed. Having a full stomach drastically increases the chance of aspiration, which can lead to a severe chemical pneumonitis known as Mendelson’s Syndrome.
This condition is characterized by a severe inflammatory reaction in the lungs caused by inhaling acidic gastric juices. Aspiration of solid food poses an even greater danger than liquids, potentially causing asphyxiation and death. Although the overall risk of aspiration is low with modern care, the potential severity means medical teams prioritize keeping the stomach empty in case of an urgent need for general anesthesia.
Origin of the Universal Fasting Rule
The practice of universal fasting became a strict rule following a 1946 paper by Dr. Curtis Mendelson. His work highlighted the devastating consequences of aspirating stomach contents in women who received general anesthesia during childbirth. In that era, general anesthesia was the primary method used for operative deliveries, including Cesarean sections.
Since general anesthesia was a common necessity for emergency interventions, and it carries the highest risk for aspiration, a blanket policy of “nothing by mouth” was implemented for all laboring patients. This mandatory restriction was a necessary precaution before sophisticated monitoring and widespread use of regional anesthesia like epidurals. The rule was established to reduce the volume and acidity of stomach contents, minimizing the danger should an emergency require rapid induction of general anesthesia.
Current Hospital Policies on Intake
Modern medical organizations, including the American College of Obstetricians and Gynecologists (ACOG), have recognized the need to update these decades-old policies. Current guidelines have relaxed restrictions for healthy patients experiencing uncomplicated labor, though the ban on solid food often remains. Low-risk patients are permitted to consume clear liquids throughout labor.
Clear liquids are defined as those without pulp or particulate matter, including water, tea, coffee, carbonated beverages, and sports drinks. These liquids pass quickly through the stomach and pose a lower aspiration risk than solids. Solid foods are restricted because they require a much longer time to digest, and particulate matter is especially dangerous if aspiration occurs.
Stricter restrictions, sometimes banning even clear liquids, are usually reserved for high-risk patients. This includes individuals with conditions like morbid obesity, poorly controlled diabetes, or other factors that increase the likelihood of needing an emergency procedure or pose an increased aspiration risk. The decision on oral intake is clinical, based on an individualized assessment of the patient’s risk factors and labor status.
Physiological Impact of Fasting During Labor
While fasting is a safety measure, it can have metabolic consequences for the laboring patient undergoing intense physical exertion. Prolonged fasting can lead to the body switching from using glucose to breaking down fat stores for energy, a process that produces ketone bodies. This metabolic state, known as ketosis, is a common occurrence in labor due to increased energy demands coupled with reduced food intake.
Ketosis itself is not generally harmful to the baby, but it is associated with maternal fatigue, nausea, and dehydration. This can impair a patient’s ability to cope with the demands of labor. To combat the lack of caloric intake and prevent significant ketosis, healthcare providers often administer intravenous (IV) fluids. These fluids may contain dextrose to provide a constant, low level of carbohydrates, helping maintain energy and hydration without increasing the aspiration risk associated with solid food.