The medical instruction “nil per os” (NPO), or nothing by mouth, has historically been a strict rule for individuals in labor, restricting them to little more than ice chips. The rationale behind this practice originated from a very real, though rare, life-threatening risk associated with emergency procedures. Understanding the origins of this restriction and subsequent medical advancements helps explain why the current medical consensus has begun to shift toward more flexible, patient-centered guidelines.
The Primary Concern: Risk of Aspiration Pneumonia
The original reason for restricting oral intake during labor was to prevent a condition called aspiration pneumonitis. This occurs when stomach contents, primarily acidic gastric juices, are inhaled into the lungs, causing severe inflammation and respiratory distress.
Labor itself, along with the pain and stress it causes, significantly slows down the process of gastric emptying. The pressure exerted by the enlarged uterus also contributes to this delayed emptying and can weaken the lower esophageal sphincter, increasing the likelihood of reflux. Consequently, the volume and acidity of the stomach contents increase, creating a dangerous scenario if the contents were to be regurgitated.
The true danger arose when general anesthesia was required, which was common for deliveries, especially cesarean sections, in the mid-20th century. General anesthesia abolishes the body’s protective laryngeal reflexes, which normally prevent material from entering the windpipe. If a patient regurgitated while under general anesthesia, the absence of these reflexes allowed acidic contents to be aspirated directly into the lungs. This could potentially lead to severe chemical lung injury, acute respiratory distress syndrome, or even death. This specific combination of delayed gastric emptying and suppressed airway reflexes established the strict NPO rule following landmark research published in 1946.
How Modern Anesthesia Changed the Rules
The strict NPO rule began to be re-evaluated with the widespread adoption of regional anesthesia techniques, such as epidurals and spinal blocks. Regional anesthesia provides pain relief by numbing specific areas of the body without causing a loss of consciousness or suppressing the protective airway reflexes. Since the patient remains awake and their reflexes are intact, the primary mechanism of severe aspiration risk is largely mitigated, even if an emergency cesarean section becomes necessary.
This shift meant that the need for general anesthesia during routine delivery became far less frequent, significantly reducing the overall risk of aspiration for the majority of laboring individuals. Anesthesia providers also developed improved techniques and medications for cases where general anesthesia is still required, further reducing the incidence of aspiration-related maternal deaths, which have declined substantially since the 1950s.
The growing body of evidence suggests that for low-risk patients, light eating or drinking during labor does not measurably increase the already minuscule risk of aspiration, especially when general anesthesia is not anticipated. This change in anesthetic practice has allowed medical guidelines to become more flexible, prioritizing the laboring person’s comfort and hydration.
Current Recommendations for Intake During Labor
Modern medical organizations, including the American College of Obstetricians and Gynecologists (ACOG) and the American Society of Anesthesiologists (ASA), now encourage a more liberal approach to oral intake for low-risk, uncomplicated labor. The current consensus is that these patients should be encouraged to consume clear liquids, particularly those containing electrolytes and carbohydrates, throughout their labor. Clear liquids are defined as non-particulate fluids such as:
- Water
- Pulp-free juice
- Carbonated beverages
- Sports drinks
- Black coffee or tea
These clear liquids help prevent dehydration and the effects of “accelerated starvation,” which can occur during prolonged fasting and lead to the production of ketones. However, solid food intake during active labor is still generally avoided. This is because there is currently insufficient scientific evidence to support its consumption, and it carries a higher risk of particulate aspiration.
Policies often differentiate between low-risk labor, where clear liquids are allowed, and high-risk labor, where stricter NPO guidelines are still maintained.
Individuals with specific pre-existing conditions, such as morbid obesity, poorly controlled diabetes, or known difficult airways, are considered higher risk. This is because they are more likely to require an emergency procedure or have delayed gastric emptying. In these cases, the healthcare team may impose stricter limitations on the amount and type of clear liquids consumed. The final decision on intake must always be made in consultation with the healthcare team, as hospital policies and individual patient risk factors create variations in practice.