For decades obstetricians, midwives, and anesthesiologists have debated the need for women in labor to be restricted to nil per os (NPO). Competing concerns include
|Figure. No caption available.|
* risk of gastric aspiration if women require general anesthesia
* energy needs of the laboring woman
* the effect of ketosis on the laboring woman and fetus
* hyponatremia due to excess intake of hypotonic fluids
* maternal stress associated with NPO status and the limitation on movement and discomfort imposed by an intravenous line
* the impact of oral intake on maternal vomiting, the duration of labor, and fetal outcomes.
The purpose of this review of literature is to assess current evidence about the safety of women's oral intake during labor and generate recommendations for nursing practice.
Cesarean births account for over 31% of all births in the United States (Centers for Disease Control and Prevention, 2007), but general anesthesia is only used in the 10% of cesarean births that are characterized as urgent (McDonald & Yornell, 2006, p. 442). Anesthesia-related deaths occur in 1.6 per million live births; most of these reflect difficulty in intubation (Chang et al., 2003).
Origin of the NPO Policy
Even after the move of childbearing into hospitals in the 1920s, birth was still a common threat to life. The twilight sleep movement of the 1930s was embraced by educated, influential women. Twilight sleep entailed the use of morphine and scopolamine to reduce pain and memory of birth. General anesthesia was commonplace even for vaginal births, although it was not necessarily administered by specialists.
In 1946, Curtis Mendelson audited records of 44,016 women, in which 66 women experienced pulmonary aspiration, of whom 40 aspirated liquid and 5 aspirated food. Although only two of the women died, Mendelson's recommendation that women fast throughout labor led to the rapid adoption of NPO policies in the United States and investigation of gastric aspiration during childbirth in the United Kingdom (O'Sullivan & Scrutton, 2003), with subsequent conformity to U.S. policies. Currently in the United States and other developed nations, general anesthesia is rarely used in childbirth and the skill level of anesthesia providers is high. In this context the question has persisted as to whether routine oral intake restriction is warranted by the scientific evidence.
Practices Within and Outside the United States
Recommendations by various professional organizations are summarized in Table 1. Obstetrical anesthesia guidelines from the American Society of Anesthesiologists Task Force on Obstetric Anesthesia (2007) include restriction of oral intake to small amounts of clear liquids for women at low risk up to 2 hours before anesthesia; further restriction for women with identified risk factors for aspiration include morbid obesity, diabetes, a difficult airway or a nonreassuring fetal heart rate pattern; and the avoidance of solid foods. Women who will undergo elective cesarean birth are advised to fast from solids for 6 to 8 hours, and before surgical procedures aspiration prophylaxis to reduce acidity of gastric contents is recommended. Recently the American Congress of Obstetricians and Gynecologists (2009) recommended intake of clear liquids.
|Table 1. Recommendations of Selected Professional Organizations on Restriction of Oral Intake During Labor|
The American College of Nurse-Midwives (ACNM ) recommends that women at low risk for pulmonary aspiration be permitted self-determined intake according to guidelines established by the practice setting. They urge midwives to participate in research to confirm the safety of ad lib nutrition for laboring women.
The World Health Organization (WHO) recommends that because the energy demands of labor are so great and because replenishment ensures maternal and fetal well-being, healthcare providers should not interfere with women's desire for oral intake during labor (WHO, 1997). The Society of Obstetricians and Gynecologists of Canada recommends that healthcare personnel offer a woman in active labor a light or liquid diet (Society of Obstetricians and Gynecologists of Canada, 1998).
Recently the Cochrane Collaboration, which maintains a set of databases providing systematic reviews of the scientific evidence related to various healthcare practices, published a review on restricting oral fluid and food intake during labor. The authors concluded that there is no evidence in support of restriction in women at low risk of complications (Singata, Tranmer & Gyte, 2010).
Parsons (2001, 2004) has published two studies related to practices in that country related to oral intake in labor. In a survey of 109 Australian maternity units, 81.7% of hospitals did not have a policy for oral intake in labor, and the remaining 18.3% reported policies that varied from permitting ice only to allowing women freedom to eat and drink whatever they desired. A total of 60.5% of the hospitals reported that they leave food and fluid requirements to the women's own discretion as long as they demonstrate no risk for using general anesthesia. In a subsequent study Parsons surveyed Australian 89 midwives to determine their views and practices related to oral intake in labor for women with low-risk pregnancies. The midwives were divided on this issue, and their own practices tended to reflect accepted practice in the hospital in which they were employed.
ACNM (2008), based on an in-depth review of literature on oral intake during labor, reported that American hospitals tend to limit oral intake during the latent phase of labor to clear liquids, and during the active phase to sips of water or ice chips. Fewer than 10% of hospitals had policies permitting food intake during the latent phase, and none permitted food intake during the active phase. A survey of British obstetrical units found that 96% of units permitted oral intake, with 32.8% allowing both fluids and food. The ACNM review found that in a survey of Dutch obstetricians and midwives, 73% of obstetricians and 67% of midwives left the decision to eat or drink to the woman.
Effects of Oral Intake During Labor
Energy Needs in Labor
No published research on the energy requirements or nutritional needs of laboring women was found in this review. Eighteen years ago a team of investigators at Walter Reed Army Medical Center (Eliasson, Phillips, Stajduhar, Carome, & Cowsar, 1992) observed that the metabolic demands of labor are similar to those of continuous moderate aerobic exercise. Believing this analogy to be apt, ACNM considers it relevant that The American College of Sports Medicine endorses ingestion of carbohydrate drinks during exercise to delay fatigue (Casa, Clarkson, & Roberts, 2005).
Pregnant women are prone to ketosis because of the metabolic demands of fetal growth and hormone changes (Dumoulin & Foulkes, 1984). Although prolonged labor increases ketone production (Kubli, Scrutton, Seed, & O'Sullivan, 2002), which can be exacerbated by fasting, ketosis has not yet been linked to birth outcome.
Hyponatremia can complicate labor when laboring women consume hypotonic fluids. Johansson, Lindow, Kapadia, and Norman (2002) published case reports of four neonates and one mother in Sweden who experienced seizures or other central nervous system (CNS) symptoms associated with maternal oral intake of between 4 and 10 L of water or water and fruit juice during labor. Pregnant women have increased extracellular fluid volume, and the activation of water-sparing systems during labor reduces the woman's ability to compensate for an acute water surplus. Both the mother and the fetus can experience rapid decrease in serum sodium.
Recently, in a study of this topic, 287 laboring women in Sweden were permitted to have oral fluids during labor (Moen, Brudin, Rundgren, & Irestedt, 2009). Hyponatremia was found in 16 of 61 women who received more than 2,500 mL of fluid during labor, and two-thirds of fluids were orally ingested. Hyponatremia was associated with prolongation of the second stage of labor, instrumental birth, and emergency cesarean birth for failure to progress. These investigators recommended that oral intake be limited, intake be documented, and hypotonic fluids not be administered intravenously.
Penny Simpkin (1986) assessed 159 women's evaluation of the stressfulness of childbirth using the Childbirth Events Stress Survey within 10 days to 2 months of birth. She found that 27% of the respondents considered restriction of food intake to be moderately or very stressful and 57% of the women reported restriction of oral fluids to be moderately or very stressful.
Armstrong and Johnston (2000) surveyed 149 Scottish postpartum women within 36 hours of birth to ascertain what proportion of them would have liked to have eaten during labor. Of the respondents, 30% indicated that they would have liked to eat during labor and 25% said that it would have made a significant difference to their overall satisfaction with their birth experience. Some women reported that they had secretly eaten in early labor; when compared to women who did not eat, no differences were found in duration of labor, age, parity, choice of analgesia, or mode of birth.
O'Reilly, Hoyer, and Walsh (1993) examined vomiting in relation to oral intake among 106 low-risk women laboring in a Michigan birthing center. The women were able to choose the types and amounts of oral intake throughout labor. Nurses completed a survey instrument to record women's patterns of oral intake and emesis during all stages of labor. Earlier in labor 103 of the women chose oral intake, decreasing to 50 women during the pushing phase. In the immediate postpartum phase, 104 women consumed food and/or fluids. Of women who ate or drank during labor, 20 women vomited and 8 of those women vomited more than once. Vomiting was associated more with food than fluid intake but no association was found with quantity of food ingested. None of the women who vomited experienced poor outcomes and the length of labor did not differ between women who vomited versus those who did not.
Scrutton, Metcalfe, Lowy, Seed, and O'Sullivan (1999) undertook a randomized trial to determine effects of a light, low-residue diet (N = 48) or water only (N = 46) during labor on women's metabolic profile, labor outcomes, and residual gastric volume. In the light-diet group, food consumption decreased as labor advanced. By the end of labor the water-only group demonstrated greater ketosis, as well as lower levels of plasma glucose and insulin. Gastric volume was greater in the eating group within 1 hour of birth. The eating group was twice as likely to vomit around the time of birth, and the volumes vomited were significantly greater than in the water group. The groups did not differ in duration of labor, use of oxytocin, mode of birth, Apgar scores, or umbilical blood gases.
Parsons Bidewell, and Nagy (2006) studied the effect of eating in early labor on maternal and infant outcomes in a prospective comparative trial of 176 low-risk nulliparous Australian women. Food was consumed by 82 women, whereas 94 consumed clear fluids only. Food intake during the latent phase of the first stage of labor was associated with longer labor. No differences were found in rate of medical interventions, adverse birth outcomes, or vomiting.
Scheepers, Thans, de Johng, Essed, and Kanhai (2002a) implemented a double-blind, placebo-controlled study in the Netherlands with 100 low-risk women. The participants received either 200 mL of a carbohydrate solution or an identically flavored solution containing aspartame. Women needing intravenous fluid received normal saline and no other oral ingestion was permitted. No statistically significant differences in quality of labor or birth outcomes were demonstrated. In particular, fetal acid-base balance did not differ between the two groups. Scheepers, Thans, de Jong, Essed, Le Cessie, and Kanhai (2002) additionally undertook a randomized study among 201 Dutch women of the effect of at-will ingestion of carbohydrate solution (N = 102) versus placebo (N = 99) on duration of labor, need for augmentation, use of pain medication, and incidence of surgical or instrumental births. The groups had a higher incidence of high-risk pregnancies, labor induction, and postterm pregnancies than was usual in the Netherlands, but the two groups did not differ. Fetal weights, Apgar scores, and acid-base balance were similar in the two groups. Length of labor did not differ between the groups, but surprisingly, the number of cesarean births was significantly higher in the carbohydrate group. More women in the carbohydrate group received narcotic-based analgesia, which delays gastric emptying. The authors concluded that further research is needed.
Kubli et al. (2002) evaluated the effect of isotonic sport drinks versus water only during labor in a randomized prospective study of 60 London women. At the end of the first stage of labor, women in the water-only group evidenced more ketosis and decreased serum glucose levels. Gastric volume was similar in the two groups after birth, as were incidence and volume of vomiting. There were no differences in maternal or infant outcomes, and the authors concluded that ingestion of isotonic sport drinks reduces maternal ketosis in labor with no adverse effects.
Parsons et al. (2006) studied labor duration and outcomes among the women referenced above. Corroborating the finding of Scheepers Thans, de Jong, Essed, Le Cessie, and Kanhai (2002), food intake during the latent phase of labor was associated with a longer mean duration of labor of 2.35 hours. No other differences were noted between the food and fluid groups. In a subsequent analysis, Parsons, Bidewell, and Griffiths (2007) compared birth outcomes among 82 women who chose to eat food during early labor only, 10 who ate during established labor only, 31 who ate during both early and established labor, and 94 who chose to consume clear fluids only during early and established labor. Eating during the early phase of the first stage of labor was associated with labor averaging 2.16 hours longer; eating during both early and established phases of labor was associated with a mean of 3.5 hours longer labor. Incidences of vomiting, medical interventions, and adverse birth outcomes were unaffected by food intake.
Tranmer, Hodnett, Hannah, and Stevens (2005) undertook a randomized clinical trial in Canada to determine if unrestricted oral carbohydrate intake during labor would reduce the incidence of dystocia in low-risk nulliparous women. Women in the intervention group (N = 163) received guidelines about food and fluid intake during labor and were encouraged to eat and drink as they pleased during labor. Women were free to consume what they desired, and they were instructed to bring their own selection of desired food and drinks to the hospital. Women in the usual care comparison group (N = 165) received no prelabor information on oral intake and were restricted to ice chips and water. The incidence of dystocia was not significantly different in the two groups, and no other maternal or infant outcomes demonstrated a difference. Although the authors concluded only that oral carbohydrate intake did not reduce the occurrence of dystocia, it also did not contribute to an increased incidence of adverse outcomes in this sample.
In the most recent investigation of the effect of food intake versus water only on labor, O'Sullivan, Liu, Hart, Seed, and Shennan (2009) studied 2,426 nulliparous, nondiabetic women at term in a prospective randomized controlled trial. The rate of spontaneous vaginal birth was similar in both groups and no significant differences were observed in duration of labor, cesarean birth rate, the incidence of vomiting, or neonatal outcomes.
|Table 2. Summary of Selected Findings of Effect of Oral Intake on Labor or Maternal-Infant Outcomes.|
|Table. No caption available.|
Conclusions and Recommendations
The scientific evidence that was reviewed supports the recommendation of the WHO that the preferences of low-risk women dictate their oral intake during labor. Studies have demonstrated that women would like restrictions to be eased. Although excess water intake can lead to maternal and fetal hyponatremia, in general adverse effects were not observed as a result of oral intake of carbohydrates. The study by Scheepers Thans, de Jong, Essed, Le Cessie, and Kanhai (2002) of the effect of oral carbohydrate intake on birth outcomes demonstrated a higher incidence of cesarean birth in the treatment group; however, other differences between the groups make it difficult to attribute that outcome to the experimental intervention in the face of contradictory evidence provided by other studies. Food ingestion may prolong labor, but no adverse maternal or infant outcomes were associated with that effect. Likewise, women who ingest food in labor may experience more vomiting, but with no associated adverse birth outcomes. Oral intake of carbohydrates does reduce the occurrence of maternal ketosis, with no detected adverse effect on fetal well-being.
The research on food intake has been inconsistent in terms of foods that were permitted. However, it is known that foods high in fats slow gastric emptying and may be a poor choice during labor. Larger scale, multicenter, quantitative studies that examine women's satisfaction as well as birth outcomes associated with ingestion of food, clear liquids, and water or ice only are needed to provide definitive guidance. Although the evidence is not definitive, the following recommendations are warranted:
* The ACNM (2008) classifies women as being at increased risk for pulmonary aspiration if they have comorbidities such as debilitating or chronic disease, hypertension or preeclampsia, a neurologic disorder, gastritis or ulcers or a history of either, previous abdominal surgery, esophageal disease, obesity, the occurrence of an obstetrical emergency, or factors associated with difficult intubation.
* The ACNM recommendations include the reaffirmation that pregnancy and birth are normal life processes; the need to assess risk for aspiration associated with anesthesia and to discuss the small risk of pulmonary aspiration with women; promotion of self-determination among women with low risk; evaluation of all women who are at increased risk for operative birth; communication with anesthesia services in a timely manner; development of institutional guidelines for identification of risk and restriction of oral intake; assessment of anesthesia service practice patterns in particular healthcare settings; and as noted earlier, continuous participation in research to identify best practices related to oral intake during labor.
* Nurses who work in intrapartum settings need to advocate for the establishment of multidisciplinary working groups to review policies that restrict oral intake among low-risk women and advocate their relaxation. Newlin and Champion (1997) described the process by which a team including a research midwife, an anesthetist, and an obstetrician formulated such a policy in Nottingham, United Kingdom, and developed an audit process to ensure that safety was maintained.
* When policies about oral intake during low-risk labor are relaxed, women need to be advised about the types of foods that are appropriate in advance of labor so that they can prepare and plan. They need to be advised that excess water intake is undesirable, whereas intake of liquids containing carbohydrates may safely confer positive effects on their well-being. Women should be informed of potential risks associated with eating and drinking in labor that the literature has identified, including vomiting and prolongation of labor, although adverse effects on birth outcomes have not been observed. When risk factors are identified, women need to receive an explanation for restriction of oral intake.
* The implementation of any changes in oral intake policies should be accompanied by a plan for evaluating patient outcomes, including women's satisfaction, incidence of vomiting and electrolyte imbalance, duration of labor, type of birth, and maternal and infant outcomes. The establishment of a protocol for monitoring outcomes should allay concerns about the potential compromise of maternal-infant safety.