Maintaining a Milk Supply
The next major challenge for mothers is maintaining their milk supply until infants are ready to feed at the breast. A number of studies have explored the effects of artificial pumping systems on the supply of human milk for preterm infants.[59,72,73] Of these studies, few systematically investigated interventions to increase milk supply and, therefore, recommendations are based on anecdotal experiences and expert opinions.[59,72,73] In a prospective observational study of 32 nonsmoking mothers and infants 28 to 30 weeks gestational age, increased volume was associated with an increase in the actual frequency ( P < 0.01) and duration of pump use ( P < 0.05). Optimal milk production was associated with 5 or more milk expressions per day with pumping durations total > 100 minutes per day. Another randomized, longitudinal study examined milk production in 39 mothers with 50 preterm infants (mean GA 27 weeks). Mothers in the high-frequency pumping group (minimum 6.25 times daily) had a significantly higher mean daily milk weight in grams (632 ± 324 vs. 319 ± 292, P < 0.01) than mothers in the low-frequency pumping group.
Several studies reported a shorter duration of pumping and breastfeeding in women who smoke.[74—76] A study that compared the milk volume and milk concentrations of smokers and nonsmokers discovered that both the volume and fat content of milk produced by women who smoke was less than that of nonsmokers, even after controlling for confounding variables.
The influence of sequential versus simultaneous breast pumping on milk production suggests that simultaneous breast pumping produced a rise in prolactin levels but did not change the overall volume of milk produced.[59,72] The sequential pumping group was instructed to pump for 10 minutes using a single pump system, and then switch to the other side. The simultaneous pumping group used a double pump system to pump both breasts at the same time. The reduced time associated with simultaneous pumping may be an important benefit.
In attempts to increase milk production, galactogogues, such as domperidone, metoclopramide, and sulpiride, have been used.[78—80] These dopamine inhibiting agents work by stimulating the release of prolactin from the anterior pituitary gland, thus increasing lactation in women with inadequate or decreased milk production. The safety and efficacy of exposure to galactogogues in preterm infants has not been well established. On June 7, 2004, the Food and Drug Administration issued a bulletin recommending against the use of domperidone because of safety concerns.
Traditionally, the timing of the first breastfeeding opportunity for VLBW infants has not been evidence-based. Clinicians have used empiric criteria such as infant weight, gestational age, and the ability of infants to bottle feed as indicators of readiness to breastfeed, despite evidence that early breastfeedings are less physiologically stressful for preterm infants than bottle feedings.[84,85] In a prospective study of 20 VLBW infants (BW < 1500 g), infants served as their own controls to measure the clinical effects of breast feedings and bottle feedings. During breastfeeding, infants had a lower incidence of oxygen desaturation ( P < 0.025); infants with bronchopulmonary dysplasia had higher oxygen saturations during breastfeeding than during bottle feeding. In a later prospective study of 12 VLBW infants (mean BW 672 ± 95 g, mean GA 26 ± 2 weeks), infants served as their own controls for the measurement of physiological variables during breastfeedings and bottle feedings. Infants had higher body temperatures ( P < 0.001) and a lower incidence of oxygen desaturation ( P < 0.05) during breastfeeding. There were no differences in respiratory rate or heart rate. Another prospective study of 25 preterm infants (BW < 1800 g) also used infants as their own controls to compare the clinical effects of breastfeeding and bottle feeding. Oxygen saturation ( P < 0.01) and body temperature ( P < 0.01) were significantly higher during breastfeeding. There were 2 episodes of apnea and 20 episodes of oxygen desaturation during bottle feeding and none during breastfeeding. The results of these studies assist clinicians in re-examining traditional criteria for transitioning infants from gavage feeding to breastfeeding.
To achieve a successful transition from gavage feeding to breastfeeding, infants must be physiologically stable and developmentally mature.[15,16] The literature examining recommendations for the introduction of oral feeding in preterm infants is based largely on the infant's physiological and neurodevelopmental progression rather than experimental studies examining feeding practices.
The anatomy and physiology of neonatal sucking behaviors, and the anatomic and physiological coordination of sucking, swallowing, and breathing in preterm infants, has been examined. The coordination of the intrinsic muscles of the tongue to produce fully formed rhythmic, rolling movements is a result of gestational maturity.[90,91] A prospective study evaluated the relationship between swallowing and respiration changes with maturation in 24 infants between 28 and 31 weeks gestational age (BW 1505 ± 77 g). Infants' sucking efficiency, pressure, frequency, duration, and respiration phase were measured during bottle feeding. The sucking efficiency significantly increased between 34 and 36 weeks postconceptional age (PCA) ( P < 0.05). There were significant increases in sucking pressure, frequency, and duration between 33 and 36 weeks ( P < 0.05). Although infants at 32 weeks PCA could feed, they had oxygen desaturations during feedings, resulting from a respiratory pause that coincided with swallowing. Another prospective study evaluated the relationship between sucking and swallowing, and swallowing and breathing, in 12 healthy preterm infants (< 30 weeks GA) and 8 healthy term infants. Sucking, swallowing, and respiration were recorded during oral bottle feedings. Preterm infants swallowed preferentially at different phases, had a significantly lower rate of milk transfer ( P < 0.01), a smaller bolus size ( P < 0.001), and less suction amplitude ( P < 0.05) than full-term infants. Both studies concluded that feeding difficulties in preterm infants are more likely to result from inappropriate swallow-respiration interfacing than suck-swallow interaction. Future research should evaluate similar variables during breastfeeding.
Two experimental studies that examined the introduction of oral feedings in preterm infants challenged the belief that maturation alone determines readiness. Instead, the role of learning and experience in acquiring breastfeeding skills has been investigated.[94,95] A prospective, nonrandomized trial assessed the development of breastfeeding behaviors in 71 singleton infants with gestational ages ranging from 26.7 to 35.9 weeks. The study used mothers' and researchers' observations of infant feeding behaviors to develop feeding recommendations. Efficient rooting, areola grasp, and latching were observed at 28 weeks and nutritive sucking at 30.6 weeks; 80% of the infants established full breastfeeding at a mean of 36 weeks and as early as 33.4 weeks. These findings indicate a possible learned response whereby early breastfeeding opportunities enhanced the development of oral motor capacity.
Another prospective study by the same investigators combined observational assessments with electromyography in 26 preterm infants between 32.1 to 37.1 weeks to examine sucking behavior during breastfeeding. Individual variation in sucking behavior was reported; however, there was no association between maturational level and oral behavior ( P > 0.05). While these studies suggest that experience plays a role in breastfeeding success, further studies with larger sample sizes must examine preterm infants' transition to breastfeeding to ensure safety of this high-risk population.
To further assist infants in converting from gavage feeding to breastfeeding, methods such as non-nutritive sucking and kangaroo care have been implemented in many neonatal nurseries. Non-nutritive sucking (NNS) is used to facilitate the development of sucking behavior and improve the digestion of enteral feedings by stimulating an increase in saliva for infants to practice swallowing. Results from a meta-analysis of 19 studies examining NNS in preterm infants indicated a significant decrease in length of hospital stay ( P < 0.05) and decreased time to establish nipple feeding in preterm infants receiving NNS.
Kangaroo mother care (KMC), in which the unclothed infant is positioned skin-to-skin with the mother, has been associated with improved milk production, improved infant growth, competence in breastfeeding, and extended lactation.[30,96—102] A meta-analysis of 3 randomized controlled trials involving 1362 LBW infants revealed that KMC reduced the following risks:
Nosocomial infection at 41 weeks corrected gestational age (relative risk, 0.49; 95% confidence interval 0.25 to 0.93);
Severe illness (relative risk 0.30; 95% confidence interval 0.14 to 0.67);
Lower respiratory tract disease at 6 months follow-up (relative risk 0.37; 95% confidence interval 0.15 to 0.89);
Not exclusively breastfeeding at discharge (relative risk 0.41; 95% confidence interval 0.25 to 0.68);
Maternal dissatisfaction with method of care (relative risk 0.41; 95% confidence interval, 0.22 to 0.75).
Infants exposed to KMC had gained more weight per day by discharge (weighted mean difference, 3.6 g/day; 95% confidence interval 0.8 to 6.4). There was no evidence of a difference in infant mortality. However, investigators had concerns about the methodological quality of the included trials weakening the credibility of these findings. Well-designed randomized controlled trials of KMC are required before implementing routine use in LBW infants.
Nipple confusion is a potential factor that may contribute to breastfeeding failure in preterm infants.[104—106] It is defined as an infant's difficulty with obtaining the correct oral configuration, latching technique, and suckling pattern needed to extract milk from the breast after exposure to an artificial nipple (pacifier or bottle).
The theory of nipple confusion and its alleged association with early weaning has many supporters; however, strong scientific data are lacking to document the presence of, the mechanisms involved in, and factors that predispose preterm infants to nipple confusion. The theory is supported by anecdotal reports from experts who would agree that the oral dynamics of breastfeeding and bottle feeding are significantly different.
A prospective randomized trial of 84 preterm infants compared supplementation by an indwelling 3.5 French nasogastric tube to bottle feeding. The infants who received nasogastric supplementation were 4.5 times more likely to be partially breastfeeding at discharge, and 9.4 times more likely to be exclusively breastfeeding ( P = 0.0001). Further research studies are required before categorizing nipple confusion as a definitive problem for the preterm population.
Adv Neonatal Care. 2005;5(2):72-88. © 2005 W.B. Saunders
Cite this: A Review of the Literature Examining the Benefits and Challenges, Incidence and Duration, and Barriers to Breastfeeding in Preterm Infants - Medscape - Apr 01, 2005.