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The Collection and Storage of Human Milk and Human Milk Banking
Key Points
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Electric pumps are not necessarily more effective than manual pumps or hand expression.
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Pumped milk volume can be increased with low cost interventions such as listening to music, relaxation, warming or massaging the breast, frequent pumping and starting to pump sooner after birth.
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Milk can be stored at room temperature for 4 hours, but under optimal conditions for 6 to 8 hours. Milk kept with ice packs in a small cooler can be stored for 24 hours. Fresh, refrigerated, milk can be used for 96 hours (4 days). Milk can be frozen for 9 months, but under optimal freezer conditions for 12 months.
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Breastfeeding outcomes are influenced by length of maternity leave and workplace conditions’ time and place for pumping.
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The optimal nutrition for feeding preterm infants is mothers' milk, which reduces necrotizing enterocolitis (NEC), late-onset sepsis, chronic lung disease, retinopathy of prematurity, and improves neurodevelopment. Pasteurized donor human milk is the recommended nutrition for VLBW infants when mother's milk is not available, as it decreases NEC, but has no effect on other outcomes.
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Health care providers should assist mothers and families who are considering informal milk sharing by advising recipients on risks and benefits, including the need to evaluate for donor's illnesses, social practices and medications.
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Parents' acceptance of donor human milk may depend on a cultural component such as religion, country of origin, age, parity, breastfeeding experience, and level of education.
The Baby-Friendly Hospital Initiative’s revised Ten Steps to Successful Breastfeeding include steps toward health care professionals possessing the knowledge, competence, and skills pertaining to human milk expression. 1 Human milk expression is accomplished either by hand expression or with a pump that is either manual or electric. Human milk is collected and stored for the infant for several reasons. For the premature infant, human milk expression allows the mother to stimulate milk production and provide optimal nutrition even before the infant is able to feed directly at the breast. For infants who are breastfeeding directly from the breast, human milk expression may be used to maintain lactation, increase the milk supply, or make human milk available when the mother and infant are temporarily separated, for example, because of maternal employment. Human milk expression is also a means for mothers to donate their human milk to infants other than their own in need of human milk, such as premature infants in the neonatal intensive care unit (NICU) or informal milk sharing for healthy term infants.
Prevalence of Human Milk Expression
A review regarding the prevalence of human milk expression found that expressing milk is extremely common and that exclusive breastfeeding at the breast is actually quite rare, at least in the developed world. 2 A 2017 study on 100 postpartum women revealed that 98% stated that they would use a breast pump to express milk for their baby, with most of this subset (69%) intending to start within weeks of delivery. 3 Over a quarter of the participants (29%) had already initiated pumping or intended to start within the subsequent few days. Primiparous women were more likely to report having already started pumping at the time of the interview. For all the postpartum women, the most common reason for pumping was to maintain their milk supply. Women who started pumping while in the hospital also noted that they pumped to increase their milk supply and overcome latch difficulties.
The prevalence of feeding healthy term infants exclusive pumped human milk, without breastfeeding, has also increased. In a study of 2450 women in Hong Kong, the rate of exclusive expressed breast milk feeding in the first 6 months in two cohorts increased from 5.1% to 8.0% in 2006 to 2007 to 18.0% to 19.8% in 2011 to 2012. 4 Factors associated with a higher rate of exclusive expressed human milk feeding included supplementation with infant formula, lack of previous human milk feeding experience, having a planned cesarean section delivery and postpartum return to work. In different locales, the prevalence of human milk expression can vary, as do the reasons for expression and storage of human milk. 5 In a report from Australia of 1003 postpartum women and at 6 months postpartum, 83% (754/911) of the women had a breast pump and 40% (288/715) were expressing at least occasionally. The most common reported reasons for any expressing in the first 6 months postpartum were “to be able to go out and leave the baby” (35%, 268/772), milk supply “not enough” (27%, 207/772), having “too much” milk (19%, 147/772), and, less commonly, returning to work (10%, 80/772).
Techniques for Human Milk Collection
The revised World Health Organization’s (WHO’s) Ten Steps, Step 5 includes teaching mothers how to collect their human milk in case they are separated from their infant or unable to initiate breastfeeding after birth. 6 Health care professionals should possess the knowledge pertaining to the skills needed to collect human milk. 7 Whether collecting for a mother’s own infant or as a donor, it is of prime importance to maintain cleanliness and minimize microbial contamination in the process of collection. Since the era of COVID-19, concern regarding microbial contamination of expressed milk has increased, including bacteria, fungi, and/or viruses from respiratory secretions or other sources. 8 (Heat treatment of the expressed milk before use as is routinely done by milk banks effectively eliminates the vast majority of microorganisms from donor milk.) Primary prevention involves that the mother should be instructed to, preferably, wash her hands with soap and water for 20 seconds and dry her hands with a clean towel before handling the equipment or pumping. If soap and water are not available, an alcohol-based hand sanitizer with 60% alcohol should be used. In the past, mothers have been advised to clean their breasts, but this is not necessary. In a study of human milk expression from mothers of preterm infants, Haiden et al. 9 measured bacterial counts in 1466 expressed human milk samples from women following one of two infection control regimens. The standard regimen used an alcohol-based sanitizer for washing hands before expressing breast milk, whereas the strict regimen comprised a 10-step process, which included additional hand hygiene steps and cleaned the breast using sterile water and an alcohol-based skin sanitizer. They found no significant differences between the standard (11.9% [94/788]) and strict (12.1% [82/678]) regimens ( p =0.92). Significantly more samples were contaminated, however, when expressed at home than in the hospital (standard regimen home/hospital: 17.9% vs. 6.1%, p < 0.001; strict regimen home/hospital: 19.6% vs. 3.4%; p < 0.001). They concluded that attempts to improve personal hygiene during milk collection seem to be of limited value, but good hygiene of collection and storage equipment is likely to be the most important way to ensure the microbiologic quality of expressed human milk, but cleaning of the breast before expression is not necessary. 9 Pumped milk for home or hospitalized infants does not routinely need to be cultured.
Mothers can choose to collect their milk several ways: hand expression, manual pump, or electric pumps intended for single or multiple users.
Hand Expression
Hand expression is a means of removing human milk manually from the breast. There are several benefits for hand expression: no equipment or apparatus needs to be bought or acquired, allowing it to be a method that is affordable by all. Many mothers are able to remove more human milk from the breast by hand expression than by using a pump, and it is always available as a method for human milk collection even in places without electricity or during a disaster. Handwashing before hand expression remains an important step. In addition, hand expression before pumping can soften engorged breasts, making pumping easier. There is no evidence that hand-expressed milk is higher in fat than pumped milk. 10 , 11 However, hand expression used in conjunction with a pump increases milk production, fat content, and caloric content of the milk (62.5 g/L vs. 25 to 45 g/L; 26.4 calories/oz vs. 20 calories/oz) more than the pump alone. 12 , 13
Techniques for hand expression starts with handwashing and preparation of a clean container to collect the human milk. This can be a spoon, cup, collection bag, or a bottle that is suitable for human milk collection. Leaning forward, not lying down, while expressing will use gravity to help the milk flow. The mother can promote milk flow by one or all of the following: making circular movements on the breasts; shaking the breasts with her hands or using something soft, such as a soft towel; or breast massage recommended from the outer areas toward the nipple.
Dr. Jane Morton from the Stanford School of Medicine has a technique of hand expression in which the mother places the thumb and forefinger approximately 1 to 2 inches from the areola, presses in toward the chest wall, and then brings the two fingers together compressing the breast 14 (see Appendix E, Manual Expression of Human Milk). Hand expression also can be used at the start of a breastfeeding session so that the flow of human milk may encourage the baby to taste and smell the milk even before starting to suck.
Another hand expression technique called Therapeutic Breast Massage in Lactation (TBML), uses techniques developed in Russia for the purposes of relieving engorgement, plugged ducts, and mastitis. 15 , 16 > TBML includes gentle breast massage facilitated by rolling the breasts between both hands or kneading the breasts with one or both hands. When needed to relieve engorgement, massaging toward the axillae can facilitate reverse-pressure softening by promoting lymphatic drainage. Hand expression in the TBML method has the mother place two fingers opposite each other near the areola and then bringing the fingers together while compressing behind the nipple. Mothers are instructed to adjust their fingers to areas where milk removal is achieved.
Drip Milk
Drip milk is the milk that drips spontaneously from the contralateral breast during the suckling of an infant. Collection of dripped milk uses the concept that stimulation to one breast will cause a milk ejection reflex by which milk also will be ejected from the second breast.
Traditionally the milk was collected with shells or “nesty cups,” which are placed inside the brassiere to collect milk; the milk was found to have lower caloric value, lower fat, and a much higher incidence of contamination. 17 In recent years, several companies have reintroduced devices to collect dripped milk either in the form of shells or soft silicone containers that are easy to clean or sterilize and stay on the breast by suction created by squeezing the container. The newer devices have a soft flange that can adhere to the breast, allowing the mother to collect drip milk in a “no-hands” manner. (See “drip milk collector” in Table 22.1 .) Studies are necessary to determine if these newer devices are safer.
Table 22.1
Manual Pumping Devices
| Hand Pump | Advantages | Disadvantages |
|---|---|---|
| Bicycle horn |
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| Plain suction pump | Inexpensive  |
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| Handle pump |
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| Cylindric | ||
| Two all-plastic cylindric tubes fit inside one another to create vacuum; inner tube has flange at top and rubber or nylon gasket |
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| Drip Milk Collector | ||
| Passive Breast milk collector | Allows every drop of milk that is leaking to be collected in a passive system when breastfeeding from the other breast or pumping with a single-sided pump  |
Not intended for use to collect large volumes of milk |
Pumped Milk
The use of breast pumps has been associated in some studies with mastitis, possibly because of nipple damage, because cracked or sore nipples have been associated with mastitis in multiple studies. 18 , 19 A case-control study of risk factors for infectious mastitis in Spanish breastfeeding women with 368 women with mastitis and 148 controls revealed that breast pumps were associated with almost three times the incidence of mastitis (adjusted odds ratio [aOR] 2.78, 95% confidence interval [CI] 1.68 to 4.58) even after controlling for other contributing factors. 20 In their study, Cullinane et al. 18 reported 20% (70/346) of participants developed mastitis. Women had an increased risk for developing mastitis if they reported nipple damage (incidence rate ratio [IRR] 2.17, 95% CI 1.21, 3.91), oversupply of breast milk (IRR 2.60, 95% CI 1.58, 4.29), nipple shield use (IRR 2.93, 95% CI 1.72, 5.01), or expressing several times a day (IRR 1.64, 95% CI 1.01, 2.68). The presence of Staphylococcus aureus on the nipple (IRR 1.72, 95% CI 1.04, 2.85) or in milk (IRR 1.78, 95% CI 1.08, 2.92) also increased the risk for developing mastitis. 18 The Academy of Breastfeeding Medicine (ABM) recommends a number of actions to prevent mastitis (effective milk removal, effective management of fullness or engorgement, prompt attention to signs of milk stasis, timely attention to other signs of breastfeeding difficulty, rest, and good hygiene), including effective milk removal from the breast by hand expression and/or pumping. 21
Manual Pumps
The advantages of manual breast pumps are that they can be used everywhere, with no need for electricity or batteries. This may be important in a disaster. In addition, there is the lower cost compared with electric pumps. Most manual pumps are single sided. Mothers should handle the manual pump with clean hands and assemble the parts as directed by the manufacturer 22 (see Table 22.1 and Figs. 22.1 and 22.2 ). As with all pumps, the flange to the manual pump should fit the mother’s nipple and areola and not be too tight or too loose to avoid nipple trauma. Manual breast pumps are designed for one user only (single use) and should never be rented or shared for safety reasons. The main parts to a manual pump are the flange, pump, and milk container. The manual pumps vary in the way the human milk is pumped. The lever manual pump is squeezed by a hand lever. Another type uses a smaller cylindrical tube that fits into a larger cylindrical tube and also creates a vacuum so that human milk can be pumped from the breast. The third type, the bicycle horn manual pump, consists of a hollow rubber bulb attached to a flange. Its use has been discouraged as the rubber bulb is difficult to clean and dry and may retain milk and bacteria. In addition, the suction generated by such pumps is not consistent and so may damage breast tissue and cause mastitis. These devices may not be enough for a woman trying to build up a supply when the infant cannot stimulate the breast directly (see Table 22.1 ).
Electrical Pumps
Electrical pumps are used by many to increase the milk supply when it is low or provide human milk at times of separation, for example, when the infant has an extended stay in the NICU or the mother is at work. Although not shown to be superior in the Cochrane review, many recommend double electric breast pumps at home and in the hospital. 11 (See Fig. 22.2 and US Food and Drug Administration [FDA] website https://www.fda.gov/medical-devices/consumer-products/breast-pumps ). Mothers should be instructed in navigating common issues faced while pumping, such as suction strength, pain with pumping, and proper flange fit. Electric pump parts should be checked for cleanliness. Problems of contamination are a significant issue with old models, because they may not protect against milk backing up into the motor or tubing, normally thought to be free of milk. Care must be taken to check each machine and follow the directions for its proper use.
Multiple use electric pumps have been referred to as hospital grade ; however, this is a misnomer because there are no FDA criteria for “hospital grade” pumps. 23 The FDA does recognize “multiple use” pumps, which refers to pumps with which human milk does not touch any part of the pump except for the kit (not the pump itself). These are safer to use by different mothers each with their own collection kit, which they maintain (see the Centers for Disease Control and Prevention [CDC] website https://www.cdc.gov/healthywater/pdf/hygiene/breast-pump-fact-sheet-p.pdf on How to Keep Your Breast Pump Kit Clean: The Essentials). 24 There does not seem to be a difference in milk contamination whether the milk is pumped or hand expressed, as long as the hands and pump parts are cleaned adequately. 25 In a study of human milk expression from mothers of infants with very low birthweight (VLBW), Boo et al. 26 reported that there was no significant difference in bacterial contamination whether the milk was expressed by hand or pump when the milk was collected in the hospital. However, when breast milk was expressed at home, the rates of bacterial contamination by staphylococci ( p =0.003) and gram-negative bacilli ( p =0.002) were significantly higher in the breast pump group than the manual group. They concluded that the difference was not considered to be due to method of human milk expression but rather to poor cleaning of the pump at home. Before use, the pump should be inspected for whether the pump kit or tubing has become moldy or soiled during storage. Moldy tubing should be discarded and replaced immediately. If using a shared pump, one should clean pump dials, power switch, and countertop with disinfectant wipe. There is no need to discard the first few drops of milk while initiating milk expression, because there is no increased risk for contamination. 9 , 25 A 2017 CDC Morbidity and Mortality Weekly Report article described an incident with a preterm infant who developed meningitis after being infected with Cronobacter sakazakii from expressed maternal milk. 27 C. sakazakii was cultured from the valves of the breast pump kit of the mother. The mother reported soaking the breast pump collection kit from her personal breast pump in soapy water for around 5 hours without scrubbing or sanitizing. She then washed and air-dried the kit and placed it in a plastic zip-top bag. At the hospital, she also pumped with the hospital pump. The collection kit from the hospital breast pump was washed and thoroughly air-dried. The mother did not report symptoms or signs of mastitis. The infant had meningitis, resulting in spastic cerebral palsy and global developmental delay, requiring a ventriculoperitoneal shunt and a gastrostomy feeding tube.
Cleaning and Care for Pump Parts
After pumping, pump parts, known as the kit , should be dismantled, scrubbed, rinsed, and air-dried by hand or by dishwasher. Because of the risk for C. sakazakii infection, the CDC has recently updated its guidelines for infants younger than 3 months old, preterm infants, or immunocompromised infants, suggesting that pump parts should be sanitized at least once daily, using steam, boiling water, or a dishwasher with a sanitize setting. 24 A recent randomized study of steam decontamination after washing the pump collection kit in women pumping to donate to a milk bank revealed that decontamination with steam resulted in a lower proportion of discarded samples (1.3% vs. 18.5%, p < 0.001) and of samples contaminated with Enterobacteriaceae (1.3% vs. 22.8%, p < 0.001) and Candida sp. (1.3% vs. 14.1%, p < 0.05) compared with samples collected with a breast pump kit that was only washed. 28 The CDC recommends that mothers positive for COVID-19 who choose to express and provide their breast milk for the baby employ measures to prevent contamination (i.e., wear a mask for breastfeeding or pumping, wash hands and breasts). 8 In the hospital, multiuse pumps should not be used but rather a breast pump should be designated for each mother. The mother should be instructed to wash her hands before touching the pump or any of its parts. After use, the entire pump and all parts should be cleaned according to the manufacturer’s recommendations. 24
Types of Mechanical and Electric Pumps
Most portable electric pumps have a battery mode for use while traveling. Fully battery-operated pumps are available, and many have rechargeable batteries. These small pumps work for some fully lactating women and for those who have no trouble with volume. Battery-operated pumps may supply dual equipment resembling a double pumping system; however, some have been reported to work sequentially instead of simultaneously. New wearable breast pumps are battery operated, portable, convenient and offer either upright or full mobility, depending on the model. The wearable pump is placed in the bra and may or may not have additional parts, depending on the type.
Small, purse-size electric pumps may be effective for the fully lactating woman ( Fig. 22.3 ). They have an advantage over a manually powered hand pump in that the electric power frees one hand for the mother to stroke the breast and encourage let-down. If flow is going well, the hand is free to perform other tasks, such as read, hold a telephone, or write, not an insignificant advantage for a busy, working, breastfeeding woman. Small, purse-size electric pumps may come equipped with single and double pumping collection kits. Double pumping allows the mother to pump both breasts at the same time, thereby lessening the total time spent pumping. Some small electric models have a small hole in the flange base that must be closed with a finger to develop the suction, as in many hospital suctioning devices. This also gives the mother control over the pressure. By rhythmically opening and closing the hole with the finger, the operator can simulate a milking action that is effective in extracting milk. Some, but not all, have multiple flange size options or serve as a double pump to express milk from both breasts simultaneously.
Full-size electric pumps may be more efficient because the motor applies the mechanical effort. The mother can concentrate on applying the cup to her breast, massaging the breast, and relaxing so that adequate let-down can take place. They are designed to cycle pressure instead of maintaining constant negative pressure, decreasing the likelihood of causing petechiae or internal trauma to the breast. The ultimate effect of pressure also depends on the length of time the pressure is applied. Tissue cannot withstand sustained high pressure. Pressure sustained for 2 seconds or at a rate of 30 pumps per minute is considered maximum time or minimum rate. 29 Negative pressures should have a governing mechanism to avoid excessive pressures. Mean sucking pressures of most normal full-term infants range from −50 to −155 mm Hg/in 2 , with a maximum of −220 mm Hg/in 2 . Manufacturers recommend about 200 mm Hg/in 2 to initiate flow in most women. An older study by Johnson 30 of more than 1000 patients at the University of Texas, using a variety of pumps, confirmed some facts about pumps. The amount of negative pressure possible and the control mechanisms were recorded ( Table 22.2 ).
Table 22.2
Expression and Pumping Methods
From Becker GE, Smith HA, Cooney F. Methods of milk expression for lactating women. Cochrane Database Syst Rev . 2016;9:CD006170.
| Type | Action | Equipment | Availability |
|---|---|---|---|
| Hand expression | Hand action stimulates milk ejection reflex and compresses milk ducts | None | Universal |
| Hot jar (base cooled with cold cloth) | Cooling creates a vacuum so that the milk flows from breast (higher pressure) to the jar (lower pressure); suction pressure may be difficult to control | Suitable glass jar, hot water, cold water, cloth | Widespread |
| Manual pump: Compressing a bulb, pulling on two connected cylinders, or squeezing and releasing a handle | Negative pressure created by hand; arm action of the pump causes milk to flow from breast to pump; suction pressure may be difficult to control; some brands designed to reduce arm/hand fatigue; some work on a “draw and hold” principle rather than an even in-out action |
|
Depends on market demand/distribution |
| Battery pump: Power provided by battery, manner of creating pressure may vary | Negative pressure at pump causes milk to flow from breast to pump; adjustable suction pressure and cycling time in some brands; some work on a “draw and hold” principle rather than even in-out action |
|
Depends on market demand/distribution |
| Small pump: Electric, diaphragm | Negative pressure created by pump action of the pump causes milk to flow from breast to pump; adjustable suction pressure and cycling time in some brands |
|
Depends on market demand/distribution |
| Large electric: Piston pump, rotary vane pump, diaphragm pump; power may be provided by car battery or by foot treadle | Negative pressure created by action of the pump causes milk to flow from breast to pump; suction pressure may be difficult to control; some brands designed to reduce arm/hand fatigue; some work on a “draw and hold” principle rather than an even in-out action |
|
Depends on market demand/distribution; larger pumps generally purchased by hospitals or rental companies for loan to mothers |
Note : Some brands of pump have a flexible breast cup that compresses the breast, and some have a choice of sizes of breast cup. Multiuser pumps require high-quality cleaning procedures and frequent servicing.
There is no one type of pump that is suitable for all mothers and all circumstances. To obtain quantities of milk by any method requires an effective milk ejection reflex.
An increasing number of pumps on the market have similar designs, but each has its special nuances. A standard electric pump capable of cycling pressures to 220 mm Hg (2.5 to 8.5 psi/Hg) is usually required to stimulate production de novo (i.e., when an infant is unavailable to suckle directly, such as a small premature infant on a ventilator in the NICU). Breast pumps have been identified repeatedly for years as the source of infection. 31 Improvement in design, with a safety trap between the collecting vessel and the machine to prevent milk getting into the mechanism, is important. In addition, all equipment that comes in contact with milk or the breast should be sterilizable or disposable. The well-designed electric pump properly used is the best system for stimulating lactation and increasing volume for hospitalized infants.
Although attention is usually given to the pressure mechanisms, the cup or flange that is applied to the breast is equally important. The diameter and depth of the flare are fixed for the hand pumps, but a choice is offered for the standard electric pumps ( Fig. 22.4 ). The nipple should have room to be drawn out, and the flange should be adequate to transmit pressure or milking action to the collecting ampullae under the areola. Finding the proper size for a breast flange is based on the diameter of the nipple, not the areola (the softer pigmented skin around the nipple). When the tunnel of the flange is placed on the breast, it should only have a few millimeters (3 to 5 mm) of space around the nipple. The tunnel of the flange fits over the nipple and forms a seal around the areola. The pumping action mimics the nipple stimulation of a baby nursing. Vacuum is created by the pump, and the nipple is gently pulled into the flange tunnel. A good fit allows the nipple to move freely and comfortably within the shaft of the flange, minimizing friction points. The areola is gently compressed, allowing for rhythmic expression of milk. A woman’s breasts may be different sizes and may require two different flange sizes. The hand pumps are too small; however, bigger is not always better. A mother may find that the smaller model of the two offered may be more physiologically suited to her anatomy. This feature does not correlate directly with overall size of the breast. The average flange size is 24 mm but typically ranges from 21 to 27 mm; however, some women may need 30 or 36 mm (see Fig. 22.4 ). 30 Silicone funnels adapt well to all sizes and shapes because of their flexibility. A study regarding the type of pump, hand and electric, shows the difference in effect on prolactin production and milk volumes obtained ( Figs. 22.5 to 22.7 and Table 22.3 ). 32 The universal availability of a double collecting system, so both breasts are “pumped” simultaneously, greatly enhances production and saves time. Table 22.2 provides data on expression and pump methods of different types of pumps.
Table 22.3
Oxytocin Results a
From Zinaman M, Hughes V, Queenan JT, et al. Acute prolactin, oxytocin responses and milk yield to infant suckling and artificial methods of expression in lactating women. Pediatrics . 1992;89:437.
| Method | Mean Net AUC | SEM |
|---|---|---|
| Infant | 224.7 | 75.4 |
| White River Electric | 174.1 | 41.3 |
| Medela Manual | 218.5 | 157.5 |
| Hand expression | 140.5 | 66.5 |
| Gentle Expressions Battery | 186.7 | 67.6 |
AUC , Area under the curve; SEM , standard error of the mean.
a Levels of plasma oxytocin with breast stimulation calculated as mean net AUC for each of the five methods for the 60-minute sampling session. No significant differences were noted.
Pump Pressures and Cycles and Efficacy
To test the effect of breast pumps on milk ejection, an electric pump was programmed to cycle 45 to 125 times per minute with vacuums between 45 and 273 mm Hg by the research laboratories of Dr. Peter Hartman. The time it took for milk to be ejected was determined by ultrasound of the opposite breast measuring the dilation of lactiferous ducts in response to a pattern of 45 cycles per minute was 147 ± 13 seconds. For patterns that more closely resemble the sucking frequency of an infant when it first attaches to the breast, milk ejection occurred between 136±12 and 104±10 seconds. This compares with ejection time when the infant suckles at 56±4 seconds. The applied vacuum affected the volume of milk that was removed up to 50 to 70 seconds after initiation of milk ejection, but not the time of ejection. 33
When this same research group investigated means of assessing milk injection and breast milk flow, they measured milk flow rates while the mother pumped milk with an electric pump at different settings. They determined the milk duct diameter by ultrasound in the other breast simultaneously. They reported a direct relationship between increases in duct diameter and increases in milk flow rates. 34
Breast pump efficiency was studied by another group working with Dr. Hartmann, using a procedure for objective determination of breast pump efficiency by measuring milk removal from one breast in a 5-minute period in 30 women using an electric breast pump. They compared these data with breastfeeding characteristics. They determined each woman’s breastfeeding characteristics by collecting milk samples before and after each feed from each breast, by either manual breast pump or hand expression, by test weighing the infant, measuring degree of fullness, and direct measurement of breast volume, techniques standardized in their laboratory. The authors concluded that pump efficiency can be measured if maternal characteristics and the amount of milk in the breast available to be expressed are known. The proportion of available milk expressed varied greatly among mothers. 35
Investigators in this same laboratory looked at the impact of vacuum on volume of milk expressed. They looked at 23 mothers (two were expressing milk only and not feeding the infant) who expressed their milk for 15 minutes. The pumps were set at their own maximum comfort levels and then at lesser vacuum levels. The mother’s maximum comfort level produced more milk than at lesser pressures. Milk flow was greatest at the onset, and cream level was highest at the end of the 15 minutes at maximum comfort level. 36 Milk output from the right and left breasts was compared in mothers who were exclusively pumping and had not fed their infants at the breast. It was reported that differences between right and left breasts are common, with the right often more productive. The difference was not related to handedness but was consistent through the day and over time. 29
Consumer Information Resources
Obviously, numerous websites and blogs provide information for mothers and families concerning the choice of a breast pump and their recommendations. We do not recommend any specific breast pumps in this text. A noncommercial resource of information is the FDA’s website with helpful information for consumers buying breast pumps, available at https://www.fda.gov/consumers/consumer-updates/what-know-when-buying-or-using-breast-pump . Breast pump recalls by the FDA can be found at https://www.fda.gov/medical-devices/medical-device-safety/medical-device-recalls . Another presumably noncommercial source of information is the Consumer Reports website, Breast Pump Buying Guide, 2016, which has reasonable information for the consumer: https://www.consumerreports.org/cro/breast-pumps/buying-guide/index.htm .
Recommendations of Breast Pumps
In the past, recommendations of breast pumps to individual women tended to be “one size fits all” despite the fact that women and infants are each different and the reasons for expressing/pumping human milk are also different. 37 A tremendous amount of research (as noted earlier) has ensued concerning human milk expression by negative pressure (vacuum, suction) and positive pressure (expression) using newer technology of ultrasound, computerized tomography assessment of breast fullness, and increasingly accurate weighing scales to measure milk transfer (volumes and ejection and flow rates). A couple of reviews of milk expression have proposed that the mechanism of human milk expression should be specific to the individual circumstances of the mother–infant dyad (breastfeeding [exclusively, partially]), milk expression for specific reasons (effective emptying, stimulate transition to lactogenesis II, storage for later use, or to increase milk production, etc.) and the health or illness of the mother and infant. 11 , 38 What has evolved is that expression or pumping to remove human milk from the breast should be in synchrony with the infant’s removal of milk by breastfeeding. One large group in Dr. Peter Hartmann’s laboratory in Australia has focused on the anatomy and physiology of milk removal, 33 , 34 , 35 , 36 and a second group led by Drs. Paula Meier and Janet Engstrom in Chicago, Illinois, has focused on the functional use of breast pumps based on the “breastfeeding infant as the gold standard,” the stage of lactation, the degree of breast pump dependency, and the characteristics of different pumps. 29 , 37 Meier et al. 37 eloquently examined the evidence regarding human milk transfer during breastfeeding and hand expression versus breast pump. They summarized the importance breast pump suction patterns, the use of percent of available milk removed as a measure of effective milk removal and measurement of pump efficiency as the number of milliliters of human milk removed per unit of time. 37 They also summarized the characteristics of commonly used breast pumps (manual, battery-operated, mini-electric; double electric, and multiuse electric) and their recommendations for pump use based on the phase of lactation and the degree of breast pump dependency. 37 They predominately recommend a multiuse electric pump for partial or complete breast pump dependency regardless of the phase of lactation (initiation, coming to volume or maintenance) and potentially a personal-use electric pump during the maintenance phase of well-established lactation depending on the mother-infant dyad specifics. Manual, mini-electric, or personal-use electric pumps are recommended as appropriate for dyads only minimally pump dependent during the phases of coming to volume and maintenance of lactation. Another publication provides discussion of the functioning of breast pumps and considerations for choosing among the different types. 39
Clearly, other factors such as sizing and temperature of the breast shields, vacuum pressures and time since last milk removal impact milk removal, and comfort and convenience of pump usage. Other important pump characteristics of modern breast pumps are valued by mothers, including cost, ease of use, simplicity versus complexity, portability, quietness, and facility of use at work or at home.
Evaluation of Milk Expression Methods
In the latest Cochrane review by Becker et al., 11 human milk expression methods were evaluated. The review included 41 trials, including 2293 participants, with 22 trials involving 1339 participants contributing data for analysis. The review also included a review of 11 trials of different pumps: hand, manual, and electric. The authors also cautioned readers that 16 of 30 trials received support from pump manufacturers, so that bias may be a factor. This current Cochrane review’s primary outcomes were maternal satisfaction/acceptability, lack of contamination of milk, and level of breast or nipple pain/damage. The only acceptable study in the category of maternal satisfaction and acceptability revealed mothers reported that they were more likely not to want anyone to see them when they used an electric pump compared with hand expression (N=68, mean difference [MD] 0.70, 95% CI 0.15 to 1.25; p =0.01). The studies reviewed could not elicit a preferred pump type. In regard to the outcome of milk contamination, no clinically significant differences were found when comparing any pump to hand expression (N=28, p =0.51), manual pump to hand expression (N=142, p =0.30), a large electric pump compared with hand expression (N=123, p =0.61), or the large electric pump compared with a manual pump (N=41, p =0.59). The final primary outcome, maternal breast or nipple pain/damage, was evaluated on 68 subjects. Large electric pumps were compared with hand expression and found similar results for sore nipples with both the manual and large electric pump (7%). Engorgement was reported in 4% and 6%, respectively, with the manual and electric pumps. Although no nipple damage was reported in the hand expression group, one case was reported in both the manual and large electric pump groups. 11
Secondary outcomes included the quantity of milk expressed, milk volume, and nutrient quality. The authors reported that relaxation, massage, music, warmth, initiation, and duration of pumping and correct breast shield sizes contributed to the increased quantity of milk expressed. This is in contrast to other interventions such as sequential versus simultaneous pumping from both breasts that did not result in different milk amounts. The Cochrane review reported differences in nutrient quality among hand expression, large manual pumps, and manual pumps: hand expression and large electric pumps provided better nutrient quality, with higher protein, compared with a manual pump. Hand expression yielded higher sodium and lower potassium than the manual or large electric pump. Breast massage combined with pump use yielded higher fat content in the milk. although no difference was found in the caloric content.
Becker et al. 11 concluded that there is no preferred type of pump, and no difference was found regarding milk contamination between methods or breast/nipple soreness of mothers. Mothers did report approval for relaxation and support interventions. Low-cost interventions, including initiation of milk expression sooner after birth when not feeding at the breast, relaxation, massage, warming the breasts, hand expression, and lower cost pumps, may be as effective, or more effective, than large electric pumps for some outcomes. 11
However, in a recent study, breastfeeding women were recruited to participate in a study to measure physical changes of the breast with a variety of human milk transfer modalities under close observation. 40 In this small study of 46 lactating women, Francis and Dickton 40 compared the physical changes of the breast after four different types of human milk transfer sessions: direct breastfeeding, hand expression (Jane Morton’s method), and by two different popular electric pumps. The study design was a randomized crossover. Inclusion criteria included women who read and spoke English, did not use breast pumps on a regular basis, had breastfeeding infants between 2 and 3 months of age with reported normal growth, and had no history of breast damage. Before and after testing of a 15-minute human milk transfer session included precise measurements obtained for nipple length, diameter, pain, erythema, or swelling to the breast tissue, including the nipple or areola. Breastfeeding and hand expression did not cause any significant changes. The two electric pumps, however, caused significant changes in nipple length and diameter ( p < 0.003) and increased pain and visible changes to the breast tissue. Pain was associated with visible changes. Limitations of the study included the use of a convenience sample in which many of the participants had received lactation guidance from an international board-certified lactation consultant early in their lactation, which may have improved their baseline breastfeeding experience, that each human milk transfer type was 15 minutes, and that the authors observed and measured each method of milk transfer only once, leaving the effect of repeated pumping episodes unknown. All women received a proper-sized flange for the electric pump at the beginning of the human milk transfer session; however, the authors noted that use of a different size flange during the session may have occurred. The authors concluded that although the use of the pumps was correct and done under the supervision of lactation-experienced professionals, many of the participants still reported pain with erythema and/or swelling evident for 20 minutes or more after the use of pumps. They recommended that health care professionals should evaluate those starting to use a pump. They recommended further research to evaluate the long-term consequences to women who experience untoward physical changes from breast pumps, especially with long-term pump use.
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