Breastfeeding, Fertility, and Family Planning

Breastfeeding is associated with many maternal and child health benefits,^{1, 2, 3} including a delay in fertility return postpartum. This has been recognized for centuries; medical literature from Aristotle to the Renaissance, and, occasionally, thereafter, noted that women who suckle are less likely to become pregnant. This physiological response was forgotten or disbelieved in scientific circles of the mid 20th century as the use of commercial infant formula displaced breastfeeding in industrialized settings, and family planning methods became more widely available. However, recent scientific evidence, compiled both by social and biomedical sciences, demonstrating the population level impact of breastfeeding on fertility and the biologic basis of lactational infertility, has reinitiated interest in breastfeeding and the mechanisms related to lactational infertility. If we allow breastfeeding to deteriorate further, the increase in fertility in settings with limited family planning use would be significant, and very difficult to remedy.^{4, 5}

Today, breastfeeding is being rediscovered and has become the normative initial infant feeding behavior; however, the optimal patterns of breastfeeding that are also associated with fertility reduction are not as yet the norm in many industrialized settings. Optimal breastfeeding for child health is defined by the World Health Organization (WHO) as six months exclusive breastfeeding⁶ followed by continued breastfeeding with age-appropriate complementary feeding for up to two years or longer.⁷ The Healthy People 2010 goals for the United States include at least 75% initiation, with 50% continuation to six months and 25% to one year, and exclusive breastfeeding among 40% for three months and 17% for six months. Data from the US Centers for Disease Control and Prevention⁸ and National Center for Health Statistics now reflect achievement of the initiation goal. Although rates fall off over time, this still means that a majority of postpartum women will be introducing some form of contraception during breastfeeding. However, there remains rapid fall off in continuation and exclusivity (see Table 1). Therefore, for optimal maternal and child health outcomes, physicians must increasingly have the knowledge and skills to support both optimal breastfeeding and appropriate family planning introduction during lactation.

Table 1: Breastfeeding in the United States and globally⁹

* percent exclusive for the full duration; **percent exclusive in a sample of 0-6 months; ^ at 20-23 months of age

Good clinical practice will depend on achieving knowledge and skills to address issues associated with breastfeeding and fertility, including basic anatomy and physiology as they apply to both lactation and the fertility aspects of breastfeeding, and the proper counseling and timing of the provision of contraceptives. The practitioner may also need the knowledge and skills to support conception during breastfeeding, when warranted.

There are research design and analysis issues that have increased the publication of apparently conflicting findings in published studies on breastfeeding and fertility.

Definitions of Characteristics under Study

The term breastfeeding is used to describe a wide variety of behaviors and physiologic states in both mothers and the children. A commonly used definition in the 1960s and 1970s was that of the commercial infant formula industry, which defined breastfeeding in relation to a formula norm. Breastfeeding was generally defined by a ‘yes’ or ‘no’ response, with limited consideration of pattern or exclusivity. Industry interests are to sell product, so the term exclusive breastfeeding was used when breastfeeding with no formula use. However, this definition allowed for other food and drink to be given, and still be defined as ‘exclusive’ breastfeeding. In the past, the US Women, Infants and Children program (WIC) defined a mother-infant pair as breastfeeding if they ever breastfed at all; others have used definitions that describe varying time periods. These definitions, which reveal little about infant nutrition or about maternal physiology, continue to be used by some researchers, creating apparently conflicting findings for the casual reader of the literature.

Many journals now accept definitions that may be more reflective of the maternal and infant behavior and its potential impact on their physiology.¹⁰ This definitional schema:

• defines the feeding pattern during a single period in time, perhaps a 24-hour recall
• defines only breastfeeding and records, but does not define, other forms of feeding
• demands attention to both the maternal and the child's involvement
• differentiates breastfeeding from human milk feeding.
• encourages additional description of the behavior beyond the basic terms in Table 2

The schema also suggests that researchers and program planners note frequency, timing and length of intervals, age of the child, use of expressed milk, how other milks are given, whether pacifier use allowed, and, where applicable, the type, timing, and amount of other feeds. If used, such a schema would allow differentiating between the specific behaviors and the physiologic consequences. Only by including these issues can one assess the patterns which impact on physiology in addition to nutritional outcomes, very important in light of the differential in the physiologic responses to different modes of milk expression and direct suckling.¹¹

A widely used set of definitions was developed subsequently by the WHO, modified from that presented above, but simplified such that they are appropriate to describe infant nutritional intake, but are less relevant for the understanding of maternal and child physiology.¹² This newer set of definitions does not take into account the impact on maternal physiology and potential milk maintenance, the potential differences in behaviors within the definitions used, nor the differences between direct breastfeeding and indirect human milk feeding, in terms of immunologic and other factors. These two sets of definitions are compared in Table 2.

Table 2. Physiology-based and infant nutrition-based definitions of breastfeeding

*Calls for age of child; feeding frequency and intervals; use of bottle, cup, spoon, pacifier; and feeding of expressed milk be recorded for each definition where available.

The immense variability in lactation and breastfeeding behaviors necessitates large samples sizes to fully explore the impact of the differences. However, the relatively short durations of lactation, and the prevalence and use of contraceptives that mask or interfere with physiologic changes have limited the number of such studies completed in industrialized countries. Therefore, much of what we understand is derived from small clinical studies, some of which have not been able to control for even the most important variables, such as sucking stimulus or age of infant. Other studies have used quasi-experimental or epidemiological methods, with intervention and assessment at the population level rather than the individual level.

Sampling Frame and Sample Size

Immense differences in lactational behaviors indicate that large samples would be necessary to control for this variable alone. However, the relatively short durations of lactation, and the prevalence and use of contraceptives that mask or interfere with physiologic changes, limit study in industrialized countries. Therefore, much of what we understand is derived from limited clinical studies, some of which have little control over sucking stimulus or age of infant or that information is inferred from larger prospective studies with limited neuroendocrinologic elements.

Selection Bias in Selection of Cases and Controls

Breastfeeding patterns are skewed, with more breastfeeding occurring among those earlier postpartum. With or without breastfeeding, normal maternal physiology undergoes changes postpartum. Therefore, the choice of infant age group/time postpartum studied can significantly influence physiologic outcomes. This is further complicated by the difficulty in random assignment of these breastfeeding and complementary feeding behaviors. It is not ethically possible, nor probable that groups of women would agree, to be assigned to breastfeed or not breastfeed. It is even more unlikely that infants will cooperate with the timing of their hunger or the intensity of their suck at any particular time. This may lead to confounding, associated with the factors that may influence self-selection into one pattern of feeding or another.

Recall Bias

Many studies include data from mothers whose children have long since stopped breastfeeding. Their recall may be biased by subsequent child health events or by the breastfeeding experience of subsequent pregnancies. CDC recently explored recall and found many definitional flaws and inconsistencies.

Analytic Plan and Techniques Used

Proper selection of statistical approach is vital. There are many textbooks designed for the clinician or occasional researcher. The analysis plan should be designed before data are gathered, because it may dictate to some extent the sample frame and size. However, it remains important to reassess the plan after data are collected. The data set may have insufficient numbers in proposed subgroups due to limited variability within the sample, or may not reflect other assumptions used in planning. For example, if all women in the sample breastfeed for about the same length of time, there will be insufficient variability in the data set to assess the biologic impacts of varying durations of breastfeeding.

Selective Presentation of Findings due to Journal Space Limits

Because journals frequently limit the length of articles, important facts in the interpretation of the findings may be inadvertently omitted. Also, negative results are rarely accepted for publication.

Misinterpretation or Confused Conclusions, and Conviction-Based Bias in Presentation

In statistics, terms such as association or determinant may be misinterpreted as meaning causation. Two things may be statistically significantly associated but have no biologically meaningful relationship. Although we like to think that scientists are unbiased, each works from personal understanding of the issue in question. This may affect how the hypothesis is stated and tested, and which data are presented. If findings do not support the author's hypothesis or do not achieve statistical significance, it is often difficult to find the energy—or the journal willing—to publish it. Finally, discussion and conclusion sections of papers may include statements that overstate or reinterpret what the findings show.

These difficulties compound the problems of data collection and analysis in this already complex area of study.

The anatomy of the breast and the hypothalamic-pituitary axis for release of prolactin and the production of breast milk may be found elsewhere in this text. These same structures are integral to the mammary-hypothalamic-pituitary-ovarian axis that mediates lactational infertility. The current understanding of the physiology of this feedback system is derived from studies of the different systems under conditions of lactation and nonlactation. Because of the difficulties in studying these phenomena, as previously outlined, this section summarizes current understanding and presents also a summary of studies that confirm the underlying conclusions presented here.

Summary

Suckling at the breast, especially with active stimulation of the nipple and areola and the structures that underlie them, stimulates an inhibition of the pulsatile release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which in turn, disorganizes the pulsatility and levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The result of the disruption of the levels of LH, and the sometimes reduced levels of FSH, is suppression of the development and release of a viable follicle and ovum. Over time, as erratic pulsatility begins, there will be some ovarian follicular development with increases in inhibin B and estradiol. When this occurs, there can be a paradoxical re-suppression of fertility, rather than the stimulation of ovulation seen in non-breastfeeding women¹³ (see Fig. 1). With increasingly normal pulsatility, associated with decreases in the suckling stimulus, a resumption of apparently normal follicle growth occurs associated with a normal increase in estradiol. However, this is often associated with the formation of an inadequate corpus luteum. Eventually, there is a return to normal ovulatory menstrual cycles.¹⁴

Oxytocin release from the posterior pituitary, which stimulates the let-down reflex, allowing milk to flow through the capillary-like mammary tubules, has not as yet been linked to suppression of fertility; however, its establishment is necessary for successful lactation, and, as such, is a necessary part of the lactational infertility.¹⁵ Plasma prolactin levels that are associated with milk production in the early days postpartum are less associated with milk production as time progresses,¹⁶ and these levels would seem to have a limited role in the feedback system that suppresses ovulation. In addition, maternal nutritional status is much less important than the pattern of infant breastfeeding; however, the maternal nutritional status may impact the feeding pattern. While much of the underlying physiology remains to be elucidated, the basic parameters of this feedback system may be seen in Fig. 1.

Discussion of Research

A recent symposium attempted to bring together scientists to discuss the current understanding and gaps in the knowledge concerning the physiologic basis of lactational infertility. Based on exploration of published and unpublished literature, three stages were identified:¹⁷ early postpartum lactational amenorrhea, continued lactational amenorrhea, and menses return.

The early postpartum period, in this context, is the 6–8 weeks postpartum during which the inhibitory mechanisms of pregnancy continue to produce an impact, with diminished pituitary response to the hypothalamic release of GnRH. This is possibly due to reduced activity of the GnRH pulse generator; however, in the first month postpartum, there is no LH response to a GnRH bolus. Studies of LH activity during this same period have yielded variable findings, indicating that there may be individual or behavior-based variation. Another study shows that the LH pulse frequency is not significantly different from that found in the early follicular phase; the peak levels, however, are significantly reduced.¹⁸ By the second postpartum month, LH response to a GnRH bolus may be seen, indicating a shift in the underlying mechanisms.¹⁹ This would imply decreased end-organ receptivity, in this case the pituitary. Opiates do not seem to mediate this shift in humans as they do in some nonhuman animal models.²⁰ The timing of this shift may be dictated by intensity and pattern of feeding or by individual physiologic differences.

Those factors that influence the duration of continuing lactational amenorrhea, in relation to the duration of lactation, are not fully understood. At the same time, ongoing diminished GnRH and pituitary responsiveness continue in relationship to the intensity of the suckling stimulus. However, quantifying this phenomenon is difficult. Other mechanisms are thought to contribute, creating a complex of sometimes-conflicting feedback loops. These include enhanced or paradoxical negative feedback of ovarian secretions on the hypothalamic-pituitary axis; failure of positive feedback actions, lack of stimulation of the hypothalamus; decreased number or function of GnRH receptors; altered biologic activity of the hormones of ovulation; and a variable role of prolactin. It was concluded that there is a possibility of redundancy in these mechanisms.¹⁵

Attempts to elucidate the role of prolactin have found little direct involvement in the suppression of fertility. One important study included 20 women, with 24-hour blood sampling every 10 minutes, at either four or eight weeks postpartum, at either time of introduction of supplements, at first menses while continuing breastfeeding, and in the follicular phase of the first cycle after weaning. Results included that the pattern of prolactin levels was responsive to breastfeeding pattern, but that there was no relationship between the plasma concentrations, day or night, and the duration of amenorrhea. There was, however, a strong and statistically significant correlation between the timing of introduction of food or liquids and the duration of amenorrhea.^{21, 22} Feeding the infant any foods in addition to breastfeeding prior to six months of age is associated with about a 4–6 fold increase in the risk of menses return prior to six months.²³ Another study of 10 women in Chile found that women who returned to fertility earlier exhibited a smaller prolactin response to suckling as early as the first month postpartum than was found among those with a delayed return of fertility.²⁴ Although prolactin levels clearly are responsive to suckling, and there is an association of prolactin response and earlier return of menses, the pattern of prolactin release is not predictive of fertility return for the individual.

Another long-held hypothesis was that maternal fat stores dictated the duration of lactational infertility. To investigate the extent to which better maternal nutrition is associated with a reduction in the duration of lactational amenorrhea, data on 339 mother-infant pairs were analyzed.²⁵ Maternal triceps skinfold was negatively associated with the length of amenorrhea; once controlled for infant feeding pattern, the effect was small; only a 0.5-month difference was seen when the 25th and 75th percentiles were compared. Improved maternal nutritional status by supplementation was not associated with change in length of amenorrhea if controlled for infant supplemental feeding. In another study, the effect of body mass index on lactational amenorrhea became nonsignificant when controlling for lack of formula feeds, maternal age, and socioeconomic status.²⁶These studies suggest that infant, not maternal, supplementation influences the duration of lactational amenorrhea, and that maternal nutritional status has modest influence. In a recent review of the physiology of lactation, Neville raises the possibility that another hormone associated with nutritional status, such as the appetite-suppressing hormone leptin, may play a role.²⁷ It may be that the physiology of the negative association of maternal overweight with breastfeeding initiation and duration²⁸ has an influence on these studies, creating a bias in which mothers enter the cohort. Although the impact of nutritional status on lactational amenorrhea is less significant than earlier believed, the factors that mediate this association remain to be elucidated.

The return of menses during lactation is highly variable, among individuals and among cultural groupings.^{29, 30} There are many behavioral and physiologic parameters that may have some impact on the timing of the return of fertility during lactation. Clearly, the sucking stimulus is a major variable and accounts for much of the variation seen. Frequency, with recovery time during the interval between feeds, intensity of the child's suckling, and hence breast stimulation, and the sensitivity of the nipple and areola of the breast, may all play a role. There appears to be increased pituitary responsiveness to GnRH over time; however, the presumed mediation by β-endorphins or opiates, has not been substantiated in humans. Whether it is dictated by individual variation in neuroendocrine response to the stimuli, the variation in bioactivity of specific hormones and end organ, including ovarian, response to the changes remains to be assessed.

Fertility does not necessarily return immediately with the return of regular vaginal bleeds. The first cycles during breastfeeding frequently are associated with abnormal ovulatory activity and luteal phase defects. Studies have found, on average, a gradual return to normality over the first three cycles. An analysis of survey data found that, in areas where breastfeeding is practiced physiologically, that is, frequently day and night with little to no supplementation given, the continuation of breastfeeding after menses return is associated with significant continuing delay in fertility. In this study, for each additional month of breastfeeding after menses return, there is about 7.4% reduction in risk of conception.³¹ This is thought to be primarily due to ongoing luteal phase defects.³²

Differentiation of the first hormonally induced bleed from continued lochia or perceived end-of-puerperium bleeding episodes may present an issue for some women, especially those interested in charting their cycles or predicting the next bleed. A multicenter multinational study of the return of a hormonally induced bleed, retrospectively defined as a bleed followed by another bleed within 21–70 days found that the duration of lochia varied significantly. The conclusion was that among intensively breastfeeding women, about 11% experienced such a bleed in the first two months postpartum.³³

The suckling at the breast is the major stimulus of the feedback; however, the specific attributes of the suckling that contribute to the suppression of fertility are not fully elucidated. Clearly, frequency of the suckling episodes is vital. In the very early postpartum stage, suckling of 10–12 times a day appears the minimum number necessary to establish full lactation and fertility suppression. During the second stage, frequency may be reduced, but increasing intervals between feeds and initiation of or increase in supplementation are associated with hastened return of both ovulation and return of menses.^{31, 34} After menses, or regular bleeds, recurs, frequent suckling continues to be associated with decreased fertility. Other parameters of the suck stimulus have been harder to study. In an effort to assess the impact of sucking intensity, a pressure transducer was attached to the nipple of exclusively breastfeeding women (n = 62) at two and five months postpartum. Although the efficiency and duration of the suckling, per se, were not correlated with duration of amenorrhea, the time at the breast in non-suckling pauses was positively associated with a delay in menses return.³⁵ This may indicate that sensory stimulation other than suckling alone may have a vital role in the feedback to the hypothalamus. Possible areas for further exploration include the importance of olfaction in early mother-infant bonding³⁶ and cosleeping. These areas remain to be studied in relation to the duration of lactational infertility, and the physiologic impact of behaviors and sensory stimuli.

Contraceptive Use During Lactation

Studies of maternal nutritional recovery postpartum and of outcomes of subsequent pregnancies have shown that spacing of births is necessary for improved outcomes. Child spacing of about 28 months is suggested as healthiest for pregnancy outcomes in a US-based population.^{37, 38} In developing country settings, spacing of this length or longer is recommended.³⁹ Although breastfeeding alone can result in spacing of this duration, the individual woman is cautioned not to rely on breastfeeding alone if she wishes to achieve this goal. Therefore, the introduction and use of family planning during breastfeeding are important health interventions.

The choice of method should be the woman's, based on complete information on which to make an informed choice. Counseling is generally necessary to ensure that this fully informed choice can occur. Generally, contraceptive technology texts emphasize efficacy as the major criterion for method selection. In fact, women's choices are generally based on various other factors, including personal experience, a desire to delay or permanently cease childbearing, lifestyle, and religious influences. She might also be influenced by the other health impacts of the method on her or her child, in addition to those directly associated with breastfeeding and contraceptive efficacy. Some of these are presented in Table 3.

Table 3. Summary of the non-contraceptive health issues associated with the use of contraceptive methods

*Hormonal methods may have long-term health benefits for women including decreased rates of reproductive tract cancers; methods that reduce menstrual blood loss would contribute to anemia reduction. (Hatcher R, Rhinehart W, Blackburn R et al: The Essentials of Contraceptive Technology pp 4–19. Baltimore: Johns Hopkins School of Public Health, Population Information Program, 1997.)

Table 4 presents the method options categorized by potential impact on breastfeeding, not on efficacy of the method or the other issues that may be of interest to the individual patient. (The American College of Obstetrics and Gynecology issued guidelines on aspects of breastfeeding. The guidelines support this table while allowing earlier initiation of hormonal methods when appropriate.)

Table 4. Family planning considerations for the breastfeeding woman

LAM, lactational amenorrhea method.
*Most pregnancy, or failure, rates as presented are from life-table analyses in studies of women who are not breastfeeding, except as indicated. These rates would be expected to be lower when used during breastfeeding due the additive impact of to its fertility suppressive effects. Pregnancy rates presented are based on studies of use during lactation. (Modified from Hatcher R, Trussell J, Nelson A, et al: Contraceptive Technology, pp 407-409, 759. Ardent Media, Inc. 2007.⁴⁵)

Nonhormonal methods are considered the first choice because they have no direct impact on breastfeeding. The lactational amenorrhea method (LAM), described later in this chapter, may be used as in introduction to other method selection, or as the primary method in the early months. In addition to LAM, the choices include physical, chemical, and temporal barriers, as well as male and female sterilization.

Second choice is the progestin-only methods that have been extensively tested and found safe in later breastfeeding.⁴⁶ In the last decade, possible association with maternal bone loss became an issue. A prospective study of levonorgestrel (Norplant), progesterone vaginal rings, and CuT380 intrauterine devices (IUDs) found no difference in bone status among the three groups at months 1 and 12 postpartum, and at six and 12 months after cessation of lactation.⁴⁷ There are many studies of vaginal rings, a method not as yet approved for use in the United States, that show this to be a safe and efficacious method for lactating women; however, there remain issues of user satisfaction.

The timing of introduction of progestin-only methods continues to be debated. There is little in the literature on the use of these methods during the first 4–6 weeks postpartum among fully breastfeeding women. Assessment of the studies available, clinical reports, and preliminary guidance from the WHO would encourage caution, recommending delay of use for at least six weeks postpartum, and calling for further research concerning this specific situation.

The estrogenic methods, despite their higher efficacy, are considered third choice because of their known negative effect on milk production. Other concerns, such as changes in micronutrients, including iron, calcium, copper and phosphorus, seem unfounded.^{48, 49} Consideration has been given to whether a woman should switch from the less efficacious progesterone-only methods to the estrogenic methods at some point during lactation. An opinion poll of 20 providers considered to be expert in the field concluded that there is no reason to switch during early lactation but that there is no problem with doing so after six months postpartum.⁵⁰

Breastfeeding can significantly reduce menstrual loss and fertility, but cannot alone provide reliable adequate child spacing for most women. Although further research is needed to understand all the neuroendocrine mechanisms underlying lactational infertility fully, clinical studies have outlined the parameters under which breastfeeding can be reliable. LAM should be considered an option in the complete picture of informed family planning choice for the lactating woman. This issue is addressed regularly by the Academy of Breastfeeding Medicine Protocol #13.⁵¹

Family Planning Based on the Physiology of Lactation

There has been interest in building on lactational infertility to create a reliable, efficacious form of family planning for more than 30 years. In the 1970s, researchers began to publish studies showing that under clinical conditions of full breastfeeding and amenorrhea, fertility would be a rare event.³⁴ At the same time, Tyson and others pursued the pituitary-gonadotrophin route, assessing the impact of thyrotropin-releasing hormone (TRH) and other related hormonal releasing hormones on fertility.^{34, 52, 53} More recently, it has been suggested that GnRH agonists might enhance the impact and duration of lactational infertility.⁵⁴ These approaches that enhance or suppress the hormonal feedback system have been associated with acceptable side effects. Although there is a high correlation of the timing postpartum of fertility return with previous breastfeeding experience when measured in a population of women, this is not a reliable indicator for the individual.

Stimulated by these early publications, researchers began to explore the relationship between breastfeeding patterns, menses return, and fertility suppression to see whether a noninvasive approach based on an improved understanding of the physiology might be possible. In 1988, the research findings of several centers around the world were shared at a meeting at the Rockefeller Bellagio Conference Center, and the scientists agreed that three criteria (i.e. full breastfeeding, amenorrhea, first six months postpartum) would be sufficient to serve as a method. These findings became known as the Bellagio Consensus.⁵⁵ A few months later, this approach was presented to a group of family planning service providers at a meeting at Georgetown, in the District of Columbia, and LAM was developed as a clinical algorithm, and guidelines were prepared.⁵⁶

LAM is a postpartum introductory method that includes three criteria for defining the period of lowest pregnancy risk and then advises immediate commencement of another method that complements the effects of breastfeeding thereafter. Clinically, the mother would be asked whether her menses have resumed, whether she is no longer fully or nearly fully breastfeeding, and whether the infant is six months of age or older. If the answer to any of these is affirmative, she is advised to begin another method of family planning, preferably one that will have no negative effects on lactation (Fig. 2). Counseling includes timely switch to another method compatible with lactation, and the encouragement of healthy birth spacing of about 2.5–3 years, allowing for maternal recovery postpartum and postlactation before another pregnancy commences.

Fig. 2. Lactational amenorrhea method

Because this method is based on behavior, there is no organization in the United States with the mandate to review its safety. For this reason among others, the WHO, Family Health International, and the Institute for Reproductive Health (Department of Obstetrics and Gynecology, Georgetown University) assembled a second internationally recognized panel. The Rockefeller Foundation approved a second Bellagio conference that was held to consider the safety and efficacy of the method. Based on LAM clinical trials and WHO multicenter studies that had confirmed that fully lactating amenorrheic women have about a 1% chance of pregnancy, this panel concluded the following:

“The Bellagio Consensus clearly has been confirmed  … The efficacy of LAM has now been well established in prospective studies, and programs should regard LAM as an additional method that increases the family planning choices for postpartum women. Lactational Amenorrhea Method should receive the programmatic and policy support necessary to become available worldwide … Programs should ensure that any LAM user is able to begin the new method in a manner that ensures continuity of protection from an unplanned pregnancy."⁵⁷

This new method of family planning has been found to be highly effective (Table 5).

Table 5. Efficacy of the lactational amenorrhea method

*Significant loss to follow-up.

This new method is now in use in more than 30 countries, and has been included in family planning and maternal and child health policy in several countries.⁶⁹ Duration of LAM use, which contributes to effectiveness of the method, varied across these studies, averaging about 4–5 months.⁷⁰ Duration of the method in common usage has been shown to depend on ambient breastfeeding norms and maternal commitment, in addition to physiologic predisposition. LAM may be used no matter what the average breastfeeding pattern may be, as it is a method for individual use, like all other methods. Studies have confirmed that there are a significant minority in nearly every country that could use this method.⁷¹

At least one study has shown that LAM provision is associated with a lengthened birth interval.⁷² However, on average, while LAM use may well be quite important to the individual, it will not have a sufficient impact on birth interval alone to allow women to achieve a healthy interval. Demographic and Health Survey data were used to explore decisions about timing of contraceptive use among postpartum women. The findings revealed that policy and program strategies that focus on counseling immediately postpartum or at a later interval, such as when menses resume, may have a substantial influence on the use of contraceptives.⁷³ The recommendation to switch to another method in a timely manner is best accompanied by counseling for at least 3-year intervals between children.

Studies reveal that the major reasons for non-use of this method include lack of health worker and maternal awareness of the method, belief that there is not sufficient breastfeeding in their population (despite global and national data that show the increasing rates of exclusive breastfeeding), fear of some undesirable effect on health, and concerns about efficacy. Additional reasons for accepting LAM include being convinced by counseling and intention to use LAM initially before switching to another method. One study found that occupation outside the home (P=0.01) and previous knowledge of LAM (P<0.001) emerged as predictors of LAM acceptance.^{74, 75, 76} These issues are readily addressed with proper information.

LAM has been shown to be efficacious in all settings, even where exclusive breastfeeding may not be the norm. Even in countries such as the US where exclusive breastfeeding may only continue for 2–4 months, the method has an important role. For example, one study found that patterns of exclusive breastfeeding may differ in different settings, e.g. women in Baltimore breastfed less often but for more minutes at each feed than did women in Manila. Nonetheless, the mean durations of lactational amenorrhea were about six months and nine months, respectively, both of adequate duration for LAM use.

Success in the provision of this method is enhanced when there is adequate breastfeeding support available to the mother and when she is properly counseled in those breastfeeding behaviors associated with fertility suppression. Based on the physiologic responses, LAM counseling should include discussion of optimal breastfeeding behaviors for both lactation maintenance and fertility suppression, and the importance of birth spacing and the timely switch to another method of family planning. Studies indicate that the frequency of the breast stimulation and the maintenance of short intervals between feeds (no longer than four hours during the day or six at night) seem to be associated with lactation maintenance.

Advantages and disadvantages of the method include its efficacy and reliability, and that it expands the ‘contraceptive options’ for women. It has been shown to be an effective transition method, encouraging initiation of a longer term method in a timely manner. The method has no additional cost beyond that associated with fully breastfeeding women and it reduces the need for contraceptive commodities needed to achieve adequate birth spacing. The disadvantages of LAM include lack of protection against STIs and that it requires optimal patterns of breastfeeding.^{58, 77}

The term ‘passive LAM use’ is used to describe the situation when the woman has adhered to the criteria but is not actively aware of the method; when the criteria are in place, the efficacy is similar to that found among women actively using the method.^{78, 79} However, to extend the use of the method, support for six months of exclusive breastfeeding is required, and international guidance recommends six months of exclusive breastfeeding.^{80, 81} Work by Dewey and colleagues involved a random assignment at four months to continue exclusive breastfeeding, or to begin a high-quality, clean supplement provided free of charge. Two important findings were noted: there was a significant decrease in the breast milk intake and amenorrhea at six months was decreased by 20%.^{82, 83} Further, exclusive breastfeeding women who do not know about LAM are at risk for not transitioning to another method of contraception at six months postpartum, while women who were aware of LAM criteria were likely to transition appropriately.⁸⁴ Research in the US found considerable overlap of breastfeeding and contraceptive use; however, many women did not use contraception.⁸⁵ A study in Egypt found that women of low empowerment index in household decisions were more likely to use passive LAM than modern contraception.⁸⁶ This may be due to lack of self-efficacy in family planning choices. Clearly, the use of this method, and the practice of optimal breastfeeding in general, are linked to lifestyle choices for the mother.

Infertility

In the diagnosis of infertility, breastfeeding and lactational amenorrhea status should be one of the first aspects of the medical history addressed. Other factors that should be considered include the possibility of subclinical infection associated with secondary infertility, and, where appropriate, extreme altitudes.^{27, 87} This normal fertility delay may not be welcome among women who wish to plan a subsequent pregnancy and are not concerned with the public health guidance concerning spacing of births.

It is not always necessary to advise cessation of breastfeeding in these cases; adjustment of feeding pattern to favor return of ovulation is a possible alternative. Because hormonal responses are thought to be greater at night, it is suggested that night feedings be limited, and that total 24-hour frequency of breast stimulation be reduced. This should not be recommended unless the infant is independent of the need for breastfeeding for nutrition, health, and immune system development. Lactational infertility may continue even after menses appear to be normal, so counseling should include the possibility of an extended time line, and assurances that optimal maternal nutritional recovery occurs with cessation of breastfeeding when mother and baby decide, followed by about six months of nonlactation, nonpregnant status.