The importance of breastfeeding has been documented in numerous scientific studies, including recent major reviews [1–3]. Breastfeeding, particularly Exclusive Breastfeeding for the initial six months of life, provides better health for both infants and mothers by preventing diseases and promoting health in the short and long term [4]. There has been an emphasis on the promotion of breastfeeding in many countries and in 2001 the Japanese government undertook a health promotion project, ‘Healthy and Happy Family 21 (Sukoyaka Oyako 21)’ that included a goal to improve the rate of Exclusive Breastfeeding at one month postpartum by 2014. The 2010 interim report on this project stated that although more than 95% of women intended, before delivery, to breastfeed their infants, the rate of Exclusive Breastfeeding at one month postpartum had not changed since 2005 [5, 6]. No specific target was set at the beginning of this project, making it hard for health professionals to evaluate if the goal was achieved. Subsequently in 2010, a target was set of 60% Exclusive Breastfeeding at one month postpartum [5].

In Japan, Exclusive Breastfeeding was the only practical feeding method to feed infants until the end of the first half of the 20th century [7]. For women, visiting temples or shrines to pray for their ability to have sufficient production of breastmilk was common practice and many special foods were consumed to help with lactation [8]. A child usually continued breastfeeding until two to three years of age, and breastfeeding up to six years of age was common [7]. Infant formula was first introduced to Japan in 1917, but it was not until the 1950s that its use increased rapidly [9]. Formula companies used the advertising slogan ‘To become a bright child’ in their marketing, and this message suggested that infant formula feeding gave advantages in infant development and weight gain, which increased its popularity among mothers [10]. The Exclusive Breastfeeding rate declined to its lowest point of 31% at one month in 1970 [Figure 1. As a result, in 1975, three goals for restoring breastfeeding rates were set by the Ministry of Welfare based on the 1974 recommendations of the WHO. These were:

1. 1)

   To exclusively breastfeed infants to 1.5 months after birth

    
2. 2)

   To exclusively breastfeed infants to three months if possible, and

    
3. 3)

   Not to change to formula, even after four months of age, without good reasons [11]

    

The Any Breastfeeding rate has gradually increased since then. The National Nutritional Survey of Pre-school Children, which has been carried out every decade since 1985, showed that Any Breastfeeding has increased from 80.7% in 1980 to 94.9% in 2005 at one month and from 59.5% to 79.0% at three months, while the duration of Exclusive Breastfeeding has remained relatively constant, but with a slight decline in recent years [Figures 1 and 2[6]. The rate of Exclusive Breastfeeding at one month declined from 49.5% in 1985 to 46.2% in 1995 and to 42.2% in 2005 [Figure 1[6]. The rate at three months has also remained relatively constant at 39.5% in 1985, 38.1% in 1995 and 38.0% in 2005 [Figure 2[6]. In 2010, another National Survey on Children’s Growth reported that the rate of Exclusive Breastfeeding was 51.6% at one month [Figure 1 and 56.8% at three months [Figure 2[13]. In this survey, Any Breastfeeding also increased to 95.4% at one month and 86.8% at three months. Compared with previous reports of breastfeeding rates in Japan, the latest rates of Exclusive Breastfeeding have improved. However, the WHO definitions of breastfeeding practices were not applied in this study and therefore it is difficult to compare 2010 results with international studies. While the Japanese government set three goals for mothers in the first breastfeeding promotion campaign in 1975 (see above), the rate of Exclusive Breastfeeding has remained unchanged for the last 30 years.

Japan was the first developed country to have a Baby-Friendly Hospital Initiative (BFHI) hospital accredited by the WHO and United Nations Children’s Fund (UNICEF) in 1991 [14]. However, Japan was also one of the three countries that abstained from voting for ‘International Code of Marketing of Breastmilk Substitutes’ in 1981 [9]. These contradictive actions suggested to Japanese health professionals that perhaps breastfeeding promotion was not a high priority and not an issue that should be applied to the whole population. Studies from other countries have found that factors that influence breastfeeding outcomes include maternal age, maternal infant feeding attitudes, breastfeeding difficulties, maternal employment status, and maternal smoking status [15–17]. However, there have been few studies published on the factors associated with breastfeeding duration in Japan. The aim of this review is to summarise factors that influence the duration of breastfeeding in Japan and the existing knowledge of breastfeeding that will assist the development of further promotion programs.

The standard WHO definitions of breastfeeding used in this review are [18]:

Unlike studies from other countries [16, 17], our review found that several factors, including maternal age, family income and maternal educational levels, were not associated with breastfeeding duration in Japan. Smoking status, low birth weight of infants and maternal perceptions of insufficient breastmilk supply were associated with shorter breastfeeding duration. Also, living with grandparents of infants in Japan may be an impediment to breastfeeding duration. These negative factors are keys to understanding potential targets for health promotion programs that are relevant to breastfeeding culture in Japan. One positive association that appears to differ from other countries was the association found in several studies between returning to work (child care facility provided) and continued breastfeeding [20]. This is an interesting finding that may relate to level of education and socio-economic status, but it requires further studies in different parts of the country to confirm the finding and explore the reasons for it.

Although the project, ‘Healthy and Happy Family 21 (Sukoyaka Oyako 21) was undertaken by the Japanese government, a survey of 757 community centres reported that only 10% had implemented breastfeeding programs to improve breastfeeding rates at the local level [46]. Countries that have improved breastfeeding rates have usually had a national promotion program and enlist society as a whole to support breastfeeding.

While the Japanese health system puts great emphasis on healthy development and prevention, the national breastfeeding rate at one month postpartum has remained relatively unchanged between 1980 and 2005 and appears to have slightly declined in some surveys. In Australia, a country with similar health status and level of economic development to Japan, the rate of Exclusive Breastfeeding at one month postpartum was 55.8% [47], higher than Japan at 42.4%. Different definitions of breastfeeding practices were also used in Australia and Japan. Australia uses the WHO definitions, while the latest Japanese survey (The National Survey of Infants Growth in 2010) used a definition of Exclusive Breastfeeding that was having breastmilk as the main source of nutrition and included having some infant formula when infants “go out” [13]. Consequently, much breastfeeding in Japan that is reported as Exclusive Breastfeeding is actually Predominant (full) or Any Breastfeeding and not Exclusive Breastfeeding according to the WHO definition. However, even though a less stringent definition has been used, there is still room for considerable improvement in Exclusive Breastfeeding rates to six months. This would be in accord with WHO policy and would optimise the health of Japanese infants.

In addition, some practices, including prelacteal feeding and supplemental feeding, which are not recommended by WHO, are still common in Japan. A cross-sectional study of 1,612 postpartum mothers in Himeji city reported that the mean age of starting infant formula was 2.8 weeks, which meant that the majority were classified as Any Breastfeeding after their discharge from hospital. More than 20% introduced infant formula within seven days after birth and this increased to almost 80% at two weeks postpartum [48]. In a study of 41 obstetric facilities in Okinawa prefecture (approximately 47% of the total number of the obstetric facilities), Nakamura showed that only 8 facilities (19.5%) routinely gave nothing to infants after birth except breastmilk from their own mother [26]. Nineteen facilities (46.3%) gave infant formula or glucose to infants while in hospital and five facilities (12.1%) gave these immediately after birth as their first feed. However, some authors have argued that giving glucose water as the first feed for infants prevents neonatal hypoglycaemia that may affect the neurological problems later in life [49, 50]. One randomized controlled trial (RCT) found that prelacteal or early supplemental feeding was associated with shorter duration of breastfeeding, although there are no reported studies that investigated this relationship in Japan [51]. Widespread use of infant formula is observed in Japan, which is consistent with the low proportion of BFHI accredited hospitals and obstetric clinics. By 2011, it was only 2% (61 out of over 3000 hospitals and obstetrics clinics) compared to Australia, where approximately 22% (74 hospitals out of 335 obstetric/maternity hospitals) were BFHI certified in 2010 [52].

In Japan, infant formula is often introduced when infants are considered to have insufficient weight gain. This often occurs when mothers perceive that they have insufficient breastmilk production [53]. These mothers may feel guilty at not being able to breastfeed and encouraging these mothers to exclusively breastfeed their infants may subject mothers to added mental pressure and stress [50]. Health professionals also sometimes suggest to these mothers to add infant formula to relieve them from these pressures and stresses [54]. Some mothers misinterpret infants’ behaviours as a sign of insufficient breastmilk [55]. Health professionals sometimes suggest adding infant formula based on their assessment of the adequacy of breastmilk [56]. The high rate of use of infant formula for supplementary feeding is reflected in the unchanged rate of Exclusive Breastfeeding since 1980. The routine use of supplemental and prelacteal infant formula feeds is not consistent with best infant feeding practice [57]. However, Any Breastfeeding is still better for the infant than receiving only infant formula and even if mothers use some supplemental infant formula, they should continue breastfeeding as much as possible.

There are other traditional customs related to breastfeeding practices that may hinder mothers from continuation of breastfeeding in Japan. For instance, many hospitals and clinics routinely measure infants and undertake other procedures immediately after birth, which separates them from their mothers. Several studies have argued that these neonatal procedures are barriers that unnecessarily delay early initiation of breastfeeding and would in turn affect the duration of breastfeeding [25, 58]. Many hospitals and obstetric clinics also accept donations of infant formula and equipment from infant formula companies and samples are sometimes distributed to new mothers while they are in hospital. Howard et al. reported that mothers who received goods from formula companies were more likely to cease breastfeeding within two weeks after birth than those who did not receive gifts [59]. A study of 151 midwives who attended an academic conference also showed that more than 45% considered that the practice of teaching new mothers to prepare infant formula not to be an obstacle to breastfeeding and 32% stated that providing free gifts of infant formula would not impede breastfeeding practices [60].

Over the past three decades, Any Breastfeeding rates in Japan have improved. The New Guidelines on Infant Feeding developed by the Japanese government in 2007 may be assisting this improvement. The new guidelines were distributed to all community health centres, encouraging all health professionals to promote breastfeeding to mothers. Health professionals can have either a positive or negative influence on the mothers’ motivation to continue breastfeeding depending on their own knowledge and attitudes and what they are prepared to promote. A study evaluating breastfeeding textbooks for Japanese midwives found that the only 40% provided accurate and consistent content on infant feeding consistent with best practice [61]. Nurses’ and midwives’ knowledge of breastfeeding would be expected to be mainly acquired from these textbooks. Mizuno et al. also reported that paediatricians (n = 90) were more aware of the importance of breastmilk than obstetricians (n = 62) (66% vs. 13%) and knowledge about the WHO marketing code was at a similar level (51% vs. 18%) [62]. Health professionals need to receive adequate education on breastfeeding knowledge and its benefits. This will enable them to deal with common concerns of mothers and will also protect mothers from confusion resulting from inconsistent information and advice in breastfeeding.

Other factors that affect breastfeeding duration including encouragement from grandmother(s) (especially, the maternal mother), husbands/partners, and other family members and society are important for continuing breastfeeding [63, 64]. However, there have been few studies, particularly of fathers’ support, in relation to breastfeeding duration in Japan, although the support of fathers is acknowledged to be important for mothers to continue breastfeeding in other countries. A study of Japanese husbands that compared them with their Canadian counterparts showed they were significantly less supportive during the postpartum period in terms of giving time for their family [65]. Without such support, some Japanese women felt more isolated, and some did not even expect their husbands to participate in childcare or home duties [65]. In Japanese culture, women have a dominant responsibility for care of children and may explain the apparent lack of interest of Japanese husbands/partners in supporting breastfeeding. The 2008 National Survey on Domestic Care reported that preparing or feeding meals including infant formula to children under one year old was third on the list of supporting tasks undertaken by fathers [66]. Yokoyama and Ooki [67] found that women who had minimal support from their spouses/partners were significantly more likely to choose formula feeding (OR = 1.85, 95% CI = 1.38-2.48), although this study focused on mothers who had twin and multiple births. More research is needed on the extent of the role of fathers in supporting breastfeeding in Japan and how this could be extended. Our findings also show that support from grandmothers of infants may contribute in negative ways in breastfeeding. In other countries, the ‘mother of the mother’ has a positive influence on breastfeeding initiation and its continuation [68]. In Japanese culture, mothers often return to their hometown for their delivery and ask for help from their mothers during antepartum and postpartum periods [69]. When mothers have knowledge about the importance of Exclusive Breastfeeding, their daughters tended to have a longer duration of breastfeeding [68].

There have been a limited number of the studies on breastfeeding factors in Japan, and there are some inconsistent results between studies. Some areas of breastfeeding practices related to breastfeeding duration need to be further studied. For example, breast problems, including nipple trauma and sore nipples, are often given as reasons for discontinuation of breastfeeding by mothers, but there are few reported studies in Japan. There is a need for further cohort studies to resolve these inconsistencies. Most reported Japanese breastfeeding studies are cross-sectional in design with small sample sizes and unclear definitions of breastfeeding. One of the largest studies (n = 46,569) by Kaneko et al. used a cross-sectional design and imprecise definitions [20]. Large cohort studies are required using standard definitions of breastfeeding and including measures of breastfeeding intention, initiation and duration, together with demographic factors, physical factors, psychological factors and other potential confounders.

The available studies of breastfeeding in Japan suggest that some factors related to breastfeeding duration in studies in other countries show inconsistent relationships in Japanese studies. Cultural and physical factors may be involved in breastfeeding practices, but more studies, particularly larger cohort studies, are needed to confirm any association. While Any Breastfeeding rates have improved in the last three decades, the trends in the rate of Exclusive Breastfeeding are less certain due to the use of inconsistent definitions. There is a need to standardise the way Exclusive Breastfeeding is defined in Japan. In order to further improve breastfeeding rates, there is a need for to improve the inconsistent knowledge of health professionals in Japan about infant feeding. In addition, cohort studies with larger representative samples sizes and clear definitions of breastfeeding type are needed to monitor risk factors of breastfeeding outcomes and to provide the basis for promoting breastfeeding. These will enable Japanese mothers, fathers, and health professionals to move towards the internationally recommended target of ‘Exclusive Breastfeeding for the first six months of life’.