Breast feeding and infant mortality

Jean Gelding*, Pauline M. Emmett, Imogen S. Rogers

Unit of Paedintrir and Perinatal Epidemiology, Imtitute of Child Health. Univmvity of Bristol 24 Tyndall Avenue, Bristol BS8 1’TQ, UK

Abstract

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The evidence linking bottle feeding to infant and early childhood mortality has been reviewed. Ecological studies of national time trends in infant mortality do not parallel breast feeding trends in those countries, and indicate that falling death rates are more likely to be

related to better health care facilities and social conditions. Direct studies of deaths provide

some contradictory findings; meta-analyses are not informative because of the many differ- ences in statistical and sample methodology. The methodology exhibited in most studies is more likely to have over- rather than under-estimated a relationship between bottle feeding and infant mortality. Retrospective analyses must take account of changes in feeding pattern due to early signs of illness. Prospective population studies able to account for large numbers of potential confounders provide the best estimates, especially if proportional hazards models are used. Two such studies have been carried out-both showed protective effects of breast

feeding. 0 1997 Elsevier Science Ireland Ltd.

Keywords: Breast feeding; Infant mortality; Bottle feeding; Diarrhcea; Developing countries; Developed countries

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1. Introduction

As this century progressed, in developed countries it was thought that artificial milk feeds would be at least as good for the baby (if not actually better) as breast feeding. This was strongly questioned by the results of a seminal study in the USA of 20 000 infants in Chicago in the 1920s who were followed to nine months of age [ 11. Among 9749 entirely breast-fed (i.e. no other milk feeds) only 15 died (i.e. 0.2%), among 8605 who had breast and other milk, 59 died (i.e. 0.7%) but there were 144 deaths among the 1707 who were wholly artificially-fed (i.e. 8.4%). Subdivision by

*Corresponding author.

0378.3782/97/$17.00 0 1997 Elsevier Science Ireland Ltd. All rights reserved. PI/ SO378-3782197)00060- 1

s144 J. Gold@ et al. I Early Human Development 49 Suppl (1997) S143-S155

cause of death showed a particularly strong relationship with deaths from gastro- enteritis.

This study was, not unnaturally interpreted as showing a strongly beneficial effect of breast feeding, but modern epidemiologists would point to difficulties in accepting a study with no published details of definition of feeding categories, and a failure to explore the factors that might be linked with both a failure to breast feed and increased risk of death (e.g. social deprivation, low birthweight or malformed infant), and which therefore might have explained the relationship.

The current perception is, however, that breast feeding prevents a large number of infant deaths. The figure quoted by UNICEF, for example, is 1.5 million deaths per year [2], although it is not clear how this estimate was made. There have actually been only a small number of studies concerned with infant mortality. Ashworth, when reviewing international differences in infant mortality in 1982 [3], concluded that the main causes were low birth weight and diarrhoeal disease. The pattern of infant mortality differed between countries with low or moderate levels of mortality (mainly developed countries) and those with high levels (mainly developing countries). In high infant mortality areas a much larger proportion of the deaths were due to diarrhoeal and respiratory diseases. These diseases are very often water born; the 1994 Human Development Report published by the United Nations [4] states that “in developing countries in 1990 safe water was available to 85% of urban people but only 62% of rural people”. Since the causes of death differ markedly between the developing and developed countries they have been considered separately below.

2. The developing world

2.1. Indirect evidence

In general, infant mortality rates in the developing world have declined in recent years at the same time as a reduction in breast feeding rates. In 1985, the Rockefeller Foundation sponsored a conference which studied the striking reduction in mortality in Sri Lanka, Costa Rica, China and the Kerala state of India [5]. In each country the mortality had fallen sharply over a relatively short period of time-and the authors identified seven conditions that they thought essential to such improvements: female autonomy; education, particularly of women; accessible health services; efficient operation of health services; minimal standards of nutrition; universal immunisation and establishment of antenatal and obstetric services. In none of the countries studied did the improvements in mortality reflect any change in breast feeding rates [6].

A paper written in 1991 looked at the reasons for the dramatic fall in infant mortality that had occurred in Nicaragua from 1970-1985. In 1970 the mortality rate had been around 130 deaths per 1000 livebirths, whereas by 1985 it was half of that. The authors [7] examined a number of possibilities including income, nutrition, breast feeding practices, maternal education, immunisation, access to health services, provision of water supply, sanitation and anti-malarial programmes. From data available to them, they thought that breast feeding was unlikely to have contributed to

J. Gelding et al. I Early Human Development 49 Suppl (1997) Sld3-S155 s145

the decline since studies in Managua, the capital of Nicaragua, had shown breast feeding rates of 58% for children of six months of age in 1977 compared with only 33% among children aged between three and five months in 1988. Thus the decline in mortality rate had occurred during a time when there appeared to have been a marked reduction in breast feeding rates. The authors decided that improved access to health services was likely to have been the most important factor influencing the fall in mortality rates.

Thus the indirect ecological evidence provides no support for breast feeding changes being of importance in the improving infant mortality rates in some developing countries. That, however, should not be interpreted as meaning that breast feeding is not relevant as a protective factor for infant deaths; to address this, study of deaths themselves need to be undertaken.

2.2. Methodological problems

In regard to assessing the contribution of breast feeding to infant mortality, important methodological points were made in analysing a cohort study which involved over 5000 births in Pelotas, Brazil [8]. Breast feeding status was identified shortly after birth and at later interview. Overall, 92% of the babies were breast-fed initially, 54% were being breast-fed at three months and the proportions at six months, nine months and twelve months were 30%, 20% and 16% respectively. The authors showed that the lower the birthweight the less likely the baby was to be breast-fed. They also showed that in this population the higher the family income the longer the breast feeding was likely to last. They pointed out that if the mortality of non-breast-fed babies is compared with breast-fed babies without taking account of differences in birthweight, an apparently beneficial effect of breast feeding will be over-estimated. From a number of calculations carried out in their paper they have concluded that “if birthweight had not been taken into account, the non-breast-fed babies would have appeared to be at 30% increased risk of death, even if breast feeding had no protective effect”. They calculate that if a study shows that non-breast-fed babies are three times more likely to die in the post-perinatal period than breast-fed babies, after allowing for the effect of birthweight, the relative risk of death that can be ascribed to non-breast feeding is likely to be of the order of 1.32.

2.3. Case-control studies

2.3. I. The Brazilian study A major case-control study was carried out in Brazil [9]. Over a one year period

multiple sources were used to identify deaths of children aged 7-364 days who were resident in the two cities of Pelotas and Port0 Alegre. From all the deaths identified, those associated with an infection or likely to have been associated with an infection were investigated further. The parents were questioned about the signs and symptoms preceding death and the breast feeding history. Deaths of babies weighing under 1500 g were excluded, as were all twins, those who had stayed in hospital for at least fifteen days after birth and those who had major congenital malformations or cerebral

S146 J. Golding et al. I Early Human Development 49 Suppl (1997) S143-S155

palsy. For each case, two controls were selected from the neighbourhood. Detailed histories identified whether breast feeding had stopped just before the terminal illness because of ill-health-such cases were counted as still being breast-fed in the analyses for this study. In all, 357 deaths from infection were compared with 714 controls. At the time of death, 29% of the deaths from diarrhoea were receiving some breast milk, but only 10% of the sample were having exclusive breast milk compared with 35% of the deaths from respiratory infections and 42% of deaths with other infections. This compares with 59% of the control sample. Logistic regression analyses allowed for the infant’s age, birthweight, interval from preceding birth, social status of the head of the household, maternal education, type of water supply, type of housing and family income. Statistical models were built for each of the three different types of death.

In relation to the exclusive breast feeding group, the relative risk of death from diarrhoea if the infant had been fed by breast but with formula feeds as well was 4.5 (95% CI, 1.7-12.4), for breast with cows’ milk the relative risk was 3.4 (95% CI, l.l-10.3), for ‘formula only’ it was 16.3 (95% CI, 6.4-41.3) and for ‘cows’ milk’ only it was 11.6 (95% CI, 4.5-29.8) (P < 0.001). The results presented here had been adjusted for confounders, which resulted in increased relative risks for the ‘formula only’ and ‘cows’ milk only’ groups-before adjustment the relative risks in these two groups were 11.9 and 7.8 respectively [9].

A subsequent analysis [lo] investigated these deaths further, and found that 62% of the diarrhoeal deaths were attributed to persistent diarrhoea rather than acute diarrhoea. The authors showed that up to two-thirds of the persistent diarrhoea and dysentery deaths may have resulted from infections acquired in hospital and that over half of these children had been admitted to and discharged from hospital prior to the final admission which terminated in their death. Although it is likely that such prior hospitalisations were the reason for breast feeding being terminated, no information on this is presented. If these children had been ascribed to the type of feed being given when the children had their first admission, a considerable reduction in the odds ratio (OR) might have been found.

Their analysis for respiratory infection deaths was less dramatic and allowing for confounders changed the relative risks very little [9,11]. Compared to the odds for ‘breast milk only’, that for deaths among infants fed both breast and formula was 2.1 (95% CI, 0.8-6.0), that for infants fed breast milk with cows’ milk was 1.2 (95% CI, 0.4-3.4), for ‘formula only’ it was 3.9 (95% CI, 1.8-8.7) and for ‘cows’ milk only’ it was 3.3 (95% CI, 1.4-7.8) (P < 0.01). Thus, the significant differences were between breast feeding and non-human milk feeding; partial breast feeding was not sig- nificantly different from the wholly breast-fed.

There were only 60 deaths from infections other than diarrhoea and respiratory causes, but these still showed an elevated risk for infants who were exclusively fed either on formula (OR 2.3, 95% CI, 0.5-11.3) or cows’ milk (OR 2.6, 95% CI, 0.9-7.0). The overall result associated with type of feed was significant at the 0.01 level.

The analysis indicated that infants who were fed non-milk supplements (such as mashed fruit and vegetables, soup or porridge) had a reduced overall risk of death,

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but that whatever allowances were made for confounders, there was a very strong relationship between deaths from diarrhoea and lack of breast feeding. The authors report that the protection afforded by breast milk to the diarrhoea related deaths ceased with weaning-in other words there was no long-term protective effect of breast feeding demonstrated in this study. The major problems here lie in the possible confounding effect of earlier hospitalisations and in the relatively small numbers in each group. The authors did not analyse all deaths from infectious disease together, which would have been useful. Nor do they state [9] what proportion of all infant deaths this infectious disease group comprised.

2.3.2. Ghanaian study There has been a more recent case-control study of deaths of children aged from

six months to four years in rural areas of Northern Ghana [ 121. Data on 317 of the 501 deaths in this age range were compared with controls matched for age, sex and locality. Malaria was the commonest cause of death (28%) followed by acute gastro-enteritis (21%) and acute respiratory infection (19%). Conditional logistic regression analysis of all deaths found independent associations with four factors: delivery in the absence of a trained attendant, short inter-birth interval, if the father beat the child’s mother and if the water source was unprotected. There was no significant association with weaning practice.

Further analysis was undertaken for the 57 deaths from acute gastro-enteritis and their matched controls. There was a significant independent association with not having been fed colostrum OR 4.4 (95% CI, 1.4-14.0). No such relationship was apparent for deaths from either malaria or respiratory infection.

This study has the major advantage of having a geographical population sample of deaths (rather than those occurring in hospital) but the disadvantage of data on only 63% of the deaths (although the authors feel that these were representative of all deaths in the area).

2.4. Prospective follow-up studies

2.4. I. Hospital based In Rwanda, a study of 2339 children aged < 2 years, admitted to hospital with

either measles, diarrhoea or acute lower respiratory disease were analysed in terms of their case fatality rate [13]. Children who were being breast-fed on admission were significantly less likely to die. The differences in case fatality rate between the breast-fed and non-breast-fed children was 22% as opposed to 33% for admissions for measles, 6.6% as opposed to 22% for admissions for diarrhoeal disease, and 13% as opposed to 27% for admissions for lower respiratory disease (P < 0.001 in all diseases). The difference in mortality was apparent among measles cases both under one year of age and for those aged between 12 and 24 months.

In response to this study, a critical letter was published in which the authors pointed out that the breast feeding group had been defined as those children breast-fed on the day of admission to hospital [14]. The authors noted that children seriously ill with measles are often unable to, or refuse to, suckle; such children could be

S148 J. Gold@ et al. I Early Human Development 49 Suppl (1997) S143-S155

classified by this definition as non-breast feeders and consequently distort the figures. They reported on their own study in Guinea-Bissau; they had identified 1471 children and their breast feeding history prior to a measles epidemic and showed no beneficial relationship of breast feeding on case fatality rate-indeed in the age group 12-35 months, 32% of the children with measles who had been breast-fed died compared with 26% of those who had not been breast-fed.

2.4.2. Population based A study from Guinea-Bissau [15] followed 734 healthy new-horns in an urban

area of the country for three years; 89 deaths occurred. There was no difference in survival according to the time of onset of breast feeding (those who started breast feeding in the first 24 hours comprised 49% of the population only). The hypothesis had been that colostrum ingestion might have protected against infection and improved survival. No assessment was made of duration of breast feeding on postneonatal mortality, however, and indeed this may have been difficult since breast feeding was almost universal in this population.

A subsequent follow-up [16] of this study which had prospectively collected data on feeding for 691 children throughout the first three years of life analysed features relating to the 48 deaths in the period 12-36 months. Children who were no longer having breast milk were at increased risk OR 2.6 (95% CI, 1.1-6.2) which further increased when allowance was made for maternal education and ethnic group OR 3.5 (95% CI, 1.4-8.3); the raised OR was said to be apparent whether onset of bottle feeding was recent or at least six months previously. Causes of death were said to be similar in breast and non-breast-fed children, but details were not given. The authors note the strength of the association in spite of their finding of relative malnutrition in children in whom breast feeding had been prolonged.

An interesting study was carried out in Bangladesh [ 171. About 5000 children aged 6-36 months were examined every month for six months. For each month of observation the risk of death in the following month was measured against whether the child had been breast-fed in that month, and the mid-upper arm circumference. Logistic regression showed that mid-upper arm circumference and acute respiratory infection, oedema, lack of breast feeding, bloody diarrhoea and chronic diarrhoea were all associated with the risk of death, and that there was a significant interaction between breast feeding and arm circumference, the increased rate of death if the child had a small arm circumference was more pronounced in non-breast-fed than in breast-fed children. Breast feeding, in fact, was associated with a lower risk of death in children with arm circumferences of less than 110 mm, whereas above 110 mm there was a slight excess of deaths in breast-fed children. Nevertheless, the number of deaths in this study (52), were too small for too much in the way of interpretation prior to repetition in another study.

A further analysis of mortality in the Bangladesh study [18] was unable to look at any protective effect of breast feeding during the first year of life, since 98% of the mothers breast-fed until twelve months of age. During the second year of life, however, the mortality among children who had been weaned for more than three months was higher than among those who had been weaned for less than three

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months, this was in turn much higher than in the children who were still being breast-fed. Possible confounders were unlikely to have accounted for this: there was no difference in breast feeding patterns between boys and girls, and breast feeding was continued longer in the poorer rather than the richer families.

In Malaysia, 1262 mothers were interviewed between 1976 and 1977, and a recall history of their 547 1 previous births elicited breast feeding duration and related this to the age at which any deaths had occurred. This study has been analysed by different researchers using entirely different statistical methods. One used a hazards-model analysis [ 191 whereas the other used logistic regression [20]. Both showed the same results-with an apparently protective effect of breast feeding. Among breast-fed infants receiving supplements, the risk was higher than among non-supplemented breast-fed infants, but the risk was still higher for infants who were not being breast-fed at all. The analyses were carried out for the feeding type at the last illness. Breast feeding was shown to be statistically significantly associated with relatively low mortality in the first six months of life though not in the period from seven to twelve months. One analysis showed that the beneficial effect of breast feeding was found only in homes without piped water or sanitation [20].

A study in the Cameroon of infants from birth to two years used a two-state hazards model, and allowed for a large section of demographic, socio-economic and housing characteristics [21]. The authors report that, compared with non-breast-fed infants at any time point, those that were breast-fed were significantly less likely to die subsequently (I’ < 0.01). This was true of both fully breast-fed (Weibull estimate - 0.90, SE 0.14) and partially breast-fed infants (Weibull estimate - 0.75, SE 0.15).

In India, 1000 babies delivered at term in a hospital in Patna were followed up for six months; 500 were breast-fed and 500 were artificially-fed [22]. Follow-up was at monthly intervals. Unfortunately this study suffered from a methodological error since any breast feeding mother who stopped breast feeding was omitted from the study. Numbers in which this occurred were not given. For what it’s worth, the authors found a lower postneonatal death rate among the breast-fed babies in both the low birthweight ( < 2500 g) and higher birthweight groups: they claimed that the differences from the non-breast-fed were significant, but on closer inspection this was not true. Nevertheless when split by cause of death, there were seven diarrhoeal deaths among the breast-fed compared with fifteen among controls; for meningitis the numbers were two breast-fed, six controls.

3, The developed world

The 1946 British national birth survey obtained data on breast feeding at eight weeks of age on over 80% of births in Great Britain in one week of 1946. The subsequent mortality rate, up until two years of life, was analysed according to breast-feeding status 1231. The death rate among those who had not been breast-fed for the first eight weeks was 18.5 per 1000 which was compared with 10.9 per 1000 among those who had been breast-fed for at least the first eight weeks (P < 0.10). Douglas carried out an analysis just for those infants that had weighed between 6.5

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and 9.5 lb at birth and found the death rate among the non-breast-fed was 17.1 compared to 9.5 among the breast-fed (P < 0.10). Therefore the findings were not dependent upon fewer low birthweight babies being breast-fed. In his discussion of the data, Douglas noted that the difference between the groups was due to deaths from gastro-enteritis, not to deaths from pneumonia. It should be noted that formula milks available in 1946 for bottle-feeding were very different from modern formula milks.

Very little information is currently available on breast feeding and post-neonatal mortality apart from information concerned with the sudden infant death syndrome @IDS). Although at one time it was thought that breast feeding protected against SIDS, a review of the available evidence in 1993 [24] showed largely inconsistent data. One of the major problems with analysing data on SIDS in regard to breast feeding lies in the fact that there are strong relationships between SIDS occurrence and maternal smoking. As we have already shown, maternal smoking itself is associated both with the failure to initiate breast feeding and with a shorter duration of breast feeding [25]. Therefore the studies that take no account of maternal smoking are likely to show an erroneous beneficial effect of breast feeding.

Most information relating to SIDS has been derived from case-control studies. The American SIDS study found the proportion of infants to have been breast-fed to have been lower among cases than controls (17% vs. 27% among blacks; 35% vs. 58% among whites), and that the differences remained statistically significant after controlling for maternal age, parity and social class [26]. Nevertheless the biased case ascertainment [27] and the failure to take parental smoking habits into account leave the results questionable.

Similar failure to take account of possible confounders occurred in a number of studies although in all instances the breast feeding rate was lower in cases than controls:

Place

Southern England (discharge after delivery) London/Cambridge (discharge after delivery) Hong Kong Copenhagen (at 2nd week)

Breast feeding of SIDS

53% 74%

0% 80%

Breast feeding of Ref. controls

68% 1281 84% WI 6% DO1

92% [311

The study from Denmark concluded from detailed analysis of feeding type that breast feeding was unlikely to have a causal relationship with SIDS since the age at death distribution of the breast-fed was identical to that of the bottle-fed deaths [31].

Three case control studies have taken account of smoking in their analyses. A study in Avon of 98 SIDS deaths and 196 controls showed that comparing never- breast-fed, with ever-breast-fed the unadjusted OR was 2.3 (95% Cl, 1.3-4.0) which fell to 1.7 (95% Cl, 0.7-3.7) after adjusting for sleeping position, maternal smoking, gestation and employment status of father, but no account was taken of likely social factors such as maternal education which is likely to have reduced it still further [32].

J. Golding et al. / Early Human Development 49 Suppl (1997) Sl43-SIT5

A major case-control study from New Zealand, concerned with SIDS cases dying between 1987 and 1988, identified 83% that had been breast-fed at some stage compared with 92% of controls. The differences were highly statistically significant after allowing for antenatal classes, antenatal care, maternal education, marital status. admission to special care, parity, social class, birthweight, gestation, race, season, maternal age, smoking and sleeping position 1331; the OR for SIDS among infants breast-fed exclusively on discharge from the maternity hospital was 0.52 (95% Cl, 0.35-0.77) in comparison with wholly bottle-fed. In Tasmania, a study of 62 cases with 121 controls showed a significant initial benefit of breast feeding [34], but once maternal smoking had been taken into account there was no remaining association: OR 0.86 (95% CI, 0.39-1.88).

There have been three prospective studies which identified feeding type early in the child’s life and linked this to outcome. The American National Collaborative Perinatal Project followed 50 000 children from birth. Although they found a higher death rate among the bottle-fed babies they felt that this was mainly due to confounding by maternal education and prematurity. They did not allow for smoking [35.1.

Two separate studies came from the Oxford Record Linkage Study, a prospectively ascertained information data base on all births in a large area in the UK. Both studies showed no relationship between breast-feeding status and SIDS once social class. parity, maternal age, and marital status had been taken into account [36,37].

Thus evidence for a protective effect of breast feeding in regard to SIDS is far from convincing. The prospective studies are all negative, and must of their nature be less prone to recall bias than case-control studies. The latter have generally shown a relationship which tends to reduce considerably in magnitude if confounders are taken into account.

4. Discussion

In discussing evidence concerned with infant mortality and breast feeding, Chavez 1381 stated “Industrialised milk per se is not harmful, although it is universally accepted that it is inadequate at least as compared with maternal milk. What encourages high infant mortality rates are the problems of inadequate dilution or preparing the milk with very poor hygienic care. This, of course, contaminates the milk or the bottle. In short, the fundamental problem is one of manner”.

From the available published data, which it must be emphasised is scant, there does appear to be a protective effect of exclusive breast feeding in developing countries which results in reduction of death from gastro-enteritis and possibly also to a less pronounced effect from respiratory and other infections.

It is notable that these findings mirror our conclusions in regard to morbidity-viz. a major and probably causal relationship with diarrhoea and gas&o-enteritis 1393 and a smaller and less convincing association with other infections [40].

The possibility of bias in many of the studies quoted is likely for a number of reasons: inadequate controls, failure to collect appropriately timed data on feeding

s1.52 J. Gelding et al. I Early Human Development 49 Suppl (1997) S143-S155

before the onset of symptoms or inadequate account being taken of the possible confounders [41]. SIDS is, for example, much more likely to occur if the mother is a smoker and, as we have shown, mothers who are already smokers are less likely to either initiate or succeed in prolonged breast feeding. The reasons are likely to be biological. In the developing world maternal smoking in general is not yet a major problem and is unlikely to have been important in the studies of infant mortality quoted here. Nevertheless this does not preclude the possibility that other toxic substances might be being ingested by the mother that are independently associated both with increased risk of mortality in the child and of the mother failing to continue to breast feed. A candidate, for example, would be DDT-it has been shown that this pesticide, still widely used in developing countries, is associated with failure to maintain lactation [42]. Whether it has any relationship with infant mortality is unknown.

Let us assume, however, that the association with artificial feeding is causal and that exclusive breast feeding will prevent deaths from gastro-enteritis. There remains the major question as to the proportion of deaths that might be saved if mothers did not resort to artificial feeding. A study from Lahore 1431 has indicated that among deaths to children aged under two years of age, one third (571158) were attributed to diarrhoea, and a further third (50/ 158) to other infections such as septicaemia, meningitis or respiratory infection, and that the majority of these deaths were in the first six months of life. Given a post-neonatal infant mortality rate of about 90 per 1000, one can make some estimates as to the likely consequences of artificial feeding. (Note that we assume here that neonatal mortality is not influenced by whether or not the child is breast-fed).

Let us arbitrarily assume an OR associated with diarrhoea of 5 and of other infection at 2. The prevalence of exclusive breast feeding at six months in Pakistan is estimated at about 90%. If x, y and z were the death rates in exclusively breast-fed populations, then the deaths in every 1 000 000 children will approximate to:

(5 X 100 000 X xl 1000) + (900 000 X xl 1000) for diarrhoea, (2 X 100 000 X y/1000) + (900 000 X y/1000) for other infection

and 1 000 000 X z/ 1000 for other causes.

Thus the total number of deaths per 1 000 000 births will be:

1400Xx for diarrhoea 1100 xy for other infection 1OOoxz for all other causes

Suppose all three categories have roughly equal numbers of deaths [43]:

z=30perlOOO y = 30/1.1 = 27.3 per 1000 x = 30/1.4 = 21.4 per 1000

This will enable us to estimate the numbers of deaths that would be prevented by exclusive breast feeding according to the prevalence of artificial feeding, whether or

J. Gelding et al. I Early Human Development 49 Suppl (1997) S143-St.55 s15.3

not as supplement to breast milk, in a country where all the above assumptions are true.

Prevalence of artificial No. deaths per feeding at six months 1OOOOOObirths

0 78 700 10% 89 990 20% 101 280 30% 112 570 40% 123 860 50% 135 150 60% 146 440 70% 157 730 80% 169 020 90% 180 310

100% 191 600

Excess no. (%) due to artificial feeding

- 0

I1 290 (13%) 22 580 (22%) 33 870 (30%) 45 160 (36%) 56 450 (41%) 67 740 (46%) 79 030 (50%) 90 320 (53%)

101 610 (56%) 112 900 (59%)

Thus in a country with 90% breast feeding at six months and a post-neonatal death rate of 90 per 1000 children, an estimated 13% of deaths might have been prevented if all mothers had breast-fed fully. The assumptions made in this cannot be justified without further studies of infant mortality in the Third World, mirroring the Brazilian study design [9] but including the following:

(a) Larger number of deaths (b) Details of all deaths from causes other than infection (c) Convincing information on feeding of the child prior to the sequence of episodes which led to the death.

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