Anemia and birthweight



Taqueco T UchimuraI; Sophia C SzarfarcII; Maria R D de O LatorreIII; Nelson S UchimuraIV; Sonia Buongermino de SouzaII

IDepartamento de Enfermagem da Universidade Estadual de Maringá. Maringá, PR, Brasil
IIDepartamento de Nutrição da Faculdade de Saúde Pública da Universidade de São Paulo. São Paulo, SP, Brasil
IIIDepartamento de Epidemiologia da Faculdade de Saúde Pública da Universidade de São Paulo. São Paulo, SP, Brasil
IVDepartamento de Medicina da Universidade Estadual de Maringá. Maringá, PR, Brasil





OBJECTIVES: To verify the influence of Low Birthweight (LBW) on child anemia and malnutrition during the first year of life.
METHODS: Sample population included all children under one year seen at Health Units of the municipality of Maringá, southern Brazil, in 1998. Total sample size was 587 children. LBW was defined as birthweight below 2,500 g. The analysis of growth for the weigh-for-age and height-for-age indicators was based on NationalCenter for HealthSstatiscs standards. For anemia diagnosis, a biochemical hemoglobin concentration dosage, using HemoCue direct colorimetric method was employed. Children with [Hb] <11,0 g/dL were considered as anemic.
RESULTS: Fifty-eight percent of the studied population were anemic, and 37 children (6.3%) presented LBW. Anemia was more prevalent during the second semester of life (p=0.0093). Undernutrition, as indicated by the height-for-age indicator, was high especially for children aged 0-3 months with LBW.
CONCLUSIONS: Although LBW rates among the studied population were similar to those of developed countries, we suggest the implementation of specific antenatal care for high-risk women, aiming at reducing LBW, an event that affects the child, hampering its growth and increasing the risk of anemia and its countless deleterious consequences.

Keywords: Anemia. Infant, low birth weight. Protein-energy malnutrition. Growth. Height weight.




The World Health Organization (OMS,10 1993) classifies as of Low Birthweight (LBW) newborns weighing under 2,500 g. This is a major factor for predicting infant survival (Puffer & Serrano,12 1988). The deleterious consequences of LBW for infant survival have been exhaustively described. If minimizing the risk of LBW is the responsibility of antenatal care, it is up to well-baby care to give LBW children special attention so as to promote their complete recovery, leveling them with term infants of adequate birthweight.

Growth is a process subject to rapid alteration during infancy, and is affected by several factors such as gender, length at birth, and genetic potential. Growth evaluation is used for the definition of health and nutritional status because health disturbances, regardless of their etiology, invariably affect child growth (Onis and Habitch,11 1996).

Along with malnutrition, anemia as well affects the nutritional status of the child (the term ‘anemia’ here refers to iron-deficiency anemia). Iron deficiency has deleterious consequences on health, reducing physical capacity, and having a negative influence on the ability to work, both at individual and community levels.

Iron deficiency during pregnancy promotes reductions in iron supplies, causing anemia to develop in the child (Ionemoto & Petlik4 1992). According to Lonnerdal and Dewey6 (1996), babies up to age four months have a high concentration of circulating hemoglobin, iron being obtained through the destruction of erythrocytes and reused for the synthesis of new hemoglobin, thus reducing the need for exogenous iron. In addition, up to this stage, children have a sizeable iron reserve in the liver. According to estimates, 25% to 30% of world population is iron-deficient, high prevalences being observed among infants and pre-school children. It is as high as 70% among children under age 12 months. Brunken1 (1999), in a study carried out in the city of São Paulo, reports an increase in this prevalence, especially among children. Between ages 12 and 24 months, there is a reduction of the prevalence of anemia due to reductions in growth rate (Olivares et al,8 1999).

Iron-deficiency anemia diagnoses based on hemoglobin concentration levels, even without any additional biochemical exams, are considered to be adequate for populations in which iron deficiency is highly prevalent. In light of what has been said, and of the different factors influencing the child’s nutritional status, the present study is aimed at identifying the prevalence of anemia and the nutritional status of children during their first year, considering birthweight.



The cross-sectional study was conducted in the municipality of Maringá, Paraná State. Data were collected at Health Units of the Secretariat of Health, which are distributed throughout the entire municipality so as to facilitate access to health services by the population. Activities developed at these facilities include physician, nurse, and dentist appointments directed towards children, pregnant women, and adults.

Studied population comprised all single-born children under one year seen at these facilities during a five-workday period. Data collection was carried out between March and July 1998, and led to a total sample of 587 children.

Interviews with the mothers who accompanied their were conducted by trained interviewers. In case a child showed up to an appointment without its mother, the latter’s presence was requested by means of an invitation letter.

Growth was evaluated in the sample population according to the National Center for Health Statistics (NCHS)7 standards, as recommended by WHO18 (1995). Indexes used were height-for-age (H/A) and weight-for-age (W/A). Child nutritional status was classified using the Z-score classification system. A Z-score represents the number of standard deviations above or below the reference median value correspondent to the studied child’s weight or height. A Z-score of –2 was established as the most adequate threshold for determining protein-energy malnutrition (WHO,18 1995).

Children were divided according to birthweight into: LBW (low birthweight, <2,500 g); INW (insufficient weight, 2,500 – 2,999 g); ADW (adequate weight, >3,000 g); and IUGR (Intra-Uterine Growth Retardation). Seven mothers (1.19%) were not able to recall their babies’ length at birth.

For the diagnosis of anemia, a biochemical hemoglobin concentration dosage [Hb] was employed. Critical values established were 11,0 g/dL for children and 11,9 g/dl for mothers (OMS,9 1975). [Hb] was measured using a HemoCue portable hemoglobinometer.

A comparison was made between observed [Hb] and estimated [Hb] in order to verify the influence of growth on hemoglobin concentration. Such an influence can be analyzed through theoretical calculations of hemoglobin concentration considering the amount of iron provided by feeding in relation to the endogenous amount existent at birth.

A database was built using Dbase III software including all coded variables. The data were analyzed with Epi-Info software. In order to analyze the relationship between studied variables and LBW, chi-squared association tests with Yates correction, Mantel-Haenzel adjusted analysis, and Pearson correlation for linear trend measurements between quantitative variables were performed. The 5% significance level was used for all the analyses.



The study included 587 children under one year who attended health facilities in the city of Maringá, of which 315 (53.6%) were male. The prevalence of anemia among these children was 58%. Concerning age, anemia was more prevalent during the second semester of life, this difference being statistically significant (p=0.0093) (Table 1). Four blood tests (0.68%) were excluded from the sample.

In this study, however, we observed that, in spite of the weight gain among adolescents being smaller, and the respective reductions after labor greater, no relationship was observed between the child and maternal anemia. Of all mothers studied, 87 (14.6%) were considered as anemic; there was no association, however, between maternal anemia and LBW (p=0.6042) (Table 2).

Mean hemoglobin concentration for the groups studied was 9.7 g/dL for LBW children, 10.6 g/dL for insufficient weight children, and 10.6 g/dL for children born with adequate weight. The concentration observed for the whole study was 11.0 g/dL. This is due to the estimated [Hb] for babies up to age four months being higher than the observed [Hb]. In all three studied groups there was a low correlation between these variables, in opposition to what is generally reported in the literature.

The evaluation of the children’s nutritional status was differentiated. Groups were analyzed according to birthweight, and height for age (H/A) and weight for age (W/A) indicators. Anthropometrical analysis was used to obtain the malnutrition prevalence according to the child’s nutritional index and current age. For children aged 0-3 months, the H/A index was 14.8% (Table 3).

Among the entire study population, 2.9% were undernourished according to the W/A index; 3.3% according to the Weight/Height index; and 10.9% according to the H/A index (Table 4).

An analysis of the LBW children group showed that the H/A index for both preterm and IUGR children was high, 52.9% and 30.0%, respectively. Among preterm children, 25.0% were undernourished according to the W/I index, and 5.0% to the weight/height index. Similar results were found by Victora et al17 (1989), with the exception of the weight/height numbers (Tabela 5).



In population-based studies, LBW and anemia are always correlated, for birthweight is a very important factor in the determination of anemia and, when growth happens at too fast a pace, anemia develops. Along with malnutrition, anemia is a deficiency of extreme importance during pregnancy, due to its high prevalence and, especially, due to the harmful effects to which it is associated.

In the present study we were able to verify the importance of birthweight for the child’s nutritional status, confirming its position as a fundamental condition for the child’s survival during its first year.

It is important to note that there are no standardized values for the identification of anemia during the first semester of life. Values usually employed refer to selected children, whose diet, most of the time, includes iron-enriched food, a nutritional practice uncommon among children seen at public health facilities. Thus we adopted the 11.0 g/dl threshold for children aged 0-6 months as well.

A study of the evolution of hemoglobin concentration for both mothers and children shows that the former recover from pregnancy and puerperium quite rapidly. The average [Hb] of mothers two months after delivery is similar to that of non-pregnant women. On the other hand, the 338 children (58.0%) diagnosed as anemic had a 3.03 odds ratio (p=0.0170) of LBW, which suggests that children born weighing under 2,500 g are three times more likely to be anemic than those weighing more than 2,500 g.

There is a large number of questions concerning the readiness of adolescents and the nutritional competition between them and their unborn children. This condition may lead to negative results for the child, including preterm birth or intra-uterine growth retardation and such children would suffer not only from alterations in growth, but in development as well. It should be added that the children of teenage mothers may be at greater risk of developing anemia and other problems for the same reasons (Silva et al,15 1992).

The amount of iron accumulated by the fetus during intrauterine life is proportional to the amount of weight it gains. Thus the lower the birthweight, the lower the amount of organic iron. This is confirmed in the present study: among LBW children, 29 (78.4%) were anemic, and in the specific case of IUGR children, 76.5% suffered from the same deficiency.

According to DeMayer et al3 (1989), during its first semester the infant uses up the iron reserves accumulated during intrauterine life in order to satisfy its needs. Due to the infant’s rapid growth rate during its first year, these reserves are already exhausted by age four months. This reduction reported at age two months was observed in the present study. Furthermore, at age four months, when iron reserves are already exhausted, its reposition was found to be adequate, for breast milk, despite its being a poor source of iron, has a high level of bioavailability, thus being the most adequate source of nutrition for the child at this age.

Several studies were conducted in developed countries, none of which reported any significant effects on hematological status or iron ingestion, adjusted for age and birthweight. There were also no references of this effect on preterm birth and IUGR (Hingson et al,5 1982).

Often associated to growth, the early introduction of diets based on vegetables, cereals and cow’s milk, aimed at terminating breastfeeding, may lead to the development of anemia around the sixth month of life, since this type of milk, more than just being a poor source of iron, actually inhibits the absorption of this mineral (Dallman & Reeves,2 1984). With this in mind, a theoretical calculation of hemoglobin concentration (estimated hemoglobin) was carried out based on birthweight and weight at the time the data was collected in order to verify the influence of growth on hemoglobin concentration, as in the study by Sichieri14 (1987).

Considering that during intrauterine life the fetus accumulates an amount of iron proportional to the amount of weight gained, an analysis was carried out of the correlation between observed and estimated hemoglobin levels for the children grouped according to birthweight, as an attempt to verify if this correlation is maintained throughout the child’s first year. We found that, from age four months on, observed hemoglobin concentrations were higher than those estimated, possibly due to the ingestion of exogenous iron available in the food given for breastfeeding termination purposes. Still, the [Hb] values observed are inferior to those proposed by WHO9 (OMS, 1975).

Although there was no correlation between estimated and observed hemoglobin concentrations, anemia is known to be associated to the child’s weight, and the study of the etiology of the former during the first year of life is of great importance due to the high prevalences of this deficiency during the child’s first two years. Anemia among mothers may be associated to malnutrition, and if an insufficient caloriy ingestion is the real cause of IUGR, failing to control it may produce an association between anemia and IUGR. Anemia, however, is merely a sign of the mother’s poor nutritional status, and not the real causal determinant of IUGR. Hence, if anemia has no independent effect on intrauterine growth, the routine use of iron supplements during pregnancy may produce no impact on the rate of IUGR. Sinisterra et al16 (1991), in a study conducted in the city of São Paulo, Brazil, found, among pregnant women in the final stage of gestation, a 29.2% prevalence of anemia and a 17.2% prevalence of malnutrition, with no association verified between the two.

Despite the erythropoiesis verified during gestation, hemoglobin concentration fails progressively until approximately the 32nd week of pregnancy, in spite of great increases in plasmatic volume being observed. Anemia, if severe, can impair the liberation of oxygen to the fetus, thus interfering with normal intrauterine growth and the duration of pregnancy. Iron deficiency, regardless of the presence of anemia, may affect important enzymes, especially cytochromes, thus leading to negative pregnancy outcomes.

It must be noted that LBW children tend to perpetuate some of the event’s determinants, such as low stature. Among the factors that interfere with the quality of pregnancy and, consequently, with birthweight, nutritional deficiency is one of the most important. It is a general rule that the weight of LBW babies, with a few exceptions, remains below average, regardless of their age (Rodrigues et al,13 1995).

In this context, long-term damages to health are not always evident, as is the case with anemia. It is thus necessary to investigate the type of food being used for the termination of breastfeeding, and the risk factors leading to the birth of LBW children by means of population-based studies with different methodological approaches. The analyses of the various risk factors must take into account the type of population, and the kinds of food available to them.

Therefore, a study of high-risk pregnant women may be helpful, mostly for the reduction of LBW rates, which will relieve the child from future suffering due to preterm birth.

Average weight gain among LBW children is currently always below that of normal children during the first year of life. This is indicative of the child’s difficulty to recover, despite its growth evolution profile being similar, as we have previously inferred, to that of the population as a whole.

Height-for-age and weight-for-age values were not considered, for 2.5% of any healthy population would be considered as being undernourished by these standards.

The 14.8% malnutrition prevalence found among children aged 0-3 months is worrisome, for it suggests that such malnutrition may be the result of intrauterine malnutrition. Milk-based feeding has a limited effect, which explains the prevalence of chronic over acute malnutrition. However, the increase in the prevalence of malnutrition observed among children during the second semester of life – 10% for children aged 7-9 months and 11,2% for those aged 10 months or above – draws attention to the need for continued special care in dealing with nutrition for all children.

Our results show that LBW children have greater malnutrition percentages according to both height-for-age (41.7%) and weight-for-age (11.1%) indexes, since the child’s size is a result of the weight with which it was born. Such a result demonstrates that the LBW children were not able to attain adequate weight.

In the Maringá study, smaller percentages for preterm children make sense in biological terms. Preterm children are born with low weight due to early birth, whereas IUGR children were already suffering from inadequate growth. However, the percentages found among preterm children, in spite of their being smaller than those of the other group, suggest that the food received is not sufficient for an adequate weight gain. Iron deficiency control through health promotion, aiming at identifying and preventing risk factors, promotes protective measures for the prevention of anemia and its consequences. Specific preventive interventions such as food enrichment and iron-supplement prescription for both children and pregnant women, and general interventions such as health education must be implemented in order to control iron deficiency. The late detection of anemia and the cost involved in its diagnosis and treatment render anemia treatment expensive, even when compared to other measures of greater start-up cost, such as food enrichment.



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Correspondence to
Taqueco T. Uchimura
Rua Arthur Thomas, 23 apto 901
87013-250 Maringá, PR, Brasil
E-mail: Taqueco@aol.com

Received on 16/7/2001.
Reviewed on 10/3/2003.
Approved on 7/4/2003.



*Part of thesis presented to the Faculdade de Saúde Pública da Universidade de São Paulo, 2000.

Faculdade de Saúde Pública da Universidade de São Paulo São Paulo - SP - Brazil
E-mail: revsp@org.usp.br