Background

The objective of this study was to determine the relationship between Exclusive Breastfeeding (EBF) duration and future height. Exclusive breastfeeding (EBF) is defined as feeding a child only breast milk, with no supplemental solid foods [1]. The study sought to determine the prevalence of EBF for specific durations (a: ≤ 6 months; b: 6-12 months; and c: ≥ 12 months) and the relationship between the duration of EBF and child height at ages 4-6. We hypothesized that children who were exclusively breastfed for more than 6 months would be taller than children who were breastfed for less time.

Breastfeeding, specifically EBF, has many positive effects, including protecting the child against respiratory infections [2], allergies [3], asthma [4], and diarrheal diseases [5], as well as promotion of brain development and higher IQs [6]. Early skin-to-skin contact through breastfeeding has been shown to promote bonding between mother and child, which has led to better clinical outcomes in infants [7].

Reducing the burden of infections and diarrheal diseases is especially important as developing countries work towards the Millennium Development Goals (MDGs) for 2015. MDG #4 targets the reduction of mortality for children under age five [8]. Currently, 19.4 of 1000 Ecuadorian children die before reaching age five [9], which is under the MDG of fewer than 23 deaths per 1000 for Latin America & the Caribbean [8], but still demonstrates room for improvement. EBF is protectant against pneumonia and diarrheal diseases, which account for 28% of child deaths under age five worldwide [8].

The World Health Organization (WHO) recommends that children be exclusively breastfed for at least 6 months, and recommends that governments adopt national policies concerning breastfeeding duration [10]. EBF of at least 6 months was linked to attaining maximal growth in children [11]. Furthermore, a neonate’s immune system does not develop the ability to produce certain antibodies until 6 months after birth, and so the newborn must rely on antibodies received via breast milk for immunity [12-14]. In many places, including both developed and developing countries, children are exclusively breastfed for less than the recommended 6 months [15] and these children may suffer from more frequent infections [15], a higher incidence of obesity, and a higher risk of hypertension [16].

Many countries in South America have a history of low prevalence for EBF over 6 months [17]. In Ecuador, only 40% of women are estimated to breastfeed for at least 6 months [18]. Certain regions of Ecuador showed a decline in “milk sufficiency” in 1999, following their economic crisis, and this insufficiency led to early weaning and EBF for less than the WHO recommendations [19]. The rates and duration of breastfeeding in San Pablo, a fishing village of approximately 7000 people on the coast of Ecuador, were unknown previous to this study.

Methods

Subjects

This cross-sectional study of first grade children took place at the three elementary schools in San Pablo, Ecuador. The vast majority of San Pablo children, regardless of socioeconomic status, attend school at one of three free elementary schools: Escuela Fiscal Mixta #7 Dr. Carlos Puig Vilazar, Centro de Educacion General, or Mixta Municipal Enrique Candell.

For inclusion in the study, students had to be enrolled in one of the three schools in año basico (the first grade of primary school). Children were excluded from the study if they were not in attendance at school for greater than one week or did not have a living mother to answer the survey. One hundred forty-eight subjects were included, but 25 students (16.9%) were lost to follow up.

Each student was given a short survey to give to his/her mother. The survey asked mothers how long they exclusively breastfed their children and consisted of socioeconomic data and other potential confounders. If the child did not return the survey, a second copy of the survey was sent home with the child within one week.

All research was performed with the approval of The Pennsylvania State University Institutional Review Board for research on human subjects. Approval of the Comite Bioetica de la Universidad Catolica en Guayaquil, Ecuador (Ecuadorian ethics committee) was also obtained. Informed consent was obtained prior to enrollment in this study.

Statistics

GraphPad Prism 5.0 was used for analysis with Fisher’s exact test to determine if heights from children who were EBF for less than or equal to 6 months were significantly different than those who were EBF for 6-12 months or 12 months or longer. Confounding data was analyzed using a Fisher’s exact test CI of 95%, chi-squared test, or Kruskal Wallis test. The comparison of risk factors for stunting was done using Kruskal Wallis tests and chi-squared tests.

Results

The population sample was divided by duration of EBF (a: ≤ 6 months; b: 6-12 months; and c: ≥ 12 months) as seen in Figure 1. The study revealed that 8.1% of women performed EBF for ≤ 6 months, 24.4% between 6-12 months, and 67.5% for ≥ 12 months. There was no difference between the three groups in maternal age (Kruskal Wallis test p=0.6201), number of participants making less than $150 a month (Fisher’s exact test p=0.8528), number of participants with only primary school educations (Fisher’s exact test p=0.8196), or median number of children in the participant’s family (Kruskal Wallis test p=0.6560). None of the women smoked cigarettes during pregnancy; one participant drank alcohol during her pregnancy. There was no difference in alcohol (Fisher’s exact test p=1.0000) or caffeine (Fisher’s exact test p=0.2976) use during pregnancy between the three groups. These variables were examined because they are potential confounders since use of cigarettes or alcohol can lead to decreases in birth weight and an increase in stunting.

Fig. 1: Description of Study Population

An objective of this study was to determine if the duration of EBF impacted future child height as measured at ages 4-6. In order to compare children of different ages, their heights were converted to percentiles as compared to children worldwide in the WHO Child Growth Standards. The WHO defines stunting as any height less than 2SDs from the mean of WHO Child Growth Standards. Figure 2 summarizes the population of children in terms of height percentile as related to the duration of EBF. As seen in Figure 3, 30.0% of children whose time of EBF was less than or equal to 6 months were stunted; 23.3% for between 6-12 months were stunted; 27.7% for 12 months or longer. The study found that stunting did not correlate to the duration of breastfeeding (Fisher’s exact test p=0.9484).

Fig. 2: Height Percentile by EBF in Months

Fig. 3: Breastfeeding Duration and Stunting at Ages 4-6

Furthermore, as seen in Figure 4, stunted children and non-stunted children did not differ in potential confounders such as maternal age, maternal education, socioeconomic status, or caffeine use during pregnancy. However, the number of children in the family was higher for stunted children than non-stunted (Kruskal Wallis test p=0.0139), which could mean that children in larger families were more likely to be stunted, probably due to economic constraints that lead to food scarcity. The overall prevalence of stunting in children in their first year of elementary school in San Pablo was 26.8%. The prevalence of stunting in ages 0-5 in other coastal communities was 20.7% in 2004 [20].

Fig. 4: Stunted Children in San Pablo, Ecuador

Discussion

In this cross-sectional study in San Pablo, Ecuador (a coastal town in the Santa Elena province), 148 mothers of first graders were surveyed about their pregnancy and breastfeeding habits. Their children’s heights were measured in the three local schools.

Most previous research indicates that mothers in Ecuador do not exclusively breastfeed their children in accordance with the WHO’s recommendation of 6 months [15, 21]. Contrary to this finding, this study discovered that only 8.1% of women who were surveyed performed EBF for less than or equal to 6 months; 24.4% of mothers performed EBF for between 6-12 months, and 67.5% for 12 months or longer. Although the WHO recommends that women EBF their children for 6 months, there has been evidence that breastfeeding alone may not adequately cover the energy requirements for a 6-month-old baby [21]. If this is indeed the case, it is very likely that EBF for 12 months or longer does not provide enough calories for growing babies in San Pablo, Ecuador.

Furthermore, this study examined potential risk factors that could lead to early cessation of EBF. Figure 1 indicates that maternal age, socioeconomic status, maternal education, and the number of children in a family did not influence early cessation of EBF (as defined as≤ 6 months). Often, childhood stunting is heavily influenced by socioeconomic status. However, this study shows that there are instances when stunting occurs regardless of family income. Communities with short average durations of EBF should look at other factors for causation.

One of the main objectives of this study was to determine if the duration of EBF impacted child height, as measured by height percentile. Stunting is defined as being any height less than 2 standard deviations below the mean height of the WHO Child Growth Standards. This study revealed that stunted children made up 30% of those exclusively breastfed for less than or equal to 6 months, 23.3% of the children exclusively breastfed for between 6-12 months, and 27.7% of the children exclusively breastfed for 12 months or longer. Stunting did not correlate to the duration of breastfeeding (Fisher’s exact test p=0.9484). This may dispute the idea that stunting occurs most readily in the first 6-18 months [21].

A study in 2004 determined that the prevalence of stunting in coastal communities in Ecuador was 20.7% for ages 0-5 [20]. The stunting prevalence in San Pablo was 26.8%, showing that the children are stunted in San Pablo compared to similar townships along the coast of Ecuador. This is an important finding, since WHO defines stunting as 2SDs from the mean as taken from world data. This data does not necessarily represent the distribution of Ecuadorians, who are on average shorter than people in many other countries. However, by comparing the prevalence of stunting against the average coastal community of Ecuador, we can see that San Pablo has a high prevalence of stunting.

Other factors that may cause stunting include smoking cigarettes or drinking alcohol/caffeine while pregnant. No mother admitted to cigarettes use in her pregnancy, although one drank alcohol. Over half (59.3%) of mothers admitted to drinking caffeine during pregnancy, but it did not correlate with stunting (chi-squared test p=0.4032).

Conclusions

Children in San Pablo have a higher prevalence of stunting than children in many other coastal communities in Ecuador. This stunting persists despite adequate duration of EBF by almost all mothers in the community. Communities in developing countries with a similar set of circumstances should look next to milk delivery and quality. Although women are breastfeeding for long enough in San Pablo, their milk may be poor quality or their technique may not be ensuring maximum feeding. Therefore, it is possible that, even though women are performing EBF for longer than 6 months, babies are not fulfilling their caloric and nutrition needs. Stunting normally occurs due to malnutrition from 6 to 18 months [21], so future investigations should target mothers who have children between these ages.

In the population surveyed, EBF does not correlate with taller children at ages 4-6. This study showed an Ecuadorian community that values breastfeeding as an inherent part of its culture. This may be because of the expense of formula and the relative poverty of people in San Pablo compared to those in other areas of Ecuador. Almost all the mothers surveyed exclusively breastfed for at least 6 months as recommended by WHO; in fact, most mothers breastfed for over 1 year. There was no problem with truncated breastfeeding in San Pablo, Ecuador, but there may indeed be a problem with delayed introduction of complementary foods. In accordance with the World Bank’s nutritional recommendations, we urge local clinics to encourage women to begin complementing breastfeeding with some solid foods starting at 6 months [22]. We recommend future studies focusing on caloric intake between months 6-18 to determine the cause of stunting in San Pablo, Ecuador. Other possible causes also deserve exploration.