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The defecation pattern of healthy term infants up to the age of 3 months
  1. Jolanda den Hertog1,
  2. Ellen van Leengoed1,
  3. Feyona Kolk2,
  4. Leonard van den Broek3,
  5. Esther Kramer1,
  6. Evert-Jan Bakker4,
  7. Esther Bakker-van Gijssel5,
  8. Anneke Bulk6,
  9. Frank Kneepkens7,
  10. Marc A Benninga8
  1. 1Jeugdgezondheidszorg, Stichting Thuiszorg Midden Gelderland, Arnhem, The Netherlands
  2. 2Jeugdgezondheidszorg, GGD Fryslan, Leeuwarden, The Netherlands
  3. 3Jeugdgezondheidszorg, GGD Kennemerland, Hoofddorp, The Netherlands
  4. 4Biometris, Isg Toegepaste Statistiek, University of Wageningen, Wageningen, The Netherlands
  5. 5Siza Dorp Group, Arnhem, The Netherlands
  6. 6Department of Youth Health Care VU University Medical Center, EMGO Institute, Amsterdam,The Netherlands
  7. 7Department of Paediatrics, VU University Medical Center, Amsterdam,The Netherlands
  8. 8Pediatric Gastroenterology, Academic Medical Centre, Amsterdam,The Netherlands
  1. Correspondence to Jolanda den Hertog, Stichting Thuiszorg Midden Gelderland, Jeugdgezondheidszorg, Arnhem, Netherlands; famcdhertog{at}hetnet.nl

Abstract

Background Defecation problems occur frequently in infants. A clearer insight into the normal defecation pattern is required to gain a better understanding of abnormal defecation.

Aim To describe the defecation pattern of healthy infants in The Netherlands.

Methods From a research population of 1175 healthy Dutch infants, 600 infants without any complaints were selected. The parents recorded details of feeding and defecation at the age of 1, 2 and 3 months using a standardised questionnaire and bowel diary.

Results In breastfed infants, average daily defecation frequency decreased significantly during the first 3 months (from 3.65 to 1.88 times per day), whereas no significant changes were observed in infants fed standard formula or mixed feeding. At every age both the average and the range of defecation frequency of breastfed infants were higher than those of infants receiving formula feeding. Breastfed infants had softer faeces than formula-fed infants and the colour more often was yellow. At the age of 3 months, 50% of stools of formula-fed infants were green coloured. There was no significant difference in quantity between the three types of feeding, but there existed a negative correlation between defecation frequency and quantity.

Conclusion This study gives insight into the defecation patterns of the largest cohort of healthy infants published so far. In the first 3 months of life, breastfed infants have more frequent, softer and more yellow-coloured stools than standard formula-fed infants. Green-coloured stools in standard formula-fed infants should be considered normal.

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Introduction

Defecation problems occur frequently in infants. In The Netherlands, the incidence of constipation in infants up to 1 year of age is estimated 40:1000, decreasing to less than 5:1000 after the age of 13 years.1 Since information concerning the normal defecation pattern of young infants is scarce and is lacking altogether in The Netherlands, there is a risk of either underdiagnosis or overdiagnosis of constipation.2 With better knowledge of normal defecation patterns in infants, better understanding of abnormal defecation patterns occurring in defecation disorders is obtained, especially regarding constipation.3 The fact that 98% of Dutch infants visit well-baby clinics provides ideal circumstances to establish the normal variation in defecation pattern of healthy infants. This prospective cohort study investigates defecation patterns (frequency, consistency, quantity and colour) of healthy Dutch infants at the ages of 1, 2 and 3 months in relation to the type of feeding. This report describes the details of 600 healthy breastfed or standard formula-fed infants without defecation problems in order to come to an optimal accuracy in the description of the normal infant defecation pattern.

What is already known on this topic

  • Defecation problems occur frequently in infants.

  • BF infants have higher defecation frequencies than FF infants in the first 3 months.

What this study adds

  • Our study gives insight into the defecation patterns of the largest cohort of healthy infants published so far.

  • The data may serve to distinguish normal from abnormal characteristics in terms of frequency, colour and quantity of stools.

  • The data may help the healthcare professional in the counselling of parents and in the decision to start or withheld treatment.

Methods

In the year 2003, 240 Dutch well-baby clinic doctors, who have visited a yearly, national youth healthcare congress, were invited to participate in a national study focusing on the defecation pattern of infants, with the Dutch acronym LOOZ (Landelijk Onderzoek naar Ontlasting bij Zuigelingen). In total, 124 doctors agreed to participate. Reasons for not participating in this study were not registered. Every participant was assigned a maximum of 15 infants. Infants were eligible for the study when the following criteria were fulfilled: (1) duration of pregnancy ≥37 weeks; (2) weight at birth ≥2500 g; (3) postnatal hospitalisation ≤2 days and (4) no congenital defect, metabolic disturbances, disorder of the gastrointestinal tract or any indication of allergy to cow's milk. At least one of the parents had to be proficient in the Dutch language. After deliberation with the ethical committee, it was decided that no ethical approval was necessary to execute this study. At the first visit to the well-baby clinic, the parents of eligible children received an information letter in which their consent to participate in the study was asked for. In every clinic, the letter was presented to the parents of a series of consecutive infants until the maximum of 15 infants was included. After parental approval, a standardised questionnaire concerning feeding and defecation was completed at every first visit after the infant had reached the ages of 1, 3 and 9 months. In addition, the parents were asked to keep a bowel diary in which they recorded the frequency, consistency, quantity and colour of the stools over 3 consecutive days, using a reference chart (figure 1), at the ages of 1, 2 and 3 months. For the diary, the parents started recording of the bowel pattern on a day with defecation. When the frequency of defecation was less than once every 3 days, the interval up to the next defecation was registered. Similar to studies from Australia4 and Italy,5 we used a standardised bowel diary, which was supported by a reference chart based on the chart used by Weaver et al.6

Figure 1

Reference chart (with permission adapted from Weaver).

Quantity and type of feeding (breastfeeding (BF), formula feeding (FF) or mixed feeding (MF)) were recorded as well. MF indicates every possible combination of breast milk complemented by infant formula.

Statistical analysis

The results were analysed using SPSS (for Windows, versions 12.0 and 16.0). Demographic details of the infants involved and their mothers were compared with those of Statistics Netherlands (Centraal Bureau voor de Statistiek), for the year 2003. Differences for quantitative variables (mother's age, birth weight) were analysed using the one-sample t test, differences for binary variables (sex, BF vs non-BF at the age of 1 month and 3 months) with the binomial test, the remaining category variables (parity, education and country of birth for the mother) with Pearson's χ2-test.

The daily stool frequency was calculated by dividing the number of stools in the 3-day diary by 3. For every type of feeding, the age-related differences in defecation frequency were analysed using the paired samples t test; for every age group, the feeding-type-related differences in defecation frequency were analysed using the two independent samples t test.

The influence of feeding frequency and type of feeding on defecation frequency at the ages of 1 and 3 months was analysed in a linear model without any interaction, with defecation frequency as the independent variable, feeding frequency as a quantitative variable and type of feeding as a qualitative or category variable (in SPSS: general linear model (GLM) – univariate). A frequency table of consistency, colour and quantity was designed per type of feeding and age, based on the number of diapers. Further analysis was necessary because diapers cannot be seen as an independent entity. We decided to interpret the averages of consistency, quantity and colour for every age per infant as numbers between 1 and 4, in line with the numbers on the reference chart (figure 1). The colour variation was also interpreted as an ordinal number, the score being higher with lighter coloured stools. The correlation between the variables defecation frequency, consistency, quantity and colour (all averaged by infant) was also analysed for every type of nutrition and for every age. Statistical significance was defined as p<0.05.

Results

Study population

Between September and mid-November 2003, the 124 well-baby clinic doctors taking part in the study asked the parents of 1598 eligible infants for their consent up to a maximum of 15 infants. The parents of 205 infants (13%) refused participation, the most common reason for refusal being lack of time (n=91). In total, 1393 infants were included in the study. In the course of the study, 158 children dropped out because of issues related to the parents (n=97; 7%: too busy; forgotten or lost the bowel diary; moved or had lost interest), or to the child (n=61; 4%: cow's milk allergy). Sixty parents (4%) returned an incomplete questionnaire or bowel diary. Finally, the results of 1175 infants could be included.

In order to come to optimal accuracy in the description of the normal infant defecation pattern, in total 575 infants (49% of the whole cohort) were excluded from this study. A total of 485 infants were excluded because the symptoms as reported by the parents could be defecation related (pain or crying, anal fissure, bloody stools, unproductive urge, straining, lengthy defecation effort), 182 because they were fed a carob gum containing formula, 43 because of using medication that influenced gastrointestinal motility. Furthermore, 31 infants were excluded because the well-baby clinic doctor diagnosed these infants as constipated. The diagnosis constipation was based on experience of defecation problems in the past and the abnormal defecation pattern at the age of 9 months. The details of the remaining 600 healthy infants without any defecation problems are the subject of the present report. Figure 2 shows the details of refusal and exclusion. Table 1 shows the demographic details of mothers and infants included in the LOOZ-substudy compared with available Dutch data.

Figure 2

Details of refusal and exclusion.

Table 1

Demographic details of mothers and infants included in the LOOZ-substudy compared with available Dutch data

Meconium passage

Details on the first passage of meconium were available in 566 infant. In 534 infants (94.3%), meconium was passed within 24 h after birth and in 30 (5.3%) between 24 and 48 h after birth. In only two infants (0.4%), the first passage was delayed until more than 48 h after birth.

Defecation frequency

As table 2 shows, for all age groups, defecation frequency was significantly higher in the BF as compared with FF infants. MF led to a defecation frequency in between those of BF and FF infants. Despite wide variation, the defecation frequency of BF infants decreased significantly over time, which was in contrast to FF and MF infants. The largest range of defecation frequency was found in BF at the age of 1 month.

Table 2

Feeding frequency, defecation frequency, consistency, quantity and colour per type of nutrition per age group

In a GLM, the influence on defecation frequency of feeding frequency and type of feeding was evaluated in months 1 and 3. In month 1, a significant relation between feeding type and defecation frequency was found (p<0.01), with BF infants having the higher frequency. Type of feeding explained 21% to 24% and feeding frequency 2% to 5% of the variation in defecation frequency. In month 3, only type of feeding remained weakly, but significantly related to defecation frequency (R2 0.06; p<0.05).

Consistency

Stool consistency was significantly softer in BF as compared with FF infants (table 2). In every feeding group, the mean consistency became softer with age, but this was only significant for FF. MF infants had stool consistencies in between BF and FF infants. Hard stools were rare in all feeding groups.

Quantity

There was no significant difference between feeding groups as regards defecation quantity (table 2). BF infants produced significantly more faeces in month 3 as compared with month 1, while the increase in FF children was not significant.

Colour

In the first 3 months of life, yellow-coloured and green-coloured stools dominated irrespective of the type of feeding. BF stools were yellow-coloured significantly more often than FF stools at 1 and 3 months. In the FF group, the percentage of green-coloured stools increased significantly from 1 to 3 months (table 2).

Relation between frequency, consistency, quantity and colour

Table 3 gives an overview of significant correlations between the various aspects of defecation. As could have been expected, a significant negative correlation was found between defecation frequency and quantity of stools, in BF and FF infants, in the first 3 months of life, and in the MF group in the first 2 months of life. A higher number of stools per day results in lesser amounts per defecation. Likewise, a significant positive correlation was seen between consistency and quantity in FF infants at 1 and 3 months, and in BF infants at 3 months. More fluidity of the stools, that is, a higher percentage of water, results in a larger quantity. Finally, a significant positive correlation was found between consistency and colour in BF and MF infants at 1 month and for all feeding groups at 3 months. Increasing fluidity of the stools was also related to more lightly coloured (ie, yellow) stools.

Table 3

Correlations between defecation frequency, consistency, colour and quantity per type of nutrition and age group

Discussion

This is the largest prospective cohort study describing the defecation pattern of young, healthy infants so far. We aimed at obtaining insight into the bowel habits of the healthy Dutch infant population. Although the infants were included consecutively in well-baby clinics scattered all over the country, the study group differed significantly from the Dutch population in several aspects (table 1). These differences are partly interrelated and may be explained because the selection criteria asked for normal pregnancy duration and birth weight, by the requirement that the parents should be proficient in the Dutch language, and because children fed with carob gum containing formula were excluded from the study. As for the relatively high percentage of parents with higher education, we realise that the spreading of participation of well-baby clinics all over The Netherlands had led to under-representation of children from the four largest cities. We suggest that the study duration and the required cooperation might have deterred parents with lower educational levels. Another 393 children were excluded for reasons pertaining to any possible relationship with abnormal defecation patterns, resulting in a ‘normal defecation reference group’ of 600 infants (51.1% of the original study group). Despite the demographic differences between the study group and the Dutch infant population, the defecation patterns we found may be considered representative of those of the Dutch breastfed and standard formula-fed infants without defecation problems.

It is difficult to compare our results with those of previous studies, as study set-up, age categories studied and nutritional habits differ and because of changes in formula ingredients over the past years. There is only a limited number of comparable studies, with group sizes ranging from 117 to 2406 and age ranges between 8 to 28 days7 and 2 to 20 weeks.6 With respect to the first meconium production, 94.3% within 24 h, 99.6% within 48 h, our results do not differ from previously published data.8 ,9 Similarly, our results for defecation frequencies in breastfed children at 1 month of age5 ,6 as well as the large range in frequencies are in line with previous reports4,,6 as was the age-related decrease in defecation frequency.4,,7 We also could confirm that breastfed infants have higher defecation frequencies than formula-fed infants in the first 3 months.4,,6 Yet, the frequencies we found for formula infants (1.48±0.77 at 1 month and 1.37±0.75 at 3 months) are lower than previously published.4,,7

It has been suggested that BF could activate the gastrocolic reflex, which would explain the higher defecation frequencies in breastfed infants.5 Our results, however, do not give much support to this concept, as we found only a very limited effect of the frequency of BF on defecation frequency, an effect that was confined to the first month of life.

The consistency of the faeces was mostly soft or runny, rarely solid or hard. This might partly be explained by the exclusion of all children having symptoms that could be attributed to constipation. On the other hand, most present-day Dutch formulas contain prebiotic oligosaccharides, which have been shown to result in softer stools10 ,11 without changing defecation frequency.12 We found a significant positive correlation between consistency and quantity of stools and a significant negative correlation between defecation frequency and quantity of stools in FF infants. This could explain why in our study the mean defecation frequency in formula-fed infants was lower than those published in 19886 and 1989.5

Although it is not connected to the health status of the infants, stool colour often is the subject of major parental concern. Like Weaver et al,6 we found BF children to have predominantly yellow-coloured stools, while yellow and green are customary colours, even with FF.

Although the same technique was used to assess stool quantity, we could not obtain similar results as Weaver et al.6 We found no significant differences in stool quantity between the three nutrition groups. A possible reason is the difference in diaper properties between the two studies, present-day diapers having greater water-absorbing capacities, which may hinder the adequate estimation of diaper contents.

We aimed at the assessment of defecation properties of healthy, term infants. By rather liberally excluding children with symptoms that could be related to stooling difficulties, however, we may have created a group wherein healthy children with hard stools are underrepresented. We hope to address this point in the future, when stooling characteristics of the whole study group, including the infants excluded because of symptoms or the use of special formulas, will be analysed further. Another possible bias of our study is caused by the way diapers were scored. Consistency, colour and quantity were scored per diaper and all calculations are based on the number of diapers per feeding group, which may result in overrepresentation of the data of children with high defecation frequencies. In conclusion, our study presents the defecation characteristics of breastfed or standard formula-fed healthy term Dutch infants without any defecation problems. The data may serve to distinguish normal from abnormal characteristics in terms of frequency, colour and quantity of stools and may help the healthcare professional in the counselling of parents who are uncertain of the stools of their young infant and in the decision to start or withheld treatment.

References

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Footnotes

  • Funding Friso Kindervoeding (Friesland Campina), The Netherlands.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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