Abstract
Objectives
Recognizing bowel dysfunction and toilet training issues can be challenging due to conflicting information about what is normal. This study aims to provide an overview of toilet training practices and bowel habits in healthy children up to 4 years.
Methods
This study among 6850 parent–child pairs was part of the Generation R Study—a population‐based prospective cohort study—and used questionnaires regarding toilet training and bowel habits. Logistic regression was used to analyze associations of demographic factors with toilet training start and completion, presented as odds ratios [95% confidence interval].
Results
At 24 months, 60.1% of children had started toilet training, and at 36 months, 60.0% had completed it. Sex, maternal education level, and the child's ethnic background were associated with having started toilet training by 24 months (girls: 1.48 [1.31–1.67], high compared to low educational level: 0.65 [0.47–0.91], and Turkish, Surinamese, Antillean, and other (outside Europe), compared to Dutch: 1.71 [1.26–2.32], 1.73 [1.29–2.31], 3.79 [2.04–7.05], and 1.53 [1.23–1.91], respectively). Only sex and ethnic background showed associations with having completed toilet training by 36 months. Reported defecation frequency varied widely in early life but stabilized to 1–2 times daily for 81.3% of children by 24 months. Infrequent bowel movements and predominantly hard feces were present in up to 6.3% and 14.3%, respectively.
Conclusion
This study demonstrates that 60% of children are toilet‐trained by 36 months. Additionally, it provides insights into healthy children's bowel habits and toilet training milestones, highlighting variations by sex, socioeconomic status, and ethnicity, which can help identify abnormal patterns.
Keywords: bowel control, constipation, continence, developmental milestones, laxative
What is Known
Most studies on toilet training in healthy children are based on data from 25 to 70 years ago.
The age for starting toilet training has increased over decades.
What is New
By 24 months, 60.1% of children had started toilet training. At 36 months, 60.0% had completed it.
Sex, maternal education level, and the child's ethnic background were associated with having started toilet training by 24 months. Sex and ethnic background also showed associations with having completed toilet training by 36 months.
In children aged 2–48 months, most had a reported frequency of one to two bowel movements per day.
1. INTRODUCTION
Toilet training is one of the milestones in a child's life. While most children eventually become toilet‐trained, children with disorders, such as colorectal conditions or developmental delay, may encounter challenges. As bowel dysfunction and incontinence impact the quality of life, it is essential to identify issues early and initiate support and treatment. 1 However, conflicting information about normal bowel habits and the appropriate age for starting and completing toilet training complicates establishing adequate bowel management and toilet training goals.
Previous studies on toilet training in healthy children are based on data from 25 to 70 years ago. 2 , 3 , 4 , 5 , 6 , 7 Since then, there have been many developments regarding the timing and methods of toilet training. It has become more child‐focused, with multiple developmental milestones identified to indicate toilet training readiness, such as the ability to complete tasks independently and understand and follow instructions. 8 , 9 , 10 , 11 , 12 Additionally, children complete toilet training later in life from generation to generation. 13 , 14 As toilet training norms evolve, it is essential to monitor their impact on bowel habits, as variations in toilet training practices may influence rates of constipation. 15 However, definitions of normal bowel function vary, with differing findings on age‐related daily bowel movement frequency. 16 , 17 , 18 Therefore, a concise reference framework that accurately reflects the normal toilet training process and normal bowel habits for different developmental stages is needed.
This study aims to describe toilet training practices and bowel habits in children up to 4 years old within the general healthy population. Insights from this study will help guide parents and healthcare providers in addressing bowel dysfunction and challenges during the toilet training process.
2. METHODS
2.1. Ethics statement
The study was approved by the Medical Ethical Committee of the Erasmus Medical Center, and written informed consent was obtained for all participants.
2.2. Study design
Data from the Generation R Study, a population‐based prospective cohort study conducted in Rotterdam, the Netherlands, following individuals born between April 2002 and January 2006 from fetal life onwards, were used. 19 In total, 7295 parent–child pairs participated in the preschool follow‐up phase. Children born prematurely (gestational age <37 weeks), with conditions associated with developmental delay, or with gastrointestinal conditions that could influence toilet training or bowel habits (e.g., celiac disease, Hirschsprung's disease, anorectal malformation, congenital diaphragmatic hernia) were excluded, leaving a total of 6850 parent–child pairs eligible for inclusion (Figure 1). Parents received six questionnaires about toilet training and bowel habits. Toilet training questions were asked at 24 and 36 months, and bowel habits questions were asked at 2, 6, 12, 24, 36, and 48 months (Figure S1). Questionnaires completed after the interval's midpoint to the next scheduled questionnaire were excluded (Figure 1).
Figure 1.
Flowchart of patient inclusion and questionnaire completion. The ages represent the mean age at which the questionnaires were completed with their standard deviation. The age range shows the youngest child who completed the questionnaire on the left and the oldest child on the right.
2.3. Outcomes
The primary outcomes of the study were the percentage of children who had started toilet training by 24 months, the percentage who had completed it by 36 months, and the impact of demographic factors on the initiation and completion rates by these ages. Secondary outcomes regarding toilet training included the percentages of children urinating and defecating on the toilet and using diapers during daytime, derived from the 24‐month questionnaire, and the percentage of children using diapers during nighttime, derived from the 36‐month questionnaire. Secondary outcomes related to bowel function, as reported by parents, included bowel movement frequency at all ages and the frequency of a selection of symptoms associated with constipation, including infrequent bowel movements (≤2 per week) and predominantly hard feces, as well as constipation diagnosed by a doctor, and laxative use at 24, 36, and 48 months. Symptoms of constipation must have been present for a minimum of 2 weeks within the past year.
2.4. Demographic factors
Key demographic factors included: sex, socioeconomic status (SES), and child's ethnic background. Maternal educational level was used as an indicator of SES. Demographic factors were collected through parental questionnaires during pregnancy. The maternal education level was determined based on the highest level of education completed and was categorized as low (no or primary education), middle (secondary or vocational secondary education), and high (higher professional or university education). The child's ethnic background was determined based on the birth country of the parents and the child itself. A child was classified as having a Dutch ethnic background if the child and both parents were born in the Netherlands. A child was classified as having a non‐Dutch ethnic background if the child or at least one of the parents was born abroad. If both parents were born abroad, the participant's mother's country of birth was used to determine the child's ethnic background. The ethnic backgrounds included Dutch, European (excluding Dutch), Turkish, Moroccan, Surinamese, Indonesian, Antillean, and Other (outside Europe), according to the guidelines from Statistics Netherlands. 20
2.5. Statistical analysis
Logistic regression models were used to analyze the associations of sex, maternal education level, and child's ethnic background with the two toilet training outcomes: having started toilet training by 24 months, and having completed toilet training by 36 months. To examine the association of sex with both outcomes, two univariate logistic regression models were conducted, with no covariates included in these analyses. To examine the associations between maternal education level and the two outcomes of toilet training, multivariable logistic regression models were performed, adjusting for potential covariates. The inclusion of potential covariates was performed in three steps. First, the following covariates were considered based on existing literature and available data from the Generation R Study: maternal age at baseline, maternal ethnic background (determined using the same criteria applied to the child's ethnic background), household's monthly income (low [<€2000], moderate [€2000–€3300 at 24 months and €2000–€3200 at 36 months], high [>€3300 at 24 months and >€3200 at 36 months]), and number of children in the household (one, two, three, four, or more) (Figure S2A,B). Second, a correlation matrix was used to analyze potential collinear relationships between covariates, using a cutoff value of greater than 0.7 for exclusion from the model. Third, covariates were added individually to the initial crude model, and only those that changed the effect estimate of the crude model by 10% or more were included in the final model. Additionally, two multivariable logistic regression models were performed to examine associations between the child's ethnic background and the two toilet training outcomes, also adjusting for potential covariates. The process for including covariates in these models followed the three steps outlined earlier. The following covariates were considered for inclusion: maternal age at baseline, maternal education level, household's monthly income, and number of children in the household (Figure S2C,D). The percentage of missing data for the covariates included in the models was 0%–6.2%. To minimize bias from this missing data, missing covariate data were imputed using Multiple Imputation using the Fully Conditional Specification method, creating 10 imputed datasets. The results presented in the manuscript are based on the pooled imputed dataset. For comparison, the crude models and analyses based on the original dataset are included in Table S3. No substantial differences were observed between the results of the pooled imputed dataset and those of the original dataset. Data from the logistic regression models were reported as odds ratios (ORs) with a 95% confidence interval (CI). Secondary outcomes regarding toilet training and bowel habits were presented descriptively as proportions. Data were analyzed using SPSS (IBM SPSS Statistics for Windows, version 28.0, Released 2021; IBM Corp). Statistical significance was assessed using a two‐sided significant threshold of p < 0.05.
3. RESULTS
3.1. Population
Table 1 provides an overview of the parent–child characteristics. In the cohort of 6850 children, 3452 (50.4%) were boys. Of the mothers, 553 (8.9%) were low educated, 2621 (42.0%) were middle educated, and 3072 (49.2%) were high educated. Furthermore, 3815 children (58.1%) had a Dutch ethnic background. Baseline characteristics of excluded parent–child pairs are shown in Table S4.
Table 1.
Baseline characteristics.
| Population, n = 6850 | Included in toilet training start analysis (24 months), n = 4949 | Included in toilet training completion analysis (36 months), n = 4494 | |
|---|---|---|---|
| Baseline characteristics child | |||
| Sex, n (%) | |||
| Boy | 3452 (50.4) | 2462 (49.7) | 2238 (49.8) |
| Girl | 3397 (49.6) | 2487 (50.3) | 2256 (50.2) |
| Missing | 1 (0.01) | 0 (0) | 0 (0) |
| Gestational age, mean (±SD) | 40.1 (±1.27) | 40.1 (±1.27) | 40.1 (±1.27) |
| Missing, n (%) | 41 (0.6) | 22 (0.4) | 20 (0.4) |
| Ethnic background child, n (%) | |||
| Dutch | 3815 (58.1) | 3207 (65.5) | 2937 (65.8) |
| European (excl Dutch) | 521 (7.9) | 413 (8.4) | 372 (8.3) |
| Turkish | 462 (7.0) | 289 (5.9) | 270 (6.1) |
| Moroccan | 398 (6.1) | 183 (3.7) | 158 (3.5) |
| Surinamese | 448 (6.8) | 263 (5.4) | 237 (5.3) |
| Indonesian | 26 (0.4) | 20 (0.4) | 18 (0.4) |
| Antillean | 185 (2.8) | 86 (1.8) | 80 (1.8) |
| Other (outside Europe) | 713 (10.9) | 432 (8.8) | 389 (8.7) |
| Missing | 282 (4.1) | 56 (1.1) | 33 (0.7) |
| Baseline characteristics mother | |||
| Age of mother at baseline, mean (±SD) | 30.5 (±5.1) | 31.4 (±4.6) | 31.5 (±4.6) |
| Missing, n (%) | 1 (0.01) | 0 (0) | 0 (0) |
| Maternal education level, n (%) | |||
| Low | 553 (8.9) | 285 (6.0) | 248 (5.8) |
| Middle | 2621 (42.0) | 1760 (37.2) | 1551 (36.0) |
| High | 3072 (49.2) | 2686 (56.8) | 2504 (58.2) |
| Missing | 604 (8.8) | 218 (4.4) | 191 (4.3) |
| Ethnic background of mother, n (%) | |||
| Dutch | 3608 (55.1) | 3129 (64.0) | 2869 (64.3) |
| European (excl Dutch) | 530 (8.1) | 411 (8.4) | 370 (8.3) |
| Turkish | 503 (7.7) | 309 (6.3) | 285 (6.4) |
| Moroccan | 379 (5.8) | 164 (3.4) | 147 (3.3) |
| Surinamese | 502 (7.7) | 275 (5.6) | 244 (5.5) |
| Indonesian | 213 (3.2) | 172 (3.5) | 159 (3.6) |
| Antillean | 152 (2.3) | 74 (1.5) | 67 (1.5) |
| Other (outside Europe) | 667 (10.2) | 358 (7.3) | 320 (7.2) |
| Missing | 296 (4.3) | 57 (1.2) | 33 (0.7) |
| Household's characteristics | |||
| Number of children in household, n (%) | |||
| One | — | 2102 (43.3) | 1196 (27.3) |
| Two | — | 2073 (42.7) | 2408 (54.9) |
| Three | — | 547 (11.3) | 642 (14.6) |
| Four or more | — | 138 (2.8) | 140 (3.2) |
| Missing | — | 89 (1.8) | 108 (2.4) |
| Household's monthly income, n (%) | |||
| Low | — | 1145 (24.7) | 981 (23.2) |
| Moderate | — | 1580 (34.0) | 1196 (28.3) |
| High | — | 1916 (41.3) | 2043 (48.4) |
| Missing | — | 308 (6.2) | 981 (6.1) |
Note: Numbers are based on non‐imputed data and presented as means (SDs) or absolute figures (valid percent). Baseline characteristics of children and their mothers are shown for the total population (n = 6850), the children included in the analysis of toilet training initiation by 24 months (n = 4949), and the children included in the analysis of toilet training completion by 36 months (n = 4494). The household's characteristics are presented only for the children included in the toilet training analyses at 24 months and 36 months, and not at baseline, as these data were collected separately in the questionnaires at 24 and 36 months.
Abbreviation: SD, standard deviation.
3.2. Toilet training
At 24 months, 3385 (68.6%) parents reported that their child (almost) never urinated on the toilet or potty, 4101 (83.2%) that their child (almost) never defecated on the toilet or potty, and 4516 (90.5%) that their child (almost) always wore diapers during the day (Figure 2 and Table S5). Furthermore, 640 (12.9%) reported that their child had started toilet training daily, 2335 (47.2%) toilet trained sometimes, and 1974 (39.9%) had not yet begun. By 36 months, 2698 (60.0%) parents reported having completed toilet training their child.
Figure 2.
Toilet training, bowel habits, and constipation. (A) Responses to the toilet training questions from the 24‐ and 36‐month questionnaires. (B) Responses to the question regarding bowel movement frequency from the 2‐, 6‐, 12‐, 24‐, 36‐, and 48‐month questionnaires. (C) Responses to the questions regarding constipation from the 24‐, 36‐, and 48‐month questionnaires. *Symptoms must have been present for a minimum period of 2 weeks within the past year.
3.3. Associations of demographic factors with toilet training
For the analysis of demographic factors related to the initiation of toilet training by 24 months and completion of toilet training by 36 months, 4949 and 4494 parent–child pairs were included, respectively (Figure 1). Table 1 presents an overview of the baseline characteristics, demographic factors, and confounders of these parent–child pairs. Table 2 shows the outcomes of the adjusted logistic regression models.
Table 2.
Logistic regression models for the start and completion of toilet training at 24 and 36 months, respectively.
| Models for having started toilet training by 24 months | Models for having completed toilet training by 36 months | |||
|---|---|---|---|---|
| OR [95% CI] | p value | OR [95% CI] | p value | |
| Sex | ||||
| Boy | Reference | Reference | ||
| Girl | 1.48 [1.31–1.67] | <0.001 | 2.63 [2.32–3.00] | <0.001 |
| Maternal education levela | ||||
| Low | Reference | Reference | ||
| Middle | 0.85 [0.61–1.16] | 0.305 | 1.32 [0.98–1.80] | 0.071 |
| High | 0.65 [0.47–0.91] | 0.011 | 1.22 [0.89–1.68] | 0.214 |
| Ethnic background childb | ||||
| Dutch | Reference | Reference | ||
| European (excl Dutch) | 1.18 [0.96–1.47] | 0.120 | 1.37 [1.09–1.71] | 0.007 |
| Turkish | 1.71 [1.26–2.32] | <0.001 | 1.97 [1.44–2.72] | <0.001 |
| Moroccan | 0.89 [0.64–1.25] | 0.498 | 1.22 [0.85–1.77] | 0.284 |
| Surinamese | 1.73 [1.29–2.31] | <0.001 | 0.99 [0.75–1.32] | 0.969 |
| Indonesian | 0.96 [0.37–2.48] | 0.937 | 0.92 [0.38–2.19] | 0.841 |
| Antillean | 3.79 [2.04–7.05] | <0.001 | 1.42 [0.87–2.34] | 0.161 |
| Other (outside Europe) | 1.53 [1.23–1.91] | <0.001 | 1.21 [0.96–1.52] | 0.103 |
Note: The results of 10 models examining the associations between sex, maternal education level (adjusted model), and child's ethnicity (adjusted model) with two outcomes—having started toilet training by 24 months and having completed it by 36 months—are presented. Values represent ORs and 95% CIs from the logistic regression models based on pooled imputed datasets. Significant p values are displayed in bold.
Abbreviations: CI, confidence interval; OR, odds ratio.
Adjusted for age of mother at baseline, mother's ethnicity, household's income, and number of children in household.
Adjusted for age of mother at baseline, maternal education level, household's income, and number of children in household.
Compared to boys, girls had higher odds (1.48 [1.31–1.67]) of having started toilet training by 24 months and of having completed it by 36 months (OR: 2.63 [2.32–3.00]). Compared to children from mothers with a low education level, those from mothers who completed higher education had lower odds of having started toilet training by 24 months (OR: 0.65 [0.47–0.91]). There were no associations between maternal education level and having completed toilet training by 36 months. Compared to children of Dutch background, those of Turkish background (OR: 1.71 [1.26–2.32]), Surinamese background (OR: 1.73 [1.29–2.31]), Antillean background (OR: 3.79 [2.04–7.05]), and other non‐European backgrounds (OR: 1.53 [1.23–1.91]) had higher odds of having started toilet training by 24 months, and children from European (excluding Dutch) background (OR: 1.37 [1.09–1.71]) and of Turkish background (OR: 1.97 [1.44–2.72]) had higher odds of having completed it by 36 months.
3.4. Bowel habits and constipation
Figure 2 (and Table S5) provides an overview of bowel movement frequency across different age groups and on symptoms, diagnosis, and treatment of constipation at 24, 36, and 48 months. In all age categories, most children had a reported frequency of one to two bowel movements a day. At 2 months, 1815 (48.3%) parents reported that their child had one to two bowel movements a day, which increased to 2081 (64.1%) and 2310 (69.2%) at 6 and 12 months, respectively, and stabilized around 80% at 24, 36, and 48 months. The reported prevalence of infrequent bowel movements was between 4.4% and 6.3%. Predominantly hard feces were reported for 10.2%–14.3% of the children aged 24–48 months. The reported prevalence of constipation diagnosed by a doctor was below 3.5% at all these ages. Laxative use was reported for 4%, 5.3%, and 4.9% of children at 24, 36, and 48 months, respectively, with 0.9%, 1.2%, and 1.1% requiring it for more than two sickness episodes.
4. DISCUSSION
This population‐based prospective cohort study of 6850 parent–child pairs offers an overview of toilet training initiation and completion rates, as well as normal bowel habits. The findings indicate that 60.1% of the children had started toilet training by 24 months and 60.0% had completed it by 36 months, with correlations found between toilet training rates and the child's sex, maternal education level, and the child's ethnic background.
Our findings revealed a discrepancy between the reported rates of toilet training initiation by 24 months and the reported rates of children urinating and defecating on the potty or toilet, suggesting that having initiated toilet training does not necessarily mean that children effectively use the potty or toilet. This may be due to challenges in the toilet training process, such as children refusing to use the toilet, or to differing interpretations of toilet training from the parent's perspective. Nonetheless, the discrepancy highlights the importance of understanding the milestones and expectations involved in the toilet training process.
The influences of sex, SES, and ethnic background on toilet training have been previously described. 2 , 3 , 5 , 6 , 7 , 21 , 22 , 23 It is widely agreed upon that girls complete toilet training earlier than boys. 2 , 3 , 5 , 6 , 7 , 23 However, studies present mixed results regarding the influence of SES, which may arise from different SES indicators used, such as parental education or household's monthly income. 3 , 22 Income may have a more direct impact on toilet training, as high disposable diaper costs may prompt early toilet training initiation in low‐income families. 21 Due to the complex nature of the influence of SES on toilet training, further research with standardized SES measures is necessary, including investigation of the direct effects of individual SES factors. When analyzing cultural aspects in toilet training, our findings align with previous research showing that non‐Caucasians tend to start and complete toilet training earlier. 5 , 23 A clear understanding of the origin of these ethnic differences is lacking. However, they are thought to stem mainly from parents' cultural beliefs about the appropriate age for toilet training, rather than biological readiness. 21
Our study also provided normal values for bowel habits, highlighting a variety in bowel movement frequencies early in life that stabilize as children grow older, consistent with the meta‐analysis by Baaleman et al. 24 Symptoms such as predominantly hard feces (14.3%) and infrequent bowel movements (6.3%) were common in children aged 24–48 months. Yet, only up to 3.5% of the children in this age category were diagnosed with constipation, and up to 5.3% used laxatives. This discrepancy, along with previous studies reporting over a 25% incidence of constipation in 24‐month‐olds, 15 suggests possible underdiagnosis and under‐treatment. However, comparing our rates to other studies is challenging, as not all symptoms defined in the Rome criteria have been evaluated. 25 Additionally, no information was collected on the type of laxative used, the dosage, or duration of treatment, which limits detailed interpretation of laxative use. These limitations highlight the importance of consistent application of the Rome criteria in both research and clinical practice, as well as the need for more detailed data on treatment in future studies.
While this study offers valuable insights into toilet training and normal bowel habits, it has a few limitations. Firstly, this study used data from the Generation R Study, which included children born between 2002 and 2006, who were followed up until 2010, while toilet training ages have increased over time in the past. 13 , 14 However, the timeframe of our study is more recent than those in previous studies, dating back 25–70 years. 2 , 3 , 4 , 5 , 6 Additionally, our findings on toilet training start and completion ages align with the few recent studies, 15 , 22 , 23 suggesting that changes in these ages might have been less significant over the past decade, making our data relevant to the current generation. Secondly, we cannot definitively state that our cohort exclusively consists of children without conditions affecting bowel habits, as these conditions were only assessed in the 24‐month questionnaire. Diagnoses made after this period were not recorded in our database. However, considering the cohort size and the rarity of these conditions, their proportion is likely negligible. Finally, our findings are based on questionnaire responses rather than clinical observations. However, self‐reported data is a valuable resource for understanding parental experiences and the prevalence of symptoms, particularly in large‐scale studies where directly observing toilet training practices may not be feasible.
The study's primary strength lies in its large cohort size, including children from diverse cultural backgrounds and SES. Our study included a higher percentage of children from non‐Dutch ethnic backgrounds compared to the general Dutch population, likely due to its urban context. While this may limit the generalizability of our findings to the broader Dutch population, it highlights variability often overlooked in more homogeneous cohorts, ensuring that our findings apply to multicultural communities. Additionally, the study's prospective and longitudinal design reduces recall error, improves the accuracy of developmental timelines, and allows for the observation of toilet training practices over time. As a result of these strengths, the insights drawn from this study are highly generalizable and reliable for informing toilet training practices across populations with varying cultural backgrounds and socioeconomic strata.
5. CONCLUSION
This study offers insights on toilet training practices and bowel habits in healthy children. By 24 months, 60.1% of children had started toilet training, and at 36 months, 60.0% of children had completed it. These outcomes are related to demographic factors, including sex, SES, and ethnicity. Across all age categories, most children experience one to two bowel movements a day, with symptoms such as infrequent bowel movements and predominantly hard feces affecting up to 6.3% and 14.3% of children, respectively. The findings from this study can help identify deviations in the toilet training process and provide valuable guidance in setting realistic toilet training and bowel management goals for healthy children and children with abdominal conditions or developmental delays.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interest.
Supporting information
Supplemental Figure S1. Translated English version of the questions regarding toilet training and bowel habits from the Dutch questionnaire. Subscript: (A) Questions included in the two, six and 12 months questionnaire (B) Questions included in the 24 months questionnaire (C) Questions included in the 36 months questionnaire (D) Questions included in the 48 months questionnaire.
Supplemental Figure S2. Directed Acyclic Graphs depicting the relationships between maternal education level (as indicator of socioeconomic status) and ethnicity of the child with having started toilet training by 24 months and having completed toilet training by 36 months and covariates.
Supplemental Table S3. Logistic regression models for the start and completion of toilet training at 24 months and 36 months, respectively Subscript: The results of models based on the original dataset (both crude and adjusted models) and the crude models based on the imputed dataset are presented. Values represent odds ratios (OR) and 95% confidence intervals (CI). *Adjusted for age of mother at baseline, mother's ethnicity, household's income, and number of children in household. **Adjusted for age of mother at baseline, maternal education level, household's income, and number of children in household.
Supplemental Table S4. Baseline characteristic of excluded parent‐child pairs Subscript: Numbers are presented as means (standard deviations) or absolute figures (valid percentages). The table is based on non‐imputed data.
Supplemental Table S5. Toilet training, bowel habits, and constipation Subscript: Numbers are presented as absolute figures (percentages). The table is based on non‐imputed data. * Symptoms must have been present for a minimum period of 2 weeks within the past year.
ACKNOWLEDGMENTS
The authors gratefully acknowledge the contributions of the Generation R children, their parents, general practitioners, and hospitals in Rotterdam. The general design of the Generation R Study is supported by funding from the Erasmus Medical Center, the Erasmus University Rotterdam, the Dutch Organization for Health Research and Development (ZonMW), the Dutch Organization for Scientific Research (NWO), the Ministry of Health, Welfare and Sport, and the Ministry of Youth and Families. The funding sources were not involved in the study's design, data collection, analysis, interpretation of data, or writing of the report.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplemental Figure S1. Translated English version of the questions regarding toilet training and bowel habits from the Dutch questionnaire. Subscript: (A) Questions included in the two, six and 12 months questionnaire (B) Questions included in the 24 months questionnaire (C) Questions included in the 36 months questionnaire (D) Questions included in the 48 months questionnaire.
Supplemental Figure S2. Directed Acyclic Graphs depicting the relationships between maternal education level (as indicator of socioeconomic status) and ethnicity of the child with having started toilet training by 24 months and having completed toilet training by 36 months and covariates.
Supplemental Table S3. Logistic regression models for the start and completion of toilet training at 24 months and 36 months, respectively Subscript: The results of models based on the original dataset (both crude and adjusted models) and the crude models based on the imputed dataset are presented. Values represent odds ratios (OR) and 95% confidence intervals (CI). *Adjusted for age of mother at baseline, mother's ethnicity, household's income, and number of children in household. **Adjusted for age of mother at baseline, maternal education level, household's income, and number of children in household.
Supplemental Table S4. Baseline characteristic of excluded parent‐child pairs Subscript: Numbers are presented as means (standard deviations) or absolute figures (valid percentages). The table is based on non‐imputed data.
Supplemental Table S5. Toilet training, bowel habits, and constipation Subscript: Numbers are presented as absolute figures (percentages). The table is based on non‐imputed data. * Symptoms must have been present for a minimum period of 2 weeks within the past year.