Table 2.

Effects of exposure to baby swimming programs on infants’ health.

1st Author, Year	Research Aim and Design	Results	Risk of BIAS
Harter, 1984 [32]	Effect of swimming pool attendance on infants’ (0–3 years of age) giardia diagnosis. The presence of giardia cysts (in stool sample) was compared between 70 participants in swimming programs (93% of children, 87% of mothers and 36% of fathers) and 18 non-swimming siblings and playmates.	Giardia positivity (G+) for 61% children, 39% mothers and 28% fathers of the swim group; G+ children were found in each of the nine programs swim classes Children G+ for control group = 0% No association between G+ and age (p = 0.35) G+ with higher prevalence (71%) for attendance > 7 sessionsG+ prevalence for < 7 sessions = 35%. Swimming pool attendance increased the odds of infants to become Giardia positive.	** Confounding Statistical analysis
Nystad, 2003 [33]	Effect of baby swimming programs attendance on respiratory tract infections and otitis media in the first year of life. The standard questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC) was applied to 2862 children 6–16-years-old to access the presence of recurrent respiratory tract infections (RRTI), bronchitis, bronchiolitis, pneumonia, otitis media during the period 0–11 months age. A second questionnaire of parental history of atopy (asthma, eczema or hay fever), demographic information, early exposures and childhood health was applied one year later.	No association between respiratory tract infections and baby swimming. Risk of RRTI [adjusted odds ratio (aOR) 2.08, 95% confidence interval (95% CI) 1.08–4.03] and otitis media (aOR 1.77, 95% CI 0.96–3.25) increases only in children of parents with atopy. Baby swimming programs increased the RRTI and otitis media in infancy among children of parents with a history of atopy.	** Confounding Measurement of exposure Outcomes measurement
Schoefer, 2008 [34]	Effect of swimming pool attendance on early infections and development of airway diseases after 1st year of life. On a 6-year longitudinal study with questionnaires administered to parents on a regular basis (aged 6, 12, 18 months and 2, 4, 6 years), information on socioeconomic factors, medical history (hey fever, asthma, eczema, airway infections, otitis media, diarrhea), and lifestyle factors of 2192 children was obtained. Parental atopy, age of first pool attendance [(a) 1st year baby swimming (N = 660), (b) 1st year occasionally (N = 655) and (c) later or never (N = 877)] and frequency of pool attendance was also accessed.	Non-swimming babies had lower rates of infection of(i) diarrhea: OR = 0.68 (0.54–0.85), CI 95%; (ii) otitis media: OR = 0.81 (0.62–1.05), CI 95%; (iii) airway infections: OR 0.85 CI 95% 0.67–1.09 in the 1st year of life. No clear association between late or non-swimmers and hay fever or atopic dermatitis were found. Higher rates of asthma were found (OR 2.15 95% CI 1.16–3.99), however, potentially due to reverse causation. Swimming pool attendance increased gastrointestinal infections (i.e., diarrhea) during the first year of life, but no association of swimming pool attendance and atopic diseases and airway infections was found.	* Confounding
Nystad, 2008 [35]	Effect of baby swimming in the first 6 months of life on respiratory diseases from 6 to 18 months. Maternal retrospective report (at 18 months age) about their infants’ lower respiratory tract infections (LRTI), wheeze and otitis media between 6 and 18 months of age (N = 30,870) in the Norwegian Mother and Child Cohort Study (MoBa). History of maternal atopy was also accessed.	LRTI and otitis media were not associated with baby swimming attendance. An increased risk of wheeze [adjusted odds ratios (aOR) 1.24 (95% CI 1.11, 1.39)], on children who attended baby swimming was only observed on children with atopic mothers. Baby swimming programs increased the likelihood of wheeze in infants with a maternal history of atopy.	** Measurement of exposure Measurement of condition Outcomes measurement
Font-Ribera, 2013 [36]	Effect of baby swimming programs attendance on respiratory symptoms and infections during the first year of life. Parent report (at 14 months age) about LRTI, persistent cough, wheezing, otitis and atopic eczema during the first year of life (N = 2205 infants). Swimming pool attendance during the first year of life and parental atopy was also accessed.	Adjusted OR of wheezing [1.06 (95%CI, 0.88–1.28)] and LRTI [1.09 (0.90–1.31)] for babies not attending vs. babies attending swimming pools. Type of swimming pool (indoor or outdoor), and parental atopy did not modify the results. Swimming pool attendance during the first year of life was not associated with LRTI, otitis, wheezing, atopic eczema or persistent cough.	** Measurement of exposure Outcomes measurement
Schuez-Havupalo, 2014 [37]	Effect of baby swimming programs attendance on infants’ (0–17 months of age) respiratory tract infections. Wheezing, bronchiolitis, number of days per year with rhinorrhea, cough or fever recorded. 1827 children were followed up from birth until 17 months of age, on baby swimming attendance, wheezing, bronchiolitis, number of days per year with rhinorrhea, fever or cough. Viral diagnostics were performed in a subset of children with all respiratory tract infections.	An increased likelihood of wheezing illness was observed in swimming children when compared to non-swimming children (p = 0.11). Rhinoviruses were more correlated with wheezing in swimming children [11/296 (3.7%)] than non-swimming children [4/339 (1.2%)] (p = 0.04). Baby swimming attendance had an odds ratio of 1.71 (p = 0.05) for bronchiolitis and 3.57 (p = 0.06) for rhinovirus- associated wheezing. Baby swimming attendance was associated with rhinovirus-associated wheezing for children with atopic eczema (p = 0.006). Infant swimming programs increased respiratory tract infections in atopic infants.	* None

Quality analysis tool: * ROBINS-I and ** JBI.