Study and sample design
This was a cross-sectional study in caregivers of infants and toddlers 0–24 months of age participants of a WIC clinic in Puerto Rico. Caregivers completed two questionnaires (socio-demographics and breastfeeding practices) and anthropometrics were taken in the infants and toddlers. This study was approved by the Institutional Review Board of the University of Puerto Rico Medical Science Campus and caregivers provided written consent before participating in the study.
We recruited a non-probabilistic convenient sample of caregivers 21 years or older of infants and toddler aged 0–24 months. Recruitment occurred every day in the WIC clinic of the Municipality of Trujillo Alto, which is within the Metropolitan area of San Juan in Puerto Rico, during a 3-month period (November 2014–February 2015). This clinic is the only clinic in this municipality, which allowed recruiting all active infant participants of that clinic (n = 476), as caregivers of infants and toddlers attend the clinic on average once per month for their appointments or to pick-up their monthly checks. A total of 296 participants were recruited during this 3-month period. Approximately 10 caregivers refused to participate and an additional 15 were younger than 21 years. In addition, infants or toddlers with any serious health condition that could alter normal feeding practices were excluded.
At the time of recruitment, participants completed the two paper questionnaires, which took about 20 min to complete, and anthropometrics were taken in the infant as explained below.
Caregivers completed a short self-reported questionnaire with questions on parent/caregivers’ age, gender, education and household size, questions on infants’ birth weight, age and gender and questions about pregnancy complications and weeks of gestation.
Breastfeeding practices questionnaire
This questionnaire was based on questions adapted from the Southampton Women’s Survey (Fein et al. 2008; Marriott et al. 2009) and Centers for Disease Control and Prevention (CDC) Infant Feeding Practices study (Fein et al. 2008). The questions assess initiation and duration of breastfeeding (Fein et al. 2008), duration of exclusive breastfeeding (Marriott et al. 2007) and timing of introduction of water and complementary fluids such as formula (Marriott et al. 2007). Other added questions included breastfeeding initiation (immediately after birth or any time during the hospital), breastfeeding practices (exclusive or partial), duration of any type of breastfeeding, and timing of introduction of juice, solid foods and cow’s milk. There were 23 questions and it was administered via interview by trained research personnel.
Weight and recumbent length were measured by trained research personnel. For this, infants were weighed with light clothing, no shoes or socks and clean diaper. Weight was taken in duplicates in pounds using a manual calibrated scale (Detecto, MO). The average of both measurements was used, which was converted to kg. Recumbent length was measured in duplicates in cm using an infantometer (Perspective Enterprices, MI) and the average of both measurements was used. Weight status was calculated using weight-for-length growth charts from the World Health Organization by age and gender. Weight was classified as: underweight (<5th), healthy weight (5th–89th) and excessive weight (≥90th). For premature infants (n = 34, 11.7 %), gestational age was adjusted first before calculating the weight-for-length percentile.
For this analysis, infants younger than 6 months were excluded to assess duration of breastfeeding for at least 6 months on weight status. Breastfeeding was analyzed as breastfed immediately after birth, at the hospital, at least once, and exclusively. In addition, breastfeeding duration was analyzed separately for any breastfeeding duration and exclusively breastfeeding duration.
For descriptive statistics, median (25th and 75th percentiles) were computed for continuous variables and frequencies for categorical values. To associate breastfeeding practices (start of breastfeeding, exclusive or non-exclusive breastfeeding and duration) with socio-demographics (age of mother, education, number of children), timing of introduction of beverages (water, formula, juice and cow’s milk) and solid foods, and infant weight status, we used Spearman correlations and logistic regression, unadjusted, adjusted for infant’s age and also adjusted for infant’s sex and caregiver’s age and educational level. To compare timing of introduction of beverages and solid foods by feeding types (never breastfed, non-exclusively breast-fed and exclusively breastfed, Kruskal–Wallis was computed. The data analysis was performed using the Statistical Package for the Social Sciences (SPSS), version 21.0. Statistical significance was set at p < 0.05.