Participants
Ethical consent has been obtained from the responsible local research Ethical Committee.
100 premature infants born at Salzburg university medical hospital reached a corrected age of 17 weeks in a 4-month study-period, ranged from 24 0/7 weeks to 36 5/7 weeks gestational age.
All parents who agreed to participate in the study provided informed consent.
Eligibility criteria included prematurity and at least one of the parents had to be fluent in either German or English.
Exclusion criteria included surgical problems that interfered with normal nutritional behaviour (e.g. gastroschisis or oesophageal atresia), genetic syndromes, metabolic diseases and mothers who suffered from an untreated psychiatric illness as well as children who were placed in foster care. In addition, an extremely prolonged necessity for gavage feeding or the recurrent need of a feeding tube around the time of inquiry was an exclusion criterion.
Questionnaires
To prevent biasing the study by raising extraordinary awareness to complementary feeding and it`s guidelines, all families were contacted as early as 16 weeks corrected age to minimise recall bias regarding the time of weaning and which food groups they were first introduced to, carers were contacted at the latest of 18 weeks corrected age.
Detailed structured interviews were administered either via telephone or in person in the outpatient clinic.
Collected data included sociodemographic data like information on the infant`s family situation, particularly information concerning the mothers, like maternal age, special diet and potential diseases before and during gestation, previous pregnancies and births, as well as educational status and family income.
Perinatal data contained gestational age, birth weight, birth height and head circumference at birth, along with gender, whether it was a singleton or multiple pregnancy, birth mode, 1,5, and 10-minute APGAR (Appearance, Pulse, Grimace, Activity, Respiration) and relevant medical problems and interventions during or immediately after birth.
Feeding Practices
Information regarding the infant`s feeding practices from birth were obtained, including detailed information on milk-feeding practices. It was documented whether the infants have been breastfed or formula-fed right after birth, if they still were breast-fed at the time the survey was conducted and if so, if they were still fully or partially breastfed along with solids and/or formula. Duration of exclusively vs. partially breastfeeding was documented both from birth and term.
Since all our participants were born preterm, information on fortifying breastmilk or feeding special preterm formula regarding the duration and type of supplementation also have been obtained.
It was documented whether the infants were already started on solids or not, and if so the corrected age as well as the uncorrected age of the complementary food introduction was noted in weeks. All mothers provided us with information about when they introduced specific food groups to their children, which were again recorded in weeks from birth and term.
Foods or food groups of interest included vegetables, potatoes, meats, cereal, cereal-milk purees, fruits, eggs, fish, water, tea and sweetened beverages.
Information was collected on how often children were introduced to new foods within one week and whether they received a special diet (for example vegetarian).
Mothers also provided information about personal reasons on why they started weaning their infants and whether they specifically sought information on this topic like talking to their paediatrician, reading on-topic books, brochures etc.
Measurements
Weight, height and head circumference at birth and at the time of the interview were collected, as well as those of previous outpatient-clinic visits.
All measurement-data has either been gathered from medical reports of our department during in- and outpatient visits, or measured by paediatricians and were provided to us by the infant`s mothers.
Weight and height data until a gestational age of 50 weeks were scaled based on the gender-specific Fenton Preterm Growth Charts [12].
Measurements taken as of 51 weeks gestational age were scaled based on the gender-specific WHO growth charts “weight for age, birth to 6 months” and “height for age, birth to 6 months” using the infant`s corrected age.
All weight measurements, whether obtained in the clinic or those taken by family paediatricians were taken on calibrated baby-scales. All height measurements were taken by measuring the infant in a supine position from the top of the head to heel, with the infant`s leg being stretched out on a flat surface.
Statistical Analysis
Data consistency was checked and data were screened for outliers and normality by using quantile plots. Crosstabulation tables with Fisher’s Exact test or Pearson’s test were used to analyze crosstabulations. Two-sided Student t-tests with and without the assumption of variance homogeneity were used to compare expectation values among different groups and 95% confidence intervals were used estimate the effects. Kaplan-Meier analyses were done and survival curves were tested using Cox-F and Gehan’s and Wilcoxon test. All reported tests were two-sided, and p-values < 0.05 were considered as statistically significant. All statistical analyses in this report were performed by use of NCSS (NCSS 10, NCSS, LLC. Kaysville, UT), Mathematica 7 (Wolfram Research, Inc., Mathematica, Version 7.0, Champaign, IL), STATISTICA 13 (Hill, T. & Lewicki, P. Statistics: Methods and Applications. StatSoft, Tulsa, OK).