Aims of the Study and Rationale for the Study Design

Both cross cultural research into the early mother-infant interaction and research into infant feeding suggest that maternal belief systems are strongly associated with the nature o f the mother's behaviour towards her infant and reflect pervasive beliefs, some cultural in origin, about infants' readiness and ability to communicate. These belief systems influence the organisation o f the daily caretaking routines and the nature of the interaction between the mother and infant.

This study has sought to bring together two areas of research covering common ground, caregiving and infant feeding, but having quite different features.

The first area covers studies of infant feeding and the mother-infant interaction during feeding. Microanalyses o f the interaction have revealed the regulatory nature of mother-infant behaviour, and have helped develop a taxonomy o f preverbal

language. Most o f these studies have been based in the Europe and the USA. The second area considers cultural variations in caregiving and infant feeding practices, with a particular subset concerned with migrant families. In this study, the immigrant ethnic minority families, within defined parameters regarding length o f residence and primaparity, are regarded as representing practices in their country o f origin. This second area has been less explored, with studies covering a broad range of cultures, but providing less detailed examinations o f particular practices. Thus, there are fewer studies which employed microanalysis.

This study is the first to apply the methodology of the first area, the nature o f the mother-infant interaction during feeding, to a closely prescribed aspect o f the

second, the cultural variations in those interactions. Necessarily, the study has had to take account o f the available cross-cultural studies. These have provided a

framework and context and contain important evidence about attitudes and behaviours that, although relevant, are outside the particular focus o f this study. They are not, therefore, included for explicit examination. Thus, for example, the assertions about the process of socialisation and the transmission o f cultural beliefs, the acculturation of migrant families, differing cultures attitudes to child rearing and to weaning and food choice are not specifically explored but will be discussed in relation to the findings of this study.

Certain factors identified as likely to confound the nature o f the feeding interaction, (low birth weight, pre-term or neurological impairments), were controlled for at the point of recruitment and are therefore not included in the sample.

The study was prompted by the concerns expressed about the health of infants in the Asian community in the UK. It is difficult to know if the observed decrease in

weight gain o f Asian infants in the UK during the first year reflects reduced intake as a result o f difficulties in the nature of the feeding interaction, deficiencies in the type o f diet provided, or a combination of both. To avoid a deficit model of comparison that has frequently accompanied research into ethnicity in the UK, the study included a third ethnic group, chosen principally because its infants' growth was identified as exceeding that of the indigenous population. Details of the infants' weight during the course of the study have been collected and are the subject o f a specific hypothesis. However, the analysis does not investigate the cause o f any apparent decrease or increase in weight gain.

The limitations o f the studies reviewed are considered in sections 3.5 and 4.6. A common feature has been the absence o f longitudinal studies exploring the

progression o f behaviour during the feeding interaction in different cultural groups. This study seeks to address this limitation.

A prospective cohort study is the preferred choice of design for an observational study (Altman, 1991). It allows a population to be classified according to the characteristic o f interest at the study outset. The cohort may then be followed and any subsequent development of differences between groups compared. In this study, the population was classified at the study outset by maternal ethnicity and the cohort were infants o f normal birth weight. The aim was to compare any subsequent

between the three ethnic groups. Specifically, the longitudinal design had two advantages:

a) It allowed repeated observations of the mother-infant interaction to be made. The stability over time of mother-infant interactions in White US samples has been reported (Barnard, 1978), but many of the available cross cultural studies rely on cross sectional data (e.g., Dixon, Le Vine, Richman and Brazelton, 1984; Caudill and Weinstein, 1969). This makes it difficult to determine if the observed differences in the responsiveness of caregivers across culture are real, or ascribable to the age differences o f the samples. Repeated observations of the same mother-infant dyads from the three groups over a period o f time would improve the validity of the findings.

b) The anthropometric assessments could be taken directly by the researcher in the home removing a potential source of measurement and sample bias: i) Collecting the data in the home would ensure more complete

attainment from the sample. The evidence suggests that women from ethnic minority groups are more likely to be registered with a GP than the general population (Rudat,1994) and that most mothers do attend baby clinics during the infants first few months (OPCS, 1992), but there is no clear understanding of how mothers from specific ethnic groups who do attend clinics differ from those who do not, nor of the frequency of attendance o f the Nigerian population. Recently

accommodation more frequently: this could impair the ability to obtain the longitudinal data on specific infants,

ii) It would not be possible to determine the reliability of measurements obtained from clinic records. Jelliffe and Jelliffe (1990) found the reliability for collecting weight data to be satisfactory, but warn that the accurate measurement of the length of infants is difficult. This conclusion is supported by authors of the Wessex Growth Study (Voss, Bailey, Gumming, Wilkin and Betts, 1990) who recommend that monitoring o f height should be carried out by the same observer using the same instruments. In addition, each observer should establish his/her own single standard deviation (SD) o f the error of the measurement (SD) calculated from the differences observed between two or more measurements s/he has made. Once established, this SD can be applied to a single future measurement made by this individual. Even with these cautions, Voss et al found that the instruments used for measuring the height of children contributed very little to the total variability of the measurements taken; the greatest source o f variability was the child him/herself.

Breslow and Day (1987) identified some o f the potential limitations o f cohort studies. Cohort studies provide the best information about causation but are rarely undertaken because they are time consuming and expensive. In an attempt to reduce the time and cost involved, the samples chosen from a population may be selected precisely because they have a higher probability than the general population o f

displaying the outcome of interest. Breslow and Day warn that the effect o f this selection will be to reduce the generalisability o f the results.

A further difficulty is the retention o f the sample for the study duration. The loss of individuals to follow up has two negative consequences:

(a) A reduction in sample size weakens the statistical power o f the subsequent analysis.

(b) There is an unquantifiable but potential source o f bias arising from those dropping out: the reasons for discontinuing may be due to individual

difficulty, perhaps in adapting to parenthood, or for structural reasons such as changes in residence or employment.

The efforts made to overcome these difficulties are discussed in sections 6.8.2, 6.8.3 and 6.8.4