Aim: The WHO Multi-centre Growth Reference Study(MGRS) used data of six national sites to propose a child growth standard that describes the optimal growth patterns. Our previous research has identified number of factors as influencing optimal child growth in different populations around the world. The aim of this study is to combine data on children and parents from numerous countries from all regions of the world to examine cross-country variation in child growth relative to the MGRS growth standard charts.

The information contained in the "ALSPAC data documentation" indicates that children of the 90's survey has child and mother physical measurements and other relevant variables for our research. Therefore, we are interested in to include survey data of Avon Longitudinal Study of Parents and Children (ALSPAC) for our sample.

Hypothesis : The socio-economic status , income, ethnicity, child birth characteristics, parental size and health detremines the optimal child growth.

The exposure variables of the study are

- Sampling details - sample weights, household weights

- Birth year, month, date

- Child ID [to allow us to identify repeat observations on the same child]

Birth circumstances

- Birth date

- Gestational age (weeks)

- Birth weight (g)

- Birth length (cm)

- Sex

- Whether single or multiple birth

- Birth order

- Ethnicity [this is not mentioned in the paper, but if available, so we can distinguish between caucasian and other groups]

Parental characteristics

- Age (years)

- Paternal height (cm)

- Maternal height (cm)

- Smoking status (Yes/No)

- Drug abuse (Yes/No)

- Alcohol consumption

- Educational level

- Years of education

- Employment

- Household and environment (needed to estimate socioeconomic status and impute per capita income)

Confounding variables are :

- Nutrition data

- Whether breast fed at time of measurement

- Whether exclusively breast fed at time of measurement

- Length of exclusive breast feeding

The outcome variables of the study are :

-- Date of anthropometric measurement

- Height/length (cm)

- Whether measurement was Recumbent length/standing height

- Body weight (g) .