Development of birth weight for gestational age charts in a Sri Lankan setting - methodological issues

This study was taken up to identify the main types of low birth weight (LBW) for the development of weight for gestational age charts relevant to the country/regional level for the formulation of preventive strategies.

A sample of mothers registered by Public Health Midwives (PHMs) from two Medical Officers of Health (MOH) areas in Colombo district were followed up until delivery in five selected hospitals. Period of gestation (POG) was assessed between 10 and 12 weeks using ultrasonography. Records of 474 mother/newborn pairs were used for development of gestational age-related birth weight charts for each sex and POG. Mothers with one or more risk factors for LBW were excluded. Mothers with POG less than 38 weeks and more than 40 weeks were limited. Information on all possible risk factors contributing to LBW were assessed.

Incidence of small for gestational age (SGA) assessed using the 10 th centile value for each POG, was 19.0% for males and 18.0% for females. Percentages of symmetrical and asymmetrical SGA newborns were 72.1% and 27.9%, respectively.

The charts were developed paying attention to all methodological aspects that highlighted the key issues relevant to development of weight for gestational age charts in a developing country setting. As action was taken to minimize the biases introduced by such issues, the charts developed could be used for assessment of incidence and risk factors for SGA until charts based on national level data are available.