Evaluation of adjustment methods used to determine prevalence of low birth-weight babies at a rural hospital in Andhra Pradesh, India.

Accurate reporting of prevalence of low birth weight (LBW) is important for monitoring health of a population. LBW is often underestimated in developing countries due to heaping of the data at 2.5 kg. UNICEF uses an average adjustment factor of 25% to re-classify babies listed as exactly 2.5 kg into the LBW category. From October 2009 to February 2010, we weighed 859 consecutive live births at a rural hospital in Andhra Pradesh, India, using analog and digital scales to evaluate the relative validity of the adjustment factor. Significantly more babies weighed exactly 2.5 kg on analog (13.4%) versus digital (2.2%) scales, showing heaping. Percentage of LBW by digital method (29.5%) was significantly higher compared to the analog method (23%) and with adjustment factors (26.4%). Conventional methods of adjusting birth-weight data underestimate the prevalence of LBW. Sensitive digital weighing machines or better adjustment methods are needed to monitor LBW in developing countries.