Anthropometric measurements
Anthropometric measurements were carried out by three trained research assistants during the enrolment visit. Unclothed infants were weighed using an electronic infant weighing scale (SECA 735; Chasmors Ltd. London, England) and weights were recorded to the nearest 10 g. The length was measured to the nearest 1 mm using a high-quality length board (Kiddimetre; Raven Equipment Ltd, Essex, England). Age- and sex-standardized anthropometric indices (length-for-age Z score [LAZ]), weight-for-age Z score [WAZ] and weight-for-length Z score [WLZ]) were calculated using the STATA macro developed by the World Health Organization (WHO) using the WHO 2006 multicentre growth standards [