Growth measurements
Growth was assessed by two medical investigators. Daily body weight and weekly body length and head circumference were measured using standard procedures [15]. Body mass was measured to the nearest 0.1 g using a precise electronic scale and body length to the nearest 1 mm using a Harpenden neonatometer (Holtain Ltd., UK), and head circumference to the nearest 1 mm using a non-stretch measuring tape. Weight gain velocity was assessed using the formula: [1000xln (Wn/W1)]/(Dn-D1), in which W = weight in grams; D = day; 1 = beginning of the time interval n = the end of the time interval [