Weight and weight gain at 4 months (The Netherlands 1998): influences of nutritional practices, socio-economic and ethnic factors.

We describe the determinants of weight gain in the first 4 months of life in a cohort of 3256 infants. The study was designed as a survey with follow-up. In the period 1 April to 1 July 1998, all infants, usually 4 weeks old but not older than 4 months, brought to a well-baby clinic for the first time were included. Nutritional practices, demographic data on mother and child, birthweight and a second weight measured between days 118 and 147 were recorded. Simple and multiple linear regression analyses were performed. The average weight gain over 4 months was 27.7 g/day for boys and 24.5 g/day for girls. Weight gain was lower with high parity and if the mother was a native Dutch speaker. Nutritional practices affected weight gain only slightly: exclusive breast feeding for 4 months lowered the weight gain by 0.06 g/day. However, because of their higher birthweight, breast-fed infants weighed a little more than formula-fed infants at 4 months. In addition, we compared the median weight at the age of 4 months with the median weight at the same age in previous Dutch growth studies. The median weight, adjusted to day 133, was higher in 1998 than in 1965, 1980 and 1997 (boys 7.15 vs. 6.85, 6.77 and 6.95 kg; girls 6.59 vs. 6.49, 6.39 and 6.45 kg respectively).