Determinants of birth size in Northeast Spain.

OBJECTIVE: To update knowledge on determinants of newborn body size in Northeast of Spain considering gestational, parental and socio-cultural variables. METHODS: Cross-sectional assessment of 1442 infants from Aragón (Spain), born at term between March 2009 and March 2010. Obstetric, neonatal, socio-demographic and parental anthropometry data were collected during the first infant scheduled health examination. Hierarchical linear regression models were used to explore associations between newborn anthropometry and included variables. RESULTS: Birth weight was significantly higher in males than in females (130.7 g), when mother did not smoke during pregnancy (126.3 g), in immigrant mothers (113.1 g) and when parity increased (67.1 g per additional birth). Body weight at birth was 16.9 g higher per kg of maternal weight gain during pregnancy, 5.4 g higher per kg of maternal pre-pregnancy weight and 5.1 g higher per cm of maternal height. Birth length was also significantly higher in males than in females (0.87 cm), when mother did not smoke (0.48 cm), in immigrant mothers (0.64 cm), and it was positively associated with parity, maternal anthropometry and paternal height. Newborn anthropometry was not associated with maternal age, educational level or living location. CONCLUSIONS: Independently of gestational age and newborn sex, the main predictors of birth weight and length were maternal pre-pregnancy anthropometry and weight gain during gestation, to smoke during pregnancy, parity and maternal origin. Our results identify potential modifiable factors influencing newborn body size.