Constitutional characteristics of humans are changing. People are becoming taller and they weigh more. These changes influence birth weight and birth length as well.
A study was conducted on 2414 mothers and their newborns from 1985 to 2009 in Zagreb, Croatia, to establish a secular change in the weight and length of infants and the factors that are most related to these changes.
Birth weight has increased significantly in the past 25 years, and it is higher in male newborns. Taller mothers, with higher weight and body mass index, deliver newborns with higher birth weight. Weight gain in pregnancy has positive impact on birth weight. Multiparas and older and more educated women deliver newborns with higher weight. Birth weight does not depend on father’s education. The number of newborns with birth weight more than 4000 g is increasing, but not significantly. Birth length was not significantly higher. Birth length is higher in male newborns, in newborns with higher birth weight and newborns of older and more educated mothers.
Better life conditions and better health care improves population constitutional characteristics that have implications in higher birth weight and birth length. This could be an important change that influences delivery modalities.