Factors influencing birthweight for gestational age, with special respect to risk factors for intrauterine growth retardation.

In a prospective clinical study from an unselected, area-based population, the influence on birthweight for gestational age of different factors was studied, with special respect to 15 risk factors for intrauterine growth retardation (IUGR) recognizable in early pregnancy. In the multiple regression analyses performed, birthweight for gestational age was used as the dependent variable. Only 10% of the variance in birthweight for gestational age could be explained. A correlation was found between the number of risk factors and birthweight for gestational age. Four risk factors had a significant negative influence on birthweight for gestational age: smoking, previous birth of a low birthweight infant, a low prepregnancy weight and addiction. No single risk factor influenced birthweight for gestational age as much as parity. When a risk factor was present the expected increase in birthweight for gestational age with increasing parity did not appear.