Objective: To identify factors associated with an increased risk of giving birth to infants weighing more than 4000 g and to study whether changes in these factors over time can explain the increasing proportion of high birth weight infants over the last decade.
Methods: Our analyses included 24,093 pregnancies of nondiabetic women with information on potential risk factors for high birth weight: maternal prepregnancy weight, height, age, parity, smoking habits, alcohol and caffeine intake, marital status, educational level, gestational age, and infant gender. Information was obtained from questionnaires completed during pregnancy and birth registration forms at the Department of Obstetrics and Gynaecology, Aarhus University Hospital, Aarhus, Denmark, from 1990 to 1999.
Results: We found a statistically significantly increased risk of giving birth to infants weighing more than 4000 g for women with high prepregnancy weight and height, parity greater than 2, gestational age greater than 42 weeks, and male infant gender and for nonsmokers. Women with a low caffeine intake or 10 or more years of education were also at statistically significantly higher risk. The variation found in birth weight over the past 10-year period was explained by changes in maternal prepregnancy weight, height, smoking habits, educational level, and caffeine intake over the same period.
Conclusion: Risk factors associated with a higher proportion of high birth weight infants may be clinically significant and have an impact on public health. High birth weight increases the risk of adverse outcomes of delivery as well as the risk of childhood morbidity.