ORIGINAL ARTICLE Maternal Pre-pregnancy Body Mass Index and Offspring Temperament and Behavior at 1 and 2 Years of Age Ryan J. Van Lieshout • Louis A. Schmidt • Monique Robinson • Alison Niccols • Michael H. Boyle Published online: 15 September 2012 Ó Springer Science+Business Media, LLC 2012 Abstract Recent research suggests that fetal exposure to increased maternal body mass index (BMI) during preg- nancy may be associated with psychopathology later in life. When this link first emerges, and if it is due to intrauterine exposures or confounding variables is not known. We there- fore assessed associations between maternal pre-pregnancy BMI and: (1) temperament at 1 year of age, and (2) Child Behavior Checklist internalizing and externalizing scales at age 2 in the 2900 mothers and infants enrolled in the Western Australian Pregnancy Study. Pre-pregnancy BMI was positively associated with externalizing scores (b = 0.131, 95 % CI 0.013–0.249) at age 2, even after adjustment for confounders, but not with internalizing scores or an increased risk of difficult temperament. These data suggest that fetal exposure to increased maternal BMI is associated with elevated levels of behavior problems as early as age 2, and that this may be linked to the intrauterine environment. Keywords Temperament Á Behavior Á Child Á Body mass index Á Pregnancy Introduction An estimated 1.1 billion people are obese (body mass index (BMI) C 30) worldwide, with women outnumbering men [1]. Despite its association with over 20 diseases and an elevated risk of premature mortality, the prevalence of obesity continues to increase [2]. Women of childbearing age have not been spared in this epidemic. Indeed, maternal obesity is among the most common complications of preg- nancy in the developed world, affecting up to 40 % of women [3]. Not only is obesity in pregnancy associated with an increased risk of health problems in the mother including diabetes mellitus (DM), thromboembolic disease and asthma [4], it has also been linked to higher rates of shoulder dystocia and fetal trauma [5]. The consequences of fetal exposure to the intrauterine conditions associated with maternal obesity may also extend to the newborn, as infants born to obese women appear to be at increased risk for a number of con- genital anomalies including neural tube defects [6]. Despite widespread knowledge of these adverse effects on mothers and their offspring, American rates of pre-pregnancy obesity rose by 69.3 % in the 1990s [7]. The process by which persistent physiological altera- tions in offspring result from exposure to intrauterine conditions is referred to as prenatal programming [8]. Such changes are thought to be made by the fetus in response to environmental signals present during gestation (e.g., nutrients, hormones) in an attempt to anticipate their postnatal environment and optimize survival. However, if these alterations fail to accurately predict postnatal condi- tions, an increased risk of disease can result [8]. Existing data suggest that intrauterine exposure to maternal obesity may have lasting effects on the health of offspring. Indeed, individuals born to women who are obese during preg- nancy are more likely to develop obesity [9] and asthma R. J. Van Lieshout (&) Á A. Niccols Á M. H. Boyle Chedoke Division, Department of Psychiatry and Behavioral Neurosciences, McMaster University, Box 2000, Central Building Rm 304, 1200 Main Street West, Hamilton, ON L8N 3Z5, Canada e-mail: vanlierj@mcmaster.ca L. A. Schmidt Department of Psychology, Neuroscience and Behavior (Dr. Schmidt), McMaster University, Hamilton, ON, Canada M. Robinson The Centre for Child Health Research, The University of Western Australia, West Perth, WA, Australia 123 Child Psychiatry Hum Dev (2013) 44:382–390 DOI 10.1007/s10578-012-0332-z