Maternal Prepregnancy Obesity is an Independent Risk Factor for Frequent Wheezing in Infants by Age 14 Months Stefano Guerra, a,b,d,i Claudio Sartini, a,b,d Michelle Mendez, a,b,d Eva Morales, a,b,d Mònica Guxens, a,b,d Mikel Basterrechea, d,e,f Leonor Arranz, g,h Jordi Sunyer a,b,c,d a Centre for Research in Environmental Epidemiology b Hospital del Mar Research Institute (IMIM) c Universitat Pampeu Fabra, Barcelona d Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Barcelona e Subdirección de Salud Pública de Gipuzkoa, Department of Health of the Basque Government, San Sebastián f Health Research Institute Biodonostia, San Sebastián g Hospital Donostia, Basque Health Service (Osakidetza), San Sebastián h University of Basque Country (EHU-UPV), San Sebastián, Spain i Arizona Respiratory Center, University of Arizona, Tucson, AZ Abstract Background: Maternal prepregnancy obesity has been linked to the offspring’s risk for subsequent asthma. We determined whether maternal obesity is associated with increased risk of wheezing phenotypes early in life. Methods: We used data on 1107 mother–child pairs from two birth cohorts from the INMA–INfancia y Medio Ambiente project. Maternal height was measured and prepregnancy weight self-reported at enrolment (on average at 13.7  2 weeks of gestation). Maternal prepregnancy body mass index was categorised as underweight, normal, overweight and obese according to WHO recommendations. Information on child’s wheezing was obtained through questionnaires up to the age of 14 (1) months. Wheezing was classified as infrequent (<4 reported wheezing episodes) or frequent (4 episodes). Weight and length of infants were measured by trained study staff at 14.6 (1) months of age and weight-for-length z-scores computed. Results: Although maternal obesity did not increase the risk of the child to have any or infrequent wheezing, children of obese mothers were more likely to have frequent wheezing than children of normal-weight mothers (11.8% vs. 3.8%; P = 0.002). In fully adjusted multinomial logistic regression models, including infants’ weight-for- length z-scores and other covariates, maternal prepregnancy obesity was associated with increased risk of frequent [adjusted relative risk (RR) 4.18, 95% confidence interval (CI) 1.55, 11.3] but not infrequent (RR 1.05 [95% CI 0.55, 2.01]) wheezing in their children. Conclusions: Maternal prepregnancy obesity is independently associated with an increased risk of frequent wheez- ing in the infant by the age of 14 months. These findings add evidence on the potential effects of in utero exposures on asthma-related phenotypes. Keywords: obesity, wheezing, asthma, pregnancy. Obesity has been linked to asthma phenotypes both in children and adults. 1 Although the exact mechanisms by which obesity and asthma are linked remain unclear, prospective studies 2–6 have demonstrated that this association cannot be simply ascribed to increased weight gain among asthmatics. Recently, maternal obesity has been proposed as a potential ‘intergenerational’ risk factor for subsequent development of asthma in the offspring up to the ado- lescent years. 7–10 Three studies 7–9 reported between 30% and 50% increased odds for asthma for children and adolescents whose mothers either were obese or had body mass index (BMI) in the top tertile. These findings are in line with results from the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) cohort, although in that study maternal prepregnancy Correspondence: Stefano Guerra, Centre for Research in Environmental Epidemiology, Doctor Aiguader, 88, 08003 Barcelona, Spain. E-mail: sguerra@creal.cat 100 doi: 10.1111/ppe.12013 © 2012 Blackwell Publishing Ltd Paediatric and Perinatal Epidemiology, 2013, 27, 100–108