Parental factors affecting respiratory function during the first year of life

In a prospective, longitudinal, population-based cohort study of familial a nd environmental influences on the development of wheezing respiratory illn ess in early childhood, we identified infant length, weight, gender, and ex posure to maternal cigarette smoking as significant determinants of lung fu nction during the first year of life. A cohort of 237 infants (106 females: 131 males) was evaluated, and 496 lung function measurements were made bet ween the ages of 1-12 months. Respiratory function was assessed using the r apid thoracic compression technique to obtain maximum expiratory flow at fu nctional residual capacity (V'maxFRC). Parental history of asthma and smoki ng habits during pregnancy were obtained by questionnaire. Data were analyz ed using a longitudinal random effects model. infants with a parental histo ry of asthma and/or in utero passive smoke exposure were compared to a refe rence group of infants who had no parental history of asthma and in whom ne ither parent smoked pre- or postnatally. Boys were found to have a consistently lower V'maxFRC (-21.05 mL.s(-1)) thr oughout the first year of life in comparison to girls (P < 0.05). Maternal smoking during pregnancy was associated with a lower V'maxFRG in both gende rs in comparison to unexposed infants (P < 0.05). V'maxFRC was unaffected b y parental history of asthma. Gender-specific normative equations for V'max FRC throughout the first year of life were derived for the infant cohort as a whole and also for subgroups of infants, based on parental asthma and sm oking history. We conclude that lung function during the first year of life differs betwee n genders and is adversely affected by in utero passive tobacco smoke expos ure. Gender-specific predictive equations for V'maxFRG should be used durin g infancy. Pediatr Pulmonol. 2000; 29:331-340, (C) 2000 Wiley-Liss, Inc.