BACKGROUND:

Over the past four decades, a significant research effort has been devoted to the understanding of the epidemiology and pathophysiology of chronic obstructive airways disease (COPD) in adult life. Epidemiologic studies uniformly have identified cigarette smoking as the predominant risk factor for the occurrence of COPD. Other factors such as socioeconomic status, environmental pollution, occupational exposures, and inherent genetic susceptibility have been observed to have very limited roles as risk factors.

A number of studies have suggested that postnatal maternal cigarette smoking has a measurable effect on lung function in children. One longitudinal analysis of this problem in children 5-19 years of ages identified significant effects on the growth of FEV1 and forced expiratory flow between the 25th and 75th percent volume points (FEF25-75) of the volume-time curve. These investigators, however, pointed out that the effects which they observed could have resulted from the in utero consequences of maternal smoking during pregnancy and/or from exposure to factors such as severe respiratory illnesses which have been documented to occur with increased frequency early in infancy and were not measured by the study.

DESIGN NARRATIVE:

Pregnant women were identified during the first trimester and followed monthly. Assessments were made of their smoking habits, urinary cotinine measurements, general medical condition, and status of pregnancy. Within two weeks of birth the infants were evaluated with partial forced expiratory flow-volume curves and measurement of passive respiratory system compliance and resistance. Measurements were repeated at intervals until age five. Babies were also observed regularly for respiratory illness experience, passive exposure to cigarette smoke, and general respiratory health.

The study helped to elucidate: the effect of maternal cigarette smoking on lung function at birth and development of function at five years; the effects of postnatal factors on lung development; the extent to which the reported increased frequency of respiratory illness in infants of smoking mothers resulted from in utero exposure to tobacco smoke products or postnatal passive smoking.