Most, of the earlier epidemiological studies of the association between cigarette smoking and late fetal plus neonatal mortality were revieffed

Considerable variation has occurred in the definition of the study population among the studies in which the relationship of cigarette smoking to fetal mortality (other than abortion) and early infant mort.ality was examined. The most commonly identified st,udy popula. tions have been perinatal deaths, neonatal deat’hs, and late fetal phIs ntwnat:~l deaths. Pcrinatal deaths are a combination of late fetal deaths (i.e., stillborn infants) and deaths occurring within the first week of life. Neonatal deaths include all deaths of liveborn infants wit,hin the first 28 days of life.