title: Effect of changes in maternal smoking habits in early pregnancy on infant birthweight.
abstract: BACKGROUND
  The inverse relationship between maternal smoking and infant birthweight is well documented.
  
  
  OBJECTIVE
  The aim of the present study was to examine whether a change in maternal cigarette consumption in early pregnancy affects the infant's birthweight.
  
  
  METHODS
  A total of 5980 women who presented to their general practitioners between 1976 and 1979 with an unplanned pregnancy and the babies resulting from these pregnancies were included in the study. Women were divided into four categories: non-smokers, smokers, quitters and reducers.
  
  
  RESULTS
  In terms of mean infant birthweight, the non-smokers had a clear benefit over the smokers whose babies were 153 g lighter (P < 0.001), and over the quitters whose infants were 39 g lighter. There was also an advantage in stopping smoking: the smokers had babies whose mean birthweight was 120 g less than that of the quitters (P < 0.001). There was no demonstrable benefit from reducing cigarette consumption without entirely stopping.
  
  
  CONCLUSIONS
  These findings may have important implications for where best to target health education.
authors.affiliation: Royal College of General Practitioners Manchester Research Unit.
authors.forename: P
authors.initials: P
authors.lastname: Frank
authors.forename: R
authors.initials: R
authors.lastname: McNamee
authors.forename: P C
authors.initials: PC
authors.lastname: Hannaford
authors.forename: C R
authors.initials: CR
authors.lastname: Kay
mesh_terms: D001294:Attitude to Health; D001724:Birth Weight / Q000502:physiology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome; D012907:Smoking / Q000639:trends*