MATERNAL SMOKING  

 

Cigarette smoking is reported in some studies as the single most common cause of impaired fetal growth (accounting for up to 40% of cases in some series) (1).

The Facts:

  1. Although it is likely that some degree of growth restriction occurs in all fetuses whose mothers smoke, the restrictive effect is only sufficiently severe enough to result in a birthweight at or below the 10th percentile in  5-25% of fetuses (2,3).
  2. Average birth weight reduction is ± 200g (4).
  3. There is an inverse relationship between number of cigarettes smoked daily and birthweight (3,5)
  4. It is probably the only pathophysiologic process of IUGR that can be reversed or prevented in the index or subsequent pregnancies, if it is stopped (6).
    The birthweights of infants of mothers who are able to avoid smoking for at least half the pregnancy, are only slightly less than the weights of infants who did not smoke at all during pregnancy (7).
  5. Although cigarette smoke contains many hundreds of active toxic substances, nicotine appears to be the prime factor causing growth restriction. Nicotine induces the release of catecholamines (especially noradrenaline) from the adrenal glands and extra-adrenal chromaffin tissue, which produces profound vasoconstriction on the uterine vessels. There may be repetitive reductions in uteroplacental perfusion (may occur up to 400 times per day in women smoking over 20 cigarettes per day) (6).

 

 

REFERENCES
  1. Ounsted M, Moar VA, Scott A. Risk factors associated with small for dates and large for dates infants. Br J Obstet Gynaecol 1985;92:226.
  2. Butler NR, Golstein H, Ross EM. Cigarette smoking in pregnancy: It's influence on birth weight and perinatal mortality. Br Med J 1972;2:127.
  3. Anderson GD, Blidner IM, McClemont S et.al. Determinants of size at birth in a Canadian population. Am J Obstet Gynecol 1984;150:236.
  4. Haworth JC, Ellestad-Sayed JJ, King J et.al. Growth retardation in cigarette smoking mothers is not due to decreased maternal food intake. Obstet Gynecol 1980;137:719.
  5. Simpson WJ. A preliminary report on cigarette smoking and the incidence of prematurity. Am J Obstet Gynecol 1957;73:808.
  6. Manning FA. Fetal Medicine: Principles and practice. Appleton and Lange Connecticut 1995:320-321
  7. Sexton M, Hebel JR. A clinical trial of change in maternal smoking and its effect on birth weight. JAMA 1984;251:911.