Smoking during pregnancy is known to affect the health of the mother and her unborn fetus. Recent research has identified and clarified some of these effects.

Mortality

A 1995 study by DiFranza and Lew provides strong evidence that smoking by the mother during pregnancy increases her infant's risk for SIDS.¹ Infants of mothers who smoked both during and after pregnancy have nearly a three times greater risk for SIDS than do infants born to mothers who did not smoke.⁸ Estimates of the number of smoking-attributable SIDS deaths and productive years of life lost are included in this databook for states that had 20 or more SIDS deaths in 1998.

Some of the documented effects of smoking on maternal mortality occur early in pregnancy. Although maternal death is a rare event, ectopic pregnancy is the leading cause of maternal death during the first trimester of pregnancy.⁹ Ectopic pregnancy is more probable among women who smoke.¹⁰ Nationally, the estimated number of smoking-attributable ectopic pregnancies was over 97,000 in 1993.^11,12 Because of the rarity of maternal death and the lack of state-level data on smoking-attributable ectopic pregnancy, data on maternal mortality related to smoking are not included in this first edition of the databook.

Morbidity

A relationship between smoking and poor maternal outcomes has been well established in the literature. Smoking has been found to increase the risk of placental complications and preterm premature rupture of the membranes.¹³ While smoking during pregnancy has also been found to protect against preeclampsia, thereby lowering a woman's risk of some severe adverse outcomes,^13,14 the net effects of smoking during pregnancy on maternal morbidity and health care costs are detrimental.¹¹ Because state-level data on smoking-attributable maternal morbidity are unavailable at this time, no data on this topic are presented here.

The effect of maternal smoking on infant morbidity is clear. The lower birth weight of babies born to mothers who smoke has been documented for almost 40 years.¹⁵ Nicotine affects the developing fetus by reducing blood flow through the placenta, which retards growth and contributes directly to low birth weight.¹⁶ The magnitude of the observed effect has also been markedly consistent: The weight of babies born to smoking mothers averages about 250 grams less than that of infants of nonsmokers.¹⁴ This first edition of the databook contains estimates of the percentage of low birth weight infants (< 2500 grams) in each state accounted for by smoking during pregnancy.

Low birth weight can lead to the higher use of neonatal intensive care units (NICU) at delivery and hence to higher health care costs.^17,2 Low birth weight and other smoking-attributable health problems at birth could also impose long-term health effects and costs, but these are not firmly documented. This edition of the databook includes estimates of the smoking-attributable probability of NICU admission, length of infant hospital stay at birth, and neonatal health care costs for each state.

Finally, although some effects of environmental tobacco smoke on infants during and after pregnancy have been established, they generally are modest.¹⁸ Data on these effects are also omitted from this edition of this databook.

Date last reviewed: 03/29/2006
Content source: Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion