A large study found that infants born to mothers who smoked during pregnancy had more than twice the risk for sudden unexpected infant death. The researchers added that this risk significantly reduced when the mother stopped smoking. Also mothers who quit in the third trimester had 23% lesser risk than mothers who smoked throughout.
Infants born to women who smoked even one cigarette per day during pregnancy had more than twice the risk for sudden unexpected infant death (SUID) compared with those whose mothers did not smoke, and that risk increased with each cigarette, a large study found. The risk fell when women reduced or quit smoking.
"Compared with the pregnant smokers who did not reduce their smoking during pregnancy (more than half), those who reduced the number of cigarettes smoked by the third trimester demonstrated a modest (12%) decrease in the risk of SUID, and quitting by the third trimester was associated with a greater reduction in risk (by 23%)," the researchers write.
The study, by Tatiana M. Anderson, PhD, Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, and colleagues, was published online March 11 in Pediatrics.
The researchers analyzed vital statistics data for 20,685,463 births and 19,127 SUIDs, adjusting for race and/or ethnicity/Hispanic origin of mother and father, mother's and father's age, mother's marital status, mother's education, live birth order, number of prenatal visits, gestational age in weeks, delivery method (vaginal or cesarean), infant sex, and birth weight.
SUID includes sudden infant death syndrome, accidental suffocation and strangulation in bed, and ill-defined causes.
Compared with nonsmokers, the risk for SUID was more than double among infants of mothers who reported any smoking during pregnancy (adjusted odds ratio [aOR], 2.44; 95% confidence interval [CI], 2.31 – 2.57).
The risk was almost twice as high with one cigarette smoked per day (aOR, 1.98; 95% CI, 1.73 – 2.28), and it increased linearly until plateauing at 3.17 (95% CI, 2.87 – 3.51) for those who smoked a pack (20 cigarettes) a day.
"This correlation was similar for each trimester when modelled independently, but the average number of cigarettes in the 3 trimesters together provided greater predictive power," the researchers explain.