Washington, DC -- Reducing cigarette smoking during pregnancy results in improved birth weight of infants, even when smoking is reduced in the last half of pregnancy, according to a new study in the November issue of Obstetrics & Gynecology. The study found that newborn birth weight is directly related to the number of cigarettes smoked during pregnancy.

Smoking during pregnancy increases the risk of preterm birth, placental abruption, placenta previa, and low birth weight. Infants born with low birth weight (less than 5 ½ lbs) are at high risk for illnesses, even into adulthood. Other risk factors for low birth weight include maternal body mass index, the number of previous births, and preterm birth.

Researchers studied data on 160 women in Vermont who were enrolled in a university-based outpatient research clinic for smoking cessation and relapse prevention during pregnancy and postpartum between June 2001 and February 2003. After controlling for other known risk factors for low birth weight, including preterm birth, they found that the number of cigarettes a woman smoked in the third trimester directly correlated with newborn birth weight. For every cigarette smoked on a daily basis in the third trimester, there was a corresponding estimated reduction of 27 grams in newborn birth weight.

This study is encouraging, say the researchers, because it suggests that continued efforts to reduce smoking during pregnancy are important and can lead to improvements in birth weight, even among women who continue to smoke but are able to at least significantly reduce the number of cigarettes in the last half of pregnancy.

Contact: Ira M. Bernstein, MD, University of Vermont, Burlington, at ira.bernstein@uvm.edu.

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