Pregnant women who quit smoking during the first trimester and women who never smoked during pregnancy have a similar risk of delivering preterm or very small infants, according to a study published in the journal Obstetrics and Gynecology, Reuters reports. Premature delivery and stunted infant growth are the most well-documented side effects of smoking during pregnancy, and the risks increase for older women, according to study author Laura Polakowski of the Centers for Disease Control and Prevention and colleagues. For the study, the researchers analyzed 915,441 birth certificates for infants born in 2005 in 11 states that include information on whether the woman smoked during pregnancy.

The study found that 10% of women who smoked for the entire pregnancy gave birth to "preterm but not too small for gestational age" infants, compared with 8% of women who quit during the first trimester. Fifteen percent of women who smoked the entire pregnancy gave birth to full-term infants who were small for their gestational age, while 2% gave birth to premature infants who were small for gestational age. Among women who quit smoking during the first trimester, these outcomes occurred 9% and 1% of the time, respectively.

After adjusting for the women's age, previous preterm births and other factors, the researchers found that women who quit smoking in the first trimester reduced their risk of giving birth to a preterm, normal-size infant by 31%. The risk of delivering a full-term, unusually small infant was cut by 55% and the risk for delivering a preterm, unusually small infant was reduced by 53%. The risks were also reduced for women who quit smoking during their second trimester, although less significantly. The researchers found that the risk reduction was particularly high for older women -- especially those older than age 40 -- who quit smoking during the first trimester. According to the study, the results indicate that the risk of delivering a preterm or small-for-gestational-age infant for pregnant women who quit smoking during the first trimester is "comparable to those who never smoke during pregnancy" (Reuters, 7/21).

Reprinted with kind permission from nationalpartnership. You can view the entire Daily Women's Health Policy Report, search the archives, or sign up for email delivery here. The Daily Women's Health Policy Report is a free service of the National Partnership for Women & Families, published by The Advisory Board Company.

© 2009 The Advisory Board Company. All rights reserved.