The earlier in pregnancy a woman quits smoking, the lower her risk for preterm birth, even if she was a high-frequency cigarette smoker, according to findings recently published in JAMA Network Open.
“A recent Ohio-based study found that women who smoke before pregnancy and quit either at the start of pregnancy or at the start of the second trimester experience approximately the same rate of preterm birth as their nonsmoking counterparts. Yet, it is not known if this association occurs nationally or varies by the frequency of prepregnancy smoking,” Samir Soneji, PhD, of The Dartmouth Institute for Health Policy & Clinical Practice, and Hiram Beltrán-Sánchez, PhD, of the department of community health sciences at the University of California, Los Angeles wrote.
They analyzed birth certificates from the offspring of 2,633,307 women (52.9% were non-Hispanic white, 23.6% were Hispanic and 14.2% were non-Hispanic black women) across the United States who smoked during the 3 months before their pregnancy.
Soneji and Beltrán-Sánchez found that the probability of preterm birth was 9.8% (95% CI, 9.7-10) among non-Hispanic white women, those who were pregnant for the first time, and those aged between 25 and 29 years who smoked one to nine cigarettes per day before becoming pregnant and maintained this frequency for the length of their pregnancy. The probability of preterm birth was 9% if smoking cessation took place at the start of the second trimester (an 8.9% relative decrease), and 7.8% if cessation took place at the onset of pregnancy (a 20.3% relative decrease).
The researchers discussed other findings from their analysis.
“First, only approximately one of four expectant mothers who smoked prior to pregnancy quit smoking throughout pregnancy. Second, about one of two expectant mothers who smoked during their pregnancy smoked 10 or more cigarettes per day. Third, smoking cessation — especially early in pregnancy — was associated with reduced risk of preterm birth,” they wrote.
“Cigarette smoking continues to represent a public health burden” for pregnant women, and stopping smoking appears to be challenging for them, Soneji and Beltrán-Sánchez concluded. – by Janel Miller
Disclosure: The authors report no relevant financial disclosures.