Prevalence and patterns of cigarette smoking before and during early and late pregnancy according to maternal characteristics: the first national data based on the 2003 birth certificate revision, United States, 2016.

A clear trend in smoking has been observed among more educated women (i.e., at least a bachelor’s degree), who smoked considerably less both before and during pregnancy, which is consistent with a study based on PRAMS (in ten states) [ 16 ].

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