Summary of derived smoking categories based on self-reported maternal smoking status recorded at the first antenatal appointment for each pregnancy.

Summary of derived smoking categories based on self-reported maternal smoking status recorded at the first antenatal appointment for each pregnancy.基于各次妊娠首次产前检查（first antenatal appointment）时记录的母亲自我报告吸烟状况所衍生的吸烟类别汇总。