Reynolds CME, et al. - In this prospective observational study, researchers intended to assess breath carbon monoxide (BCO) testing in identifying maternal smokers as well as the difference between disclosers and non-disclosers of smoking status. In addition, they investigated whether other extrinsic factors affected the women’s BCO levels in pregnancy. A quarter of women presenting for antenatal care continued to smoke, but only 60% reported their smoking to midwives based on self-report and BCO levels. Data reported that BCO measurement was an inexpensive, practical method of improving identification of maternal smoking, and it was not affected by extrinsic sources of BCO. Improved identification means more smokers could be encouraged to quit smoking in early pregnancy potentially improving the short-term and long-term health of both mother and child.