The objective of this study is to assess the level of active and passive smoking among mothers by measuring exhaled carbon monoxide (CO) and to evaluate its impact on key perinatal parameters in infants: fetal heart rate, Apgar score, birth weight, head circumference, and length. Regarding the newborn’s development and health status, the impact of this measurement on the behaviors and exemplary conduct of maternity ward professionals is not reported here. The relationship between exhaled CO levels and newborn characteristics has previously been assessed in a small sample at a single maternity ward. This study aims to replicate these measurements on a much larger sample to refine the values and broaden the scope by drawing on a large sample of maternity wards that have signed the Smoke-Free Maternity Charter. (Excerpt)