Background: Fetuses, infants and children seem to be the most susceptible populations to the harmful effects of Environmental Tobacco Smoke (ETS). Significant maternal and fetal exposure to ETS inside the home may affect fetal and child health. The aim of the study was to evaluate the toxic effects of perinatal exposure to Second-Hand Smoke (SHS) on the infant's anthropometric measures and nutritional status and assess the benefit of using serum cotinine level in early childhood as a measurable indicator to such toxic perinatal exposure. Subjects & Methods: an observational cross-sectional study including the mothers and their children (less than two years) attend Monfallout's Family Medicine Center from the period of October 2017 to October 2018. The questionnaire and serum cotinine of the infants were investigated along with the most important SHS determinants (socio-demographic and environmental). Results: The study included 400 mothers with their infants. The commonest site of SHS exposure was the home and the husband was the main responsible source. SHS infants were classified according to their serum cotinine level as active smokers (14.44%), non-smokers exposed to SHS (75.56%), and non-smokers not exposed (10%). There was a highly statistically significant difference between median birth weight, median birth length of regularly exposed babies to smoking and median birth weight, median birth length of non-exposed babies. There was a dose-dependent decrease in weight and length of babies at birth, as well as associated with reduced weight, length and hemoglobin level in different stages later on in their life with an increase in serum cotinine level. Conclusion: Regular Prenatal and postnatal ETS lead to a dose-dependent decrease in weight and length of babies at birth and later on at early childhood stages. Mothers should take adequate precautions to avoid exposure to such SHS hazards as they and their children may be more susceptible to a series of negative health effects most mothers with their children were regularly exposed to SHS in various places during daily life especially at home and the main source of smoking was husband smoking.