Objective: to examine the associations of passive smoking during 3^rd trimester of pregnancy and birth outcomes. Design: prospective (cohort) study. Setting: this study was conducted at Ain Shams University maternity hospital between period June 2015 and May 2016. Study subjects: A total of 200 women during their 3^rd trimester of pregnancy were included in the study with verbal consent from each woman Measures: through written (self-administered questionnaire) and exhaled carbon monoxide (CO) test Results: Current SHS was significantly associated with lower gestational age at delivery, lower birth weight, lower 1-min Apgar score and higher rates of SGA neonates. Conclusion: the current study showed a significant association between SHS in pregnant women and increased rates of preterm delivery, low birth weight and SGA neonates.