Background: Pregnant women are exposed to a wide range of medications, including antibiotics. Although antibiotics are many times absolutely important to prevent and treat infections as well as prevent premature labor, their overuse poses a threat to the growing fetus as well as the mother.  The ill-effects of antibiotic over-use and having them without prescription can cause developmental abnormalities in the fetus, known as teratogenicity. They could also cause maternal allergic reactions, as well as long term effects on the child's immunity and growth in future. Aim: In this study we aim to study the knowledge and attitude of pregnant women toward usage of antibiotics and risk of preterm baby. Methodology: We conducted a cross-sectional study, of 2470 women who presented in king Abdulaziz University, Jeddah, Saudi Arabia from April 2017 to December. Conclusion: We noted that most mothers were aware of that they must not take antibiotics without prescription while pregnant, especially for ailments such as common cold and abdominal pain. However, the pharmacists must be regulated for unnecessary over-dispatching of antibiotics, especially without confirming the pregnancy status of the costumers.