This study will include pregnant women in either 2nd or 3rd trimester of pregnancy. All consecutive pregnant patients in 2nd or 3rd trimester who will attend our unit for routine ultrasound exam will be asked to participate. Cervical length will be assessed in all patients, once abdominally and then vaginally (that would serve as golden standard). Correlation would be assessed between accuracy of measurement to BMI. Accuracy would be defind as the delta of cervical length between abdominal and vaginal routs.