The participants will be recruited from the HaEmek Medical Center delivery room registration. Women delivered between 24-37 pregnancy weeks will be allocated to the study group. The investigators will invite them 3 month or more after delivery to ultrasound examination of the cervical length. The participants in the control group will be the women whom term delivery follows by chronological manner to those in study group. Data of the cervucal length will be collected at the time of the examination.