This study is planned prospectively in pregnancies who applied to Etlik Zübeyde Hanım Women's Health Care, Training and Research Hospital which is a teritiary hospital with 15.000 births anually, between January 2022 and January 2023. Cerclage treatment will be performed with the McDonald technique (the type of cerclage suture will be mersilene) between the 16-23 weeks of gestation in pregnant women with a diagnosis of cervical insufficiency based on the history , physical examination or ultrasound findings according to ACOG. The investigators will measure cerclage area after cerclage treatment (within 0-4 weeks) and different parameters besides it by transvaginal ultrasound. It will be whether the collected data is related to the incidence of preterm birth.

The parameters that will be measured with transvaginal ultrasound are:

• Cerclage area in the axial plane of the cervix
• Angle between anterior uterine wall and internal os
• Angle between anterior uterine wall and external os
• Anterior and posterior cervical widht at level of stitch
• Anterior and posterior stitch depth (stitch to canal )
• Cervical length above and below cerclage stitch

Before the data collection phase ,the required sample number for the research was determined using the G*power (Faul, Erdfelder, Buchner, & Lang, 2009) 3.1 program. When the alpha level is .05 and the power is %95 , the total number of samples was found o be 22.

Inclusion Criteria:

• Singleton pregnancy between 16-23 weeks of gestation and between the ages of 18-45
• According to ACOG based on history (Having one or more painless abortions between 16-22 weeks of gestation , a history of cerclage
• According to ACOG based on physical examination ( fetal membranes prolapsed from endocervical canal or not, cervical dilation present )
• Accoding to ACOG based on ultrasound examination ( if there is no previous history of preterm birth , if the cervical length is 10mm or less, if the cervical length is less than 25mm with a history of preterm birth )

Exclusion Criteria:

• Multiple pregnancies
• Pregnant women with premature rupture of membranes
• Pregnant women with uterine anomalies
• Pregnant women with fetal anomalies
• Pregnant women with Gestational diabetes mellitus, Chronic or gestational hypertension , fetal growth restriction , oligohydroamnios or polihydroamnios

Patients aged between 18-45 years old, have not any maternal chronic ilnesses, have not amnion fluid abnormalities, underwent cervical cerclage according to ACOC criteria between 16-23 gestational weeks.