Study of Ultrasound Imaging to Predict Time and Outcome in Pregnancies With Induced Labor

Fetal head engagement measured by ultrasound as a predictive factor of labor outcome in women with induced labor

T. EGGEBØ, L. K. GJESSING, I. ØKLAND, C. HEIEN, P. ROMUNDSTAD*, K. Å. SALVESEN** Department of Obstetrics and Gynaecology, Stavanger University Hospital, Norway * Department of Public Health, NTNU, Norway, St Olavs Hospital, Trondheim University Hospital

** National Center for Fetal Medicine, Department of Obstetrics and Gynaecology, Trondheim University Hospital (St. Olav's Hospital) and Department of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology

KEYWORDS:

Ultrasound, induced labor, cervical length, engagement of fetal head, occiput posterior, Bishop score, outcome of labor

Objective The aim of the study is to evaluate any possible associations between engagement of the fetal head, the cervical status or occiput posterior position and the outcome of labor in women with induced labor, and to compare the value of ultrasound measurements with Bishop score in predicting operative deliveries.

Methods The ultrasound examinations will be carried out in 275 women immediately before induction of labor. A transabdominal scan will be performed to determine the position of the fetal occiput, a transperineal scan with transverse view to determine the degree of engagement and a transvaginal examination to evaluate the cervical length and the cervical angle.. The Bishop score will be performed by another examinator who is blinded to the results of the ultrasound examinations. The time from induction to delivery will be tested in a Cox regression analysis with fetal head engagement, cervical length and parity as possible predictive factors and maternal age, BMI, gestational age, birth weight and head circumference as possible confounders.

Inclusion and exclusion criteria:

Women were eligible for the study if they had a live singleton pregnancy with cephalic presentation and a gestational age of more than 37 completed pregnancy weeks according to a mid-trimester scan.

Statistical analysis Appropriate statistical tests for comparisons, such as Mann Whitney U test, chi-square test, Fisher's exact test, Pearson correlation, Kaplan Meier survival analysis and Cox regression analysis will be used. For receiver-operating characteristics (ROC) curves, the area under the curve will be used as discriminator. P-values < 0.05 will be considered significant.

Inclusion criteria

• Pregnancy
• Indication of induced labor

Exclusion criteria

• More than one fetus
• Less than 37 weeks of pregnancy
• Previous cesarean section
• Breach position
• Dead fetus