Routine 36-week scan

Objectives: First, to report the incidence of non-cephalic presentation at a routine 36-week ultrasound scan, the uptake and success of external cephalic version (ECV) and the incidence of spontaneous rotation from non-cephalic to cephalic presentation. Second, to determine the maternal and pregnancy characteristics that provide a significant contribution to the prediction of non-cephalic presentation at the 36-week scan, successful ECV from non-cephalic to cephalic presentation and spontaneous rotation from non-cephalic to cephalic presentation. Methods: This was a retrospective analysis of prospectively collected data from 107 875 women with a singleton pregnancy who had undergone a routine ultrasound scan at 35 + 0 to 36 + 6 weeks' gestation. Patients with breech or transverse/oblique presentation were divided into two groups: those scheduled for elective Cesarean section for a fetal or maternal indication other than abnormal presentation, and those that would potentially require ECV. The latter group was reassessed after 1-2 weeks and, if the abnormal presentation persisted, the parents were offered ECV or elective Cesarean section at 38-40 weeks' gestation. Multivariable logistic regression analysis was carried out to determine which maternal and pregnancy characteristics provided a significant contribution in the prediction of non-cephalic presentation at the 36-week scan, successful ECV from non-cephalic to cephalic presentation and spontaneous rotation from non-cephalic to cephalic presentation. Results: At the 36-week scan, fetal presentation was cephalic in 101 664 (94.2%) pregnancies and either breech, transverse or oblique in 6211 (5.8%). In 0.3% of cases with cephalic presentation at the 36-week scan, there was subsequent spontaneous rotation to non-cephalic presentation, and in half of these, the diagnosis was made during labor or at birth. ECV was attempted in 1584/6211 (25.5%) pregnancies with non-cephalic presentation at the 36-week scan and was successful in only 44.1% of cases. In the remaining 74.5% of cases, ECV was not attempted because of any of the following reasons: ECV was declined