MRI-based pelvimetric measurements as predictors for a successful vaginal breech delivery in the Frankfurt Breech at term cohort (FRABAT).

OBJECTIVES

The purpose of this study was to investigate the role of the maternal pelvis, assessed by MRI pelvimetry in nulliparous women expecting a term fetus in breech presentation, to predict a successful and safe vaginal birth.

STUDY DESIGN

In this monocentric and anonymized cohort study, we enrolled 367 nulliparous women with breech presentation at 39 to 41 weeks of gestation during a period of 8 years at the University Women's Hospital in Frankfurt/Main. Pelvic measurements were obtained by standard MRI imaging. We correlated the obstetric conjugate, the pubic angle and the distance between the ischial tuberosities (intertuberous distance) with the maternal and fetal outcomes of vaginally intended breech births. The data was evaluated using logistic regression analysis.

RESULTS

241 of 367 participants (65.7%) experienced a successful vaginal delivery whereas 126 patients (34.3%) were subjected to secondary cesarean section. An increasing obstetric conjugate was significantly associated with an increasing rate of successful vaginal deliveries. No significant correlation of the intertuberous distance and the pubic angle with the mode of delivery could be shown. Although statistically not significant, we were able to define cut-off values of 10.9 cm in the intertuberous distance and 70° in the pubic angle; below these values, no successful vaginal delivery was recorded. No significant differences in the short-term outcomes were seen between the neonates of the vaginal delivery and the cesarean section groups. Inter- and intraobserver variability showed excellent reproducibility for all MRI parameters.

CONCLUSION

The obstetric conjugate correlates with the rate of vaginal deliveries in nulliparous women at term and can be used as a useful criterion for pre-selection and counseling of women with breech presentation and the desire for a vaginal delivery.