Vaginal Birth After Cesarean Section: X-ray Pelvimetry at Term is Informative

Objective: To examine whether X-ray pelvimetry data to evaluate the likelihood of vaginal birth after previous cesarean section.

Design: Retrospective study.

Setting: University hospital.

Population: Patients with a previous cesarean delivery who underwent X-ray pelvimetry and gave birth at gestational age 37 weeks during a seven-year period.

Methods: 1190 patients with a scarred uterus were compared with 15,189 patients without a scarred uterus. In the scarred uterus group, 760 patients with a transverse pelvic diameter > or =12 cm were compared with 430 patients with a transverse pelvic diameter <12 cm.

Main Outcome Measures: The obstetrical outcomes were spontaneous or induced labor, and mode of delivery. The maternal morbidity outcomes were hemorrhage requiring transfusion of packed red cells, uterine rupture, bladder injury, and hysterectomy due to hemorrhage. The neonatal morbidity outcomes were the 5-min Apgar score, transfer to intensive care, and intubation.

Results: Patients with a scarred uterus had a significantly higher rate of cesarean section (35.5%) than those with no prior cesarean section (9%). Among patients with a scarred uterus who were selected for vaginal delivery, 81% delivered vaginally when the transverse diameter (TD) of the pelvic inlet was greater than 12 cm, 68% when the TD was between 11.5 and 12 cm, and 58% when the TD was less than 11.5 cm. Maternal morbidity was significantly higher in the patients with a scarred uterus. The neonatal results were comparable in the different groups.

Conclusion: X-ray pelvimetry tailors the information given to each patient about the likelihood of having a vaginal delivery. It can also be used to optimize the selection of patients allowed to enter labor.