Utility of the angle between the cervical canal and the anatomical conjugate line for predicting pouch of Douglas obliteration in patients with posterior placenta previa

by Satoshi Shinohara, Mayuko Kasai, Genki Yasuda, Rei Sunami

Pouch of Douglas obliteration, which prevents exteriorization of the uterus, increases surgical morbidity in patients with placenta previa. We aimed to identify magnetic resonance imaging features that can predict pouch of Douglas obliteration preoperatively.

We retrospectively assessed 39 women with posterior placenta previa who underwent magnetic resonance imaging for the preoperative assessment of placenta accreta spectrum. We defined the angle formed by the anatomical conjugate line (based on pelvimetry) and the cervical canal as the cervical inclination angle, which was measured on sagittal T2-weighted magnetic resonance imaging. Subsequently, we analyzed the correlation between the cervical inclination angle and pouch of Douglas obliteration.

The median maternal age was 34 years (range, 22–44 years) and 26 (66.7%) women delivered at term. The median cervical inclination angle was 98° (range, 71–128). Pouch of Douglas obliteration was confirmed in six patients (15.4%). The cut-off value of the cervical inclination angle for the prediction of pouch of Douglas obliteration was 102° with a sensitivity of 66.7%, specificity of 78.8%, positive predictive value of 36.4%, and negative predictive value of 92.9% (area under the curve, 0.83).

Measuring the cervical inclination angle may help in ruling out an obliteration of the pouch of Douglas. It may also be useful in the operative management of women with posterior placenta previa. However, caution should be exercised when generalizing the results of this study because of the small sample size, which makes the results prone to bias.