Intrapartum ultrasonographic depiction of fetal malpositioning and mild parietal bone compression in association with large lower segment uterine leiomyoma.

With normal flexion of the fetal head prior to and during early normal labor, the fetal biparietal diameter becomes engaged in (and subsequently traverses) the anterior posterior aspect of the pelvic inlet. Thus, the biparietal diameter (characterized sonographically by depiction of the falx cerebri, thalami, and cavum septum pellucidum) will be obtainable upon transverse suprapubic placement of the ultrasound transducer during the first stage of labor. Deflexion, or extension, of the fetal head may be demonstrated sonographically at the level of the cervical spine. Recently, during intrapartum ultrasonographic assessment of a nulliparous patient with a known, large, lower-segment, uterine fibroid, exhibiting poor progress of labor, the fetal biparietal diameter was documented upon midsagittal suprapubic placement of the transducer. In addition, mild compression of the distal parietal fetal bone was demonstrated and considered consistent with compression by the leiomyoma. Following abdominal delivery, due to fetal distress and arrest of descent, significant deflexion of the fetal head (not suspected by intrapartum cervical examinations) and mild parietal bone depression, consistent with the ultrasonographic examination, were noted.