During normal vaginal delivery, deep transverse arrest occurs. Ventous was employed for the safe delivery. This mother may have the following type of pelvis:
Criteria for the deep transverse arrest: The head is deep into the cavity. The sagittal suture is placed in the transverse bispinous diameter and, There is no progress in descent of the head even after 1/2 -1 hour following full dilatation of the cervix. Causes of deep transverse arrest: Faulty pelvic architecture such as prominent ischial spines, flat sacrum, and convergent side walls Deflexion of the head Weak uterine contraction Laxity of the pelvic floor muscles Ref: Textbook of Obstetrics by DC Dutta, 6th edition, Page 372.
Flat sacrum and convergent side walls
Gynaecoid
Platypelloid
Anthropoid