passage
Last reviewed 05/2021
The bony passage is the pelvis. The inlet, mid-cavity and outlet dimensions must be sufficient to accommodate the foetus.
The bony passage may obstruct birth if:
- the shape of the pelvis is not ideal (has a round brim)
- about 15% of women have a pelvis with a long oval brim (anthropoid)
- the pelvis is contracted
- there are tumours of the pelvic bones
The soft passages are the uterine fundus & cervix, vagina, vulva and supporting tissues.
The soft passages may obstruct birth if:
- there are pelvic tumour e.g. fibromyomata or ovarian tumours
- there are tumours of surrounding tissues e.g bowel or bladder
- the passages are abnormal e.g. cervical stenosis or obstruction by the non-pregnant horn of a bicornuate uterus