1. Delivery canal abnormalities
Lecturer: Dr. Hui Wang
Department of Obstetrics & Gynaecology
Tongji Hospital
Tongji Medical College
HUST, Wuhan, China

2. Labour canal Bony canal (pelvic cavity)
Soft canal: 1. lower uterine segment
(isthmus of uterus)
2. cervix
3. vagina
4. perineum

3. 1. Bony canal abnormalities
Abnormal shape
Abnormal size

4. Normal shape
Only one: Gynecoid pelvis

5. Abnormal shape Platypelloid pelvis Anthropoid pelvis Android pelvis
Miscellaneous: pelvic malformation

6. Good

7. The several kinds of pelvic malformation

8. Michaelis rhomboid
The shape of Michaelis rhomboid is a simple standard to judge the pelvic shape is normal or abnormal (malformation).
Method: symmetry / asymmetry ↓
malformation

9. Abnormal size: narrow pelvis
Normal pelvic external parameters
IS: interspinal diameter: 23 ~26 cm
IC: intercristal diameter: 25 ~28 cm
EC: external conjugate: 18 ~ 20 cm
TO: transverse outlet: 8.5 ~ 9.5 cm (9)

10. Narrow types Inlet plane narrow:
true conjugate diameter ≤ 10 cm (normal 11 cm)
Midplane narrow:
interspinous diameter ≤ 9 cm (normal 10 cm)
Outlet plane narrow
transverse outlet ≤ 8 cm (normal 9 cm)
Generally contracted pelvis
every plane diameter ≤ 2 cm then normal

11. Clinical presentation & Diagnosis
History: dwarf, bony disease
Fetal head engagement difficult after 37 GW
Abnormal fetal position
Cephalopelvic disproportion (CPD)
Abnormal pelvimetry (IS,IC,EC,TO)
Asymmetry of Michaelis Rhomboid

12. Maternal and fetal complications
Mother: prolonged labour
pelvic floor damage, uterine rupture
postpartum haemorrhage
genital fistula
puerperium
Infant: premature rupture of membrane (PROM)
prolapse of umbilical cord
fetal injury, cranial haemorrhage
fetal distress, neonatal asphyxia

13. Treatment Principle Hospitalized in advance Selective cesarean section
Avoid vaginal delivery for term normal weight infant

14. 2. Soft canal abnormalities
Lower uterine segment: scar, myoma,
Cervix: tough, edema, carcinoma
Vagina: diaphragm, tumour
Perineum, tough, edema
Ovarian or other tumour interfere fetal head engagement