Cephalo-pelvic disproportion exists when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal. This may be due to a small pelvis, a nongynecoid pelvic formation, a large fetus, an unfavorable orientation of the fetus, or a combination of these factors. Certain medical conditions may distort pelvic bones, such as rickets or a pelvic fracture, and lead to CPD.
Transverse diagonal measurement has been proposed as a predictive method.
The shape of the pelvis can also be a cause of CPD. The pelvis may be too small, or the shape of the pelvis may be malformed. Shorter women are more likely to suffer from CPD as are adolescents.
Diagnosis of CPD may be made when there is failure to progress, but not all cases of prolonged labour are the result of CPD. Use of ultrasound to measure the size of the fetus in the womb is controversial, as these methods are often inaccurate and may lead to unnecessary caesarian section; a trial of labour is often recommended even if size of the fetus is estimated to be large.
Theoretically, pelvimetry may identify cephalo-pelvic disproportion. However, a woman's pelvis loosens up before birth (with the help of hormones). A Cochrane review in 2017 found that there was too little evidence to show whether pelvimetry is beneficial and safe when the baby is in cephalic presentation. A review in 2003 came to the conclusion that pelvimetry does not change the management of pregnant women, and recommended that all women should be allowed a trial of labor regardless of pelvimetry results. It considered routine performance of pelvimetry to be a waste of time, a potential liability, and an unnecessary discomfort.
- Liselele HB, Boulvain M, Tshibangu KC, Meuris S (August 2000). "Maternal height and external pelvimetry to predict cephalopelvic disproportion in nulliparous African women: a cohort study". BJOG. 107 (8): 947–52. doi:10.1111/j.1471-0528.2000.tb10394.x. PMID 10955423.
- "Cephalopelvic Disproportion (CPD): Causes and Diagnosis". American Pregnancy Association. Retrieved 2016-03-22.
- McKenry, Patrick C.; Walters, Lynda Henley; Johnson, Carolyn (1979-01-01). "Adolescent Pregnancy: A Review of the Literature". The Family Coordinator. 28 (1): 17–28. doi:10.2307/583263. JSTOR 583263.
- Pattinson R, Cuthbert A, Vannevel V (2017-03-30). "Pelvimetry for fetal cephalic presentations at or near term for deciding on mode of delivery". Cochrane Database of Systematic Reviews. 3: CD000161. doi:10.1002/14651858.CD000161.pub2. PMC 6464150. PMID 28358979.
- Blackadar CS, Viera AJ (2004). "A retrospective review of performance and utility of routine clinical pelvimetry". Fam Med. 36 (7): 505–7. PMID 15243832.