Open main menu

Pelvimetry is the measurement of the female pelvis.[1] It can theoretically identify cephalo-pelvic disproportion, which is when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal. However, clinical evidence indicate that all pregnant women should be allowed a trial of labor regardless of pelvimetry results.[2]

Contents

IndicationEdit

Theoretically, pelvimetry may identify cephalo-pelvic disproportion, which is when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal. 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.[3]

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.[2] It considered routine performance of pelvimetry to be a waste of time, a potential liability, and an unnecessary discomfort.[2]

ComponentsEdit

The terms used in pelvimetry are commonly used in obstetrics. Clinical pelvimetry attempts to assess the pelvis by clinical examination. Pelvimetry can also be done by radiography and MRI.

Low-dose 3D-rendered CT scans can be used for estimating pelvimetry parameters:[4]

Parameter Image
(maximum intensity projection)
Definition Normal measures
Pelvic inlet Transverse diameter of the pelvic inlet   13 to 14.5 cm.[4]
Obstetric conjugate  
Median plane
The line between the narrowest bony points formed by the sacral promontory and the inner pubic arch 10 to 12 cm.[4]
Interspinous distance   The line between the narrowest bone points connects the ischial spines 9.5 to 11.5 cm.[5]
Pelvic outlet Sagittal pelvic outlet diameter¨   9.5 to 11.5 cm.[5]
Intertuberous diameter   10 to 12 cm.[5]

HistoryEdit

 
Pelvimeter

Traditional obstetrical services relied heavily on pelvimetry in the conduct of delivery in order to decide if natural or operative vaginal delivery was possible or if and when to use a cesarean section.[6] Women whose pelvises were deemed too small received caesarean sections instead of birthing naturally.

Traditional obstetrics have characterized four types of pelvises:

  • Gynecoid: Ideal shape, with round to slightly oval (obstetrical inlet slightly less transverse) inlet.
  • Android: triangular inlet, and prominent ischial spines, more angulated pubic arch.
  • Anthropoid: the widest transverse diameter is less than the anteroposterior (obstetrical) diameter.
  • Platypelloid: Flat inlet with shortened obstetrical diameter.

See alsoEdit

ReferencesEdit

  1. ^ "pelvimetry" at Dorland's Medical Dictionary
  2. ^ a b c Blackadar CS, Viera AJ (2004). "A retrospective review of performance and utility of routine clinical pelvimetry". Family Medicine. 36 (7): 505–7. PMID 15243832.
  3. ^ Pattinson RC, Cuthbert A, Vannevel V (March 2017). "Pelvimetry for fetal cephalic presentations at or near term for deciding on mode of delivery". The Cochrane Database of Systematic Reviews. 3: CD000161. doi:10.1002/14651858.CD000161.pub2. PMID 28358979.
  4. ^ a b c Salk I, Cetin A, Salk S, Cetin M (2016). "Pelvimetry by Three-Dimensional Computed Tomography in Non-Pregnant Multiparous Women Who Delivered Vaginally". Polish Journal of Radiology. 81: 219–27. doi:10.12659/PJR.896380. PMC 4865272. PMID 27231494.
  5. ^ a b c Gowri V, Jain R, Rizvi S (August 2010). "Magnetic resonance pelvimetry for trial of labour after a previous caesarean section". Sultan Qaboos University Medical Journal. 10 (2): 210–4. PMC 3074700. PMID 21509231.
  6. ^ Herbert Thoms (1946). "Yale - The Pelvic Survey" (PDF).