Pelvis, narrow

Relatively narrow pelvic passage making childbirth difficult or impossible. The ends of the pelvic bones form an almost circular opening through which the child must pass at birth, and the possibility of this is governed by the size of the pelvis and of the child (particularly the head). There are various forms of female pelvis. Women with slightly masculine body structure – broad shoulders and narrow hips – may have a very narrow pelvis. Another cause of narrow pelvis may be rickets, poliomyelitis or tuberculosis of the vertebrae. A pelvis broken in an accident may also be narrowed. The width of the pelvis is usually checked in a test between the 36th and 38th week of pregnancy, and a decision arises.