Page 166 - ترم ثاني كتاب تمريض صحة الام الكتروني

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Figure 4 Diameters of the pelvic outlet, viewed from below.

It is difficult to see from Figures 3 and 4, but the fetus has to rotate in order to
get through the pelvic canal. This is because the pelvic inlet is 13 cm wide, whereas the

pelvic outlet is only 11 cm wide. In order to fit through the pelvic outlet at its widest
dimension (12.5 cm from top to bottom), the fetus must rotate so it ‘presents’ its head

to the widest dimension of the pelvic cavity at every point as it passes through. The
largest part of the fetus is the skull, so the fetus’s head rotates first, and the shoulders
and the rest of the body follow.

➢ Diameter of pelvic outlet:

• Antero - posterior diameters:

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