The pelvis has been classified into four types, chiefly by the shape of the brim. Many individuals, however, have a combination of more than one type.
1. The Gyneacoid Pelvis: As described above, is the true female pelvis. Its main features are the rounded brim, the generous fore – pelvis (the part in front of the transverse diameter), straight side walls, a shallow cavity with a broad, well – curved sacrum, blunt ischial spines, a wide sciatic notch and a pubic arch of 90 degrees. It is found in women of average build and height with a shoe size of 4 or larger. It is well suited to child bearing.
2. The Android Pelvis: Is so called because it resembles the male pelvis. Its brim is heart shaped with a narrow fore – pelvis, and has a transverse diameter which is towards the back. The side walls coverage, making it a funnel shape with a deep cavity and a straight sacrum. The ischial spines are prominent and the sciatic notch is narrow. The angle of the pubic arch is less than 90 degrees. It is found in short and heavily built women who have a tendency to be hirsute. This type of pelvis predisposes to an occipito posterior position of the fetal head and is the least suited to child – bearing.
3. The Anthropoid Pelvis: Has a long, oval brim in which the antero posterior diameter is longer than the transverse. The side walls diverge and the sacrum is long and deeply concave. The ischial spines are not prominent and the sciatic notch is very wide, as is the sub – pubic angle. Women with this type of pelvis tend to be tall, with narrow shoulders. Labor does not usually present any difficulties, but a direct occipito – posterior position is often a feature.
4. The Platypelloid Pelvis: is flat, with a kidney shaped brim in which the anteroposterior diameter is reduced and the transverse increased. The side walls diverge, the sacrum is flat and the cavity shallow. The ischial spines are blunt, and the sciatic notch and the sub – pubic angle are both wide. The head must engage with the sagittal suture in the transverse diameter, but usually descends through the cavity without difficulty.
1. The Gyneacoid Pelvis: As described above, is the true female pelvis. Its main features are the rounded brim, the generous fore – pelvis (the part in front of the transverse diameter), straight side walls, a shallow cavity with a broad, well – curved sacrum, blunt ischial spines, a wide sciatic notch and a pubic arch of 90 degrees. It is found in women of average build and height with a shoe size of 4 or larger. It is well suited to child bearing.
2. The Android Pelvis: Is so called because it resembles the male pelvis. Its brim is heart shaped with a narrow fore – pelvis, and has a transverse diameter which is towards the back. The side walls coverage, making it a funnel shape with a deep cavity and a straight sacrum. The ischial spines are prominent and the sciatic notch is narrow. The angle of the pubic arch is less than 90 degrees. It is found in short and heavily built women who have a tendency to be hirsute. This type of pelvis predisposes to an occipito posterior position of the fetal head and is the least suited to child – bearing.
3. The Anthropoid Pelvis: Has a long, oval brim in which the antero posterior diameter is longer than the transverse. The side walls diverge and the sacrum is long and deeply concave. The ischial spines are not prominent and the sciatic notch is very wide, as is the sub – pubic angle. Women with this type of pelvis tend to be tall, with narrow shoulders. Labor does not usually present any difficulties, but a direct occipito – posterior position is often a feature.
4. The Platypelloid Pelvis: is flat, with a kidney shaped brim in which the anteroposterior diameter is reduced and the transverse increased. The side walls diverge, the sacrum is flat and the cavity shallow. The ischial spines are blunt, and the sciatic notch and the sub – pubic angle are both wide. The head must engage with the sagittal suture in the transverse diameter, but usually descends through the cavity without difficulty.
