The shape of your pelvic cradle is an important component in determining the outcome of your birth experience. The size and shape of this bony canal determines whether a baby of average size and shape and lying in a normal position would be able to negotiate its way out into the world.
There are 4 basic types of female pelvises and these are classified according to the shape of the brim or inlet. Although the shape of the pelvis varies, it is not a rigid, fixed structure, but an elastic system of bones that can widen and stretch, and which is very flexible at the joints so that it can open wide during labour.
The mother’s mobility and position during labour is critical in order to facilitate this process and there is a lot to be said for active labour if a mother does not have what is considered the ideal shape pelvis for birth to happen easily.
The four types of female pelvis:
The Gynaecoid or genuine female pelvis
It has an almost round brim and will permit the passage of an average-sized baby with the least amount of trauma to the mother and baby in normal circumstances. The pelvic cavity (the inside of the pelvis) is usually shallow, with straight side walls and with the ischial spines not so prominent as to cause a problem as the baby moves through.
The Android pelvis
It has a heart-shaped brim and is quite narrow in front. This type of pelvis is likely to occur in tall women with narrow hips and is also found in African women. The pelvic cavity and outlet is often narrow, straight and long. The ischial spines are prominent.
Women with this shape pelvis may have babies that lie with their backs against their mothers’ backs and may experience longer labours. It is important that these women take an active role during their labour and need to squat and move around as much as possible.
The Anthropoid pelvis
It has an oval brim and a slightly narrow pelvic cavity. The outlet is large, although some of the other diameters may be reduced. If the baby engages in the pelvis in an anterior position, labour would be expected to be straightforward in most cases.
The Platypelloid pelvis
It has a kidney-shaped brim and the pelvic cavity is usually shallow and may be narrow in the antero-posterior (front to back) diameter. The outlet is usually roomy. During labour the baby may have difficulty entering the pelvis, but once in, there should be no further difficulty.
Many women are concerned that their pelvic capacity may be limited and that they will therefore have difficulty in giving birth. The true capacity of the pelvis will only be realised during labour. Only the forces created by mother and baby during birth will allow the pelvis to open to its full potential. This may take some time, but it is the only true way of exploring the “fit” between the mother and baby during birth.