Contracted Pelvis

Original Editor - Temitope Olowoyeye Top Contributors - Temitope Olowoyeye, Kirenga Bamurange Liliane, Kim Jackson and Vidya Acharya

Introduction

Contracted pelvis considered rare in the developed world, is still prevalent in some developing countries. The contracted pelvis is the major cause of cephalopelvic disproportion, Labour Dystocia, and instrumental delivery. Labour Dystocia is the most common complication associated with a contracted pelvis which leads to increased incidence of perinatal and maternal morbidity as well as mortality.

It is described as one with reduced pelvic dimensions or shape that is sufficiently abnormal to cause difficulty in the delivery of a normal-sized fetus during labor

The female pelvis

In obstetrics, the shape, type, and diameter of the female pelvis determine the course and outcome of labor. The pelvis is made up of the sacrum, the coccyx, and two os coxae Each os coxae is made up of the ischium, the ilium, and the pubis. The pelvis is formed inferiorly between the sacrum and the coccyx (sacrococcygeal symphysis), posteriorly between the sacrum and each ilium (sacroiliac joint), and anteriorly between the pubic bodies (pubic symphysis).

The pelvic cavity is divided into the true pelvis and the false pelvis by the pelvic inlet.

The pelvic inlet, is the anatomical limit between the true pelvis below and the false pelvis above, and its regarded as the doorway to the birth canal in obstetrics. The pelvic inlet involves three of the four units of which the bone pelvis is composed. The pelvic brim involves the first sacral segment, the iliac and pubis portion, but not the ischium. The dimensions of the pelvic inlet are determined by the general shape of the female pelvis.

The shape of the pelvic inlet depends on the general shape of the pelvis. Caldwell and Moloy classified the female pelvis into 4 basic pelvic types which are, in order of frequency, gynaecoid (∼50%), android, anthropoid, and platypelloid.

The gynaecoid pelvis is the most suitable for a vaginal birth, the anthropoid pelvis is acceptably favorable. The android and platypelloid are known to be suboptimal.

The diameters of the pelvic inlet can be defined as

The anteroposterior (or "conjugate") diameter is the distance between the pubic symphysis and the sacral promontory. Three distances are:

• The anatomical conjugate or true: Measured between the sacral promontory and the upper edge of the pubic symphysis and measures an average of 11.0 cm
• The obstetric conjugate: Measured from the sacral promontory to the point bulging the most on the back of the symphysis pubis, located about 1 cm below its upper border. It measures 10.5 cm on average; it is the lesser anteroposterior diameter.
• The diagonal conjugate: Measured between the sacral promontory and the lower edge of the pubic symphysis, measuring an average of 12.5.

A contracted pelvis is established when the pelvic inlet at the interaxial dimension is less than 10 cm; this is viewed as a suspicion of the contracted pelvis, and when it is less than 8 cm it is viewed as a contracted pelvis.

Causes

• Developmental
• Metabolic: Rickets, Osteomalacia
• Traumatic: fractures.
• Neoplastic: osteoma.

• Lumbar kyphosis.
• Lumbar scoliosis.
• Spondylolisthesis: The 5th lumbar vertebra with the above vertebral column is pushed forward while the promontory is pushed backward and the tip of the sacrum is pushed forwards leading to outlet contraction.

• Dislocation of one or both femurs.
• Atrophy of one or both lower limbs.

Diagnosis of contracted pelvis

Abdominal examination:

• Nonengagement of the head: in the last 3-4 weeks in primigravida.
• Pendulous abdomen: in a primigravida.
• Malpresentations: are more common.

Pelvimetry: It is assessment of the pelvic diameters and capacity done at 38-39 weeks.

It includes internal pelvimetry (vaginal examination) for:

• inlet,

• cavity, and
• outlet.

External pelvimetry for ( Dynamic exteral pelvimetry test):

• inlet and
• outlet.

Imaging pelvimetry:

• X-ray.
• Computerised tomography (CT).
• Magnetic resonance imaging (MRI) .

CT and MRI are recent and accurate but expensive and not always available so they are not in common use in the developing countries.

Degrees of contracted pelvis

• Minor degree: The true conjugate is 9-10 cm. It corresponds to ma inor disproportion.
• Moderate degree: The true conjugate is 8-9 cm. It corresponds to moderate disproportion.
• Severe degree: The true conjugate is 6-8 cm. It corresponds to marked disproportion.
• Extreme degree: The true conjugate is less than 6 cm.

Complications

Complications of Contracted Pelvis are;

Mternal

• Pendulous abdomen.                        
• Nonengagement.
• Pyelonephritis especially in high assimilation pelvis due to more compression of the ureter.
• Inertia, slow cervical dilatation and prolonged labour.
• Premature rupture of membranes and cord prolapse.
• Obstructed labour and rupture uterus.
• Necrotic genito-urinary fistula.
• Injury to pelvic joints or nerves from difficult instrumental delivery.
• Postpartum haemorrhage.

Foetus

• Intracranial haemorrhage.    
• Birth asphyxia.              
• Fracture skull.
• Nerve injuries.                  
• Intra-amniotic infection.

Management

Timely management of contracted pelvis during labour is essential for the safety of both mother and foetus. However, management depends mainly on the degree of contraction.

• Minor degree of contracted pelvis vaginal delivery is recommended.
• Moderate degree of contracted pelvis trial labour, if failed caesarean section
• Severe or extreme degree of contracted pelvis, caesarean section is required.

Indications of caesarean section in contracted pelvis

• Moderate disproportion if trial of labour is contraindicated or failed.
• Marked disproportion.
• Extreme disproportion whether the foetus is living or dead.
• Contracted outlet.
• Contracted pelvis with other indications as;
• elderly primigravida,
• malpresentations, or
• placenta previa.

Implications for physiotherapy

Adequate knowledge of contracted pelvis, degrees and the process of labor would greatly enhance physiotherapy interventions in the management of contracted pelvis. Postural change during labour may have an effect on progress in labour as postural change enhances uterine activity, increasing the dimensions of pelvis. Increased maternal pelvic dimensions are believed to contribute to the reduction of the incidence of failure of labour to progress, ease of delivery of the baby, and reduced risk of cesarean birth during labour.

Physiotherapy is recommended in the minor and moderate contracted pelvis and is targeted at postural changes that would encourage an increase in the pelvic inlet diameters.

Also, Physiotherapy has been found efficient to reduce pain, duration of labor, anxiety, laceration, and episiotomy.