Labour is said to be obstructed when there is no advance of the presenting part despite strong uterine contractions. The obstruction usually occurs at the pelvic brim but may occur at the outlet, for example deep transverse arrest in an android pelvis.
Causes of obstructed labour
- Cephalopelvic disproportion or disparity between the size if the mother’s pelvis and fetus that precludes vaginal birth: is the most common cause of obstructed labour. The fetus may be large in relation to the pelvis, or the pelvis mat be contracted.
- Deep transverse arrest: an outcome of an occipitoposterior position can cause obstructed labour.
- Malpresentation: Vaginal birth is impossible in cases of shoulder or brow presentation, or in persistent mentoposterior position.
- Pelvic mass: Fibroids located in the lower segment or on the cervix can prevent descent of the fetal head, causing obstructed labour. Ovarian tumours or rare tumours of the bony pelvis may also prevent the head from entering the pelvis.
- Fetal abnormalities: Abnormalities such as hydrocephalus resulting in disparity between the size of the fetus and the pelvis may cause obstruction. Conjoined twins, or locked twins, are a rare cause.
Signs of obstructed labour
- The presenting part does not enter the pelvic brim despite good contractions.
- The nurse should exclude reasons such as a full bladder, loaded rectum, or excessive liquor volume as factors contributing to the failure in descent.
- As the presenting part is unable to descend, cervical dilatation is affected and dilatation is slow.
Late signs of obstructed labour
- These arise in a badly managed or neglected labour and the diagnosis of obstructed labour should be made before these signs are seen.
- On examination the mother is dehydrated, ketotic and in constant pain.
- Clinical signs also include pyrexia and rapid pulse rate.
- Urinary output is poor and haematuria may be present.
- Evidence of fetal distress may be observed and where the nurse has noted a maternal tachycardia the tow rates should be compared.
- Profound bradycardia or fetal demise may be overlooked as the tow rates are misinterpreted.
Management of obstructed labour
- Prevention of obstructed labour in the first instance, And Assessment of the risk within the antenatal period begins with noting any history of prolonged labour or difficult births.
- Antenatal assessments include abdominal examination which should alert the nurse to any Malpresentation or signs of Cephalopelvic disproportion.
- An intravenous infusion must be commenced, to correct dehydration.
- Blood is taken for cross-matching in case a transfusion is needed.
- The mother will require treatment with antibiotics, to overcome any infection that may be present.
- If obstructed labour is recognized in the first stage of labour, as when the head is extended to brow presentation, delivery should be caesarean section.
- Also, if the obstruction cannot be overcome by rotation and assisted birth, caesarean section should be performed as soon as possible.
- Following the birth of the baby and prior to repair of the uterus and abdomen, the surgeon will check carefully for any indication that the uterus has ruptured.
Complications of obstructed labour
- Trauma to the bladder may occur as a result of pressure from the fetal head during labour or as a result of trauma during delivery.
- Vesicovaginal fistula (VVF): is still a common cause of morbidity in women in developing countries.
- Prolonged compression of the tissues causes necrosis of the bladder and vaginal walls and result in urinary incontinence.
- Intrauterine infection may follow prolonged rupture of membranes.
- Intrauterine asphyxia may result in a fresh stillbirth or, if the baby is born alive, permanent brain damage.
- Ascending infection can cause neonatal pneumonia which may also develop as a consequence of meconium aspiration