Obstetrics: Abnormal Labour

Study Notes

Abnormal labour, also known as labour dystocia, refers to a situation where there is slow or no progress in labour, associated with an increased risk of adverse perinatal outcomes for both mother and baby.

Progress in labour depends on three variables: power (efficiency of uterine contractions), passenger (fetus size, presentation, and position), and passage (uterus, cervix, and bony pelvis).
Abnormal progress in labour is diagnosed when the rate of dilatation falls to the right of the projected normal labour curve plotted on the partogram.
Delay in the first stage of labour is suspected if there is cervical dilatation of less than 2 cm in 4 hours.
Delay in the second stage of labour is diagnosed once the timelines have been exceeded.

Dysfunctional uterine activity is the most common cause of poor progress in labour, and is more common in primigravida and older women.
The assessment of uterine contractions is most commonly carried out by clinical examination and by using external uterine tocography.
Ineffective contractions can be managed by:
- Hypertonic uterine contractions: analgesia, stop oxytocin, IV fluid.
- Hypotonic uterine contractions: augmentation – ARM, oxytocin.

CPD implies anatomical disproportion between the fetal head and maternal pelvis, which can be due to a large head, small pelvis, or a combination of the two.
Women of small stature (1.60 m) with a large baby in their first pregnancy are likely candidates to develop this problem.
Rarely, a fetal anomaly will contribute to CPD.
CPD is suspected in labour if:
- Progress is slow or actually arrests despite efficient uterine contractions.
- The fetal head is not engaged.
- Vaginal examination shows severe moulding and caput formation.
- The head is poorly applied to the cervix.

Malpresentation is a presentation that is not cephalic, and is more common at earlier gestations.
Breech presentation is the most commonly encountered malpresentation, and occurs in 3-4% of term pregnancies.
Etiology of malpresentation includes:
- Maternal risk factors: pelvic tumours, abnormal placental site, nulliparity, and old age group.
- Fetal factors: prematurity, multiple pregnancies, fetal abnormalities, and short umbilical cord.

Breech presentation is when the fetal buttocks or lower extremities present into the maternal pelvis.
The most common type of malpresentation, accounting for 4% of all deliveries.
Types of breech presentation:
- Frank breech: both fetal thighs are flexed and both lower extremities are extended at the knees.
- Incomplete (footling) breech: one of the baby's knees is bent and his foot and bottom are closest to the birth canal.
- Complete breech: both thighs are flexed and one or both knees are flexed, sitting in a squat position.

If breech presentation is clinically suspected at or after 36 weeks, it should be confirmed by ultrasound scan.
The three management options available are:
1. External cephalic version (ECV)
2. Vaginal breech delivery
3. Elective cesarean section

Manually convert breech fetus to vertex presentation through external uterine manipulation with ultrasonic guidance.
Success rates vary according to the experience of the operator, but are around 50% in most units.
Contraindications to ECV include:
- Uteroplacental insufficiency
- Placenta previa
- Non-reassuring fetal monitoring
- Hypertension
- IUGR
- Oligohydramnios
- Previous uterine surgery

Although evidence suggests that it is probably safer for breech babies to be delivered by cesarean section, there is still a place for a vaginal breech delivery in certain circumstances.
Factors that contribute to increased perinatal morbidity and mortality include:
- Lethal congenital anomalies
- Prematurity
- Birth trauma
- Cord prolapse
- Head entrapment
- Asphyxia and perinatal loss

Precipitate labour refers to abnormally rapid progress of delivery within 1 hr in Multipara and 3 hrs in Primipara.
Risk factors include:
- Strong uterine contractions
- Small sized baby
- Minimal soft tissue resistance
- Previous history of precipitate labour
Maternal complications include:
- Laceration: Cervix, vagina, and perineum
- Uterine inversion and Uterine atony – PPH
- Amniotic fluid embolism
- Infection: as a result of unsterile delivery
Fetal complications include:
- Intracranial hemorrhage
- Fetal distress
- Delivery in inappropriate place