Abnormal labour
Definition:When there is poor progress and /or the fetus shows signs of compromiseSimilarly;malpresentation,uterine scar and induction of labour are all examples of abnormal labour poor progress in labour:
This depend on three variables:power,passage and passenger and abnormalities in one or more of these variables can slow the normal progress in labour.
The power
Inefficient uterine contraction
Most common cause of poor progress in labour
More common in primi,and perhaps in older women
Characterized by weak and infrequent uterine contractions
Assessed by clinical exam,and use of external uterine tocography
A frequency of 4-5 contractions per 10 minutes is the ideal
Treatment is by rehydration,ARM and i.v oxytocin
Inco-ordinate uterine contractions
Irregular ,may occur in twos or threes then stop
If progress is satisfactory,no need for oxytocin
If progress not satisfactory ,oxytocin is effective
The passages
Abnormalities in the passages could be due to:
Abnormal pelvis
Abnormalities in the uterus and cervix e.g fibroid
Cervical dystocia:Non compliant cervix which effaces but fails to dilate because of severe scarring,usually as aresult of cone biopsy and may need caeserian section
Cephalopelvic disproportion
Implies anatomical disproportion between the fetal head and maternal pelvis
CpD is suspected if:
Progress of labour is slow or arrested despite efficient uterine contractions
2.The fetal head is not engaged
3.Vaginal exam.shows severe moulding and caput formation
4.The head is poorly applied to the cervix
Oxytocin can be given carefully to primigravida with mild to moderate CPD as long as the CTG is reactive
Relative disproportion can be overcomed if the malposition is corrected(i.e convertion to flexed OA position)
Passenger
Malpresentation:Vital to good progress is the tight application of the fetal presenting part on the cervixBreech and face may fail to do this leading to poor progress
Brow :mento vertical diameter-Need flexion or hyperextension to occur
Risk factors for poor progress in labour
Small women
Big baby
Malpresentation
Malposition
Early membrane rupture
Soft tissue /pelvic malformation
Patterns of Abnormal progress in labour
1.Prolonged latent phase
When the latent phase is longer than its time limits
More common in primi
Intervention as ARM or oxytocin will increase the likelihood of poor progress and need for C.S
Best management is by analgesia,reassurance and mobilization
2.Primary dysfunctional labour
Poor progress in the active phase of labour(<1cm/hour)
More common in primigravida
Causes:Inefficient uterine contractions is the commonest cause
Malposition
CPD
3.Secondary arrest
May occur in both first and second stage
When progress is initially good in the active phase of labour but then slows ,or stop altogether,typically after 7 cm diltation
Causes:Malposition
Malpresentation
CPD
Inefficient uterine contractions-less common