6.3 Pathophysiology of labour

Question 1

Labour requires good & efficient contractions for ____________ in the 1st stage & _______________ of the foetal head in the 2nd stage:
• Abnormal uterine activity is usually seen in nulliparous women
• Causes of poor power: dehydration, ketosis (results in poor uterine activity)

Answer 1

cervical dilatation;

descent, rotation, delivery

Question 2

what are possible congenital defects leading to problems in the passage during labour?

Answer 2

Congenital pelvic abnormalities (e.g. pelvic distortion

Question 3

what are acquired maternal defects leading to problems in the passage during labour?

Answer 3

• Large uterine fibroids
• Ovarian masses
• Pelvic distortion (from poliomyelitis, rickets, osteomalacia, fractures)
• Poor ripening of the cervix

Question 4

what are acquired foetal defects leading to problems in the passage during labour?

Answer 4

• Foetal hydrocephalus
• Malposition
• Asynclitism (head tilted to one side)
• Extension of head

Question 5

_______________: disparity between the dirmensions of the foetal head & the maternal pelvis –> precludes vaginal delivery

• Absolute CPD (very rare): _______________ (e.g. foetal hydrocephalus, maternal pelvic distortion) –> absolute contraindication to vaginal delivery
• Relative CPD: difficulties of foetus navigating through the pelvis (e.g. malposition, asynclitism, extension of foetal head)

Answer 5

Cephalic pelvic disproportion (CPD);

true mechanical obstruction

Question 6

What is the cause of macrosmia leading to problem in the passenger during labour and how can it be estimated?

Answer 6

Foetal size largely depends on genetic influences but may also result from uncontrolled diabetes during pregnancy:
• Estimated by abdominal palpation or US (with degree of error)

Question 7

What is the cause of hydrocephalus leading to problem in the passenger during labour?

Answer 7

CSF accumulation in the brain that increases the size of foetal head

Question 8

What is the cause of malpresentation leading to problem in the passenger during labour and how can it be estimated?

Answer 8

Includes breech (frank, complete, incomplete), transverse, brow, face, compound (presence of foetal extremity with presenting part):
• Causes: prematurity, placenta praevia, grand multiparity, multiple gestation, uterine anomalies

Question 9

What is the cause of head extension leading to problem in the passenger during labour?

Answer 9

Extreme extension of the foetal head increases diameter

Question 10

What is the cause of asynclitism leading to problem in the passenger during labour?

Answer 10

Lateral tilting of the foetal head

Question 11

what is moulding?

Answer 11

ability of foetal skull bones to compress to reduce the diameter of the head (changes in the relationship between the foetal skull bones):
• Excessive moulding may cause tears in the dura & vessels

Question 12

What is a 1+ moulding

Answer 12

Suture lines just touching

Question 13

What is a 2+ moulding

Answer 13

Bones overlap but reducible

Question 14

What is a 3+ moulding

Answer 14

Bones overlap and irreducible

Question 15

What is delay in 1st stage of labour defined as?

Answer 15

Delay in the 1st stage of labour is defined as: • Cervical dilatation of <2cm in 4h (in both primigravida & multiparous woman) • Descent, flexion, rotation of foetal head

Question 16

What is secondary arrest of labour and what are the possible causes?

Answer 16

Secondary arrest refers to no change in cervical dilatation for >2h after normal active phase:
• Causes: CPD, malposition, inadequate/uncoordinated uterine activity

Question 17

How is abnormal labour managed?

Answer 17

• Artificial rupture of membranes (AROM)
• Oxytocin infusion (increases uterine contractions)
• Adjustment of maternal posture (upright position during 2nd stage; if all is well, any position that is most comfortable can be adopted)
• Adequate analgesia & support
• Hydration (for ketosis → causes poor uterine activity)

Question 18

What are foetal consequences of prolonged labour?

Answer 18

• Hyperstimulation (secondary to oxytocin use): repeated transient foetal hypoxaemia → dangerous if inadequate recovery time between uterine contractions
• Traumatic delivery: foetal morbidity, mortality (e.g. shoulder dystocia)
• Neonatal sepsis
• Foetal death

Question 19

What are maternalconsequences of prolonged labour?

Answer 19

• Ketosis (from dehydration, anaerobic metabolism)
• Sepsis: increased risk due to prolonged rupture of membranes and repeated vaginal examinations
• Risks associated with instrumental delivery & Caesarean sections
• Traumatic delivery (e.g. shoulder dystocia) → maternal morbidity
• Uterine rupture → foetal & maternal death
• 3rd stage complications (e.g. PPH, retained placenta)
• Vesicovaginal fistulation: due to prolonged compression of anterior vaginal wall & bladder by foetal presenting part