Cephalopelvic Disproportion Flashcards

1
Q

What are the ideal diameters of the pelvic brim, cavity and outlet?

A

Brim
AP: 11.5
Transverse: 12.5

Cavity
AP: 12.5
Transverse: 12.5
Ischial spines: 10.5 cm apart

Outlet
Ap: 12.5
Transverse: 11.5

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2
Q

What is the ideal subpubic angle and inter tuberous diameter?

A

Subpubic angle: 85 degrees

Inter tuberous diameter: 10 cm

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3
Q

What are the types of pelvic abnormalities with specific examples of each?

A
  • small pelvis:
    Round/ gynaecoid
    Long oval or anthropoid
- abnormal shape/ bone development: 
Triangular brim: android
Flat brim: platypelloid 
Rachitic 
Osteomalacic 
  • disease or injury
    Spinal kyphosis
    Pelvic tumours or fractures
    Effect of polio on limbs
  • congenital
    Absent sacral alae
    High assimilation
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4
Q

What are the two types of CPD and the differences between them?

A

Absolute: normal size babies but a small or abnormal shaped pelvis
OR contracted pelvis

Relative: normal shaped pelvis but a large baby/ malposition of the fetal head. Occurs in the patois patient

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5
Q

What are the dangers of CPD?

A

Increase in fetal mortality and morbidity due to instrumental delivery

Uterine rupture especially in the parous patient

Bladder damage with the formation of vesico- vaginal fistula due to a sloughing of the bladder base

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6
Q

What would make one suspicious of CPD

A
  • patient measuring less than 150 cm
  • brim index of less than 85
  • high head that cannot be made to engage
  • past obstetric history
  • pelvimetry- clinical, X-ray or ct- poor predictive value

Hard to predict in primigravid (conduct as a trial of labour)

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7
Q

How do you diagnose CPD?

A

HAS TO BE DIAGNOSED IN LABOUR

-Pelvic assessment 
Can sacral promontory be tipped 
Sacral shape/ contour 
Convergent or divergent  side walls 
Retropubic and subpubic angle 
Inter tuberous diameter 

However This is rarely done in labour

Diagnosis in labour:

  • delay in cervical dilatation on the partogram - if alert line in crossed, assess for cause and manage
  • no change in level/ station of presenting part (head 3/5 or more)
  • other causes of delay in labour excluded
  • increased caput and molding of fetal head (3+ moulding)
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8
Q

If there was a previous c section for CPD caused by a contracted pelvis should a VBAC be attempted?

A

No

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9
Q

When can a trial of labour be attempted in patients with previous CPD?

A

If the previous CPD was due to malposition (such as OP or transverse position of the fetal head)

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10
Q

What is the size and shape of the female pelvis influenced by?

A

1) genetic factors
2) nutrition
3) socio economic factors
4) infancy and pubertal factors

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11
Q

When can disproportion at the pelvic inlet be excluded?

A

If 2/5 or less head above the brim

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12
Q

How do you grade moulding?

A

Nil: bones normally separated
+- touching each other
++- overlapping but digitally separated
+++- overlapping but inseparable digitally

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13
Q

What are differentials of poor progress of labour? Using the 3 p’s

A

Patient:
Pain
Bladder full
Dehydrated

Power:
Inadequate contractions
Ineffective contractions

Passenger: 
Lie 
Presentation
Size of fetus 
Twins
Fetal head not engaged 

Passage:
Membranes not yet ruptured
Pelvis inadequate

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