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15. Reproductive > 10. Birth > Flashcards

10. Birth Flashcards

1
Q

What happens in the first stage of labour?

A

Creation of the birth canal, onset of labour to full cervical dilation.

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2
Q

What are the phases in the first stage of labour?

A

Latent and active phases.

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3
Q

Describe the latent phase of the first stage of labour.

A

Onset to 4cm dilation, slow.

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4
Q

Describe the active phase of the first stage of labour.

A

Faster rate of cervical change, 1-1.2cm/hour. Regular uterine contractions.

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5
Q

What happens in the second stage of labour?

A

Expulsion of foetus.

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6
Q

Describe the second stage of labour.

A

Rapid (takes up to an hour), urge to bear down.

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7
Q

Describe the movements of the foetus in the second stage of labour.

A

Descended head flexes as it reaches the pelvic floor - reduces presentation diameter. Internal rotation. Head stretches vagina and perineum. Head deliver - rotates and extends. Shoulders rotate and deliver. Rest of body follows rapidly.

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8
Q

What is the risk in the second stage of labour and how is it avoided?

A

Risk of tearing perineum, avoided by episiotomy.

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9
Q

What happens in the third stage of labour?

A

Expulsion of placenta, sheared off by strong contractions of uterus.

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10
Q

Describe the third stage of labour.

A

Contraction of uterus shears off placenta, compresses blood vessels to reduce haemorrhage. 5-15 minutes.

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11
Q

Which soft tissues are expanded in creation of a birth canal?

A

Cervix, vagina, perineum.

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12
Q

What does the birth canal expand to and generally how?

A

To 10cm, structural changes + lots of force.

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13
Q

What is the maximum size of birth canal determined by?

A

The pelvic, softening of ligaments may increase it.

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14
Q

What is the cervix made of in pregnancy?

A

Tough, thick collagen, coiled for structural strength.

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15
Q

What is cervical ripening?

A

Softening of the cervix for birth.

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16
Q

What does cervical ripening involve?

A

Reduced collagen production, increased glycosaminoglycans (disrupt matrix), reduced aggregation of collagen fibres (uncoils).

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17
Q

What triggers cervical ripening?

A

Prostaglandins E2 and F2x, locally diffused from uterus.

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18
Q

How does myometrium change through pregnancy for cervical ripening?

A

Smooth muscle increases in pregnancy. Force generate with raised [Ca2+]i from spontaneous action potentials.

19
Q

How is premature labour prevented?

A

Progesterone suppresses myometrial contractions until the proper time.

20
Q

How do uterine contraction differ in early and late pregnancy?

A

Early - low amplitude, every 20 minutes, mother unaware.

Late - higher amplitude, less frequent, ‘Braxton-Hicks’ contractions.

21
Q

How are uterine contractions made more forceful and frequent?

A

Prostaglandins + ripening of cervix - increase [Ca2+]i per action potential.
Oxytocin -> more action potentials with lower threshold.

22
Q

What are prostaglandins?

A

Biologically active lipids, local hormones.

23
Q

Where are prostaglandins produced?

A

Mainly in endometrium.

24
Q

What controls production of prostaglandins throughout pregnancy?

A

Oestrogen:progesteroner ratio.
P>O -> low prostaglandins throughout pregnancy.
O>P -> increased prostaglandins at end of pregnancy.

25
Q

Where is oxytocin secreted from?

A

Posterior pituitary under control of hypothalamus.

26
Q

How is oxytocin secretion increased?

A

By afferent impulses from cervix and vagina in Ferguson reflex - mechanical stimulation of cervix from prostaglandin contraction so more oxytocin secretion, strengthened contractions, cervix stimulated more so more oxytocin etc.

27
Q

What is the role of oxytocin?

A

Acts on smooth muscle receptors, acts on more if O>P.

28
Q

What is brachystasis?

A

Uterine smooth muscle relaxes less than it contracts. A feature of uterine smooth muscle that drives the presenting part of the foetus to the cervix.

29
Q

Describe the normal physiological processes which initiate labour.

A

Increased foetal cortisol -> O>P -> increased prostaglandins from endometrium of uterus -> increased force of contractions. Then a loop: cervix stretched -> oxytocin release from posterior pituitary in Ferguson reflex -> increased uterine contractions -> cervix stretched etc.

30
Q

What are the immediate physiological changes in the neonate which enable independent life?

A

Takes first breath so foetal circulation -> adult circulation.
Reduced pulmonary vascular resistance so blood fills lungs and increased return to LA => pressure LA > RA so foramen ovale closes.
Increased arterial pO2 -> ductus arteriosus contracts.

31
Q

What is the Apgar score?

A

Assesses condition of neonate scoring 0-10 according to colour, tone, pulse, respiration, response.

32
Q

What is the risk of haemorrhage in birth?

A

Uterus contracts after neonate has been born to shear off and expel placenta which leaves maternal blood vessels exposed -> risk of haemorrhage as blood to this site is 500-800ml/minute.

33
Q

How is maternal blood loss limited after birth?

A

Uterine contraction continues to compress placental blood vessels through myometrium to close them off. Enhanced effect with oxytocic drug.

34
Q

What is the common foetal presentation?

A

Baby lies longitudinally, in cephalic presentation, well flexed so vertex presents to pelvic inlet. Diameter of presentation is 9.5cm.

35
Q

What are the elements of labour?

A

The powers, the passage, the passenger.

36
Q

What are the powers of labour?

A

Deliver of foetus depends on contraction of myometrium that has undergone hypertrophy and hyperplasia in pregnancy. Contraction and retraction of smooth muscle fibres shortens the fundus of uterus.

37
Q

What is the passage of labour?

A

Bony pelvis and soft tissues.
Pelvic inlet - shorter in AP plane, 10.5cm diameter.
Pelvic cavity - circular, 12cm diameter.
Pelvic outlet - shorter in ML plane, 11cm diameter.

38
Q

What is the passenger of labour?

A

Size and presentation of foetus - orientation of head of foetus when entering pelvis is important.

39
Q

What may failure to progress in labour be due to?

A

Inadequate power - insufficient uterine contraction.
Inadequate passage - abnormal bony pelvis, rigid perineum.
Abnormalities of passenger - foetus too big, foetal/breech presentation.

40
Q

How can labour be induced?

A

Give the mother prostaglandins + oxytocic drugs -> cervix ripens and uterus begins contractions.

41
Q

What does a foetal scalp electrode assess in labour?

A

Foetal heart rate.

42
Q

How is caesarean section delivery performed?

A

Suprapubic incision. Linea alba and anterior layers of rectus sheaths are transected and resected superiorly. Rectus muscles are retracted laterally or divided through tendinous parts allowing reattachment without muscle fibres injury.

43
Q

What tools in operative delivery assist in delivery?

A

Forceps, vacuum extraction.

15. Reproductive (12 decks)

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