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Year 2 Reproduction > Labour and Delivery > Flashcards

Labour and Delivery Flashcards

1
Q

How many Stages of labour are there?

A

3

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2
Q

What happens in stage 1 of labour?

A

Establishing the birthing canal- the pelvis readies itself, the cervix opens. The foetal head will descend into the developing birth canal.

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3
Q

What happens in the second stage of labor?

A

The baby passes down and out of the birthing canal

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4
Q

In what stage of labour is the placenta delivered?

A

Stage 3

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5
Q

What is necessary to establish a birthing canal?

A

Cervix must dilate to 10cm, examine with fingers to feel thickness and dilation of cervix

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6
Q

What is the birth canal?

A

Plevis, cervix, vagina and perineum.

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7
Q

How does uterine smooth muscle facilitate labour?

A

Uterus contracts with increasing force and frequency

The uterus only partially relaxes after each contraction- giving a shorter muscle fibre after each contraction

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8
Q

What is retraction?

A

Myometrial muscle fibre length after each contraction is shorter

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9
Q

Describe the symmetry and polarity of uterine contractions.

A

Contraction starts from two poles and travels across the funds and down the uterus. The upper uterus contracts more forcefully than the lower uterus.

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10
Q

How does the cervix ‘ripen’?

A

The cervix is a 3-5cm closed structure made up of collagen fibres in a proteoglycan matrix. Ripening involves a reduction in collagen (collegenase activity) and an increase in the glycosaminoglycans and hyularuonic acid matrix. This gives rise to a higher water content - softer cervix.

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11
Q

What stimulates cervical ripening?

A

Oestrogen
Relaxin
Prostaglandins PGE2 and PGF2(alpha)

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12
Q

Effacement and dilation are the two processes that what structure undergoes in labour?

A

The cervix (thinning and opening)

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13
Q

What initiates labour?

A

The exact mechanism is unknown.
We do know ruptured membranes releases lysosomes.This will stimulate prostaglandin release. Prostaglandins stimulate cervical ripening and uterine contraction, both of these feed back to the hypothalamus and result in oxytocin release.
Oestrogen:Progesterone ratio increases which increases prostaglandins and makes the myometrium more oxytocin sensitive.
Arguments for cortisol levels

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14
Q

What physiological mechanisms limit post part bleeding?

A

Contraction and retraction of uterus creates a blood vessel ligature in the myometrium
Pressure on the placental site by contracted uterine wall
Blood clotting

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15
Q

Outline common fetal positions.

A

Lie- transverse or longtitudinal
Attitude- head should be flexed
Presentation- Breech (frank, full or single foot)

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16
Q

How might we induce labour?

A

Rupture membranes
Anti-progesterones
Oxytocin
Prostaglandins

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17
Q

How can we monitor foetal physiology in labour

A

Heart rate- foetal stethoscope or doppler.
Colour and volume of amniotic fluid
Scalp capillary pH

(mums observation give clues too)

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18
Q

How can we facilitate delivery? (List 3 techniques)

A

Caesarian section
Forceps
Vacuum extractin

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19
Q

How do we clinically define the second stage of labour?

A

Time between fully dilated cervix and the delivery

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20
Q

The passive part of stage 2 of labour involves what?

A

Descent and rotation of the head

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21
Q

A woman pushing a baby out equates to which part of labour?

A

Active stage 2

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22
Q

Why is a long third stage of labour dangerous?

A

Increases the risk of bleeding (time between delivery and complete placental expulsion should be 5-15 mins and longer than 1 hour is very concerning)

23
Q

What happens at the start of labour?

A

Excitability f the uterus increases

Cervix ripens

24
Q

What happens to oxytocin receptors in the myometrium in late pregnancy?

A

Rapid upregulation (high oestrogen)

25
Q

The placenta produces less progesterone in the final stages of pregnancy- what is progesterone effect on the myometrium in pregnancy?

A

Inhibits contraction

26
Q

What is a prostaglandin?

A

Biologically active lipid that acts locally as a hormone

27
Q

What ratio regulates prostaglandin levels?

A

Oestrogen:Progesterone

28
Q

If prostaglandin is given systemically what may happen?

A

Powerful sooth muscle contractor- diarrhoea, myometrial contraction
Cervix softens
Temp goes up

29
Q

Which organs make prostaglandins in labour?

A

Placenta, decidua, myometrium and all membranes

30
Q

What action does oestrogen have on the myometrium?

A

Increases communication via gap junctions - better more coordinated contractions.

31
Q

What mechanical factor gives rise to increase uterine contractility in labour?

A

Stretching

32
Q

Which hormone stimulates uterine contraction?

A

Oxytocin (in pregnancy this is inhibited by progesterone and relaxin, plus low receptor numbers)

33
Q

Which gland releases oxytocin and from what gestational age is the myometrium responsive?

A

Posterior Pituatary

36 weeks the receptor number is high enough to respond

34
Q

Which gland releases oxytocin and from what gestational age is the myometrium responsive?

A

Posterior Pituatary (under hypothalamic control)

36 weeks the receptor number is high enough to respond

35
Q

What is Ferguson reflex?

A

Afferent cervical and vaginal impulses positively feedback on oxytocin release

36
Q

Which gland releases oxytocin and from what gestational age is the myometrium responsive?

A

Posterior Pituatary (under hypothalamic control)

36 weeks the receptor number is high enough to respond (high oestrogen:progesterone)

37
Q

What pathology may result in oxytocin and thus uterine contraction?

A

Infection or bleeding

38
Q

What determines the maximum size of the birth canal?

A

The pelvis inlet (normally 11cm in diameter, ligament softening may increase this)

39
Q

What happens to levator anti and the central perineum in birthing?

A

Fibres stretch and so almost a transparent membrane remains.

40
Q

What role does elevator ani have infeotal head position in delivery?

A

Head will start facing laterally and when it hits elevator ani it will rotate to face posteriorly with in the mum

41
Q

What regulates uterine contraction?

A

Local pacemakers

42
Q

Which ion stimulates myometrial contraction?

A

Rise in intracellular calcium levels

43
Q

Does the myometrium thicken or thin in pregnancy?

A

Thickens ready for birth

44
Q

What are the actions of prostaglandins and oxytocin on the myometrial contractions?

A

Prostaglandins- increases Ca2+ influx with each action potential - harder contraction
Oxytocin- lower action potential threshold so more action potentials fired.

45
Q

Why does the head flex initially?

A

Presents smallest diametere to birth canal

46
Q

What is crowning?

A

The head is coming out and stretching the skin and perineum

47
Q

When does the head extend and externall rotate in childbirth?

A

When the head is out

48
Q

What happens when the head is out?

A

Shoulders rotate and deliver quickly followed by the rest of the body

49
Q

How does uterine contraction lead to placental evacuation?

A

Uterus retracts and contracts and this causes placental site size to decrease until it separates. The inelastic placenta is compressed by the uterus

50
Q

How much of a woman cardiac out put flows through the placenta?

A

500-800ml/minute

Thats a lot to lose in a bleed

51
Q

Which stimuli lead to the baby taking their first breath?

A

Trauma of birth
Cold
Light
Noise

52
Q

Why is the first breath the hardest?

A

Have to inflate alveoli- surfactant will keep them a bit open after this.

53
Q

At birth outline foetal/neonatal circulation changes.

A

Umbilical cord clamped, breathing started.
Tissue resistance in lungs decreases with breathing.
Right trail pressure drops.
p[O2] increases in arterial blood which shuts the ductus arteriosus.
Foramen ovale shuts as left heart pressure is above right.

Year 2 Reproduction (8 decks)

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