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Reproductive System > Labour and Delivery > Flashcards

Labour and Delivery Flashcards

1
Q

Define Labour

What is Micarriage/ Spontaneous abortion?

What is Pre-term labour?

A
  • Expulsion of Fetus and Placenta after 24 weeks of gestation
  • “” Before 24 weeks of gestation
  • Labour that occurs before week 37 of Gestation
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2
Q

What 3 processes happen in Stage 1 of Labour?

Regular contrations until cervix is dilated

A
  • Creation of birth canal
  • Release of structures which normally retain fetus in utero
  • Enlargement and realignment of cervix
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3
Q

What process happens in Stage 2 of Labour?

A

Expulsion of fetus

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4
Q

What process happens in Stage 3 of Labour?

A

Expulsion of placenta and changes to minimise maternal blood loss

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5
Q

When does the uterus first become palpable?

A

Week 12

Reaches Umbilicus at W20, Xiphisternum at W36

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6
Q

What is the ‘Lie’ of the fetus?

What is the commonest ‘Lie’?

A

Relationship of long axis of fetus to long axis of uterus

Longitudinal, with head or buttocks posterior (Normally has a flexed attitude)

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7
Q

What is the ’Presentation of the fetus’?

A

This describes which part of fetus is adjacent to the pelvic inlet

(May be Head/ Cephalic or Breech/ Podial if lie is longitudinal)

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8
Q

Most commonly the baby lies longitudinally, in a Cephalic presentation, well flexed.

What is the diameter of presentation in this case?

A

9.5 cm

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9
Q

The birth canal cannot dilate beyond the limits determined by the Pelvis (True diameter is 11cm)

What are the Posterior, Lateral and Anterior boundaries of the Pelvic Inlet?

A

Posterior: Sacral Promontory

Lateral: Ilio-Pectineal line

Anterior: Superior Pubic Rami and upper margin of Pubic Symphysis

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10
Q

Softening of pelvic ligaments allows some expansion of the pelvic inlet.

What are 2 important things that must happen for a birth canal to be created?

A
  • Cervical dilation
  • Anterior retraction of cervix

(During this creation process, Fetal membranes rupture and amniotic fluid is released)

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11
Q

How is Cervical Dilation facilitated and produced?

A
  • Facilitated by structural changes known as Cervical Ripening/ Softening
  • Produced by forceful contractions of uterine smooth muscle, which first thin the cervix (EFFACEMENT), then dilate it
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12
Q

The cervix has a high CT content and is made up of collagen fibres embedded in a proteoglycan matrix.

How does Cervical Ripening/ Softening change this?
What does this lead to?

A
  • Reduction in Collagen, Increase in GAGs-> Reduced aggregation of collagen fibres
  • This leads to Collagen Bundles ‘loosening’
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13
Q

Other than changes to the CT content of the Cervix, what changes occur in Cervical Ripening/ Softening

A
  • Influx of inflammatory cells

- Increased NO output

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14
Q

What triggers all the changes in Cervical Ripening?

A

Prostaglandins (namely E2 and F2-Alpha)

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15
Q

What 2 factors cause increased thickness of the myometrium in pregnancy?

What generates force? (Hint: it’s smooth muscle)

A
  • Glycogen deposition
  • Increased cell size (10x)

An intracellular apparatus containing actin and myosin, triggered by a rise in [Ca]i

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16
Q

Why can some parts of the Myometrium act as ‘Pacemakers’?

Hence the myometrium is spontaneously motile

A

Some Smooth Muscle Cells are capable of spontaneous depolarization and AP generation

17
Q

Describe the contractions in early pregnancy and as it continues

(None are forceful enough to have an effect on the fetus)

A

Early;

  • May occur every 30mins
  • Low amplitude

As pregnancy continues;

  • Frequency falls
  • Increase in amplitude-> ‘Braxton-Hicks’ contractions
18
Q

The onset of labour is a relatively sudden increase in frequency and amplitude of contractions.

What are 2 hormones involved in this change and how do they work?

A
  • Prostaglandins: Enhance Ca release from intracellular stores
  • Oxytocin: Lowers threshold for triggering APs

(Onset of labour is associated with increased prostaglandin synthesis and release, in conjunctival with increased oxytocin sensitivity)

19
Q

As contractions increase, the Ferguson Reflex increases Oxytocin secretion. Describe this

A
  • Sensory receptors in Cervix and Vagina are stimulated by contractions
  • Excitation-> Hypothalamus by Afferents-> Oxytocin release

(This +ve feedback makes contractions more forceful and frequent)

20
Q

Uterine smooth muscle has a property called Brachystasis.

Describe this

A
  • At each contraction, muscle fibres shorten but do not relax fully
  • The uterus (especially the fundus) shortens progressively, pushing the fetus downwards and stretching the cervix

(Thus, descent of the fetus occurs during labour)

21
Q

Although unclear in humans, evidence from animals suggests that labour is initiated by what?

A
  • Increased Prostaglandin production and Oxytocin sensitivity
  • Triggered by a fall in Progesterone levels relative to Oestrogen
22
Q

Will prostaglandins induce labour when given medically?

A

Yes

23
Q

Explain how can labour progression affect placental blood flow.

What can this lead to?

A
  • Increasingly forceful uterine contraction may temporarily reduce placental blood flow, reducing O2 supply to Fetus
  • May lead to brief reductions in fetal heart rate
  • If flow reductions are greater than usual, larger ‘dips’ may occur, and the Fetus becomes ‘Distressed’
24
Q

When does the First Stage of Labour end?

How long does the Second Stage last in the Multiparous woman and in Primigravida? (Ends with delivery of fetus)

A

When cervical dilation reaches 10cm

Multiparous;
- Up to an hour

Primgravida;
- Up to 2 hours

25
Q

What 5 thing occur in Stage 2 of Labour?

A
  1. Head flexes as it meets the pelvic floor
  2. Internal rotation occurs
  3. Descends to vulva, stretching vagina and perineum
  4. ‘Crowning’ (head delivered), as it emerges it externally rotates back to original position and extends
  5. Shoulders rotate, followed by the head and are then delivered
26
Q

Describe the events of Stage 3 of Labour

A
  • A powerful uterine contraction separates the placenta, positioning it into Upper part of Vagina OR Lower Uterine segment
  • Placenta and membranes are expelled within 10mins usually (This completes Stage 3)
  • The uterine contraction also compresses vessels to reduce bleeding
27
Q

With reference to Stage 3 of labour, why is an Oxytocic drug administered?

A

This enhances blood vessel compression to reduce bleeding

28
Q

Suggest 2 stimuli that trigger the fetus to take its 1st breath

How does this affect Left Atrial pressure?

A
  • Delivery trauma
  • Temperature change
  • Causes a drop in Pulmonary Vascular resistance, reducing pulmonary arterial pressure, increasing LA pressure
29
Q

What happens to the three shunts after first breath?

A
  • Foramen Ovale closes due to LA pressure
  • Rising paO2 causes Ductus Arteriosus to constrict
  • Ductus Venosus sphincter constricts
30
Q

Describe use of the APGAR score

A
  • Used to assess Fetal wellbeing soon after delivery and 5 mins later
  • Score from 1 to 10, the higher the better
31
Q

Clinically, what are the 3 classifications of the elements of labour?

A
  • The Powers
  • The Passage
  • The Passenger
32
Q

In Labour, what do ‘The Powers’ refer to?

A

Fetal delivery is depend on mymetrium contraction

Uterine contractions can be assessed in terms of frequency, amplitude, duration

33
Q

In Labour, what does ‘The Passage’ refer to?

Passage is formed by bony pelvis and soft tissues
(Resistance of soft tissue can slow labour)

A
  • Pelvic inlet is shorter Antero-Posteriorly
  • Mid cavity is circular, between Pelvic Inlet and Outlet
  • Pelvic outlet is narrowest Medio-Laterally usually
34
Q

In Labour, what does ‘The Passenger’ refer to?

A
  • Size and presentation of fetus is critical in labour

- Moulding of fetal cranium may occur since sutures aren’t fused yet

35
Q

Progress in labour is plotted on a Partogram

Suggest 3 types of causes of failure to progress in labour

A
  • Inadequate power (insufficient uterine contractions)
  • Inadequate passage (abnormal bony pelvis, rigid perineum)
  • Abnormalities of passenger (macrosomia, presentation)

Reproductive System (21 decks)

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