Physiology of Pregnancy and Labour Flashcards

1
Q

List the cell stages a fertilised ovum goes through before implantation

A

Fertilised ovum
Cleavage (4-cell/8-cell stages)
Morula
Blastocyst

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2
Q

During which days following fertilisation does the blastocyst enter the uterus and attach to the lining of the uterus respectively?

A

Days 3-5

Days 5-8

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3
Q

Which surface cells help the blastocyst penetrate and adhere to the endometrium?

A

Trophoblastic cells

Tunnel deeper into endometrum, carving out a hole for the blastocyst

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4
Q

List the components of a blastocyst and the relative function of each

A

Inner cell mass - becomes embryo and fetus

Trophoblast - accomplishes implantation and develops into fetal portion of placenta

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5
Q

By what day following fertilisation does the blastocyst become fully buried in the endometrium?

A

Day 12

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6
Q

Which tissue is the placenta derived from?

A

Trophoblast and decidual tissue

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7
Q

How is the placental cavity formed?

A

Trophoblastic cells differentiate into syncitotrophoblasts which invade the decidua of the endometrium to form cavities filled with maternal blood

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8
Q

How does the embryo communicate with the placenta?

A

Placental villi containing foetal capillaries

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9
Q

There is no direct contact between foetal and maternal blood. True/False?

A

True

Thin membrane in intervillous space acts as an AV shunt, seperating maternal and foetal blood

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10
Q

By which week of pregnancy are the foetal heart and placenta fully functional?

A

5th week

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11
Q

List functions of HCG

A

Stimulates progesterone to prevent involution of corpus luteum
Development of male sex organs

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12
Q

Oxygen-saturated blood goes to the foetus via which vessel?

A

Umbilical vein

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13
Q

Oxygen-poor blood goes from the foetus to the mother via which vessels?

A

Uterine veins

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14
Q

What 3 factors increase the supply of O2 to a foetus?

A

Foetal Hb has increases carrying capacity
Higher Hb concn in foetal blood
Foetal Hb can carry more O2 in low PCO2 (Bohr effect)

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15
Q

List some substances that are transferred in placental exchange

A
Water
Electrolytes (follow water)
Glucose
Fatty acids
Waste products
Drugs (teratogens)
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16
Q

What is the effect of human chorionic somatomammotropin (HCS)?

A

Decreases insulin sensitivity of mother
Protein tissue formation
Breast development

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17
Q

What are the main hormonal effects of progesterone ?

A

Development of decidual cells
Decreases uterus contractility
Preparation for lactation

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18
Q

What are the main hormonal effects of oestrogen?

A

Increases size of uterus
Breast development
Relaxation of ligaments

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19
Q

What happens to the cardiac output during pregnancy?

A

Increases to cope with demands of uteroplacental circulation (30-50%)
Decreases in last 8 weeks due to uterus compressing vena cava

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20
Q

What happens to blood pressure during pregnancy?

A

Decreases during second trimester as uteroplacental circulation expands and peripheral resistance reduces

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21
Q

What happens to Hb levels during pregnancy? What is the consequence?

A

Decrease due to dilution of blood

Require iron supplements

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22
Q

What effect does progesterone have on CO2 levels?

A

Stimulates brain to lower CO2 levels by increasing respiratory rate

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23
Q

How is renal function affected during pregnancy?

A

GFR and RPF increases

Postural changes affect function - upright position reduces and increased when supine or sleeping

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24
Q

Taking folic acid during pregnancy reduces the risk of what?

A

Neural tube defects

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25
Taking vitamin B during pregnancy helps what?
Make red blood cells (erythropoeisis)
26
Taking vitamin K before birthing prevents what?
Intracranial bleeding during labour
27
Towards the end of pregnancy, how does the ratio of oestrogen:progesterone change?
Ratio increases - oestrogen promotes contractility
28
Which hormone secreted from the posterior pituitary helps stimulate contractions in labour?
Oxytocin - stimulates uterine contractions and produces prostaglandins
29
Give an example of positive feedback from the foetus that increases contractility during labour
Cervical stretch due to foetus head | N.B. also increases oxytocin release
30
What are the 3 stages of labour?
1: cervical dilation (8-24hrs) 2: passage through birth canal (0-120mins) 3: expulsion of placenta
31
Oestrogen and progesterone inhibit milk production. True/False?
True | After birth, levels drop to facilitate lactation
32
Which hormone stimulates lactation?
Prolactin
33
What 2 stimuli cause lactation in the "milk let-down" reflex?
Baby crying | Baby suckling
34
What is pre-eclampsia? What is a main clinical sign?
Pregnancy-induced hypertension and proteinuria | Oedema in hands and feet due to salt and water retention
35
What is eclampsia? List clinical signs
``` Extreme preclampsia (lethal without treatment) Vascular spasms, extreme hypertension, chronic seizures, coma ```
36
State the average maternal weight gain in pregnancy
24lbs
37
State the extra calories per day that should be consumed during pregnancy
250-300 extra kcal/day
38
State the two phases of pregnancy and the relative demands of the fetus
ANABOLIC PHASE (up to week 20) Small nutritional demands of fetus CATABOLIC PHASE (from week 21) High metabolic demands of fetus
39
What is the effect of the catabolic phase of pregnancy on the mother?
Accelerated starvation
40
What is colostrum?
First breast milk produced after birth, loaded with immunoglobulins, protective effect for baby
41
What should be expelled from the uterus in normal labour?
Foetus Membranes Umbilical cord Placenta
42
What is Ferguson's reflex in labour?
Pressure on the cervix triggers a hormonal pathway that leads to uterine contractions and dilation of cervix
43
There are 3 stages in labour. What does stage 1 comprise of?
Latent phase: 3-4 cm cervical dilation | Active phase: 4-10 cm cervical dilation
44
There are 3 stages in labour. What does stage 2 comprise of?
Full cervical dilation (10cm) to delivery of baby
45
There are 3 stages in labour. What does stage 3 comprise of?
Delivery of baby to expulsion of placenta and membranes (typically 10 minutes)
46
Describe the clinical features of the latent phase of stage 1 of labour
Mild irregular intrauterine contractions Cervix softens and shortens May last a few days
47
Describe the clinical features of the active phase of stage 1 of labour
Contractions become more rhythmic and intense Cervix achieves full dilation Slow descent of presenting part of baby
48
When is stage 2 of labour considered prolonged in a nulliparous woman?
If it exceeds 3 hours where there is analgesia | If it exceeds 2 hours where there is no analgesia
49
When is stage 2 of labour considered prolonged in a multiparous woman?
If it exceeds 2 hours where there is analgesia | If it exceeds 1 hour where there is no analgesia
50
Why are oxytocic drugs recommended for stage 3 of labour?
Help contractions | Reduce risk of post-partum haemorrhage
51
What chemical causes cervical softening?
Hyaluronic acid
52
What causes cervical ripening during labour?
Decrease in collagen fibre alignment and tensile strength
53
What are Braxton Hicks contractions?
Tightening of the uterine muscles to aid body to prepare for birth Not usually felt until 2nd/3rd trimester
54
How long typically are the gaps between "true labour contractions"?
5 minutes
55
How do Braxton Hicks contractions differ from true labour contractions?
BHC: irregular, do not increase in frequency/intensity, resolve with change in activity TLC: regular, increasing frequency/intensity, don't resolve
56
What does it mean if a baby is "born in a caul"?
Born with some membrane/amniotic sac still surrounding it
57
Describe the "normal" presentation of a baby as it passes through the pelvic canal
Longitudinal lie, cephalic presentation | Occipito-anterior, then occipito-transverse with flexed head
58
What presentations are classified as "abnormal" in a baby's birth?
Transverse/oblique/breech lie | Occipito-posterior engagement
59
There is a relationship between the clinical state of the cervix and the onset of labour. Which 5 parameters are assessed under the Bishops score?
``` Position Consistency Effacement Dilatation Station in pelvis/ Level of presenting part ```
60
List options for analgesia during labour
``` Paracetamol/ co-codamol TENS Entonox Diamorphine Epidural anaesthesia Remifentanyl Combined spinal/ epidural ```
61
What would be considered an abnormal amount of blood loss during labour?
More than 500ml | Blood loss prior to delivery apart from 'show'
62
When does placental expulsion occur following delivery?
5-10 mins | Considered normal up to 30 mins
63
How long does it take tissues to return to non-pregnant state in puerperium?
6 weeks
64
What harmonal change occurs to initiate labour?
Change in oestrogen/ progesterone ratio
65
What is the role of progesterone in onset of labour?
Keeps uterus settled Prevents formation of gap junctions Hinders contractility of myocytes
66
What is the role of oestrogen in onset of labour?
Makes uterus contract | Promotes prostaglandin production
67
What is the role of oxytocin in onset of labour?
Initiates and sustains uterine contractions | Acts on decidual tissue to promote prostaglandin release
68
What is the role of liquor during labour?
Nurtures and protects fetus and facilitates movement
69
List potential timings for membrane rupture
``` Preterm Prelabour 1st stage 2nd stage Born in a caul ```
70
List the 3 key factors that interplay to determine a smooth labour
POWER: uterine contractions via the uterine muscle PASSAGE: shape of maternal pelvis PASSENGER: fetal position
71
What is the pacemaker of the uterus?
Region of tubal ostia, waves spread in downward direction
72
List the features of normal uterine contractions
Frequency: 3-4 in 10 minutes Duration: 10-45 seconds and adequate resting tone Intensity: maximum in 2nd stage
73
What is the most suitable shape of maternal pelvis?
Gynaecoid: wide inlet and outlet narrow ischial spines
74
How is the position of the fetal head determined during labour?
Fontanelles can be felt during vaginal examination
75
What can be used to record progress of labour?
Partogram
76
List the 7 cardinal movements of labour describing the position of the baby's head in the pelvis
1. Engagement 2. Descent 3. Flexion 4. Internal rotation 5. Crowning and extension 6. Restitution and external rotation 7. Expulsion
77
When is the fetal head classed as 'engaged'?
When widest diamter of fetal head has passed below the pelvic inlet 3/5 of fetal head entered pelvis, 2/5 abdominal
78
During descent of the fetus, what position is adopted so that the widest part of the head passes through the widest diameter of the pelvis?
Occiput-transverse psition
79
How often is a vaginal exam carried out for cervical assessment?
4 hourly
80
Describe the change in position of the fetal head during internal rotation in labour?
Occiput-transverse to occipito-anterior position as it passes through the pelvis
81
When does extension and crowning occur in labour?
Once fetus has reached level of interoitus, bringing base of occiput in contact with symphysis pubis
82
What is meant by restitution during labour?
Return of fetal head to correct anatomical position in relation to fetal torso (optimal for position of shoulder)
83
Which part of the fetus undergoes expulsion during labour first?
Anterior shoulder
84
What is the purpose of delayed cord clamping? When does it occur?
Increase the flow of RBCs to fetal organs and reduce rates of anaemia in the fetus From cessation of pulsations, up to 3 minutes after expulsion
85
List clinical signs of the third stage of labour
Uterus contracts, hardens and rises Umbilical cord lengthens permanently A temporary gush of blood Placenta and membranes appear at introitus
86
List methods for active management of labour
Prophylactic administration of syntometerine or oxytocin 10U Cord clamping and cutting Controlled cord traction Bladder emptying
87
What is the most common method of placental separation?
``` Matthew Duncan (separation at margin) Shultz (separation from central aspect) ```
88
List uterine changes that occur in puerperium
Uterine involution Uterine weight loss Fundal height reduces Endometrium regenerates
89
What physical and harmonal processes initiate lactation?
Placental expulsion | Reduction in oestrogen and progesterone
90
Describe how oestrogen and progesterone inhibit milk production
Block release of prolactin from pituitary gland by making mammary gland cells unresponsive to this pituitary harmone