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Year 2 Revision > RDA- Placenta and Labour > Flashcards

RDA- Placenta and Labour Flashcards

1
Q
  1. What are the functions of the placenta
A
  1. Exchange of nutrients and waste products
    1. Connection/anchorage to last the 9 months
    2. Separation between fetal and maternal vascular systems
    3. Biosynthesis
    4. Immunoregulation to ensure no rejection of conceptus
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2
Q
  1. Describe the structure of the maternal surface of placenta
A
  1. Subdivided into cotyledons

2. Each one contains one or more villi

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3
Q
  1. How does the placenta develop
A
  1. 9 days post fertilisation conceptus is implanted in decidualising endometrium
    1. Outer layer of conceptus = multinucleated synctiotrophoblast with fluid filled lacunae
      a. Underneath is a layer of cytotrophoblast -> will become placenta
    2. Cytotrophoblast -> proliferate into syncytium
    3. Columnar structure formed (cytotrophoblast column) -> branches to become villous sprouts
    4. Centre of each villus are mesenchymal cells which will form the villus vascular system
      Branching continues
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4
Q

How does the placenta change through pregnancy

A
  1. At term there are fewer cytotrophoblasts so there is a closer apposition between the synctium and placental capillaries to maximise nutrient transfer into fetal blood and enhance fetal growth
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5
Q
  1. How does the placenta form a barrier between foetus and mum?
A
  1. Conceptus is still in contact with maternal endometrial cells at the beginning
    As it grows it makes transient contact with maternal capillaries but the rapidly proliferation cytotrophoblast cells form a shell around the conceptus isolating it from 4 weeks post fertilisation
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6
Q
  1. How does the nutritional source for the placenta change?
A
  1. At first it is the maternal blood (haemotrophic nutrition)
    1. Decidual glands of the uterus hypertrophy in the first trimester providing nutrition for the placenta and baby (histotrophic nutrition)
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7
Q
  1. What happens between 10-12 weeks of gestation
A
  1. Spiral arteries are blocked by cytotrophoblast plug. These slowly break down starting in the periphery
    1. This results in spiral arteries providing maternal blood to the placenta forming the main supply of nutrients to the placenta and baby
    2. If placenta is not anchored properly then the inc in pressure can cause it to detach when exposed to mother’s blood supply
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8
Q
  1. How are the spiral arteries remodelled and why
A
  1. Remodelled by the cytotrophoblast cells where the vascular endothelium and smooth muscle cells are lost and replaced by cytotrophoblast
    1. Begins during 1st trimester until 16-18 weeks
    2. Converts narrow vasoactive spiral arteries to wide-bore vessels that can transport v large volumes of maternal blood to placenta
      Loss of smooth muscle cells means the blood flow remains high as they to no respond to vasoconstrictors
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9
Q
  1. Define stillbirth
A
  1. Death of an infant within the uterus so delivered without any signs of life
    1. Can occur at any gestational age including term
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10
Q
  1. How are fetal movements assessed
A
  1. Ultrasound assessment
    1. Assessment of fetal blood flow (doppler ultrasound)
    2. Dec in/lack of fetal movements may indicate inc risk
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11
Q
  1. What is the difference between miscarriage and stillbirth
A
  1. Miscarriage sometimes defined as before viability limit (23 weeks) = non viable infant delivered
    1. Stillbirth after
    2. But viability before 28 weeks gestational age is very variable so best to say stillbirth is delivery without any signs of life
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12
Q

What happens in the first 8 weeks of embryonic development/ week 10 of gestation

A
  1. 2nd week = Development of bilaminar disc
    1. 3rd week = Formation of trilaminar disc (mesoderm), CNS + somites, Blood vessel initiation, Formation of placental villi
    2. 4th week = closure of neural tube. Heart, face, arm initiated. Umbilical cord and elaboration of placental villi.
    3. 5th week = face and limbs
    4. 6th week = face, ears, hands, feet, liver, bladder, gut , pancreas
    5. 7th week = face, ears, fingers, toes
    6. 8 week = lungs, liver, kidneys
    7. LOW OXYGEN ENVIRONMENT
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13
Q
  1. Which organs and systems develop later in the foetus - when are these undeveloped if the baby is born too early?
A
  1. Lungs
    1. digestive system
    2. Immune system
    3. Brain
    4. Dangerous before 32 weeks gestational age
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14
Q
  1. What is the congenital abnormalities that are viable?
A
  1. Trisomy 21 = down’s
    1. Extra sex chromosome = kleinfelters XXY
    2. Loss of sex chromosome = X0 Turner’s
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15
Q

What is term delivery

A
  1. 37-41 weeks
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16
Q
  1. Define pre-term
A

22-37 weeks

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17
Q

define very pre-term

A

28-32 weeks

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18
Q
  1. What are the key tissues in labour
A
  1. Placenta
    1. Umbilical cord
    2. Fetus
    3. Amniotic fluid
    4. Cervix myometrium
    5. Fetal membranes
19
Q
  1. What regulates the cervix in labour
A
  1. Prostaglandin E2
    1. IL-8
    2. Matrix metalloproteinases (MMPs)
20
Q
  1. What regulates the myometrium in labour
A
  1. Prostaglandin F2a(E2) levels inc from fetal membranes
    1. Oxytocin receptor increased
    2. Contraction associated proteins increased
21
Q
  1. What regulates the fetal membranes in labour
A
  1. Inflammatory process in fetal membranes
    1. Prostaglandins
    2. Interleukins
    3. Matrix metalloproteinases
22
Q
  1. Why are these inflammatory molecules dangerous
A
  1. Fetal brain is particularly sensitive to inflammatory mediators
    1. If intrauterine infection causes preterm labour then brain damage is a high possibility
23
Q
  1. What is the process of cervical effacement and dilation in labour
A
  1. Cervical ripening (softer and flexible) and dilation (thinner and stretched sideways)
    1. Requires extensive modelling of ECM of cervix which can take many hours
    2. Can be accelerated by inc pressure of fetal head causing inc strength and dec gaps between myometrial contractions
24
Q
  1. What are the three stages of labour
A
  1. Onset of uterine contractions through the period of dilation of the os uteri, usually includes rupturing of fetal membranes
    1. Period of expulsive effort beginning with complete dilation of the cervix and ending with expulsion of the infant
    2. Period beginning at the expulsion of the infant and ending with the completed expulsion of the placenta and membranes
25
Q
  1. What happens in the third stage of labour
A
  1. Very powerful contractions of the uterus leading to rapid dec is size = involution
    a. Very important as it is how blood flow through spiral arteries is stopped
    b. Thought to be oxytocin induced
26
Q
  1. What differentiates cells in an embryo and ordinary cells
A
  1. Same functions: proliferation, movement, differentiation, apoptosis
    1. Embryo cells can show first three characteristics simultaneously
27
Q

How is embryonic development regulated

A
  1. Autocrine/paracrine bc embryo does not have vascular system so not under endocrine control
    1. Expression of receptors for these regulators is also v important bc it determines the response
28
Q
  1. What does development involve from first principles
A
  1. Gradients of regulatory factors
    1. Combinations of regulatory factors
    2. Spatial changes in these factors, or in the responses to them
      Temporal changes in these factors, or in the responses to them
29
Q

When do the major organs develop and which in particular

A

days 19-28 (weeks 3-4)

CNS and GI

30
Q
  1. How are centile charts used in fetal growth
A
  1. 10th centile = most sensitive
    1. 3rd centile = most specific
    2. These do not take into account parental characteristics
    3. Check serial measurements to see how baby is growing
31
Q
  1. How are babies classified with birthweight
A
  1. LBW =<2500g
    1. VLBW = <1500g
    2. ELBW = <1000g
32
Q

Define IUGR

A
  1. Failure of infant to achieve its predetermined genetic potential for a variety of reasons
    1. Only used when definite evidence that growth has altered
33
Q
  1. What causes IUGR (maternal medical)
A
  1. Chronic hypertension
    1. Connective tissue disease
    2. Severe chronic infection
    3. Dm
    4. Anaemia
    5. Uterine abnormalities
    6. Maternal malignancy
    7. Pre-eclampsia
    8. Thrombophilic defects
34
Q
  1. What causes IUGR (maternal behaviour)
A
  1. Smoking
    1. Low booking weight (<50kg)
    2. Poor nutrition
    3. Age <16, >35
    4. Alcohol
    5. Drugs
    6. High altitude
      Social deprivation
35
Q

What causes IUGR (fetal factors)

A
  1. Multiple pregnancy
    1. Structural abnormality
    2. Chromosomal abnormalities
    3. Intrauterine infection
      Inborn errors of metabolism
36
Q

What causes IUGR (placental factors)

A
  1. Impaired trophoblast invasion
    1. Partial abruption or infarction
    2. Chorioamnionitis
    3. Placental cysts
    4. Placenta praevia
37
Q
  1. What is the link between IUGR and pre-eclampsia
A

Main cause of pre-eclampsia is diminished remodelling of the spiral arteries by the cytotrophoblast causing dec blood flow and hence dec nutrient supply to placenta and foetus

38
Q
  1. Define pre-eclampsia
A
  1. Hypertension 140/90 on 2 separate occasions at least 4 hours apart
    1. Significant proteinuria of at least 300 mg in a 24hr collection of urine after 20th week in a previously normotensive woman and resolving completely by 6th post partum week
39
Q

How do you screen and detect for IUGR

A

Maternal BMI
Symphsis fundal height
Targeted ultrasound

40
Q
  1. What is the management of IUGR?
A
  1. Timing of delivery balancing risks in utero and hazards of prematurity
    a. Evidence of fetal compromise on CTGs or abnormal Dopplers
    1. Corticosteroids <36 weeks to improve neonatal wellbeing
41
Q

What do thecal cells do

A

a. Produce estrogens

42
Q
  1. What do granulosa-luteal cells do
A

a. Produce estrogens and progesterone during the second half of the ovarian cycle

43
Q
  1. What are the stages of the endometrial cycle and what is the hormonal control
A

a. Menstrual phase (5 days)
i. Shed blood and endometrial lining
ii. Remaining basal endometrium is very thin
b. Repair and proliferative phase (9 days)
i. Stimulation of endometrial cell proliferation (by 17 b oestradiol from ovaries)
ii. Inc in thickness, number and length of glands and length of arteries
c. Secretory phase (13 days)
i. Production of nutrients and other factors
1) Stimulated by progesterone and estrogen produced by corpus luteum
ii. Epithelial glands widen
iii. Endometrium thickens
iv. Inc coiling of spiral arteries
1) Stimulated progesterone from corpus luteum

Year 2 Revision (22 decks)

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