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YR2: Reproduction, Ageing and Development > Pregnancy > Flashcards

Pregnancy Flashcards

1
Q

What does “conceptus” refer to?

A 
Everything resulting from fertilised egg:
Baby
Placenta
Foetal membranes
Umbilical cord
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2
Q

In the UK, what gestational age is attempt at revival made if they are born pre-term?

A

24 weeks

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3
Q

In which trimester is spontaneous loss of pregnancy common?

A

1st

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4
Q

In the absence of an ICU cot, what is the absolute limit of gestational period for survival of a pre-term baby?

A

26-27 weeks

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5
Q

With an ICU cot, what is the absolute limit of gestational period for survival of a pre-term baby?

A

22-23 weeks

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6
Q

Which gestational weeks are considered “term”?

A

37-41

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7
Q

Summarise the hormonal changes during the first trimester

A

hCG peaks

Oestrogens, Progesterone + placental lactogen begin to increase in parallel with growing placenta

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8
Q

How do levels of progesterone and oestrogens in pregnancy compare with menstrual cycle levels?

A

They greatly exceed those in the normal menstrual cycle

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9
Q

Describe the levels of LH and FSH throughout pregnancy

A

Very low as high levels of Oestrogens + Progesterone suppress the HPG axis

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10
Q

Which hormone must be at very high levels to allow pregnancy to continue? What can low levels or an antagonist cause?

A

Progesterone

Low levels/ antagonist leads to loss of pregnancy

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11
Q

Which hormone is associated with morning sickness?

A

hCG

Peaks in 1st trimester

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12
Q

Recall 2 possible mechanisms for the altered immune response in pregnancy

A
  1. Endogenous immunosuppressant production at utero-placental interface
    Decreasing Th1 responses
    Increasing Th2 system
  2. Placental HLA-G expression
    Provides immunological signal that shows tissue is human
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13
Q

Recall 3 major maternal changes in the 3rd trimester

A
  1. Loosening of pelvic joints
  2. Weight gain of 10-15kg
  3. Increased urination frequency
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14
Q

Recall the source of progesterone throughout pregnancy

A

Till 8 weeks: Corpus luteum, production driven by hCG
Placenta can also produce P, but small size means small contribution
Post 8 weeks: Luteo-placental shift

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15
Q

Recall the source of oestrogens throughout pregnancy

A

Till 8 weeks: corpus luteum
Following LPS: maternal pregnenolone is converted by foetal andrenals to DHEA-S
Placenta converts DHEA-S to 17-B-oestradiol
Fetal liver converts DHEA-S to precursor, placenta converts to Oestriol

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16
Q

To where does the placenta anchor in the uterus?

A

Decidua

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17
Q

Describe the development of the placental blood supply during pregnancy

A
  1. Cytotrophoblast columnar structure forms + branches into villous sprouts
  2. At 8 weeks: cytotrophoplast plug breakdown; spiral artery formation
  3. During 2nd + 3rd trimesters there is increased branching, placental diameter = 5–> 20cm
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18
Q

What is the gestational age limit for a foetal death to be considered “miscarriage”?

A

23 weeks

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19
Q

How is still birth risk assessed?

A

Foetal movement on ultrasound

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20
Q

What makes the foetus so vulnerable in the first trimester?

A

Abnormal chromosomal make-up (excess/ deficient chromosomes)

Incomplete anchorage of placenta (increase in pressure can lead to detachment

21
Q

Depending on type of gain or loss of chromosomes, what consequences are seen in the infant?

A

Autosomal loss: inviable
Autosomal gain: Chr.21 Trisomy Down Syndrome
Sex Chr. gain: Viable with variability
Sex Chr. loss: Turners syndrome / inviable

22
Q

Why is placental anchorage essential for maintaining pregnancy?

A

Cytotrophoblast plugs break down, so spiral arteries provide main supply of nutrients to the developing placenta + fetus.
If not fully anchored to maternal decidua, the increase in pressure on exposure to the maternal arterial supply can detach the placenta + lead to miscarriage

23
Q

What is the major risk in the second trimester?

A

Early delivery due to:
Labour starting before term
Deteriorating maternal or fetal health, such that delivery is required to save life of mother, fetus, or both

24
Q

Why are infants born before 32 weeks GA at greater risk of stillbirth?

A

Development of lungs, digestive system, brain + immune system is incomplete

25
Q

What is the most dangerous process in pregnancy for the mother?

A

Labour
Remodelling of spiral arteries allows loss of large volumes of blood after delivery.
Only limited by contraction of the uterus after delivery of placenta, which diminishes blood loss strongly- may require induction
Must ensure complete Placenta has been delivered, as it inflexible + will prevent uterine contraction, permitting blood loss through spiral arteries.

26
Q

What changes does the mother go through/ begin to go through in the first trimester?

A 
Increased breast size 
Increased basal body temperature
Increased nausea + vomiting 
Increased vaginal mucus production 
Increased urination frequency
Altered appetite 
Altered brain function
Altered emotional state
Altered joints
Altered hormones 
Altered immune system
27
Q

What changes does the mother go through/ begin to go through in the second trimester?

A

Increased weight
Increased blood volume
Increased blood clotting tendency
Decreased BP

28
Q

When are the terms conceptus, embryo, foetus and infant used?

A

Conceptus: everything resulting from the fertilised egg (baby, placenta, fetal membranes, umbilical cord)
Embryo: before it’s clearly human
Fetus: rest of pregnancy
Infant: after delivery

29
Q

What are the 5 main placental functions?

A

Separation: of vascular systems
Exchange: of nutrients (maternal to fetal) + waste products (fetal to maternal)
Biosynthesis: Placenta is synthetically very active
Immunoregulation: Interactions between placenta + maternal tissues prevents rejection of conceptus
Connection: strong connections with underlying maternal decidua to last 9 months. Placenta is in contact with maternal arterial blood, so anchorage is essential.

30
Q

Which is essential for pregnancy survival, uterus or placenta?

A

Placenta
As ectopic pregnancy (implantation not in uterus) + occasional survival of such pregnancies until delivery, demonstrates uterine lining is not essential

31
Q

What primary subunits is the placenta composed of? How are these optimised for their function?

A

Placental villi

Complex branched structure, provides a large SA for exchange

32
Q

Describe the oxygenation states of vessels in the placental villi

A

Arterial: de-oxygenated blood; carry blood away from fetal heart to placenta
Venous: oxygenated; returns blood to fetal heart

33
Q

What is the maternal surface of the placenta composed of? How does variability in shape and size affect placental function?

A

Cotyledons
Each contains >,1 villi, with larger cotyledons containing more
Variability in shape + size of cotyledons doesn’t affect function

34
Q

Describe the composition of the conceptus 9 days post-fertilisation

A

Outer layer: Syncytiotrophoblasts (contain fluid-filled lacunae)
Layer of cytotrophoblasts (proliferates adjacent to embryo: this is where the placenta will develop)

35
Q

Describe placental development post-implantation into maternal decidualising endometrium

A

Cytotrophoblasts proliferate into surrounding syncytium; as fingerlike projections, which then undergo branching (villous sprouts).
At the centre of each villus are mesenchymal cells, from which the villus vascular system develops.
Branching continues throughout pregnancy, giving rise to complex branched villi

36
Q

How does number of cytotrophoblasts differ at term? Why?

A

There are fewer
Allows a closer apposition between the syncytium + placental capillaries
Maximises efficacy of nutrient transfer into fetal blood, + enhances fetal growth in later pregnancy

37
Q

What happens to decidual glands during the 1st trimester? What is their function?

A

Decidual glands hypertrophy

Provide nutrients for placenta + baby

38
Q

What isolates the conceptus from maternal blood by 4 weeks post fertilisation? For how long does this remain?

A

Proliferating cytotrophoblasts, form a shell around conceptus
Shell remains till 8 weeks post-fertilisation, with spiral arteries blocked by cytotrophoblast plugs

39
Q

What allows spiral arteries to become the main nutrient supply to the placenta and foetus? In what distribution does this occur?

A

Breakdown of cytotrophoblast plugs (periphery to centre of placenta)

40
Q

How does the diameter of the placenta change? What is this due to?

A

5cm to 20cm

Growth due to increased size + branching of villi

41
Q

What happens during the remodelling process of spiral arteries by cytotrophoblast? When does it begin and end?

A

Loss of vascular endothelium + smooth muscle
Replacement by cytotrophoblast
1st trimester to 16 weeks GA

42
Q

What is the purpose of spiral artery remodelling?

A

Converts narrow, vasoactive spiral arteries, to wide bore vessels that can transport large volumes of maternal blood to placenta to provide sufficient nutrients.
Blood flow remains high as they can’t respond to vasoconstrictors

43
Q

What are the effects of the neuronal system on the placenta?

A

Placenta has no nervous system, thus is not regulated by NS in any way

44
Q

What regulates growth of the placenta?

A

Placenta regulates its own growth through autocrine mechanisms
Maternal decidua has a modulatory role to prevent excess growth

45
Q

How is pregnancy dated by obs-gynae terminology?

A

Pregnancy is counted from 1st day of last menstrual period, with other events dated from this time.

46
Q

How is pregnancy dated by embryologic terminology?

A

Pregnancy counted from fertilisation

47
Q

What is a miscarriage?

A

Delivery before viability limit of a non-viable infant

48
Q

What is a stillbirth?

A

Death of an infant within the uterus, so it’s delivered with no signs of life
Can be a complication of pregnancy or labour
Can occur at any GA

49
Q

What are the 2 preferred methods of assessing foetal wellbeing?

A

Ultrasound

Fetal blood flow (doppler ultrasound)

YR2: Reproduction, Ageing and Development (9 decks)

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