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Module 203 Reproduction & endocrinology > T2 L17 Placenta and IUGR > Flashcards

T2 L17 Placenta and IUGR Flashcards

1
Q

Describe what happens after fertilisation

A

Sperm and ovum meet in Fallopian tube 12-24 hours after ovulation
Fusion occurs and 2nd meiotic division occurs
Acrosome reaction makes ovum impermeable to other sperm
Enters uterine cavity at 8 cell stage

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2
Q

What are the steps from a zygote to a blastocyst?

A 
Zygote
2 cell stage
4 cell stage
8 cell stage
Morula
Blastocyst
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3
Q

How long does it take to form a morula?

A

72 hours

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4
Q

How long does it take to form a blastocyst?

A

4 days

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5
Q

What happens during days 4-5?

A

1) Morula develops a cavity to form a blastocyst
2) Blastocyst thins out to form trophoblast (start of placenta)
3) Rest of cells are pushed up to form inner cell mass (creates embryonic pole)
4) Blastocyst has now reached uterine lumen and is ready for implantation

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6
Q

What happens during days 6-7?

A

Bilaminar disc of embryo
Inner cell mass differentiates into epiblast and hypoblast layer. 2 layers are in contact
- hypoblast forms extra embryonic membrane and primary yolk sac
- epiblast forms embryo
Amniotic cavity develops within epiblast mass

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7
Q

What happens on day 16+?

A

Bilaminar disc develops further by forming 3 distinct layers (gastrulation)

  • initiated by primitive streak
  • epiblast becomes ectoderm
  • hypoblast is replaced by cells from epiblast to become endoderm
  • epiblast gives rise to mesoderm
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8
Q

What gives rise to the germ layers?

A

Epiblast

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9
Q

Describe the development of the placenta

A

Syncytiotrophoblast burrows into myometrium of uterus to invade spiral arteries and start formation of primary, secondary and tertiary villi
Syncytiotrophoblast invades decidua
Cytotrophoblast cells erode maternal spiral arteries and veins
Lacunae between them fill up with maternal blood
Mesoderm develops into foetal vessels

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10
Q

Describe cytotrophoblast cells

A

Undifferentiated stem cells
Invade maternal blood vessels and destroy epithelium
Give rise to syncytiotrophoblast cells
Reduce in number as pregnancy advances

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11
Q

Describe syncytiotrophoblast cells

A

Fully differentiated cells
Direct contact with maternal blood
Produce placental hormones

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12
Q

Give examples of hormones produced by the placenta

A

HCG

HPL

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13
Q

What does HCG do?

A

Maintenance of corpus luteum during pregnancy

Production of progesterone and oestrogen

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14
Q

What does HPL do?

A

Growth, lactation

Carbohydrate and lipid

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15
Q

Describe the placental barrier

A

Maternal blood in lacunae are in direct contact with syncytiotrophoblasts
Mono layer of syncytiotrophoblast / cyntotrophoblast / foetal capillary epithelium is all that separates foetal and maternal blood
Cytotrophoblasts decrease as pregnancy advances
Barrier thins as pregnancy advances to increase SA for exchange

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16
Q

What molecules are transferred across the placenta?

A 
Gases - O2 and CO2
Water and electrolytes
Steroid hormones
Proteins (poor transport by pinocytosis)
Transfer of maternal antibodies
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17
Q

When are maternal antibodies transferred?

A

After 12 weeks

Mainly after 34 weeks hence the lack of protection for premature infants

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18
Q

What is decidua capsularis?

A

Endometrium overlying embryo and chorionic cavity

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19
Q

What is decidua parietalis?

A

Endometrium overlying side of uterus not accompanied by embryo

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20
Q

What is vasa praevia?

A

Fetal blood vessels cross or run near the internal os

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21
Q

What is the management of vasa praevia?

A

Deliver by Caesarean section once foetus is above 34 weeks

22
Q

Where can the placenta be positioned?

A

Fundal (most common)
Anterior or posterior
Low lying or placenta praevia

23
Q

What are the consequences of placenta praevia?

A

Massive bleeding in pregnancy
Painless bleeding
Foetal death
Maternal death

24
Q

What are the consequences of trophoblastic invasion failure?

A

Poor maternal foetal mixing of blood
Lack of oxygen and nutrients to the foetus
Foetal growth restriction
Pre-eclampsia

25
Q

What is placenta accreta?

A

Placenta has invaded too deep into myometrium and is unable to separate at birth

26
Q

What are the consequences of placenta accreta?

A

Uterus can’t contract down

Massive bleeding

27
Q

What is the treatment for placenta accreta?

A

Hysterectomy

28
Q

What is placenta abruption?

A

Separation of placenta during pregnancy leading to disruption of blood to foetus

29
Q

What are the consequences of placenta abruption?

A 
Foetal distress
Massive bleeding in pregnancy
Extremely painful
Foetal death
Maternal death
30
Q

When does cleavage of the placenta occur to get dichorionic / diamniotic twins?

A

Days 1-3

31
Q

If cleavage of placenta occurs at day 4-8, what is the result?

A

Monochorionic / diamniotic twins

32
Q

When does cleavage of placenta occur to get monochorionic / mono amniotic twins?

A

Days 8-13

33
Q

What happens if placenta is cleaved at day 13-25?

A

Conjoined twins

34
Q

What is SGA?

A

Small for gestational age
<5th centile
Normal variant or growth restricted

35
Q

What is IUGR?

A

<5th centile

Growth restricted - failure to achieve growth potential

36
Q

What happens in foetal growth restriction?

A

Deficient placental invasion leads to reduced placental reserve
Foetal need exceeds the supply leading to IUGR
Hypoxia
Foetal vascular redistribution
Oliguria
Abnormal CTG
Foetal death

37
Q

How is IUGR diagnosed?

A

Clinical measurement of uterine size

Ultrasound scan

38
Q

How is uterine size measured?

A

Symphysis to fundal height

SFH = weeks +/- cms

39
Q

What is symmetrical foetal growth restriction?

A

Head circumference and abdominal circumference are all reduced

40
Q

What are the causes of symmetrical foetal growth restriction?

A

Chromosomal anomaly
Viral infection
Severe placental insufficiency
Normal small baby

41
Q

What is asymmetrical foetal growth restriction?

A

Only abdominal circumference is reduced

42
Q

What does abdominal circumference reflect?

A

Size of the liver

43
Q

Causes of asymmetrical foetal growth restriction?

A

Placental insufficiency - no excess glycogen is being deposited in the liver

44
Q

What are the consequences of hypoxia in the foetus?

A

Blood flow is redirected away from areas of lesser importance to areas of greater importance

45
Q

What are the ultrasound findings in IUGR?

A

Small abdominal circumference
Decreased amniotic fluid
Increased blood flow to the brain

46
Q

Why does hypoxia cause decreased amniotic fluid?

A

Kidneys produce amniotic fluid

Hypoxia causes blood flow to be redirected away from kidney

47
Q

What are the clinical features of IUGR?

A

SFH is smaller than expected
Reduced movements to conserve energy
Foetal heart range changes as hypoxia develops
Foetal death

48
Q

Why should you wait to deliver in IUGR?

A

Low chance of survival outside body
Need to give steroids
Reduce need for caesarean

49
Q

When should you deliver in IUGR?

A

Once above 32 weeks
If there is doppler abnormality
If there are decreased movements
If CTG is abnormal

50
Q

What does betamethasone do?

A

Give to mother, crosses placenta and stimulates alveoli cells to produce surfactant gene
Prevents respiratory distress syndrome

51
Q

What does surfactant do?

A

Coats alveoli cells to reduce surface tension and stop collapse of alveoli cells

52
Q

When is surfactant normally produced?

A

Between 24 and 34 weeks

Baby usually has enough by 34 weeks for a term delivery

Module 203 Reproduction & endocrinology (52 decks)

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