Fetal Development Flashcards

1
Q

What day does ovulation occur?

A

Day 14

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2
Q

Where does fertilisation commonly occur?

A

Fallopian tube

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3
Q

What steps occur after an egg is fertilised?

A

Zygote - morula - blastocyst

= as moving to uterine cavity

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4
Q

What day does implantation occur?

A

Day 23

= beginning of fetal-maternal dialogue

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5
Q

At what stage does a morula become a blastocyst?

A

At 32 cell stage

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6
Q

What happens when the blastocyst implants?

A

The decida (modified endometrium) produces hCG which stimulates the ovaries to produce progesterone which alters maternal physiology

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7
Q

What level of hCG can be detected?

A

Urine pregnancy test positive over 25IU/ml

= hCG rises rapidly <10wks

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8
Q

When does organogenesis occur?

A

2-8wks post conception

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9
Q

What happens to the inner cell mass and the trophoblast?

A

Inner cell mass = embryo

Trophoblast = placenta

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10
Q

What are the layers of the amniotic cavity?

A

Amnion = membrane lining cavity, expands as placenta progresses
2nd layer = chorion

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11
Q

What is the vascular of the cord?

A

2 arteries = carry deoxygenated blood from fetus to placenta

1 vein = carry oxygenated blood from placenta to fetus

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12
Q

What is the main pregnancy hormone?

A

Progesterone

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13
Q

List some CV modifications of maternal physiology

A
  • 40% increase in plasma volume by 32wks (RBC increases by 20%)
  • 40% rise in CO
  • Reduced peripheral venous return causes BP drop in early pregnancy (return to pre-pregnancy level later)
  • Haemodilution: overall amount of Hb rises but the concentration falls
  • Increased clotting risk: Increased factor VII, VIII, X, and rise in fibrinogen
  • Increased RBC mass: protects against the approximate 0.5L delivery loss (1L if twins of caesarean section)
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14
Q

List some respiratory modifications of maternal physiology

A
  • 40% increase in tidal volume

- Oxygen demand increases by 15%

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15
Q

List some renal modifications of maternal physiology

A
  • Renal pelvis and ureters dilate (due to pressure and progesterone) = risk of acute pyelonephritis
  • GFR increases by 50%: reduces plasma urea, creatinine and osmolality
  • Increased urinary protein loss (but >500mg in 24 hrs is abnormal)
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16
Q

List some endocrine modifications of maternal physiology

A
  • Insulin secretion doubles (physiological glycosuria may occur)
  • Thyroid binding globulin doubles  T3 and T4 fall slightly
    = Goitre more common
  • Anterior pituitary doubles in size
  • Risk of ischaemia in postpartum haemorrhage = Sheehans syndrome
  • Rise in total and free serum cortisol and urinary free cortisol
17
Q

List some MSK and skin modifications of maternal physiology

A
  • Joints of lower back and pelvis soften

- Increased risk of rashes, epistaxis, hyperpigmentation, spider naevi, erythema

18
Q

List some calcium and phosphate modifications of maternal physiology

A
  • Increased demand of calcium especially in 3rd trimester and puerperium = leads to increased absorption (Calcium is actively transported across placenta)
  • Serum calcium and phosphate levels fall = bound to albumin
  • Ionised calcium remains stable
19
Q

List some liver modifications of maternal physiology

A
  • Hepatic blood flow unchanged

- ALP levels rise by 50% and albumin falls by 10g/L = causes a fall in total protein

20
Q
What can be seen in an USS at these gestational weeks:
4-5wks
5-6wks
6wks
6-7wks
8wks
A
4-5 weeks = gestation sac at 6mm
5-6 weeks = yolk sac (good sign for health)
6 weeks = fetal pole at 5mm - 
6-7 weeks: fetal heart activity
8 weeks: limb dubs and foetal movements

FOETUS DOUBLES IN SIZE EVERY WEEK UNTIL 12 WEEKS

21
Q

List the tetratogenic drugs

A

TERATOWA

Thalidomide
Epileptic medications (valproic acid, phenytoin)
Retinoid (Vit A)
ACE inhibitors / ARBs
Third element (lithium)
Oral contraceptives / hormones
Warfarin
Alcohol
22
Q

When is a miscarriage most likely to occur?

A

Before 12 weeks

23
Q

List some major roles of the placenta

A

Gas exchange, nutrient/waste transfer, steriodogenesis

24
Q

What is SGA?

A

Small for gestational age = foetus that has failed to achieve a specific biometric or estimated weight threshold be a specific gestational age

  • Either constitutionally small or IUGR
25
Q

What is does the biophysical profile involve chichis performed if the baby is SGA?

A
  • Fetal breathing movements
  • Fetal movements
  • Fetal tone
  • Amniotic fluid volume
  • Doppler studies to assess blood flow in foetal arteries (using pulsatility index and resistance index)
26
Q

List some major risk factors for SGA

A
  • Maternal age >40yr
  • Smoker >11/day
  • Previous SGA
  • Previous stillbirth
  • Cocaine use
  • Low PAPP-A