Fetal Development

Question 1

What day does ovulation occur?

Answer 1

Day 14

Question 2

Where does fertilisation commonly occur?

Answer 2

Fallopian tube

Question 3

What steps occur after an egg is fertilised?

Answer 3

Zygote - morula - blastocyst

= as moving to uterine cavity

Question 4

What day does implantation occur?

Answer 4

Day 23

= beginning of fetal-maternal dialogue

Question 5

At what stage does a morula become a blastocyst?

Answer 5

At 32 cell stage

Question 6

What happens when the blastocyst implants?

Answer 6

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

Question 7

What level of hCG can be detected?

Answer 7

Urine pregnancy test positive over 25IU/ml

= hCG rises rapidly <10wks

Question 8

When does organogenesis occur?

Answer 8

2-8wks post conception

Question 9

What happens to the inner cell mass and the trophoblast?

Answer 9

Inner cell mass = embryo

Trophoblast = placenta

Question 10

What are the layers of the amniotic cavity?

Answer 10

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

Question 11

What is the vascular of the cord?

Answer 11

2 arteries = carry deoxygenated blood from fetus to placenta

1 vein = carry oxygenated blood from placenta to fetus

Question 12

What is the main pregnancy hormone?

Answer 12

Progesterone

Question 13

List some CV modifications of maternal physiology

Answer 13

• 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)

Question 14

List some respiratory modifications of maternal physiology

Answer 14

• 40% increase in tidal volume

- Oxygen demand increases by 15%

Question 15

List some renal modifications of maternal physiology

Answer 15

• 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)

Question 16

List some endocrine modifications of maternal physiology

Answer 16

• 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

Question 17

List some MSK and skin modifications of maternal physiology

Answer 17

• Joints of lower back and pelvis soften

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

Question 18

List some calcium and phosphate modifications of maternal physiology

Answer 18

• 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

Question 19

List some liver modifications of maternal physiology

Answer 19

• Hepatic blood flow unchanged

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

Question 20

What can be seen in an USS at these gestational weeks:
4-5wks
5-6wks
6wks
6-7wks
8wks

Answer 20

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

Question 21

List the tetratogenic drugs

Answer 21

TERATOWA

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

Question 22

When is a miscarriage most likely to occur?

Answer 22

Before 12 weeks

Question 23

List some major roles of the placenta

Answer 23

Gas exchange, nutrient/waste transfer, steriodogenesis

Question 24

What is SGA?

Answer 24

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

Question 25

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

Answer 25

- 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)

Question 26

List some major risk factors for SGA

Answer 26

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