3.5. The Developing Fetus

Question 1

What are the key functions of the placenta?

Answer 1

Oxygenation- transfer of oxygen from maternal to fetal circulation
Protection- infection, some drugs
Excretion- elimination of waste products
Nutrition- amino acids, glucose, fatty acids, minerals, water balance
Endocrine- production of prostaglandins, hCG, oestrogens, progesterone

Question 2

What are spiral arteries and why are they so important?

Answer 2

Maternal blood is pulsated into the intervillus space by spiral arteries in the decidua basalis

Question 3

How does transfer of nutrients/other products occur?

Answer 3

Nutrients diffuse across the placental membrane and into the fetal blood and provide the fetus with nutrition

Question 4

What is the Chorion?

What does it produce?

Answer 4

The OUTER membrane of the amniotic sac

Produces prostaglandins, oxytocin and platelet-activating factor which stimulates uterine activity
Produces enzymes that decrease progesterone levels

Question 5

What is Amnion?

What does it produce?

Answer 5

The INNER membrane of the amniotic sac

Produces amniotic fluid and prostaglandin E2
Can rupture, causing amniotic bands that can affect growth of fetal limbs

Question 6

What blood vessels are found in the umbilical cord?

Answer 6

2 arteries

1 vein

Question 7

In the umbilical arteries, is it oxygenated or deoxygenated blood?

Answer 7

Deoxygenated blood

Question 8

In the umbilical vein, is it oxygenated or deoxygenated blood?

Answer 8

Oxygenated

Question 9

What is the substance called that surrounds the blood vessels in the umbilical cord?

Answer 9

Wharton’s jelly

Question 10

State 2 fetal developments which happen at around 9-12 weeks

Answer 10

• Growth in body length and limbs accelerates
• Ears low set, eyes fused
• Skull and long bones develop
• Intestines return to abdominal cavity and body wall fuses
• Urine formation
• Fetal swallowing of amniotic fluid

Question 11

State 2 fetal developments which happen at around 13-16 weeks

Answer 11

• Rapid growth
• Coordinated limb movements
• Active ossification of skeleton
• Slow eye movements
• Ovaries differentiate, contain primordial follicles
• External genitalia
• Eyes + ears closer to normal positions

Question 12

State 2 fetal developments which happen at around 17-20 weeks

Answer 12

• Growth slows down
• Limbs reach mature proportions
• Fetal movements felt by mum
• Skin covered with vernix caseosa, held in position by lanugo (downy hair)
• Brown fat deposited

Question 13

State 2 fetal developments which happen at around 21-25 weeks

Answer 13

• Fetus gains weight
• Skin wrinkled, translucent, red-pink
• Rapid eye movement
• Blink-startle responses to noise
• Surfactant secretion begins but respiratory system immature
• Fingernails present
• May be viable if born prematurely

Question 14

State 2 fetal developments which happen at around 26-29 weeks

Answer 14

• Lungs capable of breathing air
• CNS can control breathing
• Eyes open
• Toenails visible
• Fat deposited under skin so wrinkles smooth out
• Erythropoeisis moves from spleen to bone marrow

Question 15

State 2 fetal developments which happen at around 30-34 weeks

Answer 15

• Pupillary light reflex
• Skin pink and smooth, limbs chubby
• White fat is 8% of body weight
• From 32 wks, survival is usual

Question 16

State 2 fetal developments which happen at around 35-38 weeks

Answer 16

• Firm grasp
• Orientates towards light
• Circumference of head and abdomen are approx. equal
• White fat is 16% of body weight, 14g fat gained per day
• Skin bluish-pink
• Term fetus is about 3400g, CRL is about 360mm