3. Parturition

Question 1

The placenta is effective from the end of the 1st trimester.

True or False?

Answer 1

TRUE

Question 2

What is the placenta responsible for?

Answer 2

1. Hormone production
2. Nutrient provision + toxin removal
3. Gas exchange

Question 3

How is the foetus adapted for efficient gas exchange?

Answer 3

1. Capillaries have a large SA due to folding of villi.
2. Foetus has higher affinity for O2 as it has HbF rather than HbA.
3. Higher concentration of Hb than the mother.
4. Reduced binding of 2,3-DPG to foetal Hb.

Question 4

Is the O2 dissociation curve of the foetus shifted to the left or right of the mother?

Answer 4

Left.

Bohr effect.

Question 5

From 24 weeks of pregnancy, what do type II pneumocytes produce to keep the alveoli open at end-expiration?
What stimulates its production?

Answer 5

Surfactants consisting of phospholipids and apoproteins.
This decreases surface tension in the alveoli.

Foetal glucocorticoids (and slightly by thyroid hormones).

Given to babies being born prematurely to improve their chances of survival.

Question 6

What is the myometrium?

Answer 6

Smooth muscle of uterus

Question 7

How does the myometrium prepare for labour throughout the course of pregnancy?

Answer 7

1. ↑ resting membrane potential

2. ↑ in gap junctions (connexin 43) between cells (depolarisation can spread)

Question 8

There is a greater risk of the baby dying if pregnancy continues for more than 40 weeks.
True or False?

Answer 8

TRUE

Question 9

What conditions diagnose labour?

Answer 9

1. Regular PAINFUL contractions
2. Progressive shortening + dilation of cervix
3. Presenting part of cervix descends

Question 10

Why are contractions painful?

Answer 10

Blood supply to the myometrium is being trapped, resulting in ischaemia of the tissue - hurts.

Question 11

Fill in the gaps.

Labour

Answer 11

Prostaglandins

Oxytocin

Question 12

What is birth asphyxia and how does it occur?

Answer 12

Baby is starved of oxygen during each contraction, can lead to brain damage.

1. Myometrial arteries are compressed.
2. Therefore blood flow is disrupted.
3. Baby becomes hypoxic.
4. Leads to gradual lactic acidosis

Question 13

How is the baby monitored during labour to check how it is doing?

Answer 13

Fetal heart rate is monitored.

It is very difficult to monitor the baby, another method is to stab the babies scalp to check blood pH.