Normal Pregnancy

Question 1

What are the physiological changes in pregnancy?

Answer 1

Hormonal

• Progesterone decreases smooth muscle excitability
• Oestrogens induce breast and nipple growth
• Thyroxine levels rise
• Prolactin rises throughout pregnancy

Genital

• 100g uterus to 1100g by the end of pregnancy
• Cervical ectropion

Haemodynamic
- Gestational anaemia (higher plasma than RBC)
- Cardiac output increases
- BP drops then rises
From 20 weeks, uterus compresses the IVC

Other

• Tidal volume increases
• Reduced gut motility

Question 2

What is some pre-pregnancy counselling?

Answer 2

• Ensure rubella immune
• Stop smoking
• Weight loss to normal BMI
• Exercise encouraged
• Folic acid supplementation with 400mcg a day from pre-conception to 12 weeks
• Vit D supplementation to at risk groups
• Reduce alcohol, preferably to 0
• Reduce recreational drug use
• Optimise medical disorders
• Alter medication
• Genetic counselling if indicated

Question 3

Describe the development, circulation and functions of the placenta

Answer 3

Develops when blastocyst implants into the decidua and forms from trophoblastic cells. It then forms villi which form from 6 weeks and stem villi are established by 12 weeks. The placenta grows until 16 weeks.

Placental villi are the functional units of the placenta and each has around 60, formed into groups of 3/4 called cotyledons. The maternal surface have syncytiotrophoblasts which is in direct contact with maternal blood. Then there is cytotrophoblasts and the basement membrane, then the basement membrane of foetal vessels. Maternal surface rough and spongy, foetal surface smooth and shiny.

Circulation has two systems. These never mix.
Uteroplacental has maternal blood travelling through intervillous spaces. The uterus received 500-600ml of blood a minute. The spiral arteries become dilated low-pressure and high-flow vessels.

Fetoplacental circulation has two umbilical arteries which carry deoxygenated blood from the foetus to the placenta. Blood is oxygenated and goes to baby through umbilical vein.

The placenta attaches the foetus, is the organ of gaseous exchange, endocrine functions, barrier between mother and foetus. At term it is 1/6th the weight of the baby.

After delivery the placenta can be examined and blood taken for testing.