Physiology of Pregnancy and Labour Flashcards
List the cell stages a fertilised ovum goes through before implantation
Fertilised ovum
Cleavage (4-cell/8-cell stages)
Morula
Blastocyst
During which days following fertilisation does the blastocyst enter the uterus?
Days 3-5
During which days following fertilisation does the blastocyst attach to the lining of the uterus?
Days 5-8
Which surface cells help the blastocyst penetrate and adhere to the endometrium?
Trophoblastic cells
By what day following fertilisation does the blastocyst become fully buried in the endometrium?
Day 12
Which tissue is the placenta derived from?
Trophoblast and decidual tissue
How is the placental cavity formed?
Trophoblastic cells differentiate into syncitotrophoblasts which invade the decidua of the endometrium to form cavities filled with maternal blood
How does the embryo communicate with the placenta?
Placental villi containing capillaries
There is no direct contact between foetal and maternal blood. True/False?
True
By which week of pregnancy are the foetal heart and placenta fully functional?
5th week
HCG stimulates the corpus luteum to secrete what hormone?
Progesterone
Oxygen-saturated blood goes to the foetus via which vessel?
Umbilical vein
Oxygen-poor blood goes from the foetus to the mother via which vessels?
Uterine veins
What 3 factors increase the supply of O2 to a foetus?
Foetal Hb has increases carrying capacity
Higher Hb concn in foetal blood
Foetal Hb can carry more O2 in low PCO2 (Bohr effect)
Drugs can cross the placental barrier - list some teratogens
Thalidomide Carbamazepine Tetracyclines Alcohol Nicotine Heroin, cocaine
What is the effect of human chorionic somatomammotropin (HCS)?
Decreases insulin sensitivity of mother
Protein tissue formation
Breast development
What effect does progesterone have on uterine contractility?
Decreases contractility
What effect does oestrogen have on the uterus?
Increases size of uterus
Relaxation of ligaments
What happens to the cardiac output during pregnancy?
Increases to cope with demands of uteroplacental circulation
Can be up to 50% above normal around 24wks!
When does cardiac output typically decrease in pregnancy?
Last 8 weeks due to uterus compressing vena cava
What happens to Hb levels during pregnancy? What is the consequence?
Decrease due to dilution of blood
Require iron supplements
What effect does progesterone have on CO2 levels?
Stimulates brain to lower CO2 levels by increasing respiratory rate