Normal Pregancy and Labour Flashcards
(174 cards)
At what stage of development does an embryo implant
Fertilised ovum with divide to the blastocyst stage then move from the ampulla to the uterus - day 3-5
Blastocyst implants at day 5-8
Becomes the trophoblast
What do the different parts of the blastocyst become
Inner cells develop into embryo
Outer cells burrow into uterine wall and become placenta
How does the blastocyst implant
Cords of trophoblastic cells from the surface begin to penetrate the endometrium.
This creates the space for the blastocyst to develop
When implantation is finished the blastocyst is completely buried in the endometrium - by day 12
What is the placenta derived from
Trophoblast and decidual tissue - outer cells of blastocyst
What happens when the trophoblast cells start to differentiate
They become multinucleate cells (syncytiotrophoblasts) which invade decidua and break down capillaries to form cavities filled with maternal blood
How does the foetal blood supply contact the developing placenta
Developing embryo sends capillaries into the syncytiotrophoblast projections to form placental villi
Each villus contains fetal capillaries separated from maternal blood by a thin layer of tissue
Is there direct contact between maternal and foetal blood
No
There a thin layer of tissue between them
At what point does the placenta become functional
5th week of pregnancy
Foetal heart also starts functioning
How does exchange occur through the placenta
2 way exchange of respiratory gases, nutrients, metabolites between mother and foetus, largely down diffusion gradient
How does HCG maintain a pregnancy
signals the corpus luteum to continue secreting progesterone
Progesterone stimulates decidual cells to concentrate glycogen, proteins and lipids
How does the developing foetus receive oxygen
The placenta plays the role of the foetal lungs
Done through exchange of maternal blood and the umbilical blood
Oxygen diffuses from the maternal into the foetal circulation
CO2 does the reverse
The umbilical veins carries the O2 rich blood to the foetus
How is the foetal circulation designed to get sufficient oxygen
Foetal haemoglobin has a higher affinity for oxygen than adult
There is also 50% more Hb to maximise oxygen transport
Bohr effect (Foetal Hb can carry more oxygen in low pCO2 than in high pCO2)
How do water and electrolytes reach the foetus
Water diffuses into placenta along its osmotic gradient
Exchange increases during pregnancy up to the 35th week
Electrolytes follow H20
What is a developing foetus’ main energy source
Glucose
Passes through the placenta via simple transport
Can drugs cross the placenta
YES
Must be careful when prescribing as can lead to problems for the baby
What is the role of human placental lactogen in pregnancy
Produced from ~ week 5 of pregnancy
Growth hormone-like effects - protein tissue formation.
Decreases insulin sensitivity in mother which means more glucose for the foetus
Involved in breast development - cause of tender breasts in pregnancy
What is the function of progesterone in pregnancy
Development of decidual cells
Decreases uterus contractility - can therefore be given to those with recurrent miscarriage to try and prevent
Preparation for lactation
What is the role of oestrogen in pregnancy
Enlargement of uterus
Breast development - contributes to tender breasts with HPL
Relaxation of ligments
How quickly should HCG rise
Serum levels should double every 48 hours in a singleton early pregnancy
Start falling again from 12-14 weeks after it peaks
What may be happening if HCG levels aren’t rising quickly or at all
If HCG levels aren’t rising quickly enough then it suggests an ectopic pregnancy
If the levels are falling it suggests a failing pregnancy
What do very high HCG levels suggest
Multiple pregnancy
Molar pregnancy
What is the side effect of HCG production
N and V
It is the rising HCG that causes morning sickness
Worse in multiple/molar pregnancy due to higher HCG
How can increase Ca demands in pregnancy affect the mother
Can lead to hyperparathyroidism
What happens to cardiac output in pregnancy
Cardiac output increases by up to 50% in pregnancy to cope with the increased demand of supplying the foetal circulation
Plasma volume increases
Caused by increased stroke volume and reduced systemic vascular resistance, in combination with an increased heart rate