Normal Fertilisation and Pregnancy Flashcards
Where does fertilisation normally occur?
Ampulla of the fallopian tube
What happens at days 1-3, days 3-5 and 5-8?
1-3 = fertilisation occurs at the ampulla and cell starts to divide into blastocytes 3-5 = movement from ampulla into uterus 5-8 = implantation into the endometrium
How does implantation occur? When should this be complete?
The trophoblastic cells will extend cords into the endometrium to ‘dig’ and penetrate to form a hole for the blastocyst. This should be complete by day 12
Describe the organisation of the blastocyst
Outer layer is made from trophoblasts (become the foetal portion of the placenta and help to establish blastocyst in the endometrium)
Inner cell mass will become the foetus
What is the hormone marker for pregnancy? how soon after fertilisation can it detect?
beta-HCG, about 10 days
What are the boundries of the trimesters?
1st trimester ends at 12 weeks
2nd semester ends at 28 weeks
3rd semester ends at 40 weeks
How common is bleeding in early pregnancy?
20% (pretty common)
What is the decidua?
This is the modified mucosal lining (endometrium) that is formed during pregnancy under the influence of progesterone - shed during childbirth
How does the placenta form?
Walls between the trophoblast cells will break down to form a continuous layer (foetal placenta)
Endomentrium will undergo modification to become the decidua (maternal placenta)
Is there contact between maternal and foetal blood during pregnancy?
No - due to the placental barrier
What is the purpose of HCG?
To signal for the corpus luteum to continue production of progesterone > stimulate decidual cells to concentrate glycogen, protein and phospholipids
What produces HCG?
Placenta
Give some facts about Hb in the foetus
foetal Hb has a greater ability to carry O2
Higher concentration of Hb in foetal circulation
Bohr’s effect (can carry more O2 in lower CO2 concentrations)
How does water diffusion across placenta change through pregnancy?
Increases in exchange up to week 35
How do electrolytes move?
Follow H2O diffusion - iron can only transfer mother to child
What is the foetal main source of energy? (how does it enter?)
Glucose (simplified transport)
What are the hormonal changes through pregnancy?
HCG - will reach peak around week 10 and gradually decrease
Human chorionic somatomammotropin - produced from about 5 weeks and steadily increases
Progesterone - increases with gestation
Eostrogen - increases with gestation
What is the function of human chorionic somatomammotropin?
Growth-hormone-like effects and will decrease insulin sensitivity in mum to provide foetus with more glucose
What is the function of progesterone?
Will signal for decidual cells to concentrate glycogen, protein and lipids, decrease uterine contractability and preparation for lactation
What is the function of oestrogen?
enlargement of uterus, breast development, relaxation of ligaments
What is used as a marker of foetal vitality?
oestriol level
What hormones pass from placenta to mum? and what is their effect?
Corticotrophin releasing hormone -> ACTH -> increased aldosterone (hypertension) and cortisol (gestational diabetes)
HHC -> (causes hyperthyroidism)
Increased Ca+ demand -> hyperparathyroidism
How does cadriovascular output (CO) change throughout pregnancy?
Will be 30-50% above normal from 8 weeks - this is due to the placental circulation, increased matabolism, increased renal circulation and increased need for skin thermoregulation. All of these will result in ECG changes, murmurs and heart sounds (all of which are normal)
CO will decrease in the last 8 weeks due to foetal position (compress vena cava)
CO will increase again by 30% during labour
How does heart rate change through pregnancy?
Up to 90bpm to increase CO further
How does BP change in pregnancy?
BP will drop in the second semester due to expansion of uteroplacental circulation and a decrease in peripheral resistance
How are BP and CO affected in pregnancy with twins?
BP will decrease further in the second semester
CO will increase more
What happens in the blood during pregnancy?
There will be an increase in plasma volume proportional to the CO (50%) and an increase in erythropoiesis by 25%. This causes an overall haemodilution - so Hb will drop.
What can be done to help with anaemia during pregnancy?
Iron supplements - requirements are greater in the second semester (6/7mg per day)
How does progesterone and growing foetus affect the lung function?
Progesterone - will signal the brain to lower CO2 levels (so will increase respiratory rate as respiraroty centres more sensitive to levels)
Growing foetus will cause mechanical obstruction of the lungs
How are GFR and renal function affected in pregnancy?
GFR will increase by about 30-50% (peaking in weeks 16-24). this is to allow for greater absorption of the ions and placental steroids. Renal function is also increased by the formation of aldosterone by the placenta.
Will be affected by postural position (increased in supine and lateral supine position)
How much weight should be gained during pregnancy?
11kg (24lbs) but this due to foetal growth, placental growth and growth of maternal tissue e.g. breasts and increased blood volume
How many extra calories should be ingested by the mother?
250-300kcal/day