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
What are the 2 phases of pregnancy in relation to metabolism?
weeks 1-20 = anabolic phase of the mother and low demands of the foetus
weeks 21-40 = catabolic phase (accelerated starvation of the mother) to meet the high metabolic demand of the foetus
What happens in the anabolic phase?
normal or increased sensitivity to glucose
lower plasmatic glucose levels
lipogenesis and increase in glycogen stores
breast and uterus growth, and weight gain
What happens in the catabolic phase?
Maternal insulin resistance (caused by HCG, cortisol and growth hormone)
increased transport of nutrients to the baby
lipolysis
What may be required for nutritional supplementation?
What sort of diet should be adopted?
Folate - for reduction in risk of neural tube defects
Iron - for anaemia
B-vitamins - for increased erythropoiesis
Vitamin D - bone development
High protein diet with higher energy intake
What is ‘parturition’?
Birth of the baby
How do hormones change during parturition and why?
The eostrogen to progesterone ratio will increase (P reduces uterus excitability whilst E will increase excitability)
Oxytocin will also increase contractions and excitability
What foetal hormones are released at parturition?
Prostaglandins, oxytocin and adrenal hormones (all control the timings of labour)
Prostaglandins will stimulate more vigorous muscle contractions
What mechanical changes help to bring about labour?
Increased muscle stretch will increase muscle contractility
Dilation of the cervix will also stimulate muscle contractions
What are the stages of labour?
1 - cervical dilation (8-24 hrs)
2 - passage of foetus through the birth canal (mins to 120mins)
3 - expulsion of placenta
What is the function of eostrogen, progesterone and prolactin in regards to lactation?
What about oxytocin?
Eostrogen - development of the ductile system
Progesterone - Development of the lobule-alveolar system in the breast
Prolactin - increases milk production (gradually increases from 8 weeks until birth and stays high), within first 7 days of birth it will stimulate the high milk production (colostrum)
Oxytocin - cause smooth muscle contraction is response to stimuli to increase the ejection of milk
Do eostrogen and prgesterone increase milk production?
No - they actually inhibit milk production
There will be a sudden decrease in E and P after birth.
What is the ‘milk let down reflex’?
also called the suckling stimulus - will promote the release of oxytocin from the post. pituitary gland to cause smooth muscle contraction within the breast and ejection of milk.
What are Braxton-Hicks contractions?
These are ‘practice contractions’ caused by the contraction of the uterine muscles. These differ from labour contractions as they are shorter, less painful and can be relived by changing activity level, position or taking sips of water.
What is Bishop’s score?
Score of the cervical readiness for labour and the foetal station: Dilation Effacement Consistency Position Foetal station
What is meant by ‘foetal station’?
The distance the foetal head is from the ischial spines:
- 3 cm is above the ischial spines
0 cm is at the ischial spines
+2cm is past the ischial spines
What is meant by cervical effacement?
How thin the cervix is - by 2nd stage of labour the cervix should be >80% effaced
What is meant by the cervical position?
How the cervix is orientated - in the first stage of labour it will move from the posterior to the anterior position
What occurs in the 1st stage of labour?
This is the movement of the foetus to the level of the ischial spines associated with cervical dilation/effacement/other changes.
What is the latent stage of stage 1 labour?
This is characterised by 3-4cm dilation and irregular contractions
Can last for a few days
What is the active stage of stage 1 labour?
Characterised by >4cm dilation and regular contractions (should be monitored every 30mins)
How much should the cervix dilate during active stage of stage 1 labour last in a nulliparous and multiparous woman?
N = 1cm/hr MP = 2cm/hr
What is stage 2 labour?
the progression from complete dilation to birth
How long should stage 2 labour take in nulliparous and multiparous women?
NP = 2 hrs (3 hrs with analgesia) MP = 1 hr (2 hrs with analgesia)
What is stage 3 labour?
The expulsion of the placental products - should take 5-10 mins if actively managed.
How is stage 3 labour managed actively?
With syntometrine infusion (oxytocin) - this will decrease blood loss after delivery
if >60 mins then indication to operate.
What is the pueperium?
This is the period of time after delivery where the tissues become normal again (usually about 6 weeks)
What is lochia?
This is vaginal discharge that is present after birth what contains blood, mucous and uterine tissue - it may be present for 2 weeks
What happens to CV system in the pueperium?
Returns to normal within 2 weeks
How fast will the vagina return to normal?
Will usually return to normal tone very quickly (within a week) but may be fragile for 1-2 weeks post-partum
How will the uterus be after birth?
It will be the size of a 20 week gestation baby but will decrease in 1 finger breath per day - day 12 should be non-palpable
What are some contraindications to induction of labour?
Malpresentation foetal distress vasa praevia placenta praevia tumour
When should IOL be considered?
If bishops score >7 but no active labour
How can IOL be carried out?
Manual amniotomy (rupture of membranes)
PEG2 (gel or pessary)
Oxytocin (to induce uterine contractions)
What are the options for analgesia in labour?
Non-pharma = massage, water bath, TENs machine Pharma = entenox, paracetamol/NSAIDs, IM opiods, Epidural, spinal, epidural+spinal
What are the considerations in an IM opiod?
It can cause a sleep like pattern on the CTG - reducing foetal HR, and flattening variation
What is an epidural?
Opiods are injected into the epidural space
- midwife administered
- patient admin
- continuous
What is a spinal?
This is when LA or opiods are injected into the sub-arachnoid space
What is the benefit to an epidural/spinal combo?
Can top up the spinal with epidural infusion
How is labour assessed?
Partogram and CTG
What is a CTG?
Cardiotocogram = assesses the foetal HR and contractions
What is a partogram?
This is a sheet that compiles all relevant information about the labour e.g. contractions (frequency and strength), cervical dilation, foetal station, FHR, duration of labour, signs of obstruction, amniotic fluid
What are some signs of obstruction that can be recorder?
Caput, moulding, vulval oedema, anuria, haematuria
What are the 3P’s in failure to progress?
Passage
Passenger
Power
Describe the 3 Ps in failure to progress
Passage - short stature, trauma, shape
Passenger - big baby, malpresentation
Power - inadequate frequency or strength
How should a foetus be assessed in stage 1 labour?
With doppler USS to monitor FHR - during and after each contraction (every 15 mins)
How should a foetus be assessed in stage 2 labour?
With doppler USS to monitor FHR during and after each contraction for at least 1 minute ( every 5 mins)
should also monitor maternal HR every 15 mins
What is the acronym used when interpreting a CTG?
DR C BRaVADO - determine risk, contractions, baseline, rate, variability, accelerations, decelerations, overall impression
What should you do if the foetus shows signs of distress during labour?
Reposition the mother, give IV fluid, stop syntocinon, give scalp stimulation, monitor foetal blood, monitor mothers vitals and consider tocolysis.
if appropriate then c-section
What is tocolysis?
The use of medication to suppress labour
When monitoring foetal blood what is normal and abnormal?
pH = 7.25 (normal) pH = 7.2-7.25 (borderline - repeat in 30 mins) pH = < 7.2 (abnormal - DELIVER)
