Pregnancy Flashcards
Before fertilisation, where is the egg situated?
Within the Fallopian tube
What is the role of the fimbriae?
They sweep the egg from the ovary into the Fallopian tube at ovulation
When sperm enters the body, what is the passage it takes?
How does the uterus aid in movement of the sperm?
It moves up the cervix, through the cervical mucus and into the uterus
It passes through the ostia and into the Fallopian tube
The uterus contracts to aid the movement of the sperm
What are the ostia?
Small openings where the Fallopian tubes meet the uterus
What forms when the oocyte is fertilised?
The zygote
This is surrounded entirely by the zona pellucida to prevent entry of further sperm
What is early cleavage?
After fertilisation, the zygote begins to divide
When it reaches the 4-cell stage, this is early cleavage
What is formed 3-4 days post-fertilisation?
The morula
This is formed by further divisions of the fertilised oocyte
What is formed 4-5 days post-fertilisation?
Blastocyst
This consists of an inner cell mass and a blastocoele (fluid-filled space)
What is the trophoblast of the blastocyst?
It is the outer layer of cells that will go on to form the placenta
When does the blastocyst implant into the endometrium of the uterus?
Day 6 post-fertilisation
What are the 5 stages of early implantation?
- shedding of the zona pellucida
- pre-contact blastocyst orientation
- apposition cellular contracts
- adhesion
- penetration of endometrium
What happens during pre-contact blastocyst orientation?
The trophoblast cells invade the endometrium
The amniotic cavity forms within the inner cell mass
What will the amniotic cavity go on to form?
The amniotic fluid
What is the decidua?
it is part of the endometrium
What is the extravillous trophoblast?
The trophoblast cells which are burying their way into the decidua
What did Medawar suggest?
The foetal allograft survival
Why does the foetus survive in the body even though it is “foreign”?
What does Medawar suggest as the reasons why the foetus survives?
- antigenic immaturity in the foetus
- placental protection
- the foetus can block certain antibodies
- immune privilege
- altered host immunity
What is meant by placental protection?
The placenta doesn’t make certain chemicals that would usually be recognised by the body as foreign
e.g. MHC class I
How can the foetus block antibodies?
There are certain antibodies that do not make it across the placenta as they are too big
What is meant by immune privilege and altered host immunity?
In the maternal blood, there are less cell-mediated immune cells
e.g. cytotoxic T cells
What are the 2 types of trophoblasts involved in the decidua interaction?
Villous trophoblast - this is inert
Extravillous (invasive) trophoblast
What antigens are expressed on the surface of the extravillous trophoblast?
What is not expressed?
ONLY class I human leucocyte antigens
It does NOT express:
Cw, G, E, A and B
What is significant about the invasive trophoblast not expressing certain antigens?
This makes it less attractive to cytotoxic T-cells
It enables binding to NK cells
The mother’s immune system does not attack the foetus
What type of NK cells are secreted during the luteal/secretory phase of the cycle?
Why are they present?
CD56 (bright)
Their presence is due to progesterone
What is the role of the CD56 NK cells?
They have the capacity both to facilitate and impede trophoblast invasion
How may the CD56 NK cells determine the maternal response to pregnancy?
They are the main source of decidual cytokines
What is an example of systemic signalling in pregnancy?
As the trophoblast comes into the decidua, it begins to make hCG
The hCG acts on the ovary, causing it to make more progesterone
How do levels of hCG vary in early pregnancy?
hCG levels roughly double every 48 hours
It rises rapidly to peak at just over 2-3 months
When do hCG levels drop?
They drop rapidly between 2-3 months
It then plateaus and remains at a lower level until the end of pregnancy
How do progesterone and oestrogen levels change during pregnancy?
They both steadily rise throughout pregnancy
Oestrogen is at a higher concentration than progesterone
What happens to the levels of hCG, oestrogen and progesterone at parturition?
The levels rapidly drop down to 0
What type of molecule is hCG and from where is it produced?
It is a glycoprotein with a similar structure to LH and FSH ( alpha and beta chains)
It is produced by trophoblast cells
Why is hCG described as a luteotrophic hormone?
It continues to stimulate the corpus luteum to make progesterone
What is meant by the production of hCG being autonomous?
Production is independent of the hypothalamus and pituitary
What is hCG thought to be the cause of?
Morning sickness
Morning sickness usually tends to drop off when the levels of hCG begin to drop
What is the clinical use of hCG?
Pregnancy test
this uses an immunoassay that detects the beta subunit of hCG in urine
How is pregnancy dated clinically?
From last menstrual period
What will be visible in a pregnancy image in weeks 5, 6, 7, and 8?
5 - gestation sac, placenta (brighter white)
6 - foetal pole, yolk sac, vitelline veins
7 - fetal heart activity, 3 vessel cord
8 - foetal limbs, movement
yolk sac, amniotic and chorionic cavities
how may imaging in pregnancy be conducted?
Either transvaginally (easier to see much smaller pregnancies) or transabdominal
At which stage may pregnancy be dated through imaging?
11 weeks
What % of fertile women will have a miscarriage?
How does this change with age?
25% of fertile women will have at least one miscarriage
- 6.4% under 35
- 14.7% 35-40
- 23% over 40
What is an incomplete miscarriage?
Some pregnancy tissue is left behind from the foetal pole or the placenta after miscarriage
What is expectant management of miscarriage?
This is allowing the body to deal with the miscarriage and do things naturally
What are the medical treatments for miscarriage?
- progesterone receptor antagonist - mifepristone
combined with
- prostaglandin analogue - misoprostol
What is the usual prognosis for miscarriage?
Usually a good prognosis
Even after 3 miscarriages, there is a 70% chance of success
Why is misoprostol used in miscarriage?
It will open up the cervix and start some contractions of the uterus
What is recurrent miscarriage?
Having 3 or more miscarriages in a row
There is a higher chance of having a further miscarriage
What is ectopic pregnancy and how many pregnancies does it affect
It accounts for 1% of all pregnancies
It is implantation outside of the uterine cavity
What are the 3 reasons for a rising incidence of ectopic pregnancies?
- assisted conception
- pelvic inflammatory disease
This is scarring in the fallopian tubes due to chlamydia, that narrows them
- sterilisation reversal
What is a scar ectopic pregnancy?
When a pregnancy implants within a scar that is present from a previous C-section
What is meant by the decidual reaction?
This is where you would expect to see the pregnancy on an ultrasound
There may be an ectopic pregnancy that has implanted elsewhere
What are the 3 ways of managing an ectopic pregnancy?
- expectant
- medical - one off dose of methotrexate
- surgical - salpingectomy - removal of uterine tube and ectopic pregnancy
When is ectopic pregnancy managed expectantly?
When hCG levels are monitored and they begin to fall naturally
How does ectopic pregnancy affect future pregnancies?
There is an increased risk of recurrence in future pregnancies
Why must methotrexate only be given to terminate an ectopic pregnancy?
it is teratogenic so will cause foetal abnormalities
Why is methotrexate often not used in older patients?
it has a long half life so people must wait at least 3 months before trying to get pregnant again
What are the 2 different types of oestrogens?
Estradiol (E2) is produced by the corpus luteum and the placenta
Estriol (E3) is produced by the foetus and placenta (feto-placental unit)
what is the function of oestrogens?
To encourage growth and increase the strength of the myometrium
How does oestrogen allow for accommodation of the growing foetus?
It increases the amount of contractile proteins
How does oestrogen affect the sensitivity of the uterus?
Increases the sensitivity of the uterus to smooth muscle uterotonics towards term
e.g. PGF2a, oxytocin
How does oestrogen affect the breasts?
it prepares the breasts for lactation
What does oestrogen stimulate?
it stimulates hormone binding proteins that act as a reservoir
CBG, SHBG, TBG
How does oestrogen affect blood flow through the placenta?
It increases blood flow through the placenta
This allows for more efficient exchange of nutrients and waste products
How does progesterone affect the uterus?
It reduces uterine smooth muscle contractility to keep the uterus quiescent during pregnancy
What will progesterone block/inhibit?
- inhibits production of PGF2a and oxytocin (these start contractions)
- blocks T-lymphocyte cell-mediated responses and the cellular immune response
What is HPL?
human placental lactogen
How does HPL secretion change as pregnancy progresses?
It is secreted in increasing concentrations during pregnancy as the placenta grows
How will HPL affect energy substrates within the mother?
- stimulates lipolysis to increase free fatty acids as an energy substrate
- inhibits glucose uptake in the mother
- favours glucose and protein transport into the foetus
How does HPL affect the breasts?
It promotes the growth and differentiation of the breasts in preparation for lactation
How does blood volume change in pregnancy?
There is a 40% increase in blood volume
There is an increase in total body water content and plasma volume
What hormone is increased during pregnancy that affects the cardiovascular system?
There is an increase in erythropoietin
This leads to an increase in red cell mass
Why is there sodium and water retention in pregnancy?
Oestrogen stimulates the renin-angiotensin-aldosterone system
What is meant by the physiologic anaemia of pregnancy?
The red cell mass increases, but not as much as the blood volume increase
How does cardiac output change in pregnancy?
Cardiac output increases 30-50% in pregnancy
Stroke volume rises by 30% and cardiac output rises by 10%
How does blood pressure change during pregnancy?
Greater fall in TPR leads to initial drop in BP
BP then rises to prepregnancy levels later in pregnancy
What blood pressure readings may be indicative of pre-eclampsia?
What other symptoms should be looked for?
Persistent BP > 150/90 mmHg
This is accompanied by:
- high blood pressure
- proteinuria
- peripheral oedema
How does pre-eclampsia tend to affect women later on in life?
Tendency to have hypertension in later life
What are the cardiovascular clinical consequences of pregnancy?
- fainting
- haemorrhoids
- varicose veins
How does coagulation change during pregnancy?
There is increased clot formation
There is decreased clot lysis
Why is there an increase in clot formation during pregnancy?
Due to an increase in factors I, V, VII, VIII, IX, X, XII
Why is there decreased clot lysis in pregnancy?
- the placenta increases plasminogen activator inhibitors
- activated protein C resistance
- reduced protein S levels
What factors lead to increased clot formation?
- thromboplastin
- fibrinogen
- fibrin
What factors are decreased in pregnancy that reduce clot lysis?
- antithrombin
- plasminogen
- plasmin
What is the problem with increasing coagulability of the blood?
There is an increased risk of thromboembolism
How does oxygen consumption change during pregnancy?
There is an increase in oxygen consumption
This is due to the demands of the developing foetus
What is meant by respiratory compensation during pregnancy?
- increase in tidal volume
- increase in alveolar ventilation
- vital capacity is unchanged
What is the result in changing central control of respiration during pregnancy?
There is altered chemoreceptor PaCO2 sensitivity
This triggers and increase in respiration
What is the clinical consequence of respiratory changes during pregnancy?
There is a disproportionate sense of dyspnoea on exertion
How does renal blood flow during pregnancy and why?
There is an increase in renal blood flow due to:
- rise in plasma volume and cardiac output
- fall in renal vascular resistance
- increase in renal vasodilatory prostaglandins - PGI2, PGE2
What is the result of an increase in GFR during pregnancy?
- urea and creatinine fall as there is no change in production
- renal threshold to glucose diminished
- RAAS activated in first trimester
What are the other renal changes in pregnancy?
- pelvicalyceal and ureteric dilatation (smooth muscle)
2. bladder capacity decreases
What are the clinical consequences of the renal changes during pregnancy?
- increased frequency of micturition
2. tendency to UTIs
What are the consequences of a decrease in gastrointestinal motility during pregnancy?
- prolongation of gastric emptying and transit time
- increase in water reabsorption
- this leads to constipation
What are the other gastrointestinal consequences of pregnancy?
- altered appetite (cravings)
2. lower oesophageal pressure and incompetence of cardia
What are the clinical consequences of the gastrointestinal changes during pregnancy?
- nausea and vomiting - can lead to hyperemesis gravidarum
- heartburn
3, constipation
