Physiology - Pregnancy and Lactation Flashcards
what does the fertilised ovum divide and become?
a blastocyst
what occurs in the first 3-5 days following fertilisation?
transport of the blastocyst into the uterus
what happens 5-8 days post fertilisation?
the blastocyst attaches to the lining of the uterus
what do the inner cells of the blastocyst become?
the embryo
what do the outer cells of the blastocyst become?
the placenta
what happens when the blastocyst adheres to the endometrium?
cords of trophoblastic cells begin to penetrate the endometrium
when is implantation of the blastocyst completed?
by day 12
what is the placenta derived from?
trophoblasts
decidual tissue
what is another name for the trophoblast cells?
chorion
what do the trophoblast cells differentiate into?
multinucleate cells called synctiotrophoblasts
what do the syncytiotrophoblast cells do?
invade the decider and break down capillaries, forming cavities filled with maternal blood
what forms the placental villi?
capillaries from the developing embryo entering the syncytiotrophoblast projections in the decider
what do placental villi contain?
foetal capillaries separated from maternal blood by a thin layer of tissue
when are the placenta and foetal heart functional?
by the fifth week of pregnancy
what provides early nutrition to the embryo?
trophoblastic cells that have invaded into the decidua
what takes over providing nutrition to the embryo later in the pregnancy?
the placenta
what effect does HCG have on the corpus luteum?
signals it to keep secreting progesterone
what effect does progesterone have on the decidual cells?
stimulates them to concentrate glycogen, proteins and lipids
what is the outcome of the placental villi extending into the uterine wall?
increases contact area between the uterus and placenta allowing gate exchange of nutrients and waste
what plays the role of the foetal lungs?
the placenta - allows supply of oxygen and removal of CO2 from the foetus
which has higher oxygen concentration - maternal or foetal blood?
maternal
in which direction does oxygen diffusion in the placenta occur?
from the maternal circulation to the foetal circulation
PO2 maternal > PO2 foetal
in which direction does CO2 diffusion occur in the placenta?
from the foetal circulation to the maternal circulation
maternal CO2 < foetal CO2
where does foetal blood go after getting oxygen from the placenta?
returns to the foetus via the umbilical vein
where does maternal blood go after giving oxygen to the placenta?
back into the uterine veins
what three factors facilitate the supply of the foetus with oxygen?
foetal Hb
higher Hb concentration in foetal blood
Bohr effect
how is foetal Hb different from adult Hb?
has an increased ability to carry oxygen
which has a higher Hb concentration - foetal blood or maternal blood?
foetal
this enables greater oxygen transport
how does the Bohr effect facilitate oxygen transport in the foetus?
foetal Hb can carry more oxygen in low pCO2 than in high pCO2
this is good because foetal CO2 < maternal CO2
in which direction does water travel across the placenta and via what mechanism?
from mother to foetus
via osmosis
what amount of water is exchanged across the placenta in pregnancy?
increases up to the 35th week where it is around 3.5L per day
how do electrolytes cross the placenta?
follow the water that moves via osmosis
which electrolytes go ONLY from mother to child across the placenta?
iron and calcium
need to ensure mothers have adequate levels of these substances
how does glucose pass across the placenta?
via simplified transport
what is the foetuses main source of energy?
glucose
at which point in pregnancy is most glucose required?
in the third trimester
how do fatty acids move across the placenta?
via free diffusion
name four hormones that change throughout pregnancy
HCG
HCS/HPL
oestrogen
progesterone
what does HCG stand for?
human chorionic gonadotrophin
what does HCG do?
prevents involution of the corpus luteum
this stimulates progesterone and oestrogen production
what effect does HCG have on male foetuses?
aids in the development of the sex organs
describe the levels of HCG throughout pregnancy
highest in early pregnancy
what is another name for human placental lactogen (HPL)?
human chorionic somatomammotropin
when is HPL produced?
from around week 5 in pregnancy
continues to rise throughout pregnancy
what are the three main effects of HPL?
growth hormone like effects - protein tissue formation
decreases maternal insulin sensitivity
involved in breast development
what effect does decreasing insulin sensitivity in the mother have on the foetus?
allows more glucose to be provided for the foetus
what three effects does progesterone have throughout pregnancy?
development of decidual cells
decreases uterine contractility
prepares the body for lactation
describe levels of progesterone and oestrogen throughout pregnancy
rise throughout pregnancy
what three effects do oestrogen have during pregnancy?
enlargement of the uterus
breast development
relaxation of the pelvic ligaments
what happens to serum HCG levels in early singleton pregnancy?
double every 48 hours
what are HCG levels like in an ectopic pregnancy?
static or slow rising
what are HCG levels like in a failing pregnancy?
reducing
what side effects can HCG cause?
nausea and vomiting
when can HCG levels be higher than normal?
multiple pregnancies
molar pregnancy
when do HCG levels start to fall?
from 12-14 weeks
what effect does placental CRH have on the mother?
increased ACTH resulting in increased aldosterone and cortisol
what effect can increased aldosterone have in a pregnant mother?
hypertension
what effect can increased cortisol have in a pregnant mother?
oedema
insulin resistance = gestational diabetes
what possible effect can HCG have on a pregnant mother?
hyperthyroidism
what possible effect can increased calcium demands in pregnancy have on the mother?
hyperparathyroidism
what happens to CO during pregnancy?
rises to 30-50% above normal
what causes the increase in CO during pregnancy?
the demands of the uteroplacental circulation
describe the CO throughout pregnancy?
begins to rise at 6 weeks
peaks around 24 weeks
decreases in the last 8 weeks
increases again during labour
what change in heart rate occurs during pregnancy?
increases up to 90/min to increase CO
what change in blood pressure occurs during pregnancy?
does during the second trimester
what causes the drop in BP in the second trimester?
the uteroplacental circulation expands and peripheral resistance decreases
how are the cardiovascular changes in pregnancy different when it is a multiple pregnancy?
CO increases more
BP drops more
is average pregnancy BP usually higher or lower than pre-pregnancy BP?
lower - usually by 15mmHg
what are BP levels like by the time the baby reaches term?
back to pre-pregnancy levels
what three haematological changes happen in the mother during pregnancy?
plasma volume increases
erythropoiesis increases
Hb is decreased by dilution
what happens to iron requirements during pregnancy and what can be done for this?
they increase significantly
iron supplements are often needed to prevent anaemia
what is the definition of anaemia in the first trimester?
Hb <110g/L
what is the definition of anaemia in the second and third trimesters?
<105g/L
what is the normal definition of anaemia?
Hb 120-160g/L
what causes respiratory changes during pregnancy in the mother?
progesterone increases
enlarging uterus interferes with lung function
what happens to the GFR and renal plasma flow in a pregnant mother?
increase
peaks at 16-24 weeks
what drives the increased re-absorption of ions and water in pregnancy?
placental steroids
aldosterone
what effect does an upright position have on renal function in pregnancy?
decreases
what effect does an supine position have on renal function in pregnancy?
increases
what effect does a lateral position during sleep have on renal function in pregnancy?
increases LOTS
what is the reference range for ALT in a pregnant individual?
<30
what is the reference range for urea in a pregnant individual?
<3.5
what is the reference range for creatinine in a pregnant individual?
<50
what is the reference range for albumin in a pregnant individual?
20-40
what change occurs to maternal coagulation during pregnancy?
hyper coagulable state
what effects does the maternal hypercoagulable state have?
reduces risk of haemorrhage
increases risk of VTE
what happens to factor II levels in pregnancy?
no change
what happens to factor VII, IX, X and XII levels in pregnancy?
increase
what happens to fibrinogen levels in pregnancy?
increases
what happens to factor XI levels in pregnancy?
reduce
what happens to protein S levels in pregnancy?
reduce
what happens to protein C levels in pregnancy?
no change
what happens to antithrombin levels in pregnancy?
no change
what happens to plasminogen levels in pregnancy?
increase
what happens to D-dimer levels in pregnancy?
increase
what happens to vWF levels in pregnancy?
increase
what weight change is normal during pregnancy?
average weight gain of around 11kg
can sometimes be up to 30kg
how many extra calories per day should be ingested by a pregnant mother?
200
what should the protein intake of a pregnant mother be?
extra intake of 30g/day
what are the two phases of pregnancy as defined by the mothers metabolism?
mothers anabolic phase in 1st - 20th week
21-40 week - catabolic phase
describe the metabolic needs of the mother and foetus during weeks 1-20
anabolic metabolism of the mother
quite small nutritional demands of the foetus
describe the metabolic needs of the mother and foetus during weeks 21-40
high metabolic demands of the foetus
results in accelerated starvation of the mother
what causes maternal insulin resistance?
HPL
cortisol
growth hormone
what effect does folic acid have in pregnancy?
reduces the risk of neural tube defects
how much folic acid should be taken throughout pregnancy?
400mcg per day in the first 12 weeks
ideally also for three months prior to conception
what dose of vitamin D supplements should be taken during pregnancy?
10mcgs a day
20mcgs if BMI > 30
what happens to the uterus towards the end of pregnancy?
it becomes progressively more excitable
what effect do progesterone and oestrogen have on uterine contractility?
progesterone = inhibits oestrogen = promotes
what happens to progesterone levels towards term and when labour starts?
levels fall
what is parturition?
the birth of the baby
what are prostaglandins produced by during parturition?
placenta
myometrium
decidua
membranes
what do prostaglandins do during parturition?
help to ripen the cervix
play a role in the onset of labour
what produces oxytocin?
the maternal posterior pituitary gland
what does oxytocin do during parturition?
increases contractions and excitability
what effect does increasing foetal size have on parturition?
stretches uterine muscles, increasing contractility
what substances are given to induce labour and how do they work?
prostaglandins - ripen the cervix
oxytocin when membranes have ruptured - increase contractions of the uterus
when do Braxton Hicks contractions increase?
towards the end of pregnancy
what are Braxton Hicks contractions?
sometimes called practice contractions
mild, irregular, don’t require pain relief
when does cervical ripening occur?
just before the onset of labour
what is cervical ripening?
the softening of the cervix ti allow duration
what causes cervical ripening?
oestrogen
relax
prostaglandins
what hormone is released in response to cervical stretching in labour?
further oxytocin release
what causes intense abdominal muscle contractions in labour?
strong uterine contractions + pain cause neurogenic reflexes from the spinal cord, that have an impact on the abdominal muscles
what is the first stage of labour?
cervical dilation
how long does the first stage of labour take?
8-24 hours
what is the second stage of labour?
passage of the foetus through the birth canal
how long does the second stage of labour take?
from a few minutes to two hours
what is the third stage of labour?
expulsion of the placenta
what effect does oestrogen have on lactation?
stimulates growth of the ductile system
what effect does progesterone have on lactation?
development of the lobule alveolar system
overall, what effect do oestrogen and progesterone have on milk production?
INHIBITION
levels drop at birth
what hormone stimulates milk production in lactation?
prolactin
what hormone triggers the “milk let down” reflex?
oxytocin
