Physiology of Pregnancy Flashcards
What happens during day 1 of fertilisation?
fertilisated ovum is in the ampulla
What happens during days 3-5 of fertilisation?
the blastocyst is transported to the uterus
What happens during days 5-8 of fertilisation?
the blastocyst attaches to the lining of the uterus
What do the inner cells of the blastocyst turn into?
embryo
What do the outer cells (trophoblasts) of the blastocyst turn into?
placenta (they burrow into the uterine wall)
What is the role of the trophoblasts on the outer surface layer of the blastocysts?
form cords of trophoblastic cells and penetrate the endometrium carving out a hole for the blastocyst
What happens on day 12 of fertilisation?
implantation is finished and the blastocyst is completely burried in the endometrium
What is the placenta derived from?
decidual and trophoblast tissue
What is decidual tissue?
mucosal lining of the uterus in pregnancy
What do trophoblast cells differentiate into?
syncytiotrophoblasts
What do syncytiotrophoblasts do?
invade the decider and break down capillaries to form cavities filled with maternal blood - developing embryos send capillaries into these to form placental villi
What makes up a placental villi?
maternal blood and foetal blood separated by a thin layer of tissue eg NO DIRECT CONTACT
By what week in pregancy is the placenta functional by?
week 5
What stimulates the corpus luteum to keep secreting progesterone?
HCG
What is the role of progesterone on the decidual cells?
makes them concentrate glycogen, proteins and lipids for nutrition of the placenta
What do the placental villi do as it develops?
extend into the uterine wall to provide more nutrients and exchange of materials
What does the intervillious space act as?
atriovenous shunt - thin membrane develops between mothers and babies blood
How does the placenta take on the role of the foetal lungs?
allows the supply of oxygen and removal of CO2 between the uterine veins and the umbillical veins
What goes from the maternal -> foetal circulation - O2 or CO2?
O2
What goes from the foetal -> maternal circulation - O2 or CO2?
CO2
What 3 factors lead to the foetus being supplied with oxygen?
increased ability of foetal Hb to carry CO2
50% higher Hb conc in foteal blood
Bohr effect - foetal Hb can carry more oxygen
Why does lung function change in pregnant mothers?
progesterone signals to the brain to lower CO2 levels therefore: resp rate increases, PCO2 decreases, tidal and minute volume increases
What percentage must O2 consumption increase to meet demands in a pregnant mother?
20%
How much does cardiac output increase in a pregnant woman?
40% - due to demands of uteroplacental circulation
What haematological changes occur in a pregnant mother?
plasma volume increases
25% increase in erythropoesis
Hb decreases
blood viscosity decreases
How much iron is needed a day in the 2nd half of pregnancy?
6-7mg
Why does the BP drop in 2nd trimester?
uteroplacental circulation expands and peripheral resistance decreases
From what day of pregnancy is HCG detectable?
day 8
What is HCGs effect on males?
development of male sex organs - the testes
When does HCG levels peak during pregnancy?
day 60
What is Human Placental Lactogen?
secreted by the placenta/chorion
When is HPL produced?
from week 5 of pregnancy
When does HPL peak?
32 weeks
What is the role of HPL?
growth hormone like effect
decreased insulin sensitivity in the mother - leads to GESTATIONAL DIABETES
involved in breast development
Where is betaHCG secreted from?
placenta from the synctiotrophoblastic cells
What would HCG levels be in an ectopic pregnancy?
static or slow rising
What would HCG levels be in a failing pregnancy?
levels fall
What would HCG levels be in a viable pregnancy?
levels are doubling or >60% rise
When do HCG levels fall naturally?
weeks 12-14
What happens to serum HCG levels every 48hours in a one baby pregnancy?
double every 48hours
What urinary changes occur during pregnancy?
increase GFR and renal plasma flow
increased reabsorption of ions and water
increase in urine formation
How do positional changes in pregnancy affect renal function?
upright - decreases it
supine position - increases it
lateral position - increases it a lot
What is the average maternal weight gain?
11kg - can be as much as 30kg though
How many extra kcal a day does a mother need?
200 kcal a day
What extra protein intake does a mother need?
30g a day
What phase occurs in the 1st-20th week of pregnancy?
anabolic phase
- small nutritional demands of the foetus
- lower plasma glucose, glycogen stores increase
What phase occurs in the 21-40th week of pregnancy?
high metabolic demands of the foetus accelerated starvation of the mother maternal insulin resistance lipolysis increased transport of nutrients through the placental membrane
What hormone stimulates milk production?
prolactin
What hormones inhibit milk production?
oestrogen and progesterone
What is the role of oestrogen in terms of lactation?
causes growth of the ductile system
What is the role of progesterone in terms of lactation?
causes development of the lobule-alveolar system
