Physiology of Pregnancy Flashcards
What happens on day 1?
fertilisation takes place
Where does fertilisation take place?
Ampulla of fallopian tube
What happens on day 3-5?
transport of the blastocyst into the uterus
What is a blastocyst?
fertilised ovum on day 4
How does a fertilised ovum divide?
zygote - 2 cell stage - 4 cell stage - 8 cell stage - morula - blastocyst (4 days)
What occurs on day 5-8?
blastocyst attaches to lining of uterus
What do the inner cells of the blastocyst become?
embryo
What do the outer cells of the blastocyst become?
placenta
What happens when the blastocyst adheres to the endometrial lining?
Cords of trophoblastic cells begin to penetrate the endometrium
Tunnel deeper into endometrium, creating hole for blastocyst
By what day is implantation finished?
12 - blastocyst is completely buried in endometrium
What is the placenta derived from?
Trophoblast and decidual tissue
By what week is the placenta functional?
week 5
What hormone signals the corpus luteum to continue to make progesterone?
human chorionic gonadotrophin (HCG)
What increases the contact area between uterus and placenta?
Placenta extends villi into uterine wall - more nutrients and waste material can be exchanged
Describe the oxygen transport between mother and fetus?
through placenta
- between maternal oxygen rich blood and umbilical oxygen poor blood (mixed arterial and venous)
- O2 diffuses from maternal to fetal circulation (PO2 maternal > PO2 fetal)
- CO2 follows reversed gradient (partial pressure increased in fetal blood)
- fetal oxygen saturated blood returns to fetus via umbilical vein
What facilitates the supply of oxygen to the fetus?
1 - fetal Hb (increased ability to carry oxygen)
2 - higher Hb concentration in fetal blood
3 - Bohr effect -
What is the Bohr effect?
fetal Hb can carry more oxygen in lower pCO2 than high pCO2
Describe what happens to progesterone production during pregnancy.
HCG prevents breakdown of corpus luteum and stimulates progesterone production
What does progesterone do during pregnancy?
Decreases smooth muscle excitability (uterus, gut, ureters)
and raises body temperature
What do oestrogens do during pregnancy?
Mainly estriol
increase breast and nipple growth, water retention and protein synthesis
What hormone decreases insulin sensitivity in mother? Why?
HCS (human chorionic somatomammotrophin)
More glucose for fetus
What happens to cardiac output in pregnancy?
Increases and peaks at 24 weeks (due to demands of uteroplacental circulation)
Decreases in last 8 weeks
What happens to heart rate in pregnancy?
Increases - up to 90/min
What happens to blood pressure during pregnancy?
Falls during second semester
Rises to non pregnancy levels by term
What are some haemodynamic changes that occur during pregnancy?
Plasma vol increases (proportional with CO)
Increase in erythropoiesis
Hb decreases (by dilution)
Iron requirements increase
What respiratory changes are made?
O2 consumption increases (to meet metabolic needs of mother fetus and placenta)
Progesterone signals brain to decrease CO2 levels:
- resp rate increases
- tidal vol increases
- pCO2 slightly decreases
- vital capacity and Po2 stay the same
What happens to the renal system in pregnancy?
Increased GFR
Increased reabsorption of ions and water
Increased urine formation
When and what is the anabolic phase of pregnancy?
Weeks 1-20 - small nutritional demands of conceptus
- normal or increased insulin sensitivity
- lipogenesis and increased glycogen stores
When and what is the catabolic phase of pregnancy?
Weeks 21-40 - increased metabolic fetal demands
- maternal insulin resistance
- increased transport of nutrients transplacentally
- lipolysis
How many extra calories does the mother need during pregnancy?
250-300 extra kcal/day
