9- Maternal Changes of Pregnancy Flashcards
what factors cause the decrease in blood pressure in pregnancy despite the increase in blood volume?
progesterone has an inhibitory effect on angiotensin II vasoconstrictive effects
oestrogen drives increase in endothelial nitric oxide synthesis = increased peripheral vasodilation decreases TPR, increases cardiac output
describe the process of decidualisation
occurs if pregnancy/ fertilisation occurs, and the corpus luteum & its high progesterone production is maintained
decidual cells of the endometrium undergo changes due to high progesterone 9-10 days after fertilisation
changes:
- decidual cells filled with lipids and glycogen
- endometrium expresses adhesion molecules
- tiny spiral arteries grow, become more twisted = bigger SA to exchange oxygen and nutrients
- secretory glands secrete growth factors and sugars
- endometrium becomes receptive for implantation
describe the process of implantation from day 7 to 14
6-10 day window for fertilisation following LH surge. fertilised zygote develops into blastocyst within 6 days, with inner cell ball mass, trophoblast and zona pellucida.
day 7-8 = blastocyst attaches to the surface of the endometrium as trophoblast cells bind and invade, interacting with the decidua. trophoblast cells fuse together to form a synctiotrophoblast - one big cell with many nuclei, allows all the trophoblasts work together as a syncytium.
day 9-11: trophoblast cells continue invading decidua basalis. by day 11, blastocyst is almost completely buried in decidua.
day 12: decidual reaction occurs - high progesterone causes endometrial cells to enlarge and express fluid-filled spaces rich in glycogen and lipids. fluids taken up form decidual cells to synctiotrophoblast - fluid provides nutrients for blastocyst until placenta develops.
day 14: synctiotrophoblast starts protruding out, forming primary villi. decidual cells near primary villi clear out, leaving spaces which enlarge and become lacunae. tiny spiral arteries of endometrium expand and interact with villi, fill lacuna with maternal blood. allow for transmitting oxygen and nutrients between mother and baby.
describe the placenta as the maternal-foetal interface
allows for the exchange of oxygen and nutrients, gases and waste products
primary villi become highly vascularised and develop into chorionic villi as finger-like projections
one cell thickness between lacuna filled with maternal blood and foetal chorionic villi allows for efficient exchanges
maternal and foetal blood circulations are separate. maternal blood with oxygen and nutrients passes through endometrial spiral arteries, pools in lacuna and is taken up by foetal chorionic villi.
what secretes hCG?
synctiotrophoblast
what is the importance of hCG secretion?
prevents death of the corpus luteum - hCG binds to LH receptors on CL (same alpha subunit) so it continues producing high oestrogen and progesterone until the placenta is developed at week 9-10 to take over
stimulates endometrial changes for implantation and stops FSH & LH secretions
how does progesterone contribute to pregnancy?
- decidualisation
- smooth muscle relaxation of uterine wall and other areas
- contributes to cardiovascular changes = increased blood volume and cardiac output, decreased blood pressure
- promotes breast development of mammary glands and stroma
describe production of oestrogen in placenta
placenta can’t directly produce oestrogen from cholesterol = lacks aromatase
maternal and foetal adrenals provide DHEA - converted to oestrogen using other enzymes
how does oestrogen contribute to pregnancy?
contributes to cardiovascular changes
increases clotting factor production = hypercoagulable state
promotes breast development
induces insulin resistance
promotes growth and development of uterus and myometrium
describe how pregnancy works as a high-volume, low-pressure system
high volume = increase in blood volume
low pressure = decrease in blood pressure due to progesterone inhibiting angiotensin II vaoconstrictive effects, decreasing TPR with peripheral vasodilation
