Lecture 18 & 20 - Physiology of Pregnancy Flashcards
What hormone tested on pregnancy urine dipsticks?
where is it produced in majority initially?
what happens when there are twins?
bHCG
-this is produced by syncytiotrophoblast of preimplantation blastocyte and placenta
- Ovary - main source of progesterone initially then after 8 weeks the placenta takes over
- more hCG with twins
Functions of hCG in 6-8 weeks
hCG binds to LH/hCG receptor (does similar things to LH)
- promotes growth and survival of corpus luteum (this produces progesterone and oestrogen) to stop menstruation and prevents normal cycle
- prevents the uterus returning to normal cyclic pattern by causing CL to continue secreting oestrogen and progesterone
- prevents menstruation and maintains endometrium in decisdualsised form
What stimulates testosterone production at 6-8 weeks?
hCG - LH like activity stimulates testosterone production in the leydig cells of the testis (prior to synthesis of LH by fetal pituitary)
Progesterone
- where does it come from?
- functions
Comes from both corpus luteum, and placenta
placenta - synthesised by the syncytiotrophoblast of placenta
-these express LDL receptors and can convert the cholesterol to progesterone
Function
- maintains uterine quiescence (relaxes myometrium)
- makes uterus ready for pregnancy - induces formation of decidua - important for providing nutrients prior to when we have the maternal blood supply
- receptors are in the stromal cells in endometrium/decidua
- stops milk production
What is required for production of oestrogen?
what does progesterone need?
how is oestrogen made by placenta?
- Live fetus
- functioning feteal adrenals
- intact feto-placental circulation
- functioning placenta
Progesterone - only needs placenta
Placenta can not make oestrogen
placenta produces progesterone, this goes into the fetal circulation
-then in fetal adrenals and liver it is converted to androgens
-then these androgens are taken by fetal blood back to the placenta where aromatase can convert them to oestrogen and then these are sent back into the maternal blood (increase levels of maternal oestrogen)
-path to maternal circulation much shorter than to fetal circulation
what would cause low levels of oestrogen in utero?
Ancephalic pregnancies - adrenals usually atrophic, have low levels because cannot convert progestrogen to androgens
maternal adaptation
Changes to - cardiovascular system
- haematological system
- maternal immune system
- genital system
Pre eclampsia
- elevated maternal blood pressure w protein in urine
- more common for first pregnancies
- triggered by placenta (e.g toxin)
- is an exaggerated inflammatory response leading to vascular dysfunction
- failure of normal vascular adaptation to pregnancy
- loss of normal maternal peripheral vascular resistance
Maternal cardiovascular adaptations
- Increase CO (increase in SV and pulse rate) by 10%
- reduce peripheral vascular resistance
- if dont get the change in peripheral resistance then will get increase blood pressure –> pre eclampsia
- oestrogen can act on the blood vessels to relax them
- angiotensin produced - made but doesn’t really respond in mother
- NO is produce in response to share stress, but activity of this is increased in pregnancy
- if endothelial cells become activated, however if put vesicles from the normal placenta on the endothelial cells, then you can stop this activation of endothelial cells
Haematological changes
Increased blood volume- plasma volume expands much more than the blood volume
- haematocrit changes
- these changes are much more gradual than the CO
-mum adapts to blood loss after pregnancy and haematocrit slowely returns to normal
Immune system
- Immune reaction to sperm when they enter the vagina
- however repeated exposure may dapen the immune response and be beneficial to pre eclampsia
- White cell count increases due to increase in neutrophil population, which commences in the luteal phase of the cycle and doesn’t drop in pregnancy
- neutrophils are important for preparing the cervix for labour
-more th2 than th1 - drive immune system towards antibody mediated response
Contains many NK cells - act by antibody dependent cell mediated cytotoxity
what is T cell levels for miscarriage compared to normal cell pregnancy
T cell levels are much higher in pregnancy than miscarraige
Cervix
- softens
- glands proliferate
- collagen content decreases
- water content increases
- makes it so you can deliver a baby
- incompetent cervix is associated with recurrent miscarriage
Uteroplacental blood flow
- Increasing evidence that there is minimal or no blood flow to placenta during the first trimester
- trophoblasts grow into spiral arteries and form plugs to reduce the blood flow
- at 10 weeks these plugs break, and blood flows into the intervillous spaces
Blood flow to abdominal wall and skin for mother
- Blood flow to skin is increased
- pregnant women often have warm clammy hands
- flow to the hands is increased 6-7 fold
- flow to the feet is also increased
- show that there is overall raised blood flow to skin
Pigmentation changes
- niples and areola become pinker
- linea nigra line forms
- cholasma may develop around neck and face
- due to an increase in MSH hormone
-more hair is losed
