Physiology of Pregnancy Flashcards
How is hormone production different in humans vs animals?
- Placenta not responsible for steroid production in other species
- Humans produce greater quantity of hormones
hCG shares an alpha chain with which hormones?
TSH, LH and FSH
Which structural difference gives hCG a longer half life than LH?
Extended B chain
hCG is produced exclusively by ____ and ____
Syncytiotrophoblast of the placenta and trophodecterm of the preimplantation blastocyst
When do hCG levels peak in pregnancy?
~10 weeks gestation
hCG levels peak at ___units/mL then drop to about ___units after 10 weeks
100,000
20,000
What is the main function of hCG?
Luteal support
Oestrogen and progesterone prevent ____ and maintain the endometrium in a _____ form (in pregnancy)
Menstruation
Decidualised form
What kinds of tumours would cause an increased hCG?
Trophoblastic tumours - choriocarcinoma and hydatidiform mole
What is the role of hCG in male fetus pregnancies?
- Stimulates Leydig cells
- Allows production of testosterone before pituitary has developed (no LH)
How can women with choriocarcinoma or hydatidiform mole become hyperthyroid?
- Produce hCG
- Bind to TSH receptor or LH receptor in thyroid
What is the biggest risk associated with tubal pregnancy?
Invasion of ovarian artery by extravillous trophoblasts -> exanguination
Oestrogens are produced by the ____
Feto-placental unit
What four things are necessary for oestrogen production?
- Live fetus
- Functioning fetal adrenals
- Intact feto-placental circulation
- Functioning placenta
The placenta does not express ____ and cannot produce oestrogen de novo
17a hydroxylase
Placenta produces ___ and ____
Oestrone and oestradiol
Anencephalic pregnancies usually have low levels of ____
Oestrogens
Pregnancies complicated by preeclampsia are characterised by higher/lower than “normal” peripheral resistance
Higher
What are the two cardiovascular adaptations in pregnancy?
- Increased CO
- Reduced PVR
The placenta produces ____ which is shunted to the ___ circulation and converted to ____ in the adrenals which are then taken back to the placenta where they are converted to ____
Progesterone
Fetal circulation
Androgens
Oestrogen
How does oestrogen influence the cardiovascular adaptations of pregnancy?
- Reduces vascular resistance
- Alters ratio of type I:type III collagen in vessel wall
- High levels not reached until 9 weeks (fetal adrenals induce synthesis)
How does progesterone influence the cardiovascular adaptations of pregnancy?
- SM relaxant
- Effect primarily in the uterus
- Effect not till ~10 weeks
How does angotensin influence the cardiovascular adaptations of pregnancy?
- Vasoconstrictor
- Uteroplacentalunit produces large amounts of RAS
- Effects of AII blunted in normal pregnancy
How does NO influence the cardiovascular adaptations of pregnancy?
- Produced by endothelial cells in response to shear stress of blood
- Short half life, causes arterial wall relaxation and dilation
- NO synthetase activity in some tissues is inc. in pregnancy