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
Do haematological changes drive cardiovascular changes in pregnancy?
- No
- Haematological changes are gradual and occur later
In pregnancy, blood volume increases/decreases and haematocrit increases/decreases
- Blood volume increases
- Haematocrit declines
In pregnancy plasma volume increases by ___mL by ___ weeks and thereafter remains stable
1250mL
30 weeks
How does the body account for hypervolaemia post partum?
- Decline of blood volume by diuresis
- Slow loss of red cells with time postpartum
What is the approx. blood loss in a singleton delivery?
500mL
How do sperm affect the maternal immune system?
- Seminal plasma immune suppressive
- Reduces effectiveness of components of immune system in vivo
How does sperm exposure related to pre-eclampsia?
- Repeated exposure beneficial in preventing
- Changing partners resets susceptibility
Which infections are more severe in pregnancy?
- Incidence of listerosis increased
- Leprosy more severe later in pregnancy
What is the role of neutrophils in pregnancy?
- Expansion in luteal phase of cycle
- Peaks at 30 weeks and rises again in time for labour
- May be importnat in cervical ripening
What is the lymphocyte composition of the decidua?
- Almost no B cells
- 10% T cells
- 70% specialised uterine natural killer-like T cells
uNK cells lack the ____ receptor
CD16
What is the distinction between spontaneous and recurrent miscarriage?
- Spontaneous miscarriage - usually caused by genetic abnormalities in the embryo that are not compatible with life (25% pregnancies)
- Recurrent miscarriage - when a woman has 3 or more miscarriages with the same partner
What is the postulated role of T cells in recurrent miscarriage?
In pathological pregnancies there might be a maternal immune response to the foetus
What is the mechanism of uterine growth in pregnancy?
Stretching of existing cells (vs proliferation of cells)
How do the dimensions of the uterus change in pregnancy?
- Mass
- Volume
- Length
70g -> 1100g
10mL -> 5L capacity (up to 20L)
- 50um -> 400-600um
How does the composition of the cervix change in pregnancy?
- Softens
- Glands proliferate to occupy approximately 1/2 of cervical mass
- Mucus plug
- Decrease in collagen
- Elastin unchanged
- GAGs and water increase
When is the growth trajectory of the fetus the greatest?
In the 2nd and 3rd trimesters
How does uterine blood flow change?
- 10 weeks
- 28 weeks
- term
- 10 weeks = 50mls/min
- 28 weeks 185 mls/min
- term 500-700 mls/min
What changes occur in the abdominal wall and skin in pregnancy?
- Increased blood flow to skin
- Pigmentation changes
- Striae gavidarum (stretch marks)
- Hair loss reduced
What are the pigmentation changes that may occur in pregnancy?
- Darkened nipples and areola
- Linea nigra
- Cholasma in neck and face
