Session 8 - Group work Flashcards
What effects would you expect maternal smoking to have upon the placenta? What
effect may this have upon the baby?
May reduce placental blood flow and growth. Poorer fetal nutrition will reduce birth weight,
by on average, 200g.
How does alcohol cross the placenta? What implications does this have for the
development of a baby whose mother drinks significantly during pregnancy?
By diffusion – lipid soluble
Possible cause of Fetal Alcohol Syndrome in which the maternal (mis)use of alcohol leads to
a fetus of low weight and with growth retarded (potentially with mental retardation, head and
facial abnormalities)
Why might cytomegalovirus, which normally just causes a mild flu-like illness in
infected adults, be a significant health hazard in pregnancy?
Can cause teratogenesis
1 Following the birth of a rhesus positive baby to a rhesus negative mother it is
customary to administer ‘anti-D therapy’ in the form of anti-D antibody. Why is this
done?
Mother may have made antibodies to fetal Rhesus antigens if fetal blood has entered the
maternal circulation. The anti-D antibody neutralises these antigens. The presence of
maternal anti-Rh antibodies in the fetal circulation causes rapid haemolysis when they bind
to the fetal red blood cells. (The Kleihauer test is used to demonstrate the presence or
absence of fetal cells in the mother’s circulation (which is especially important in Rh
isoimmunization). If the foetal cells contain antigens which the mother’s cells lack then the
mother could raise antibodies against these antigens.)
In the third stage of labour, what tissue of maternal genetic origin is shed with the
afterbirth?
The decidua
From where does the IgG in fetal blood derive?
the mothers blood
Could, in principle, a neonatal immune disease be mediated by IgM? If not, why not
No, because the IgM class of antibodies does not cross the placenta
i) hCG is released from trophoblastic cells (syncytiotrophoblasts) of the blastocyst
peaking at 10 weeks gestation
ii) hCG (human chorionic gonadotrophin) mimics the action of LH on the corpus
luteum, hence preventing degeneration of the latter
iii) Oestrogen and especially progesterone secretion is important in maintaining
pregnan
How does early pregnancy support itself?
hCG is released from cells of the developing fertilized ovum. By stimulating the corpus
luteum, hCG maintains (and indeed increases) the release of progesterone and oestrogen
characteristic of the luteal phase of the menstrual cycle. Hence, oestrogen and progesterone
maintains the endometrium and hence the pregnancy.
hCG reduces maternal IgA, lgG and 1gM. Speculate
(i) why may this benefit the fetal-placental unit?
(ii) what consequence may it have on the mother?
) Humeral immunity is depressed and is probably necessary to stop rejection of the
placenta by the mother and vice-versa.
ii) The mother is more susceptible to viral infections
Progesterone relaxes smooth muscle. Identify two effects increasing progesterone
levels may therefore have on GI tract function that the mother may complain of?
By reducing motility it may lead to heartburn and constipation.
Oestrogen and progesterone both stimulate breast growth, along with which other
hormone from the anterior pituitary?
Prolactin
Explain how inhibin (from the corpus luteum and placenta) prevents further
pregnancies occurring?
Suppresses FSH secretion, hence blocking follicular growth
In early pregnancy, progesterone stimulates appetite and promotes maternal
deposition of fat (on average 3 kg of fat are accumulated by the mother; i.e. 25% of
her weight gain). How is this beneficial to the mother in later pregnancy and after the
birth of the baby?
Maternal preparation e.g. breast growth, and also may provide a reserve for later pregnancy
when fetal demands are greater. In later pregnancy fat rather than glucose is the primary
source of energy for the mother.
4 The above process can lead to maternal hypoglycaemia between meals. However,
hPL (hCS) also promotes lipolysis. How is this of value?
Lipids and ketones released are available for energy. In early pregnancy, progesterone
increases maternal appetite and promotes the storage of glucose in fat stores. hPL (hCS)
promotes lipolysis of these fat stores.
Plasma volume increases by about 50%, (red cell mass by about 20%). Cardiac
output increases from 4.5 to 6 L/min. This is achieved mainly through increase in
stroke volume as compared to heart rate (18%). What change in mother’s blood
pressure do these adjustments induce? (TPR changes considered in question 8.25,
below)
Mean BP remains the same, but the increased stroke volume raises systolic BP a little and
the stroke volume, flowing so rapidly into additional tissue, reduces diastolic BP a bit.