2a: Pregnancy Flashcards
What are the Risk of pregnancies in the first trimester?
There is a high risk of miscarriage, often due to
- placental abnormalities
- chromosomal abnormalitiesof the foetus
*
What are the features of the first trimestern in pregnancy for the mother?
- Altered brain function [1st & later]
- Altered emotional state [1st & laterr
- due to: Altered hormones [1st & later]
- Altered appetite (quantity and quality) [1st & later] – GI imbalance
- Altered immune system [1st & later]
What are the main changes that happen to the mother during the 2nd trimester of pregnancy?
- Altered fluid balance [2nd & later]
- Increased blood volume [2nd & later]
- Increased blood clotting tendency [2nd & later]
- Decreased blood pressure [2nd]
+ all changes from 1st trimester
What are the main maternal changes in the 3rd trimester?
Increased weight [3rd]
Altered joints [3rd]
–> plus symptoms from 1st and 2nd trimester
Explain the differentiation and characteristics of the trimesters of pregnancy
- 0-13 Weeks
- High risk of miscarriage
- 13-26 Weeks
- (Barely) no viability if delivery before that
- 26-40 Weeks
- Term, viable outside uterus
Summarise the hormonal changes during Pregnancy
Overall: very very high hormone levels
What are the main maternal risks of Pregnancy?
Generally: Low risk except delivery itself (risk of bleeding)
What is a conceptus?
Conceptus – everything resulting from the fertilised egg (baby, placenta, fetal membranes, umbilical cord)
What is an embryo?
Embryo – the baby before it is clearly human Ca. 0-9ssw
What is a fetus?
Fetus – the baby for the rest of pregnancy (clearly human and not just an embryo)
When does Pregnancy start?
Normally counted as the first day of the last menstrual cycle
- because ovulation is difficult to determine (expecially with infrequent periods etc)
But embryologist would start at time of conception/fertilisation
What is the source of the high levels of progesterone in pregnancy?
0-8 Weeks: Corpus Luteum
After 10 Weeks: Placental produces all progesteone
–> Called: ‘luteo-placental shift’
What are the sources of the high oestrogen levels in pregnancy?
Early Weeks: Corpus Luteum
Then: Shift to
- Maternal adrenals
- Placenta
- And Fetal Adrenals/Liver
Steroidogenesis: recognise pregnancy as a three-way interaction between mother, fetus and placenta with steroidogenesis as an example of this
The human placenta does not express the enzyme (Cytochrome P450 17A1, or CYP 17, or Cytochrome P450 17,20-lyase) that converts pregnenolone to androgens, so this part of biosynthesis takes place in the fetal adrenals (which are large and well-developed even in the first trimester). The weak androgen produced (dehydroepiandrosterone, DHEA) is sulphated as well to give DHEA-S, which is inactive. Hence a female fetus is not exposed to an androgen during development. The DHEA-S circulates to the placenta, where it is converted to 17beta-oestradiol as shown.
In human pregnancy, very high levels of oestriol are found, which are produced by a parallel mechanism (Figure 3.5), which includes hydroxylation of DHEA-S in the fetal liver to produce the precursor 16OH-DHEA-S.
Explain the immunological changes durig pregnancy
Need to tolerate foreign Baby
- downregulation of maternal immune system
- HLA (almost invariant) expression on Placenta
What is the main structural (and functional) unit of the placenta?
Cotyledons (structural SU with groovs inbetween that are filled with maternal tissue)
- One cotyledon can have one or several villi (placental villous trees)
Explain the basic structure of a placental villous tree
Structure that allows exchange between maternal and fetal circulation
- it has one main branch
- with many small branches coming off again
- complex blood supply, including arterial and venous vessels, connected to smaller capillaries in the terminal portions of each villus
- huge surface area
What is the state of the placenta 9 days post fertilisation?
The conceptus is almost fully implanted
- Placenta will form from Cytotrophoblast
- Proliferate under layer of syncytiotrophoblast, which contain fluid-filled lacunae
What happens to placental development after implantation?
cytotrophoblast proliferate into the syncytium
- first a columnar structure is formed (cytotrophoblast column),
- which then undergoes branching (villous sprouts).
- At the centre of each villus are mesenchymal (extra-embryonic mesoderm) cells, from which the villus vascular system develops.
- –> Further Branching later in pregnancy
What is the cytotrophoblast shell?
Shell that is formed around the developing fetus that minimised exchange between Fetus and Mother
- To protect fetus (e.g. from free oxygen radicals) (fetus is cery vulnerable during that time)
- Achieved via cytotrophoblast plugs that block spiral arteries
What are Spiral arteries?
Are modulated wide, maternal arteries without SM layer or endoethelial layer but replacement with cytotrophoblast cells –> no contraction and allows constant high Blood flow to Baby
