Pregnancy/ Labour Flashcards
When is the child viable?
end of second trimester
What are the main maternal changes?
General changes – abdominal changes in the mother only become apparent during the 2nd trimester +
Main maternal changes:
- Increased weight
- Increased hormone levels
- Increased body temperature (possibly by role of progesterone. Also, mediated by increased foetal size)
- Increased blood clotting (protective against losing blood at delivery)
- Decreased BP (is lowest during 2nd trimester and is why pregnant women should not stand for long)
- Increased breast size
- Increased vaginal mucus
- “Morning sickness”
- Altered brain function (due to high levels of steroids, such as progesterone)
- Altered appetite (due to +height of fundus, stomach may be impinged and mother may need smaller meals)
- Altered fluid balance and urination frequencey (– kidney functions change -> ~50%+ in plasma fluid volume by term)
- Altered emotional state (due to hormone levels and can vary in people)
- Altered joints (changes in pelvis to make connections more flexible to permit child-birth)
- Altered immune system
What causes increased weight?
(+10-15kg) – baby, placenta, amniotic fluid, increased fluid retention, increased stores
How do hormone levels change?
hCG – peaks 1st trimester and decreases thereafter
All other hormones (progesterone, oestrogens, lactogen) – slowly increase as the pregnancy progresses
What is the source of progesterone?
progesterone antagonists -> loss of pregnancy at ALL gestational ages
Progesterone source:
- Fertilisation -> 8 weeks’ gestation – corpus luteum source via hCG
- 8+ weeks – placenta supplies progesterone
- The change-over = “Luteo-placental shift”
What is the source ofoestrogen?
- Fertilisation -> Luteo-placental shift – corpus luteum
- 8+ weeks – complex interplay between foetal/maternal adrenals and placenta
- Human placenta – does not express the enzymes needed to convert pregnenolone -> androgens so this occurs in foetal adrenals
- The weak androgen produced (DHEA) is sulphated to give DHEA-S which is inactive (so female foetus is not exposed to androgens) - DHEA-S goes to the placenta to be converted to 17b-oestradiol.
*High levels of oestriol are produced by a parallel mechanism including hydroxylation of DHEA-S in foetal liver to give 16OH-DHEA-S
What causes low FSH and LH throughout?
high steroidal levels supress HPG-axis
What causes an altered immune system?
- Production of factors – supress the maternal immune system from the utero-placental interface. This results in a reduction of Th1 responses and increased Th2 responses
- Placenta expresses unusual HLA – placental HLA are almost invariant (HLA-G has 5 known sequence variants – normal HLA-A and others have millions of variants) and very simple. This is thought to identify the tissue as human but due to its simplicity, no other information is given. HLA-G can also supress some leucocytes and down-regulate maternal immune responses
Define the following terms:
- conceptus
- embryo
- foetus
- infant
- Conceptus – everything resulting from the fertilised egg
- Embryo – the baby up to week 8 of development
- Foetus – the baby for the rest of pregnancy
- Infant – applied after delivery typically
How does the weight of the foetus?
- First trimester – 50g
- Second trimester – 1050g – viable at 500-820g stage (21-24 weeks)
- Third trimester – 2100g
What are the functions of the placenta?
- Separation of blood supplies of mother and baby
- Exchange of nutrients (maternal to foetal) and waste products (foetal to maternal)
- Connection (or anchorage)
- Immunoregulation – allows the maternal immune system to switch off, allowing for pregnancy
- Biosynthesis (e.g. progesterone, oestrogens and hCG)
Describe the anatomy of the placenta
- Primary subunit is the placental villus that has the branches - provides a large surface area for exchange between the maternal and foetal vascular systems
- the veins contain oxygenated blood and the arteries contain deoxygenated blood as the placenta carries out a parallel function to the lungs during pregnancy
Cotyledons – the maternal surface of the placenta is sub-divided into cotyledons (30-60/placenta). Each contains one or more villi
Describe the development of the placenta
- Day 9 post-fertilisation, the conceptus is almost completely implanted within the endometrium
- At this stage of development, the outer layer of the conceptus is multinucleated syncytiotrophoblasts
- These syncytiotrophoblasts contain fluid-filled lacunae
- The underlying layer of cytotrophoblast is proliferating adjacent to the embryo
- This is where the placenta will develop.
- Following implantation, the cytotrophoblast proliferate into the
- First a columnar structure forms (cytotrophoblast column), which undergoes branching (villous sprouts)
- At the centre of each villus are mesenchymal (extra-embryonic mesoderm) cells
- From these cells, the villus vascular system develops
- The branching process continues through out pregnancy, giving rise to the complex branched villi
How does part of the placenta cut itself off from maternal blood supply?
- Cytotrophoblast cells block spiral arteries in the uterus
- They are part of the way of remodelling the arteries
- The arteries in the uterus normally have a vascular endothelium and a smooth muscle layer
- The ability of the spiral arteries to carry large volumes of blood is limited (due to narrowness)
- To get enough nutrients to the baby, it is necessary for these arteries to become wider
- Spiral artery remodelling involves loss of endothelium and smooth muscle cells
- You end up with distended, non-vasoactive vessels – can carry large volumes of blood at low pressure
- More nutrients can be delivered to the baby, and it can be extracted easily by the placenta
What is labour?
uterus undergoes regular coordinated contractions - fundally domianted
cervical ripening and effacement
