2 - pregnancy

Question 1

how gestational age and post-fertilisation age relate

Answer 1

GA = PF age + 2 weeks

Question 2

1st trimester - define, features, risks

Answer 2

0-13 weeks

Most embryology takes place in this period - structural development

95% of pregnancies that survive the 1st trimester reach term
most dangerous time for foetus
- chromosomal abnormalities — miscarriage
- most susceptible to insult – congenital abnormalities
- placental problems - miscarriage

Question 3

2nd trimester - define, features, main purpose, point of viability

Answer 3

13-26 weeks
- foetus becomes viable in this trimester

viability limit = 24 weeks
at 25 weeks = 50% survival

main purpose = growth of structures

Question 4

3rd trimester - define features, main purpose, risks

Answer 4

26-40 weeks
- growth ( a lot, increases by 2kg)
maturation of the brain, immune system, lungs and digestive tract (BILD)

highest risk to mother at this time - labour and haemorrhage

Question 5

Maternal changes in the 3 trimesters

Answer 5

1st
- altered emotional state
- altered hormones
- altered brain function
altered immune system
altered appetite

2nd  (blood stuff)
increase blood volume
increased clotting
decreased blood pressure
altered fluid balance

3rd
increased weight
altered joints

Question 6

placenta functions

Answer 6

SEBIC

Separation of foetal and maternal vascular systems
Exchange of nutrients and waste
Biosynthesis of hormones e.g. P
Immunoregulation - prevent rejection of conceptus
Connection - anchorage to uterine wall

Question 7

Placental structure:
spiral arteries function
placental villous tress create......
umbilical vessels which is oxygenated ....
what maximises nutrient exchange
functional unit

Answer 7

spiral arteries provide blood supply to foeti-placental unit

placental villous trees create large SA

umbilical artery = deoxygenated (carrying away from the foetal heart)
umbilical vein = oxygenated (carrying oxygen to foetal heart)

Countercurrent flow

Unit = cotlyedon

Question 8

Development of the placenta - stages

Answer 8

1 - Implantation of the conceptus

2 -development of villi and anchoring

3 - contact with maternal tissues

4 - contact/ hypertrophy of decidual glands (maternal) - histrotrophic nutrition

5 - spiral arteries (supply placenta with blood) – remodelling of cytotrophoblast plugs and haemotrophic nutrition

Question 9

Describe 1 - Implantation of the conceptus

Answer 9

conceptus consists of trophoblast layer sand embryo

• trophoblasts develop into the placenta
• (cytotrophoblast later and synciotiotrophoblast –outer)

Question 10

Describe 2 - development of villi and anchoring

Answer 10

cytotrophoblasts proliferate and some use with the synctium - known as the cytotrophoblast column

they branch and form villous sprouts

mesenchyme in the centre of each villous where the vascular system develops

Question 11

Describe 3- contact with endometrium

Answer 11

endometrial contact

brief contact with maternal capillaries - but then contact is cut off by cytotrophoblast plug

Question 12

Describe 4 - contact with decidual glands

Answer 12

conceptus is not in contact with maternal arterial blood until the end of the first trimester
- moves from histrotrophic nutrition to haemotrophic nutrition

decidual glands provide nutrition to the foetus in the 1st trimester while the placenta is still developing

spiral arteries feeds the foetus in the last 2 trimesters

Question 13

Describe 5 - spiral arteries

Answer 13

spiral arteries are invaded by cytotrophoblasts
they remodel - lose SM and can no longer vasoconstrictor
- becomes wider
can carry more blood to placenta

cytotrophoblast plug gradually breaks down to expose the placenta to maternal blood

Question 14

what can happen if placental development goes wrong

Answer 14

miscarriage - placenta not attached properly
pre-eclampsia
small baby if not receiving enough nutrition

Question 15

placental regulation of growth

Answer 15

autocrine regulation

maternal decidual tissue restricts growth to protect mother

Question 16

interaction of mother foetus and placenta - steroidogensis

Answer 16

to make oestrogen in pregnancy - all 3 are needed

Question 17

main hormones of pregnancy and when they rise

Answer 17

hCG peeks around week 9 then rapidly falls

P, E (estriol) and human placental lactogen increase throughout pregnancy — P highest

Question 18

when terms miscarriage and stillbirth used

what is foetal monitoring (US, doppler USSs) used for

Answer 18

viability limit - 24 weeks
<24 weeks - miscarriage
>24 weeks - stillbirth

foetal assessment - monitor foetal movement and blood flow - may indicate increased risk but cannot predict it