Lecture 3 - Pregnancy

Question 1

What are the different stages of the egg after ovulation

Answer 1

on fertilization, the zygote forms
4 cell stage - early cleavage
morula (3-4 days)
zona pellucida undergoes structural change to prevent polyspermy
blastocyst- 8 or 16 cell 4-5 days after fertilization ( inner cell mass)
implantation in the uterus

Question 2

stages of early implantation

Answer 2

shedding of zona pellucida
pre-contact blastocyst orientation
apposition cellular contacts
adhesion molecules
penetration of endometrium

Question 3

How is the foetal maternation tissue protected from materal rejection?

Answer 3

the trophoblast contains HLA- G genes a non-polymorphic gene instead of MHC genes

Question 4

Fetal allograft survival

Answer 4

antigenic immaturity
placentral protection by trophoblast
blocking antibodies - fetal (trophoblast?)
immune privelege
altered host immunity

Question 5

Trophoblast - decidua interaction

Answer 5

villous trophoblast is inert (neutral)
extravillous trophoblast (invasive) trophoblast: only class 1 HLA a
(G,E) - A and B not expressed
less attractive to cytotoxic T cells
enables NK cell binding

Question 6

What do NK cells do (local signalling )?

Answer 6

they are unique to luteal phase
presence due to progesterone
characterstic phenotype - CD56 bright
capacity to faciliate/impede trophoblast invasion
main source of decidual cytokines and so may determine response due to pregnancy

Question 7

What happens in systemic signalling?

Answer 7

trophoblast of blastocyst releases HCG and stimulates ovaries to secrete progesterone to maintain pregnancy

Question 8

What is the function of HCG

Answer 8

produced by trophoblast
glycoprotein
similar to LH and FSH
luteotrophic - continues to stimulate corpus luteum
production is autonomous - independent of hypothalamus and pituitary
cause of morning sickness?

Question 9

clinical use of HCG

Answer 9

Pregnancy tests

immunoassay detects Beta subunits of HCG

Question 10

Imaging in pregnancy

Answer 10

Transvaginal or transabdominal
clinical dating from last menstrual period
- 5 wks - gestation sac
6 - fetal pole, yolk sac
7 - fetal heart activity
8 - fetal limbs, movements

Question 11

Concentrations of HCG and Estrogens and progesterone during pregnancy

Answer 11

HCG - peaks during the first 3 months

Progesterone and oestrogen - gradually increase until birth

Question 12

cardiovascular changes in pregnancy

Answer 12

40% increase in Blood volume
- increase in body water and plasma
- red cell mass increase - not as much as BV
- physiologic anaemia
- sodium and water retention
- mechanism: oestrogen stimulates RAA
cardiac output - 30-50% increase
rise in stroke volume and heart rate
Fall in total peripheral resistance -initial drop in BP

Question 13

What happens if there is persistent 150/90 mmHg

Answer 13

can be indicative of pre-eclampsia
high BP, proteinuria, peripheral oedema
tendency to develop hypertension in later life with these women

Question 14

consequences of pregnancy

Answer 14

fainting - pressing on iVC
haemorrhoids
varicose veins

Question 15

Coagulation during pregnancy

Answer 15

increased clot formation - 1,5,7,8,9,10,12
decreased clot lysis
- increased plasminogen activator inhibitor by placenta
activated protein C resistance
reduced protein S levels

Question 16

What occurs in clot formation and clot lysis?

Answer 16

clot formation - thromboplastin
increased fibrinogen and fibrin
clot lysis - antithrombin, plasminogen, plasmin

Question 17

Respiratory changes during pregnancy

Answer 17

increased O2 consumption
respiratory compensation
- increase in Tidal Volume
- increase in alveolar ventilation
-vital capacity unchanged
change in central control of respiration PaCO2 sensitivity - increase increase respiration
- clinical consequence - dyspnoea

Question 18

renal changes during pregnancy

Answer 18

increase increase renal blood flow
-rise in blood volume CO
-fall in vascular resistance/increase in renal vasodilatory prostaglandins (PGI1;PGE2)
increase in GFR
- urea and creatinine fall - no change in production
- renal threshold to glucose diminished
- RAA increased in 1st trimester
-pelvicalyceal and ureteric dilation (smooth muscle)
- bladder capacity decreases
-increase frequency of micturition
tendency of UTI’s

Question 19

GI changes during pregnancy

Answer 19

altered apetite
lower oesophageal pressure and incompetence of cardia
decrease in motility - longer emptying, transit time, increase water reabsorption
constipation - transition time extended, greater water reabsorption
clinical - nausea, vomiting, - hyperemesis gravidum
heartburn
constipation