Lecture 3 - Pregnancy Flashcards
What are the different stages of the egg after ovulation
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
stages of early implantation
shedding of zona pellucida pre-contact blastocyst orientation apposition cellular contacts adhesion molecules penetration of endometrium
How is the foetal maternation tissue protected from materal rejection?
the trophoblast contains HLA- G genes a non-polymorphic gene instead of MHC genes
Fetal allograft survival
antigenic immaturity placentral protection by trophoblast blocking antibodies - fetal (trophoblast?) immune privelege altered host immunity
Trophoblast - decidua interaction
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
What do NK cells do (local signalling )?
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
What happens in systemic signalling?
trophoblast of blastocyst releases HCG and stimulates ovaries to secrete progesterone to maintain pregnancy
What is the function of HCG
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?
clinical use of HCG
Pregnancy tests
immunoassay detects Beta subunits of HCG
Imaging in pregnancy
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
Concentrations of HCG and Estrogens and progesterone during pregnancy
HCG - peaks during the first 3 months
Progesterone and oestrogen - gradually increase until birth
cardiovascular changes in pregnancy
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
What happens if there is persistent 150/90 mmHg
can be indicative of pre-eclampsia
high BP, proteinuria, peripheral oedema
tendency to develop hypertension in later life with these women
consequences of pregnancy
fainting - pressing on iVC
haemorrhoids
varicose veins
Coagulation during pregnancy
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
What occurs in clot formation and clot lysis?
clot formation - thromboplastin
increased fibrinogen and fibrin
clot lysis - antithrombin, plasminogen, plasmin
Respiratory changes during pregnancy
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
renal changes during pregnancy
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
GI changes during pregnancy
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
