Fetal Development Flashcards
What day does ovulation occur?
Day 14
Where does fertilisation commonly occur?
Fallopian tube
What steps occur after an egg is fertilised?
Zygote - morula - blastocyst
= as moving to uterine cavity
What day does implantation occur?
Day 23
= beginning of fetal-maternal dialogue
At what stage does a morula become a blastocyst?
At 32 cell stage
What happens when the blastocyst implants?
The decida (modified endometrium) produces hCG which stimulates the ovaries to produce progesterone which alters maternal physiology
What level of hCG can be detected?
Urine pregnancy test positive over 25IU/ml
= hCG rises rapidly <10wks
When does organogenesis occur?
2-8wks post conception
What happens to the inner cell mass and the trophoblast?
Inner cell mass = embryo
Trophoblast = placenta
What are the layers of the amniotic cavity?
Amnion = membrane lining cavity, expands as placenta progresses
2nd layer = chorion
What is the vascular of the cord?
2 arteries = carry deoxygenated blood from fetus to placenta
1 vein = carry oxygenated blood from placenta to fetus
What is the main pregnancy hormone?
Progesterone
List some CV modifications of maternal physiology
- 40% increase in plasma volume by 32wks (RBC increases by 20%)
- 40% rise in CO
- Reduced peripheral venous return causes BP drop in early pregnancy (return to pre-pregnancy level later)
- Haemodilution: overall amount of Hb rises but the concentration falls
- Increased clotting risk: Increased factor VII, VIII, X, and rise in fibrinogen
- Increased RBC mass: protects against the approximate 0.5L delivery loss (1L if twins of caesarean section)
List some respiratory modifications of maternal physiology
- 40% increase in tidal volume
- Oxygen demand increases by 15%
List some renal modifications of maternal physiology
- Renal pelvis and ureters dilate (due to pressure and progesterone) = risk of acute pyelonephritis
- GFR increases by 50%: reduces plasma urea, creatinine and osmolality
- Increased urinary protein loss (but >500mg in 24 hrs is abnormal)