Embryo physiology, morphology and ET Flashcards
In vivo what temperature do embryos grow at?
37 degrees
In vivo what pH do embryos grow at?
7.2-7.4
In vivo what oxygen concentration do embryos grow at?
low
In vivo what is the metabolic profile of the oviduct fluid which embryos develop in?
high pyruvate and lactate
low glucose
In vivo what is the metabolic profile of the uterine fluid which embryos develop in?
high glucose
low pyruvate and lactate
How is a good embryo measured?
through growth rate and morphology
Morphology is an easy and quick assessment of predicting which embryos have the highest chance of resulting in pregnancy. However the method has its limitations, what are to consider in respect to morphology as a tool for determining a good embryo?
morphology and genetics are not well correlated
Morphological features have proven no biological significance
embryologists are not trying to make embryos better but just trying to not stress them out
On a day 1 fertilisation check at 17 hpi, what are you looking for?
2 pronuclei (dents in the oocyte)
2 polar bodies
On a day 1 fertilisation check at 23 hpi, what are you looking for?
0 pronuclei (only if two were seen at 17 hpi)
2 polar bodies
On a day 2 fert check at 44 hpi, what do you expect to see?
4 cell
When cleavage is occurring what factors are taken into consideration when grading?
cell number
- 2 cell, 4 cell or 8 cell
- what should it be for the time period you are checking?
Even or uneven cell numbers?
- we expect even numbers
- but cells do not cleave at the same time (a 3 cell with one large cell and two small may be just about to cleave and become a 4 cell vs 3 even cells which is not good as not showing signs of cleaving)
Fragmentation
- present or not present?
- high fragmentation is not good
Multinucleation
- seen through ‘dents’ in embryo
- more than one sperm has fertilized the egg
On a day 3 fert check, 68 hpi, what do you expect to see?
8 cell
In regard to in vivo development, what important changes are occurring between day 3 (8 cell) to day 4 (morula) that should be known when considering in vitro embryo culturing?
going from fallopian tube to uterus (important transition phase)
- environmental changes
- goes from high pyruvate to high glucose (changes metabolism to be equipped for glycolysis and higher energy is now needed) - embryo metabolism changes
- fallopian tube: high pyruvate (embryo uses TCA metabolic pathway
- uterus: high glucose (embryo uses glycolysis) - Embryo genetics change
- before 8 cell: cell division controlled by maternal genome
- at 8 cell stage: embryonic genome activation (EGA) under control of own genome for first time
on a day 4 embryo check, 92 hpi, what do you expect to see?
Morula
- compaction of cells (as a result of EGA)
- single entity instead of discrete cells
On a Day 5 embryo check, 116 HPI, what do you expect to see?
Blastocyst
- formation of 2 distinct cell types
— trophectoderm (edging cells - precursors for placenta)
— inner cell mass (ICM)
- blastocoel forms
— fluid filled cavity ( seen by blurring) - zona pellucida thinning and hatching
If the clinic performs cultures to Day 7 on Day 6 what do you expect to see?
hatching blastocyst
- known as a zona breach when hatching
What is the most common graded embryo used for embryo transfer (ET)?
Day 5 blastocyst stage
During an ET where is the catheter placed?
about 1 cm from the fundus
What are essential consideration for an embryologist during an ET procedure?
- witnessing
- must have independent witness checks to confirm patient matches embryo - speed
- ambient conditions can easily stress embryo
- need to show competency (1 minute to complete procedure from incubator to threading) - results
- implantation rates need to be within 5% of clinic peers
Why does the embryo and endometrium need to have synchronized development?
to ensure the embryo is introduced to the endometrium during the narrow window of receptivity so it can implant
After an ET there is a two week wait for the beta hCG blood test. What factors are prioritized by the patient during this time?
progesterone
- luteal support and supports endometrial lining
pregnancy diet
- avoiding particular foods and taking vitamins
normal routine
- avoid vigorous exercise, hot baths and saunas
Following the ET and 2 weeks wait, the patient receives a positive beta hCG test (YAY)! Why so they not take a regular urine pregnancy test?
With the antagonist cycle (most common) hCG can be used as a trigger and this would not have cleared her system yet. This could give a false positive read
What occurs 7 week after ET if a patient has a positive beta hCG test 2 weeks after the ET?
An ultrasound to confirm if they are clinically pregnant
- heart beat?
- presence of sac?
Once the patient is confirmed clinically pregnant what occurs next?
patient will leave the care of the IVF clinic to an OB
or
if their fertility dr is an OB their care will be transferred to the dr’s OB practice
