Lecture 3 Flashcards
What makes a good embryo?
Morphology and growth
Embryo development
Day 1 (17 HPI): Fertilization confirmed by 2 pronuclei and 2 polar bodies.1
Day 1 (23 HPI): Syngamy (fusion of pronuclei).1
Day 2 (44 HPI): Ideally reaches 4-cell stage. Cell number, evenness, fragmentation, and multinucleation are assessed.1 2
Day 3 (68 HPI): Ideally reaches 8-cell stage. Embryonic Genome Activation (EGA) occurs.2 3 4
Day 4 (92 HPI): Compaction starts. Ideally forms a morula.4 5
Day 5 (116 HPI): Blastocyst formation with trophectoderm and inner cell mass (ICM). Expansion, zona thinning, and blastocoel formation are observed.5
Day 6 (and sometimes Day 7): Hatching of blastocyst begins. ICM and TE are graded.
What is the ideal temperature, pH, and oxygen concentration for in vivo embryo development?
Temperature = 37°C2
pH = 7.2–7.42
Oxygen concentration = LOW
Describe the difference in metabolomic profile between the oviduct and uterine fluid.
Oviduct fluid: HIGH pyruvate and lactate, LOW glucose3
Uterine fluid: LOW pyruvate and lactate, HIGH glucose
What is the primary tool embryologists use to assess embryo quality, and what are its limitations?
Morphology (visual appearance) is the easiest/quickest assessment tool.
Limitations:
Morphology alone has significant limitations in predicting pregnancy success.4
Morphology and genetics are not well correlated.5
Many morphological features have no proven biological significance.
What does the acronym EGA stand for, and when does it occur?
EGA: Embryonic Genome Activation
Occurs: At the 8-cell stage (around Day 3)
What are the ideal embryo stages and characteristics for each day of development from Day 1 to Day 6?
Day 1 (17 HPI): Fertilization – 2 pronuclei and 2 polar bodies7
Day 1 (23 HPI): Syngamy – 0PN and 2PB7
Day 2 (44 HPI): 4-cell embryo8
Day 3 (68 HPI): 8-cell embryo8
Day 4 (92 HPI): Morula (compacted cells)9
Day 5 (116 HPI): Blastocyst (trophectoderm, ICM, blastocoel)9
Day 6: Hatching blastocyst (zona breach)
What are the essential considerations for an embryologist during an embryo transfer (ET) procedure?
Witnessing: Independent checks to confirm the correct patient and embryo.
Speed: Completing the procedure quickly (e.g., within 1 minute) to minimize embryo stress outside the incubator.
Results: Achieving embryo implantation rates within 5% of peers at the unit.
Describe the key metabolic shift that occurs in the embryo around Day 3
The embryo transitions from using pyruvate and lactate in the TCA metabolic pathway to using glycolysis (utilizing glucose) as the primary energy source
What happens after embryo transfer?
Two-week wait” before pregnancy test.
Luteal support (progesterone).
Pregnancy diet and lifestyle recommendations (avoid strenuous activity, hot baths, etc.).
Referral to an obstetrician at around 7weeks post-ET if pregnancy is successful.
True or False: Time-lapse imaging and AI analysis provide fundamentally different information about embryo quality compared to traditional morphology assessments.
Time-lapse and AI are essentially alternate versions of morphology assessments. They may offer more detailed observations but do not necessarily have significantly higher predictive power.
