IVF Flashcards
What are the basics of reproduction?
Oocyte is released from the ovary, moves down the fallopian tubes via the fimbriae; is fertilised and implants in the uterine lining.
2-CELL STAGE 4-CELL STAGE 8-CELL STAGE MORULA EARLY BLASTOCYST FULLY EXPANDED HATCHING
2-cell stage covered in glycoprotein coat to stop implantation. ICM give rise to embryo when hatching, embryo pushes through coat and implants in lining.
How are the embryo cells compacted?
E-cadherin creates adhesion sites to create junctions in the 8-cell stage. Single cells can no longer be seen. Causes epithelial cell polarity.
What is CAVITATION?
How is expansion caused?
The blastocyst formation - the second morphological event of preimplantation. Trophectoderm (TE) and ICM.
TE transports nutrients to the ICM blastocoel cavity.
Expansion caused by Na/K pumps, seal in cells created by tight junctions.
List the 4 causes of female infertility.
1 - OVULATION (25%)
Annovulation, oligoovulation, luteal phase defects.
1* - removed/damaged ovaries, PCOS (minute cysts in ovary and excess of androgens. weight gain, hair growth, no periods. Treat = weight loss, clomiphene tablets to induce ovulation, FSH/hCG stimulation)
2* - stress, tumour, weight gain/loss
LPD - defects of progesterone by corpus luteum or inadequate endometrium
2 - TUBAL PROBLEMS
Damaged fimbriae prevent movement of oocyte to fallopian tube, tubal block, tubal adhesions.
Caused by infections or endometriosis (misplaced endometrial tissue outside the uterus, reduce fertility. PAIN, treated with NSAIDS or contraceptive pill)
3 - UTERINE PROBLEMS
Fibroids - benign uterine growths prevent implant
Uterine Polyps - growth interfere w/ conception
Congential problems - no, double or septum uterus
4 - AGE
Fertility declines as women age. Egg quality decreases. Increases chromosome instability and miscarriage.
List the 4 causes of male infertility.
1 - POOR SPERM QUANTITY/QUALITY
Low sperm motility, abnormal shape, cause by infections or drugs. (90%)
2 - AZOOSPERMIA
No spermatogenesis, blocked vas deferens. Caused by testicular trauma (chemo, kleinfelter’s disease)
3 - SPERM DYSFUNCTION
Defective fertilising capacity - defective acrosome, decreased movement.
4 - EJACULATION DISORDERS
Retrograde ejaculation (backward) or impotence
List the 2 causes of both male and female infertility.
1 - IMMUNOLOGICAL INFERTILITY
Anti-sperm antibodies in either male (aggregate, no release) or female (no transport or fertilisation).
2 - UNEXPLAINED INFERTILITY
Investigations prove no cause, potentially psychological
List the steps of IVF. (7)
1 - Preliminary testing
2 - Downregulation - Stopping body’s normal ovulation control mechanisms. GnRH releasing hormone as Nafarelin nasal spray. Tested by oestradiol levels in blood. Side effects.
3 - Ovarian Stimulation - Increase # of eggs with FSH and hCG injections. Monitor follicle growth using ultrasound. hCG final injection when size correct, stop spray/injections.
4 - Egg Retrieval - Thin needle collects follicular fluid (ultrasound), find eggs.
5 - Insemination + Fertilisation - Semen collected, washed and concentrated. Fertilised (incubate) over night.
6 - Embryo transfer - If fertilised, transfer to uterus via catheter at 2-8 cell stage or as blastocyst.
7 - Test for pregnancy - Blood tests measure hCG, check for foetal heartbeat.
How are embryos selected for IVF? (3)
Selected based on morphological criteria.
Rate of cleavage - @2-cell by 24hr, @4-cell by 48hr. Early cleavage = better chance.
Embryo scoring system - Grade 1 = even blastomeres, no fragmentation - MOST VIABLE.
Blastocyst scoring system - Grade 4A = expanded blastocyst, ICM and TE tightly packed = MOST VIABLE.
Advantages and disadvantages of using a blastocyst culture over an embryo in IVF treatment.
+ Blastocyst can go to the uterus, embryo has to go to the fallopian tube.
+ Can assess viability before transfer
- Prolonged time in artificial culture.
- Requires a lot of oocytes.
What is PGD?
Preimplantation genetic diagnosis
Undergo IVF to biopsy a culture of embryos to see which are unaffected by possible monogenic disorders from parents. Eliminates the need to terminate pregnancies.
Cannot be used to determine sex.
Can be contaminated by allelic dropout - use multiplex PCR to overcome this.
Name the two types of preimplantation genetic screens.
FISH - fluorescence in situ hybridisation
Analyse 10 chromosomes of a blastomere. Spread and label specific chromosomes of interest with fluorescent DNA probes. Sex determination and aneuploidy.
ARRAY-cGH - comparative genomic hybridisation
Screens all chromosomes, requires whole genome amplification. Tests for aneuploidy and unbalanced translocations. Probes specific for chromosomes, loss/gain measured by ratio of intensity - Faster than FISH
Ethics (3)
- Strain on women to do IVF
- Slippery slope to designer babies
- Ethical to have a child just to provide cure for diseased child? (Fanconi’s Anaemia - BM transplant)
Tightly regulated by authority board. (HFEA)
