IVF Flashcards
What does IVF involve?
- fertilising an egg with sperm in a lab, then injecting the resulting embryo into the uterus.
- very expensive and complicated process so couples are limited to a set number of cycles funded by the NHS
- each attempt has a roughly 25 – 30% success rate at producing a live birth.
What does a cycle of IVF involve?
- A cycle of IVF involves a single episode of ovarian stimulation and collection of oocytes (eggs)
- A single cycle may produce several embryos
- Each of these embryos can be transferred separately in multiple attempts at pregnancy, all during one “cycle” of IVF
- Embryos that are not used immediately may be frozen to be used at a later date.
- Frozen embryos can potentially be used years later, even after a successful pregnancy.
What are the steps of IVF?
- Suppressing the natural menstrual cycle
- Ovarian stimulation
- Oocyte collection
- Insemination / intracytoplasmic sperm injection (ICSI)
- Embryo culture
- Embryo transfer
What are the 2 protocols for suppression of the natural menstrual cycle?
- Suppression of the natural cycle involves either the use of GnRH agonists or GnRH antagonists
- The choice between the GnRH agonist and GnRH antagonist protocol depends on individual factors
Describe the GnRH agonist protocol for supression of the natural menstrual cycle
- an injection of a GnRH agonist (e.g. goserelin) is given in the luteal phase of the menstrual cycle, around 7 days before the expected onset of the menstrual period
- This initially stimulates the pituitary gland to secrete a large amount of FSH and LH.
- However, after this initial surge in FSH and LH, there is negative feedback to the hypothalamus, and the natural production of GnRH is suppressed. This causes suppression of the menstrual cycle.
Describe the GnRH antagonist protocol for supression of the natural menstrual cycle
- daily subcutaneous injections of a GnRH antagonist (e.g. cetrorelix) are given, starting from day 5 – 6 of ovarian stimulation.
- This suppresses the body releasing LH and causing ovulation to occur.
Why is there a need to suppress the natural menstrual cycle?
Without suppression of the natural gonadotropins (LH and FSH) using one of the above protocols, ovulation would occur and the follicles that are developing would be released before it is possible to collect them.
Describe the initial ovarian stimulation step of IVF
- Ovarian stimulation involves using medications to promote the development of multiple follicles in the ovaries
- starts at the beginning of the menstrual cycle (usually day 2), with subcutaneous injections of follicle-stimulating hormone (FSH) over 10 to 14 days
- FSH stimulates the development of follicles, and this is closely monitored with regular transvaginal ultrasound scans
When is the FSH stopped during the ovarian stimulation step of IVF?
When enough follicles have developed to an adequate size (usually around 18 millimetres),
What is given after FSH is stopped during the ovarian stimulation step of IVF?
- an injection of human chorionic gonadotropin (hCG) is given
- this is given 36 hours before collection of the eggs
- hCG works similarly to LH does naturally, and stimulates the final maturation of the follicles, ready for collection
- This is referred to as a “trigger injection”.
Describe the oocyte collection step of IVF
- The oocytes (eggs) are collected from the ovaries under the guidance of a transvaginal ultrasound scan
- A needle is inserted through the vaginal wall into each ovary to aspirate the fluid from each follicle
- This fluid contains the mature oocytes from the follicles
- fluid from the follicles is examined under the microscope for oocytes
- procedure is usually performed under sedation
Describe the oocyte insemination step of IVF
- male produces a semen sample around the time of oocyte collection (Frozen sperm from earlier samples may be used)
- sperm and egg are mixed in a culture medium
- Thousands of sperm need to be combined with each oocyte to produce enough enzymes (e.g. hyaluronic acid) for one sperm to penetrate the corona radiata and zona pellucida and fertilise the egg.
Describe the Intracytoplasmic Sperm Injection step of IVF
- Intracytoplasmic sperm injection (ICSI) is a treatment used mainly for male factor infertility, where there are a reduced number or quality of sperm.
- It is an addition to the IVF process.
- After the eggs are harvested, and a semen sample is produced, the highest quality sperm are isolated and injected directly into the cytoplasm of the egg.
Describe the embryo culture step of IVF
- Dishes containing the fertilised eggs are left in an incubator and observed over 2 – 5 days to see which will develop and grow.
- They are monitored until they reach the blastocyst stage of development (around day 5).
Describe the embryo transfer step of IVF
- After 2 – 5 days, the highest quality embryos are selected for transfer.
- A catheter is inserted under ultrasound guidance through the cervix into the uterus
- A single embryo is injected through the catheter into the uterus, and the catheter is removed
- Generally, only a single embryo is transferred. Two embryos may be transferred in older women
- Any remaining embryos can be frozen for future attempts at transfer
