Cycle monitoring in IVF and frozen embryo transfer
Cycle monitoring
- Careful monitoring helps control and optimise ovarian response during hormone stimulation in preparation for egg collection.
- Careful monitoring helps control and optimise endometrial development during hormone therapy in preparation for frozen embryo transfer.
- Careful monitoring helps assess the change during the menstrual cycle in preparation for frozen embryo transfer in a natural cycle.
- Monitoring includes repeated transvaginal ultrasound scans to track follicle number and size, endometrial development, and can also include blood tests to check the hormone levels.
- Monitoring during controlled ovarian stimulation (COS) helps in achieving the best possible outcome for you while avoiding potential complications and cycle cancellation. The main reasons for monitoring include:
- To determine the best timing for egg retrieval.
- To assess the risk of hyper-response (over-response puts patients at higher risk of ovarian hyperstimulation syndrome, known as OHSS).
- To make necessary mid-course adjustments to your treatment protocol by increasing or decreasing dosage of medications or adding new ones.
What happens during the transvaginal ultrasound?
- The ultrasound procedure only takes about 10-15 minutes.
- You will be asked to empty your bladder prior to undergoing the scan.
- When you enter the ultrasound or consulting room you will be asked to remove your underwear and either put on a gown or to cover yourself with a clean paper sheet, and then lie down on the bed with your feet on a lower platform or on stirrups.
- You need to inform the operator performing the ultrasound scan if you have any allergies, especially to latex.
- The transvaginal ultrasound probe is sanitised between procedures, and is covered with a clean condom during each examination.
- With your verbal consent, the small narrow transvaginal transducer is gently inserted into the vagina.
- The probe is moved from side to side to gain views of the ovaries and count the follicles on each side.
- At each ultrasound examination, the number and size of the follicles are measured, as well as the thickness of the endometrium (lining of the womb) and its appearance.
- The transvaginal ultrasound scan very occasionally may cause some discomfort but does not usually cause any pain.
- Some gentle suprapubic pressure may be applied in some cases if visualisation of the ovaries is not good, or to determine what access would be like at the time of egg collection.
What are the blood tests done for?
- Blood tests measuring your hormone levels during ovarian stimulation or in preparation for the frozen embryo transfer may be done, on the same day as having the ultrasound scan.
- The commonly measured hormones are the oestradiol and the progesterone.
- The hormone oestrogen correlates with increasing follicle size and numbers, and in some cases the blood test is arranged to confirm the findings seen at ultrasound scan.
- The hormone progesterone may be measured before egg collection to decide whether you are fine to go ahead with a fresh embryo transfer, or alternatively if too high you would benefit from a freeze all and do the embryo transfer in a subsequent cycle.
- The hormone progesterone may also be monitored in a frozen embryo transfer cycle to determine if any changes with absorption, and rapid drops, throughout the administration period before and after embryo transfer.
- Other hormone and non-hormone tests may be requested by your fertility consultant during the treatment cycle.
How much monitoring is needed?
- The first monitoring ultrasound scan is done between days 1-3 of your menstrual period.
- At that first appointment, your ovaries should be non-active, or “quiescent”, or “resting” meaning that none of the follicles should be more than 10 mm in diameter, and your endometrial lining should be thin (less than 5 mm).
- If a cyst is detected, your fertility consultant might postpone the start of your ovarian stimulation, and schedule another ultrasound scan for the next cycle. A small number of cases require cyst aspiration under ultrasound guidance.
- Ovarian stimulation usually starts on day 2 or 3 of the menstrual period or after the withdrawal bleed.
- After 5-6 days of ovarian stimulation, another ultrasound scan is done. At this stage you may also be asked to have a blood test.
- Depending on the size of the follicles the next ultrasound scan is scheduled, but generally 2-4 days later.
- Most patients will need between 3 and 5 ultrasound scans during the ovarian stimulation cycle. Blood tests may be done only on some of the appointments, depending on the response as well as the outcome of previous cycles.
- Hormonal stimulation and close monitoring will continue until the day of ‘trigger’, which is usually determined by the presence of 2-3 leading follicles greater than 17mm.
- In some cases, for instance, if there were no mature eggs in a previous cycle, or if you are older than 39 years, or depending on the fertility consultant’s practice, you may be advised to wait until the leading follicles reach 20mm before getting to the point of ‘trigger’.
- The trigger injection containing the hormone human Chorionic Gonadotrophin (hCG) is self-administered at a specific time, as advised by the fertility team 34-36 hours before egg collection.
Cycle monitoring for the frozen embryo transfer (FET) cycle
- FET can be done in a natural cycle or in a hormonal replacement treatment (HRT) cycle.
- Natural cycle preparation occurs with no supplementation of hormones and ovulation occurs spontaneously, although in some cases it can be triggered when the follicle reaches 18-20mm, to better time the embryo transfer procedure.
- Cycle is monitored by ultrasound scan to time ovulation.
- Endometrial thickness is measured.
- FET of a blastocyst is generally done 7 days after ovulation.
- In the HRT cycle the endometrial lining is prepared using oestrogen and progesterone treatment.
- Oestrogen is started on day 2 or 3 of the period.
- After 7-10 days of treatment a transvaginal ultrasound scan is done to measure the lining of the uterus.
- Oestrogen treatment and monitoring continues until the endometrial thickness is greater than 7 mm.
- Progesterone is added, and the embryo transfer is carried out 4-6 days later according to the fertility consultant’s practice and the centre’s protocol.
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