- Once the FSH stimulating injections have started, you will be offered blood and ultrasound testing. This starts on day five of stimulation and continues every one to two days until egg retrieval.
- The doctor will be check the following:
- Follicle size – the size of the fluid-filled sac in which the eggs develop
- Oestrogen levels –the hormone responsible for building up the thickness of your uterine lining
- Progesterone levels – if this hormone level is too high, too early, some clinics may advise freezing the embryos
- Lining of your uterus – The endometrium is the innermost layer that thickens in anticipation of an embryo implantation
- When the size of your follicles, the level of oestrogen and the thickness of your uterine lining reach the optimum level it means your body is ready for the all-important trigger shot.
- This stage of the IVF treatment is incredibly emotional. You are likely to hang on every word your doctor says and think of little else but the growing size and number of your follicles.
What is the optimum size of a follicle for egg retrieval?
The ideal follicle should be between 18 to 20 millimetres. The larger the follicle, the nearer the egg is ready for collection. As stimulation progresses through the early stages (the first 5 days) the follicles grow slowly.
Once they reach about 12 to 14mm, they will grow fairly predictably at a rate of 2mm per day. The average number of follicles is around 10-12, but this number can be higher or lower depending upon your age. It should be noted that not every follicle will have an egg.
How many mature follicles (18-20mm) do I need for egg retrieval?
You need 3- 4 mature follicles for egg retrieval.
How thick should the lining of my uterus be?
The lining should ideally be no less than 7mm. Progesterone given towards the end of the IVF cycle will help to maintain the thickness of the uterine lining.
What should my oestrogen levels be?
Oestrogen is measured in pmol per litre. Every woman is different, but if the oestrogen level baseline level on day 2-5 is 60-150 without stimulation, this is a satisfactory measure.
Oestrogen levels reflect the number of follicles that are growing. A quick rise in levels can mean too many follicles. If your oestrogen levels are too high or too low, your doctor may make mild course adjustments.
- If your oestrogen levels rise too rapidly, your doctor will adjust your medication to slow down stimulation (called ‘coasting’).
- Coasting involves abruptly stopping your stimulation drugs, while continuing to administer the GnRH agonist to suppress ovulation (e.g. Lupron or Buserelin). The trigger shot is then deferred until the oestrogen levels safely drops below 12000 pmol.
- Your doctor may retrieve the eggs but not go ahead with embryo transfer until your levels have returned to normal.
- Your doctor may cancel your cycle, as you could be at risk of hyper ovarian simulation syndrome (OHSS). Anything over 12000 pmol is considered high risk.
- With patients who have high risk of hyper stimulation, some doctors may use the antagosnist protocol with a GnRH analogue trigger.
- If the levels are too low, the cycle will be discussed by your doctor.