IVF Treatment - Embryo freezing

• Frozen embryo cycle instructions

Embryo freezing is now a well-established technique, but it raises complex practical and ethical issues that we are happy to discuss. Simply lowering the temperature of embryos results in ice formation and cell breakage. We therefore use a cryoprotectant known as propanediol and a liquid nitrogen based, programmable machine to freeze the embryos. Thereafter, they are stored in tanks of liquid nitrogen which require a complex back-up system to safeguard them.

It is important to realise that not all developing embryos are suitable for freezing. The scientists select only those that they think will survive the process. Even when they freeze the 'best', approximately 10% of embryos still do not survive. Nevertheless, as was mentioned earlier, about 50% of treatment cycles do have more than two ‘suitable’ embryos and this ‘surplus’ can be frozen, thereby reducing the need for repeated ovarian stimulation and further egg collections. Thus, cryopreservation offers more chance of getting pregnant from the one complete treatment cycle. This can have physical, emotional and financial benefits, but it is important to 'look ahead' and consider the implications before starting treatment. We ask people to consider, for instance, what they would want done with surplus embryos if any remain in cryostorage when they consider their family complete. They can be simply allowed to regress when removed from storage, be given for research or given to other anonymous couples who are in need of donated embryos. The decision is left entirely with the couple.

The National Perinatal Statistics Unit accumulates data on all pregnancies from ART and current evidence indicates that babies born after cryostorage are just as healthy as those from 'fresh' embryos. The success rate per transfer attempt is usually around two thirds that of the ‘fresh’ attempts, influenced by many factors but particularly the number transferred.

Should the ‘fresh’ IVF/ICSI cycle not be successful, we normally suggest at least one complete cycle’s rest before considering thawing the frozen embryos, and transferring them into the uterus. Most people have their frozen embryos thawed and transferred within six (6) months. The National Health and Medical Research Council, (which governs all our activities), in 1996 issued revised guidelines stating "embryos may be kept for a period not exceeding 10 years but this can be varied on compassionate grounds with approval by an Ethics Committee".

Frozen embryo cycle instructions

1	Start: within the first few days of menstrual bleeding, the woman telephones our nurses. Depending on her cycle pattern she will have either: (a) Ovulation Monitoring: arrangements are made to commence hormonal monitoring by doing a blood test usually around day 11 of the cycle. After the blood test, the nurses often provide a urine testing kit (if it is not planned to do all the testing with blood tests). The urine test kit comes with instructions - the urine is tested each morning, until the required colour change. Once we detect the necessary hormone changes we organise for the embryo transfer 3 - 5 days later (depending on the embryo development at the time of freezing).
	or, (b) Hormone Preparation: on the third day of the period Progynova, one tablet twice a day, is started. We arrange an ultrasound appointment around day twelve(12) to measure the lining of the uterus Progesterone pessaries are then supplied and after three days of pessaries the embryo transfer is performed. The pessaries and the Progynova are continued until the pregnancy test, which is done 14 days after the transfer. If a pregnancy occurs, the medication needs to be continued for a further six(6) weeks.
2	Embryo Transfer: the embryos are thawed the day before the expected transfer and cultured overnight. The embryo transfer is a procedure that is no more uncomfortable than a Pap smear and is discussed earlier. Please Note - Not all embryos survive the freezing/thaw process, and we only transfer those that are suitable and offer a realistic chance of achieving a pregnancy.
3	Following Transfer: If periods have not begun 14 days after embryo transfer, we arrange a blood pregnancy test.