test tube baby
Fig 1. 6 frozen embryos, after thawing. Note that they look as good as fresh embryos !

What is embryo freezing ?

Embryo Freezing

Since most IVF programs superovulate patients to grow many eggs, there are often many embryos. Since the risk of multiple pregnancies increases with the number of embryos transferred (and in fact the law in the UK prohibits the transfer of more than 2 embryos to reduce this risk), many patients are left with "spare" or supernumerary embryos. These can be discarded; or used for research.

However, it is best to freeze these embryos and store them in liquid nitrogen ! stored embryos can then be used later for the same patient - so that she can have another embryo transfer cycle done without having to go through superovulation and egg collection all over again. You can also use them for your next baby !

Moreover, since this embryo transfer is done in a "natural" cycle ( when she is not taking any hormone injections ) some doctors believe the receptivity of the uterus to the embryos is better. For women with irregular menstrual cycles, frozen embryo transfer can also be done in a " simulated natural cycle", in which the endometrium is primed to maximize its receptivity to the embryos by using exogenous estrogens and progesterone.

In our clinic, because our pregnancy rates with frozen embryos are so good, we actually recommend a "freeze all" policy for all our patients !

Since pregnancy rates with good-quality frozen-thawed embryos are as good as with fresh embryos, we encourage all our patients to freeze and store their supernumerary embryos, rather than discard them. Freezing is very cost-effective, since transferring frozen-thawed embryos is much less expensive than starting a new cycle, so that it serves as a useful "insurance policy" in case pregnancy does not occur. However, since it is worthwhile freezing only good quality embryos, the option of freezing is a "bonus" which is available to only about 50% of all IVF patients.

Using the technique of vitrification, practically 100% of embryos frozen will survive the freezing -thaw process. It is reassuring to know that the risk of defects is not increased as a result of freezing. These frozen embryos can be stored for as long as is needed - even for many years. When they are in liquid nitrogen, at a temperature of -196 C, they are in a state of suspended animation, and all metabolic activity at this low temperature stops, so that a frozen embryo is like Sleeping Beauty !

Once stored, embryos can be used by the couple during a later treatment cycle, donated to another couple or removed from storage. These options should only be undertaken after considerable discussion and written consent from the parties concerned.

embryo freezer
Fig 2. The Programmable embryo freezer. You can see the liquid nitrogen vapours clearly.

Egg freezing

Fig 3. Mature oocyte ( egg).

We can also freeze unfertilised human oocytes efficiently, using a new technique called vitrification ( which uses ultra-rapid cooling together with an increased concentration of cryoprotectants ) . This allows us to offer this option to our patients, allowing the facility of egg storage and egg banking.

What happens if the IVF cycle fails ?

Analysing a failed IVF cycle

If you don't get pregnant after your IVF attempt, you are likely to be very disappointed and disheartened. However, remember that this is not the end of the road - it's just the beginning ! At the end of the IVF cycle, you need to sit down with your doctor and analyse what you learnt from it. Was the ovarian response good ? Was the endometrium receptive ? Did fertilisation occur ? Was the embryo transfer easy and atraumatic ? Why didn't pregnancy occur ( the million dollar question, though this is usually a question we still cannot answer !) Can you repeat the same treatment, or do you need to make changes before going in for your next attempt ? When can you go in for your next IVF cycle ? And even if you do not get pregnant, at least the fact that you attempted IVF should give you peace of mind that you tried your best , using the latest technology medical science has to offer.

What about your next IVF cycle ?

The second time around - the next IVF cycle

Most doctors would advise you to wait for a month before starting a new cycle. While it is medically possible to do the next cycle immediately, most patients need a break to marshall their emotional strength before starting again. Your doctor may need to modify your treatment, depending upon an assessment of your previous cycle. For example, if the ovarian response was poor, the doctor may advise you to increase the dose of drugs used for superovulation. If fertilisation did not occur, you may need to go in for microinjection ( ICSI). If the quality of the embryos was poor, you may be advised to consider a ZIFT ( ZIFT Video ) rather than IVF. ZIFT will also be advised if the embryo transfer was difficult and traumatic, as this allows us to bypass the cervix and transfer the embryos directly into the fallopian tubes. However, if the cycle was satisfactory, the doctor will often advise you to repeat exactly the same treatment again - and all that it may take to achieve your IVF success is time, patience, and another attempt.

Interestingly, we often find that couples going through a second IVF cycle are much more relaxed and in control. This may be because they are aware of all the medical and procedural minutiae, and are better prepared for these; and also because they have had a chance to establish a personal relationship with the medical team. Also, since they have already faced failure the first time around, many of them are much better able to cope with the stress of IVF, since they are prepared for the worst. With today's IVF technology, we can confidently reassure any patient that we can help them to get pregnant, provided they have inexhaustible resources of time, money and energy !


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