Freezing of spare embryos and pregnancy testing
Following embryo transfer, any remaining viable embryos are then cryopreserved (frozen) for later transfer. Not all embryos are suitable for freezing. The embryos can be frozen at the pronucleate, early cleavage or blastocyst stage. Overall about 50% of frozen embryos survive the thawing process. In the United Kingdom, the embryos can be frozen for up to 10 years with the intent of thawing and transferring them at a later date.
• Cryopreservation is accepted in some countries but banned in others.
• Freezing spare embryos allows multiple embryo transfers from a single egg collection and improves the chance of live birth. Freezing is very cost effective, since transferring is much less expensive than starting a new IVF treatment cycle.
• Frozen embryos can be thawed and replaced in either natural or artificial cycles. In women who ovulate regularly, the likelihood of a live birth after replacement of frozen thawed embryos is similar whether natural or artificial cycles are used.
• The success rates with frozen embryo transfer vary greatly from center to center.
• Babies born following embryo freezing have the same risks of abnormalities as those born following IVF, i.e. the same as those conceived normally.
• If you decide that you no longer require the frozen embryos, they may be allowed to perish, be used for research or donated to infertile couple(s) according to your wishes and the current legislation in your country.
• Not all clinics are able to offer freezing facilities.
Luteal phase support. Once the eggs have been removed, the follicles start to produce a hormone called progesterone.
Progesterone. Progesterone stimulates the endometrium and prepare it for implantation. In addition, it reduces uterine contractions. However, the amount of progesterone produced by the follicles is usually not enough to support the lining of the uterus. Hormone supplements are usually given for two weeks or longer to assist implantation especially if you were given GnRh agonists to achieve down-regulation.
The choice for luteal phase lies between intramuscular hCG injections and progesterone. While hCG may result in higher pregnancy rates, there is an increased likelihood for OHSS (ovarian hyperstimulation syndrome) and for this reason routine use of hCG is not recommended. There are different forms of progesterone to choose from.
• Daily intamuscular injections e.g. gestone
• Daily vaginal pessaries e.g. cyclogest. These are mounted in wax, which melts as progesterone is absorbed causing discharge. It may be necessary to wear a panty liner.
• Daily vaginal tablets e.g. utrogestan
• Daily vaginal gel e.g. crinone
Pregnancy testing. Most IVF clinics will offer you a blood tests about two weeks after embryo transfer, to check the level of Beta hCG (pregnancy hormone) and may also check the level of blood progesterone. In the happy event that the pregnancy test is positive, the patient will be asked to repeat the blood tests at intervals between 2-5 days to check the rising levels of these hormones.
HCG levels are the only way of monitoring early pregnancy. HCG levels which do not increase as rapidly as they should may indicate that there is a problem with the pregnancy such as ectopic pregnancy.
An ultrasound scan is usually performed about 5 weeks after embryo transfer or earlier. The scan will check that the pregnancy is normally located, appears normal and viable, and to see if there is more than one fetus.
The patient may have some vaginal spotting or bleeding prior to the pregnancy test. She may think that her period has already started and decline having the pregnancy test however it is recommended that the pregnancy test is done as it is the only way to determine whether there is a pregnancy.
