New technologies have made it possible to freeze embryos for future use. Couples who are experiencing hurdles in conceiving are often recommended to try In Vitro Fertilization (IVF) or Intra Cytoplasmic Sperm Injection (ICSI) techniques to conceive. Since it is fairly common to be left with many unused embryos after these treatments, many women prefer to freeze these embryos for later use, donate them to other couples or for research purposes. Although the likelihood of becoming pregnant by thawing a frozen embryo is not affected by the length it has been stored, not all embryos survive freezing and eventual thawing when they are to be used.
How does embryo freezing work?
The egg and sperm of the female and male respectively are fused to make an embryo. This early-stage embryo then undergoes a computerized and highly controlled freezing process and the temperature is lowered to that of liquid nitrogen, i.e. -1960C. At this temperature, no biological activity can take place; hence, the embryos get frozen and remain viable for many years. They can be thawed to use when needed. Both, you and your partner are required to give written consent for your embryos to be stored.
Who should consider embryo freezing?
There are various reasons for women to consider embryo freezing, the main reason being advancing age. These reasons include:
· For future use during your IVF or ICSI cycles
· For women who have medical conditions that impair the fertility or increase risk of infertility e.g. PCOD, hypothyroidism
· For women who are being treated for certain medical conditions and the treatment effects the fertility e.g. cancer
· For women who are at risk of death or injury especially members of the Armed Forces
· For women who want to undergo a sex change operation
How are the frozen embryos used?
There are multiple ways this is done depending on your doctor office and your menstrual cycle.
· If you have a regular menstrual cycle
Various tests are performed to see when the desiring mother will ovulate. Ultrasound scans are performed to monitor the progress of the developing eggs and the thickness of the endometrium.
· If you have an irregular menstrual cycle or no periods
Your doctor may suggest medications to suppress your natural menstrual cycle and trigger a ‘fake’ period. The medications help prepare the endometrial lining for receiving an embryo.
After all medical parametersare thoroughly checked and the endometrium is at its utmost receptive state, the clinic will thaw the embryos and have them ready for implantation. Up to three embryos can be transferred at one time. Your doctor may suggest single embryo transfer (SET) minimize the risk of multiple births.
What are the risks associated with embryo freezing?
It is not unusual for embryos that survive to freeze and thawing to lose a cell or two. This can be attributed to technical or human error. Though most clinics use active measures to prevent any errors along with the Human Fertility and Embryology Authority’s (HFEA) Adverse Incident Reporting System, there is still a risk of contamination.
All cells, including embryos, tend to bear some insult during freezing. Regardless of the strictly controlled environment there is a chance of ice formation, water movement through the membrane, and extreme changes in the electrolyte balance.While further research needs to be done on the changes in gene expression after freezing, current evidence suggests that the incidence of pre-term birth, birth defect and low birth weight are similar to that of a fresh embryo transfer.