Frozen Embryo Transfer During A Natural Cycle
With regards to IVF, a natural cycle refers to a woman’s normal menstrual cycle without the use of hormones to prepare the uterine lining for implantation. Frozen embryo transfer is possible during a natural cycle for women who ovulate regularly within their menstrual cycle. A number of studies have shown that successful pregnancy rates during natural cycles are equivalent to pregnancies in prepared cycles.
Success rates
Despite the equivalent success rates, in practice, frozen implantation during a natural cycle can be difficult to perform due to the fact that to be successful, the frozen embryo must be transplanted on the exact day on which the lining of the uterus is most receptive. The exact timing can be very difficult to determine during a natural cycle. It requires knowledge of the time of ovulation, which can be monitored using ultrasounds or blood tests. During a natural cycle the day of ovulation is not controllable, so if it is missed or the cycle is not optimal, then the transfer date may be delayed.
What is a prepared cycle?
For a prepared cycle IVF the woman will receive certain medications in the month before IVF. These may include birth control pills and leuprolide injections. Together, these medications prepare the woman’s body for ovulation induction.
Birth control pills help by preventing the formation of ovarian cysts and to help regulate the woman’s cycle so that the doctor can accurately time ovulation. The use of birth control pills for pre-treatment is usually used or women who have irregular menstrual cycles. Leuprolide injections contain synthetic hormones which prevent the woman from ovulating too early.
Frozen Embryo Transfer
Whether the frozen embryo transfer is done during a natural or prepared cycle, the procedure is the same. Frozen embryos from a previous cycle or form a donor are thawed and transferred to a woman’s uterus. Optimizing the uterus before the transfer can sometimes improve the success rate of implantation because the timing can be more precise.
Frozen embryo transfer is usually performed at least one month after egg retrieval to allow time for the uterus to prepare. During the transfer, the embryo is put into a catheter that passes through the cervix into the uterus. The transplantation procedure takes around fifteen minutes and is typically very successful.
