The Great IVF Debate
Embryo transfer is the final yet most important step of in vitro fertilization (IVF), a type of fertility treatment. After ovulation induction, the fertility specialist retrieves the eggs and fertilizes each with a sperm sample. After fertilization, the embryos are grown in a lab and then prepared for transfer or frozen. A fresh embryo transfer happens within 3-7 days of retrieval. Frozen embryos are stored to be transferred at a later date. The seemingly simple choice between fresh or frozen has become a subject of debates and studies. Is one approach more likely to result in better pregnancy outcomes?
Live birth rates
One key indicator of successful pregnancies is the live birth rate (LBR), a metric tracked by fertility clinics. In addition to the type of embryo transfer, the patient’s age also significantly affects the LBR. A report revealed that LBR following a fresh embryo transfer for women under 35 is 34.6%. The figure decreases to only 8.5% for women older than 40. On the other hand, LBRs for frozen embryos are higher, with a success rate of 43.9% for women under 35 and 38.5% for those over 40. Frozen embryo transfers are more likely to result in a live birth than fresh embryo transfers for all age groups.
The power of time
What makes frozen embryo transfer more effective? IVF with fresh embryos is time sensitive. The woman must be ready for the transfer soon after retrieval, which can be mentally and physically stressful. For fresh transfers, the medication for ovulation induction may leave the woman with elevated hormone levels at the time of embryo transfer. Hormone imbalances can also affect endometrial linings, reducing the success rate. A frozen embryo transfer slows the process down, allowing fertility medication to leave the woman’s system and hormone levels to stabilize.
An extra check with PGT
Pregnancy rates may also be higher with frozen embryos thanks to the extra time for testing. Fertility clinics will often recommend preimplantation genetic testing (PGT), especially for couples with a history of miscarriages. PGT takes a few cells from the retrieved embryo to perform genetic testing. The test can identify chromosomal abnormalities and other genetic problems capable of affecting pregnancy. The clinic can then use the best available embryos during the frozen embryo process, improving success.
Both fresh and frozen embryos can result in a successful pregnancy. Clinics have used fresh embryos for years before the advent of cryopreservation. Most patients respond well to hormone medication and can have fresh transfers during the same cycle as the retrieval. However, studies have found that frozen embryo transfers lead to higher success rates. The extra time to prepare, check for genetic problems, and time the transfer perfectly can all help improve outcomes. The choice is always up to the hopeful couple, but the frozen approach is likely a quicker path to parenthood for most people undergoing IVF.