When a woman decides to use donor eggs for in vitro fertilization (IVF), she has many decisions to make. One of those decisions is whether to use fresh or frozen embryos to achieve a pregnancy.
Recent research from Brigham and Women’s Hospital offers patients new information to help guide their decisions. The study found that, when using embryos created from fresh donor eggs, women achieved significantly higher pregnancy and live birth rates using fresh rather than frozen embryos.
The term “live birth rate” refers to the percentage of IVF cycles (attempts to achieve pregnancy using IVF) that result in the birth of a living baby.
“This decision is somewhat complicated, but it’s important for patients and physicians to think about,” said Janis Heidi Fox, MD, attending reproductive endocrinologist in the Brigham’s Center for Infertility and Reproductive Surgery. “I want people to understand these complexities so they can make well-informed decisions.”
Dr. Fox worked on the study, which appeared in JAMA*, with four Brigham and Women’s colleagues.
Fresh and frozen donor eggs in IVF
A patient may opt to use donor eggs for IVF if there is a problem with her own eggs. After an infertility doctor harvests a donor’s eggs, three things may happen:
- The unfertilized fresh eggs may be frozen for future use. These are called frozen donor eggs.
- The fresh eggs may be fertilized to create an embryo that is transferred to the patient’s uterus after developing for several days. This is called a fresh embryo transfer.
- The fresh eggs may be fertilized to create an embryo that is then frozen for a future transfer. This is called a frozen embryo transfer.
The Brigham uses advanced cryopreservation techniques to freeze eggs, embryos and sperm.
“We don’t want to tell women what to do. We want to empower patients to make their own informed decisions based on scientific data and their personal values and circumstances.”
Janis Heidi Fox, MD, attending reproductive endocrinologist
Comparing IVF success rates
While previous studies have analyzed birth rates using embryos created from frozen donor eggs, Dr. Fox’s study looked at outcomes from embryos created using fresh donor eggs. It compared live birth rates using fresh embryos (those that were transferred after developing for several days) with rates using embryos that had previously been frozen.
Over the years, Dr. Fox had noticed that more live births seemed to be happening for patients who used fresh embryos created from fresh donor eggs than for patients who used frozen embryos created from fresh donor eggs. She decided to put her theory to the test. “I wanted to answer this question scientifically,” she said.
Using data collected by the Society for Assisted Reproductive Technology (SART), Dr. Fox and her team analyzed more than 50,000 embryo transfers in nearly 34,000 women across the United States.
“We found that when using embryos created from fresh donor eggs, pregnancy rates were 66.7 percent after fresh embryo transfer compared to 54.2 percent after frozen embryo transfer,” Dr. Fox said. Miscarriage rates in both groups were about the same, just under 10 percent.
“What it comes down to is this: If you can use a fresh embryo from a fresh donor egg, you have a 12 percent higher likelihood of a live birth,” said Dr. Fox.
Weighing the options of using fresh vs. frozen embryos
What do these findings mean for patients? Should patients limit themselves to using only fresh embryos created with fresh donor eggs? “Not at all,” Dr. Fox said.
Using frozen embryos from fresh donor eggs makes sense for many women in many cases. For example, consider the following scenario: An egg donor donates a number of eggs that, once fertilized, develop into a number of viable embryos. A single fresh embryo is transferred to the IVF patient. “Under such circumstances, we would then recommend that any remaining embryos of good quality be frozen,” explained Dr. Fox.
“If the patient gets pregnant, and a couple of years later, she wants another baby, we would certainly recommend she then use one of the frozen embryos. Even though the live birth rate might potentially be slightly lower compared to the fresh embryo transfer, it is still going to be excellent.”
Using frozen embryos made from fresh donor eggs may also offer greater convenience than using fresh embryos made from fresh donor eggs. In order to transfer a fresh embryo made from a fresh donor egg, both the donor and the recipient must have their cycles perfectly lined up. Synchronizing cycles in this way can be complicated and challenging to schedule.
Another factor to consider is an option known as “preimplantation genetic testing (PGT).” This testing checks to make sure the embryo has the correct number of chromosomes. Fresh embryos are tested, but then must be frozen while awaiting the results.
“There does not appear to be strong scientific data to support genetically testing the embryos in this situation,” claims Dr. Fox. “It does not appear to improve the likelihood of a live birth. In fact, our study demonstrated that it lowered the live birth rate by about 6 percent.”
Making an informed decision about IVF donor egg choices
Women undergoing IVF with donor eggs have many choices to make. These decisions can sometimes feel overwhelming. Your physician should review your options with you and answer all of your questions. Together, you can decide what is best for you. Dr. Fox believes it’s important to have as much reliable information as possible so you can decide what’s best for you and your family.
“We don’t want to tell women what to do,” Dr. Fox said. “We want to empower patients to make their own informed decisions based on scientific data and their personal values and circumstances.”
* Insogna IG, Lanes A, Lee MS, Ginsburg ES, Fox JH. Association of Fresh Embryo Transfers Compared With Cryopreserved-Thawed Embryo Transfers With Live Birth Rate Among Women Undergoing Assisted Reproduction Using Freshly Retrieved Donor Oocytes. JAMA. 2021 Jan 12;325(2):156-163.