If you are a single woman considering egg freezing, should you consider freezing some embryos with donor sperm too? It's a good idea, according to Mark Leondires, M.D., a fertility doctor with Reproductive Medicine Associates of Connecticut (RMACT).
"I work in a bedroom community for New York City, and we don't have a very high proportion of single 30-somethings that are thinking about this," Dr. Leondires says. "The ones that I have seen in my practice [who are considering elective egg freezing] are all older than 35," he says. "When we have this conversation, I am very frank and say you might also want to freeze some embryos."
Freezing embryos in addition to eggs is like covering your bases, according to Dr. Leondires. "If you've created embryos with donor sperm and frozen them, they have perhaps a 15 to 30 percent improved take-home baby rate than your frozen eggs," he says.
Why do embryos have more success have freezing? When an egg is frozen, it is during a process called meiosis, which is a type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes. In contrast, embryos are in mitosis, a process in which the cell divides in two producing a replica with an equal number of chromosomes. "When we're trying to freeze an egg, it's in the middle of a cell division called meiosis 1, and the chromosomes are exposed and the meiotic spindle is exposed, and that's why it's more challenging to freeze eggs," Dr. Leondires says.
The advanced freezing technique known as vitrification has vastly improved egg and embryo freezing, which is why the number of live births from frozen eggs has improved so dramatically over the last few years. The process takes minutes compared to hours.
"With vitriification, it takes 15 minutes to freeze an egg or an embryo because they take the egg or embryo and put it into two or three solutions to get water out so ice doesn't form, and they put sugar molecules in to act as a preservation agent," Dr. Leondires explains. "Then the embryologist literally takes the egg or embryo and plunges it into liquid nitrogen, so it goes from 37 degrees to -170 in less than a second. So it's a much more efficient stop-start. It's like pushing pause in the middle of the movie — it starts up right where it left off."
Even with these advances, its a good idea to consider all of your fertility preservation options. "Women want to freeze eggs because they think in the future that they may meet a gentleman that they want to have a child with, so they want this option with this future partner," Dr. Leondires says. "But if this future partner never shows up, then it serves them well to also freeze embryos."
The decision of whether to also freeze embryos may come down to how well a woman responds to fertility drugs. "If I have a 35-year-old and I get 15 eggs, well that's easy — I would recommend freezing eggs and some embryos. If I have a 35-year-old, and I just get four, then I'm probably just going to freeze eggs because that's why she came," he says. "But if I only get four, that means their chances are even lower — because they probably have ovarian reserve problems — that they will be successful in the future with these eggs." Dr. Leondires admits that adding the frozen embryo question to the overall process can add a bit of stress. "it drives home the social component of this because they have to choose a sperm donor and think about whether they might be a mother by choice," he explains. "It amps it up a little bit and is more stressful for people, but I think it's something they should definitely consider.
"It really has to be very individualized and patient focused elective cryoprservation decision," Dr. Leondires continues. "And it's not something that people rush into."
February 28, 2013
Posted by Leigh Ann Woodruff