This Is What Makes Bachelorette Kaitlyn Bristowe's Fertility Decision Unusual

Over the weekend, former Bachelorette Kaitlyn Bristowe took to Twitter and Instagram to explain why she chose to freeze her eggs. Then, today on Good Morning America, she spoke more about the details of her decision. Since 31-year-old Bristowe is engaged to Bachelorette winner Shawn Booth, this move may come as a surprise to those who think of egg-freezing as purely the domain of single people — and in reality, although the procedure is more common than you might think (thousands of people with ovaries do it every year), it's still pretty rare among those in relationships.

"It is incredibly uncommon for women in serious committed relationship to freeze their eggs," says Deborah Anderson-Bialis, co-founder of fertility data startup FertilityIQ. Although the company hasn't collected statistical data specifically around this, "having talked to thousands of these patients, I would say less than five percent are people who are engaged, married, or in very committed relationships," she says.

So why did Bristowe decide to go through with the procedure? "This is kind of a backup plan for us," she explained on GMA. "It's kind of like insurance."

Let's hold up here for a sec: Although that's a common way to describe egg freezing, Anderson-Bialis says it's really just not that simple. Although most thawed eggs will lead to pregnancy, says Zsolt Nagy, PhD, who works with egg-freezing startup Prelude, there are several complex factors that determine how likely that really is for you. That includes the age at which you freeze your eggs, how many good-quality eggs are retrieved during your procedure, and whether or not you have to go through more than one retrieval.

On top of that, the amount of people who actually go back to thaw their eggs remains quite low (about 10% of those who have them frozen). "Anybody who thinks of this as insurance has misinterpreted the facts," says Jake Anderson-Bialis, FertilityIQ's other co-founder.

That's partly why it's more common for those in committed relationships to freeze some embryos rather than just eggs, Jake says. That requires fertilization in the lab before freezing, which means you'll need to spend a larger chunk of change up front (by about $2,000-$4,000). But it also means you'll know that each embryo has a good chance of becoming a viable pregnancy down the line because, unlike eggs, they've already gone through the (sometimes tricky) process of fertilization.

Granted, you'll be locked in to using your current partner's sperm, which means you're stuck with that person as the father if you ever want to use those embryos. But for those in serious relationships, that's probably not as big a deal as it might be to someone who's single or otherwise less committed.

Just because freezing embryos is a more expensive process doesn't mean it's the pricier option overall, though: If you end up using frozen eggs later on, the cost evens out with that of freezing your embryos because you'll have to thaw and fertilize the eggs, Jake says. Plus, if your relationship does come to an end, it's much easier for each of you to take your separate pieces with you if you're still just dealing with frozen eggs and sperm rather than a fertilized embryo.

Whatever the case may be, if Bristowe and Booth know they want kids but aren't ready to start trying just yet, it's probably a smart move to freeze her eggs now — since she's willing and able (financially and physically) to do it — rather than to just wait and see what happens. "Women who freeze their eggs at 30 years are likely to get pregnant much easier 10 years later using those frozen eggs than if they try to get pregnant at age 40 with their fresh egg at that time," Dr. Nagy explains.

So, although freezing your eggs when you're in a relationship might not always make the most sense for every couple, we're glad Bristowe and Booth were able to make a choice that made sense for them.