Chrissy Teigen Chose Her Baby's Sex During IVF: Here's What You Need to Know About Gender Selection

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In light of the backlash Chrissy Teigen has faced after revealing that she chose the gender of her baby-to-be, ET is looking into the process of gender selection and how it really works.

The process, which can cost up to $20,000, was originally created to screen out serious genetic diseases, not for choosing a baby's sex.

WATCH: Chrissy Teigen Defends Choosing Gender of Her 'Darn Science Baby'

Some patients travel to America from abroad just for the procedure, as the U.S. is one of only a handful of countries that allows the process for non-medical reasons. There seems to be high interest in the process for some women living under one-child policies, especially if there is a cultural preference towards one gender or the other.

In one method, an embryo's chromosomes are tested to determine if it's male or female.

In Chrissy's case, she explained that she chose a girl, thinking that her husband John Legend would be the best father to a daughter. After undergoing in vitro fertilization, choosing the baby's sex didn't even register as all that unusual.

WATCH: Chrissy Teigen Reveals She Chose to Have a Daughter

"What is that difference though?" the model tweeted. "I've already created embryos with a doctor. only after must it be random.This is all so interesting. I said it so casually because i'm just open. I'm around so many open-minded people & forgot it's controversial. anyhow I am not mad at anyone's beliefs but I don't really actively seek out people to make them feel bad about their decisions either."

The happy couple are expecting their first child this spring.