When model Chrissy Teigen recently admitted that she and her husband, John Legend, chose their baby’s sex through in vitro fertilization (IVF), the topic of preimplantation sex selection was brought into the media spotlight. In Teigen’s case, who underwent IVF for infertility, the revelation was met with both praise for her candor and a firestorm of criticism for “playing god” by choosing a baby girl. What is sex selection and why is it so controversial? Why are more couples than ever opting to choose their baby’s sex?

Here are 4 things you need to know about choosing your baby’s sex.

The reason. The reasons for sex selection are manifold. Cultural conditioning may play a role. Even today, baby boys are often preferred in countries such as India and China. In some cases, sex selection is used to prevent serious X-linked conditions, such as Duchenne Muscular Dystrophy, from being passed on. For some, “family balancing” or the desire to “even out” a family consisting of all male or female children is the motivation. For others, it’s purely the desire of raising a little girl or boy that drives them to manipulate nature.

The Process. The gold standard of sex selection is IVF. Dr. Jaime Knopman, Director of Fertility Preservation at CCRMNY, notes that “most good fertility clinics screen genetics for success,” and a by-product of these tests is the identification of the embryo’s sex. Once the embryo is created, it is left to develop for 5 or 6 days. A few cells are then biopsied and undergo Preimplantation Genetic Diagnosis (PGD) and/or Preimplantation Genetic Screening (PGS). All 46 chromosomes are examined to determine the health and viability of each embryo, which dramatically improves the chance of pregnancy. An offshoot of these highly accurate screenings is that couples can opt to choose the sex of the embryo for transfer.

The Drawbacks. As with any medical procedure, there are risks and drawbacks. First, one must consider the physical and emotional toll of the IVF process itself. Aside from the bevy of unpleasant side effects from the powerful fertility drugs, success cannot be guaranteed even by the most reputable clinics. For those trying for a girl or boy, there’s the possibility that embryos of the “preferred” sex will not be produced. And in the incidence of an unsuccessful pregnancy, the emotional toll may be compounded when the sex of the baby is known. Dr. Knopman points out, “it personalizes it more if you know the gender, there can be an unhealthy attachment.”

Finally, there is the exorbitant cost, which can be tens of thousands of dollars and is not covered by insurance in most cases. Jennifer Saltzman* is a mother of three boys who recently underwent an unsuccessful elective round of IVF in the hopes of having a girl. She commented that IVF is often “not a one-round thing. It is time consuming and expensive; and for sex selection you have to pay out of pocket. I learned that most cases of IVF call for several rounds to get the hormones and medications right.”

Ethics. IVF with the use of PGD and PGS for sex selection is a highly controversial topic, particularly when employed for non-medical reasons. Even the American Society for Reproductive Medicine (ASRM) has not reached consensus on the ethicality of the practice.

Proponents argue that it is a matter of protecting patients’ reproductive autonomy and liberty, no different than providing women access to abortion. Critics cite potential unknown long-term risks associated with IVF and PGS to the offspring. There is also fear of gender bias, sex stereotyping and the non-acceptance of offspring if they don’t live up to particular gender stereotypes held by the parents. Then there’s the “slippery slope” argument that sex selection will devolve into eugenics, leading people to seek out other non-health related traits like skin color, eye-color, height and sexuality. The equitability of the practice has also been questioned as currently only the wealthy can afford elective IVF for sex selection.

Dr. Knopman points out that in the 20 years since genetic screening has been available, gender selection has “always been something people have done, but have been hush-hush about.” A 2008 study gleaning data from 2005 estimates some 9 percent of IVF patients underwent the procedure for non-medical sex selection. Given the controversial nature of the procedure, it is no surprise that many couples choose to keep their decision under wraps.

“We didn’t tell anyone, including our close friends and family, that we were going through IVF for sex selection because we didn’t want anyone’s opinions on our decision,” Saltzman told me. “Also, had we had a baby via IVF, I would not want everyone to have opinions of that child vis-à-vis the sex selection process.”

While technology may allow us to choose the sex of an embryo, there is no science that can determine the nature of your child. The “princess” of your dreams may turn out to prefer soccer to hair bows, and that “Lil Buddy” you always imagined playing catch with might prefer dance class and Princess Elsa. If you’re considering undergoing IVF to choose your baby’s sex, it’s important to keep your own expectations in check and to be prepared to love your child unconditionally, whoever he or she turns out to be.

* Name has been changed for privacy