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A fertility doc explains when and how this is done.

Amanda MacMillan
March 03, 2016

Chrissy Teigen, who has talked publicly about her struggles with infertility, recently told People that she had the option of choosing a female embryo while undergoing in vitro fertilization (IVF). For anyone unfamiliar with the IVF process, the option to choose the gender of your baby may seem futuristic, even controversial. But gender selection actually happens quite often in fertility clinics around the country—and it’s just one small aspect of the genetic testing that can take place before a mom-to-be even gets pregnant.

It’s all possible thanks to a procedure known as pre-implantation genetic diagnosis (PGD) or pre-implantation genetic screening (PGS), says Avner Hershlag, MD, chief of the Center for Human Reproduction at North Shore University Hospital in Manhasset, New York. During IVF, a doctor creates embryos by combining a woman’s eggs with a man’s sperm in a lab. When those embryos are a few days old, the prospective parents can choose to have them screened for genetic abnormalities using PGD.

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This means that the embryos are put under a microscope, and (very delicately) a few cells are removed. The cells are then analyzed to ensure that they have a normal genetic makeup—that is, pairs of chromosomes 1 through 23.

Doctors also take a close look at the X and Y chromosomes to check for abnormalities there; and at that point, the gender of each embryo, XX or XY, becomes obvious. When the prospective parents are briefed on which of their embryos are healthy and viable, they may also be told which are female and which are male.

“If more than one embryo is normal, and there happen to be both males and females, we don’t impose on patients which one they should use,” Dr. Hershlag says. “If all other things are equal, it becomes their personal choice.” (Patients can also choose to freeze other healthy embryos for use in later pregnancies.)

What's the catch?

This type of genetic screening comes at a cost. Most clinics charge anywhere from a few hundred to a few thousand dollars for PGD. (Some clinics charge per embryo, while others charge a lump sum.) This is on top of the expense of basic IVF, which averages $12,400, according to the American Society for Reproductive Medicine.

When you consider the investment patients are making, the additional cost for PGD may not seem so high, Dr. Hershlag points out. It may indeed be worth it to ensure a successful pregnancy, and a healthy baby—never mind one of a specific gender.

This is especially true, he adds, for women who have had multiple miscarriages, or who are in their mid-30s or older. (The risk of having a genetically abnormal embryo goes up as a woman gets older.)

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Prospective parents who are carriers of genetic diseases may also want to ensure they don’t pass on those traits, like the BRCA gene. “We are creating babies who don’t have to worry,” says Dr. Hershlag. “Instead of having extremely high lifetime risks, their risk levels are now the same as anyone else’s.”

Now that the technology exists, “it’s almost unfathomable to me to transfer an embryo whose genetics are unknown,” says Dr. Hershlag. “At this point, the only obstacle to doing it for every IVF patient is financial.” Right now virtually no insurance companies cover PGD—many don’t even cover IVF. But Dr. Hershlag hopes that will change in the future. “[The insurance companies] need to understand that if we are creating healthier babies, we will ultimately save money on testing and treatment in the long run.”

What about couples who simply want a daughter (or son)?

Some clinics do practice “family balancing” for parents with children of one gender who want a child of the other sex. But with first-time parents who have no fertility or genetic concerns, it's "really unacceptable" for doctors to use IVF and PGD solely for gender selection, Dr. Hershlag says. He worries that it could lead to sexist preferences and lopsided populations, as seen in other countries. “I warn people against going to clinics that don’t have clear ethical guidelines, because they will also be less reputable,” he says. “In our clinic, we mainly screen embryos for health. And if a patient wants to know the gender as a byproduct, I see very little wrong with that.”

RELATED: 9 Things Every Woman Must Know About Her Fertility

Could genetic screening go a step further?

Could PGD, say, help parents choose a tall, athletic, brown-eyed girl? Experts say the science isn’t there yet—and even if it were, it’s unlikely that many doctors would agree to assist such a highly controlled pregnancy. In 2009, a fertility clinic in New York City advertised the “pending availability” of such services, but removed its ad after receiving a disapproving letter from the Vatican. And last year, the United Kingdom became the first country to approve a procedure known as three-parent IVF, which combines the DNA of two mothers and a father—but only in cases in which a woman could pass on genetic health conditions to her baby.

For now, PGD is used primarily to help parents have less stressful pregnancies and healthier babies—enormous, life-changing benefits in their own right.

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