Chances are, you’re already familiar with the concept of surrogacy — maybe in part to celebrities, like Kim Kardashian and Neil Patrick Harris, who have used surrogates. But where it can get confusing is that when we talk about surrogacy, we tend to discuss gestational surrogacy rather than traditional surrogacy. So, what exactly is gestational surrogacy? In short, in gestational surrogacy, the surrogate carries the baby, but the egg has been provided by someone else. This differs from what’s considered traditional surrogacy.

What is the difference between gestational surrogacy and traditional surrogacy?

“In traditional surrogacy, the surrogate who carries the baby also provides the egg that will become the child. Whereas in gestational surrogacy, the egg is provided by another individual, whether a female parent or egg/ovum donor,” says Dr. Wendy Chang, at the Southern California Reproductive Center. “Gestational surrogacy is far more common for many reasons: legal and biological. Many hopeful parents may be unable to carry a pregnancy, but can still provide a healthy egg with their own genetics.”

When IVF started in the late ’70s, typically it was the same woman who served as the egg donor as well as the gestational carrier. But, due to a variety of legal challenges, traditional surrogacies became fraught with ethical questions. So, now the norm is a gestational surrogacy. “This means the carrier is not genetically related to the embryo or fetus itself,” says Dr. Rashmi Kudesia, a reproductive endocrinologist at the Colorado Center for Reproductive Medicine in Houston.

“Traditional surrogacy can be much simpler and less expensive, because a traditional surrogate can simply be inseminated with sperm at the time of ovulation and conceive without arduous and expensive in vitro fertilization (IVF) treatment,” Dr. Chang says. “For single men without partners and gay men, working with a traditional surrogate would be an inexpensive and simple process.”

However, she notes that traditional surrogacy is rare. In fact, only a few states allow traditional surrogacy because of how difficult it makes parentage to define when the surrogate is delivering her genetic child.

Who should consider a gestational surrogate?

For some individuals, it’ll be obvious that gestational surrogacy is the best route to having biological children. “For a single father or gay dad couple, it’ll be evident from the get-go,” Kudesia says. Likewise, women who don’t have a uterus — whether it’s a congenital absence or the result of a hysterectomy — require a surrogate.

But others may want to seek a gestational surrogate too. Some common reasons for considering surrogacy:

• You’ve tried and have failed to have a successful pregnancy.
• You have health issues that may affect your ability to have a safe and healthy pregnancy.
• You have done multiple embryo transfers without success.

How to find a gestational surrogate

There are two options for finding a gestational surrogate. You can use a known gestational carrier — which could be a friend, sister, cousin, or even your mother — or you could select a surrogate who you do not know personally.

If you’re going with a stranger, you can find a surrogate through either a reproductive endocrinologist, who will evaluate and treat both the intended parent and surrogate throughout the process, or you can go directly to a surrogacy agency.

Even if you choose the latter route, Dr. Chang urges prospective parents to find an agency through your doctor. “Surrogacy has become highly sought after and increasingly common. As a result, the number of surrogacy agencies has grown tremendously, but not all were established by capable or reputable people,” she says. “The past 10 to 15 years has witnessed a few reports in which hopeful parents had paid large sums of money to engage a surrogate, only to find that the agency had closed or disappeared. Getting the referral from an experienced reproductive endocrinologist gives reassurance that the agency has a long-standing reputation.

What’s the process for using a surrogate?

As complex as it might seem, gestational surrogacy is essentially a two-step process, once a surrogate has been selected. First, quality embryos are created through IVF. Then the surrogate’s uterus is prepared to receive the embryo, Dr. Chang says.

What makes a good surrogate?

The American Society of Reproductive Medicine has specific guidelines for selecting surrogates:

• They should be at least 21 years of age.
• They should have had at least one healthy pregnancy in the past.
• They should be young and in good health.
• They should have no significant medical problems, such as hypertension or diabetes.

The most important requirement for a surrogate is a history of having a full-term, healthy pregnancy in the past, according Dr. Kudesia. This is for a few reasons: For one, it helps ensure that there’s a good chance of carrying a healthy pregnancy. Then, although serious complications are rare, it’s preferable that the carrier has her own children — and has even finished family-building. Finally, “It’s impossible for a woman who has never been pregnant to gauge the emotions involved and then have that child go to another intended parent,” Dr. Kudesia says.

There’s also an intensive training progress involved, as well as medical, genetic, and psychological screenings. For those who are considering becoming a surrogate, Dr. Kudesia says to familiarize yourself with what all is required of you. “It’s an amazing gift to give, but it is a lot to ask from someone,” she says. Make sure you really understand the involvement and risks so that you really feel ready. It’s heartbreaking for a couple when they’re committed to a surrogate and things change.”