This summer, the practice of surrogacy was brought front and center when Kim Kardashian and husband Kanye West announced their decision to use a surrogate for baby number three. While the idea of surrogacy is making headlines, not many understand the actual science behind it. Here’s a quick guide to surrogacy, and what parents can expect from the process.

Kardashian chose a San Diego mom in her late 20s to be her surrogate, and the woman is already 4 months pregnant and set to give birth in January 2018, US Magazine reported. Kardashian opted to use a surrogate for her third child after experiencing placenta accreta, a serious and sometimes life threatening condition where the placenta doesn't attach properly, during her first two pregnancies.

What Is Surrogacy?

There are two types of surrogacy techniques that parents can choose: traditional surrogacy and gestational surrogacy. In traditional surrogacy, the surrogate mother is fertilized with either the sperm of the adoptive father or donor sperm. She then carries the child for the expectant parents and hands over all parental rights after birth. However, she is the biological mother of the child as it was her egg that was used during conception, WebMD reported.

In the case of gestational surrogacy, expectant parents will use in vitro-fertilization to conceive an embryo, which is then implanted into the surrogate. Although the surrogate is the birth mother in this case, as she carries and delivers the child, she has no biological ties to the child.

Who Uses Surrogacy?

Many women, like Kardashian, use surrogacy because they have a medical condition that prevents them from safely carrying a child. This can include placenta accreta, such as what Kardashian had, where the placenta grows too far into the uterus causing blood pressure to drop dangerously low. Women with severe heart problems, issues with their uterus, or women who have had their uteruses removed with a hysterectomy may also opt to use a surrogate, WebMD added.

The service is also helpful for patients who cannot conceive and carry themselves due to biological constrictions, such as single parents, infertile parents, or same-sex couples.

What To Expect?

Expectant parents are usually paired with a surrogate via a surrogacy agency. Surrogates are preferred to have been mothers before, so that they understand what to expect during childbirth and delivery. Women are also asked to undergo a psych evaluation and medical exam to ensure they are fit for pregnancy and won't struggle to part with the child after birth, Sensible Surrogacy reported.

Once a couple has selected a surrogate, the fertilization process begins. Here, either the surrogate is fertilized with donor sperm, or a fertilized egg is implanted into her uterus via IVF. During the pregnancy, the surrogate will attend regular checkups, and the expectant parents can also attend if they wish.

Finally, during birth, the parents are usually also present to share in the birth of the child. According to Sensible Surrogacy, depending on where you live, you may be able to pass on parentage of the baby before birth, but if not, parentage is decided soon after birth through the signing of the birth certificate.

Although extremely costly -- US Magazine reports that Kardashian is paying nearly $70,000 for the process -- reports suggest that surrogacy is growing in popularity, The Independent reported. While some worry that there's a risk surrogate mothers will be taken advantage of, most agree that when done for altruistic reasons, the process can be a great way to give a child to those who otherwise would not have been able to conceive.