(NEW YORK) — Celebrities such as Kim Kardashian and Gabrielle Union have put surrogacy in the spotlight in recent years by sharing that they welcomed children via surrogates.

In the United States, the use of surrogacy has been on the rise, with more than 18,000 babies born via gestational carrier cycles between 1999 and 2013, the most recent data available, according to the U.S. Centers for Disease Control and Prevention (CDC).

Gestational surrogacy occurs when a woman carries a pregnancy that was made with another woman’s egg and another man’s sperm, so the surrogate has no genetic relation to the baby. In traditional surrogacy, the surrogate’s eggs are used, so she is the biological mother of the child she carries.

Surrogacy is legal in the U.S. but is not federally regulated, so laws vary from state to state. The cost of surrogacy can go into the hundreds of thousands of dollars.

Angela Hertenstein, 43, a registered nurse in Indianapolis, has been a surrogate for four different families over the past decade. She is currently pregnant with her fifth surrogacy after working with Gift of Life Surrogacy Agency, near Toledo, Ohio, to find a match.

Below, Hertenstein describes what it is like to be a surrogate and what she wants other people to know about the process:

I have been a surrogate for four different families, given birth to three sets of twins, two singletons, and I am currently pregnant with my fifth family.

From previous relationships, I’ve had two children of my own, and my husband has three. We contemplated having children together for about 30 seconds, but decided having a blended family of five, all within six years apart, was enough.

But when the opportunity to have a baby for someone else, who couldn’t have their own, presented itself, I jumped at the chance. Beyond enjoying being pregnant, I really loved the thought of helping another couple. So, being a surrogate was a perfect fit for me.

I was working in a doctor’s office in 2012 when I met the person who would change my life, another nurse who had just been hired.

She was talking to a group of us one day and had mentioned in passing that she had been a surrogate before.

I told her that I had always wanted to be a surrogate and had actually looked into it at one point. She informed me that the fertility doctor she worked with was looking for trustworthy individuals to be surrogates for his clinic. I gave her my information, she gave the clinic my information, and within the next couple of hours they called and set me up with an appointment for the following month for testing.

I told my husband when I got home, and he immediately took off work that day to take me to the appointment, about a 3.5-hour drive from Indianapolis.

We got to the clinic not knowing what to expect. The appointment involved an ultrasound, blood work and forms to fill out. The purpose of the ultrasound was to make sure that everything I possessed for the job was in good shape and I was healthy enough to become pregnant.

It was only a short six months later that I was pregnant with my first family.

After finding out that I was pregnant, I had to travel to the clinic every other week for check-up appointments until I was 12 weeks along. I consider myself a superstitious person, so the first time I drove to the clinic alone, it was cold, and I wore a pair of black yoga pants, knee-high rainbow socks and black boots.

I made it there and back safely and on time, so every time after that, I wore those socks and boots with every visit. Nine years later I still wear these socks to every appointment. Every time I walk into the office for labs, an ultrasound or the anticipated day of transfer, I always hear, “The rainbow sock lady is here!”

My husband and I got to meet the IPs (intended parents) at the signing of the paperwork for my first journey. We went out to eat with them after that and spent the afternoon getting to know each other. They were from overseas, and the most interesting people we have ever met. Not only were they interesting, but they were so passionate about having a family that it melted our hearts.

The first ultrasound revealed that I was having twins, and the parents were just over the moon with happiness and excitement.

Through this journey, I got to know the parents very well. I looked forward to talking with them every day. I loved sharing how the babies were doing, what it felt like to have two little humans wiggling around inside me, and how both babies already seemed to have their own personalities.

The biggest difference in a surrogate pregnancy and my own, is the happiness factor is tripled. For every milestone, ultrasound and defining moment, there is not only my excitement, but the parents’ as well.

The three most common questions I get when asked about being a surrogate are: Did you know the parents before this or are they family? How do you feel about giving up the baby/babies? And of course, how much do you get paid?

To the first question my answer is always: I didn’t know them prior, but I know them now, and I feel like we are family.

To the second question my answer is always: These people have tried so hard for so long to become parents and have been through so much that seeing the look on their faces when they hold their child or children for the first time is priceless.

My answer to the third question circles back to my answer to the second question: The look is priceless.

After giving birth to the first set of twins, I stayed with the family for a week. I pumped breast milk for the babies, helped take care of them while the parents arranged for their birth certificates and passports and helped teach the dad how to properly hold and dress his sons. This is just another example of the unparalleled joy that comes with being a surrogate.

I love sharing my story as a surrogate, because it gives me the opportunity to educate people on what it actually means to be a surrogate and how infertility affects everyone.

There is so much more to having babies for other people than is portrayed in the media. Not only do you forever change the lives of the expecting parents, but you are now eternally apart of something greater than yourself.

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