Twin-to-twin transfusion syndrome caused a teen's kidney to fail. Her transplant came from her identical twin.

• Daisy and Sadie Delrie are identical twins born in 1993.
• They experience twin-to-twin transfusion syndrome in the womb, leaving one smaller than the other.

This as-told-to essay is based on a conversation with Daisy and Sadie Delrie. The following has been edited for length and clarity.

Lots of people like to hear their birth stories growing up. But ours was always different, to say the least. We're identical twins who were born in 1993. Ultrasound technology wasn't the same 30 years ago as it is today, so doctors didn't realize we were experiencing twin-to-twin transfusion syndrome.

That's a rare pregnancy complication where two — or more — babies share one placenta. The blood flows unevenly, keeping one twin from growing. In our case, Daisy got plenty of nourishment, but Sadie didn't. Right after we were born, Sadie's organs began shutting down.

Our mother didn't have much time to focus on that, though — she still had to deliver Daisy, who was breech. Daisy was born 57 minutes later, vaginally. Our mother is a saint.

Sadie had lifelong complications that ultimately led to kidney failure

Luckily, Sadie's organs began to regenerate. Except her kidneys. Since the time we were babies, we would travel four and a half hours from our home in Louisiana to see a pediatric nephrologist (or kidney doctor) at Tulane University in New Orleans.

We loved the trips to the city and loved our doctor. But Daisy always stayed in the waiting room — she had a bit of a phobia about doctors. Whether it was a dentist trip or a yearly physical, Daisy was always anxious.

When we were 18, we went to New Orleans with our mom. I, Sadie, was sad because I knew my pediatric nephrologist was going to suggest I change providers now that I was an adult. I had no idea the news was so much worse. My doctor told me my kidney function had dropped. I either needed to start dialysis or get a transplant.

Daisy didn't hesitate to help

I, Daisy, was in the waiting room for that appointment, but someone came to get me. I thought the doctor, who I knew well by then, just wanted to say hi. But as soon as I saw my mom and Sadie, I knew something was very wrong.

The doctor explained, "She needs a kidney transplant. Obviously, you would be the best match. But I want you to know that doesn't mean you have to do it."

My sister later said if the doctor hadn't told me that, she would have. But I immediately knew I'd donate. My fear of doctors didn't matter at that moment. I felt God had put me on this earth to save my sister.

We took about nine months to prepare for the transplant

We learned that Sadie needed a transplant in March of our senior year. In some ways, life went on as usual: we graduated and moved out for the first time. In the fall, we started college. But along the way, we were moving forward with transplant testing.

There was a bit of a hiccup: Daisy needed to lose 30 pounds before she could donate because of BMI requirements. Daisy joined Weight Watchers, and together as a family, we all worked to get ourselves as healthy as possible before surgery. In January, doctors transplanted Daisy's kidney into Sadie.

A few days after the surgery, our pediatric nephrologist visited us. We thought we looked terrible, but he told Sadie she already looked healthier. At a routine follow-up, Sadie's kidney function was even better than Daisy's. We joked that she got the good kidney.

We both work in healthcare now

We were so close before surgery. Maybe, it made us closer, if that were even possible. It certainly changed our lives.

During the surgery screening, we met with nurses and doctors — but the social workers really stood out to Daisy. She decided that's what she wanted to do with her life. Now, she works with dialysis patients and talks to them each and every day about transplants and hope.

Sadie helps people with physical health now. This summer, she started training to become a physical therapist's assistant.

We both work in advocacy, urging more people to become living donors. We're lucky that we share DNA, so it was essentially like Sadie was getting one of her very own kidneys—just an improved version. But you don't have to be a twin, family, or even a blood match to give someone the gift of life. It's our wish that every person with kidney failure could experience the success we've had.