I had a benign tumor in my abdomen. I still needed chemo to make it smaller and now I'm infertile.

• Andrea St. Sauver was diagnosed with a desmoid tumor.
• The tumor was benign, but needed to be treated with chemo.

This as-told-to essay is based on a conversation with Andrea St. Sauver. It has been edited for length and clarity.

When I was pregnant with my first daughter, who is now 3, I noticed that my bump looked lopsided. Even after she was born, I felt a strange mass on the left side of my stomach. I was leaving a checkup when I was about four months postpartum when I realized I'd forgotten to ask my doctor about the mass, so I turned back.

My doctor felt my stomach and confirmed what I knew in my gut: the mass didn't feel normal. I had tried to tell myself it was just organs that had been rearranged during pregnancy. I already had some serious health conditions, and my mother had died from colorectal cancer at 35. I had just turned 36, so I knew I was enjoying years my mother never had. Now, with a new baby and a stepson, I was facing what my mom had gone through in a very real, very serious way.

I learned my mother had the same rare disease

My doctor ordered additional tests, and I was at home when the hospital called with my results. The tumor was 13 by 11 by 7 centimeters. I remember thinking that seemed really big and very alarming.

My aunt, who had become a surrogate mother after my mom died when I was 9, told me that in addition to cancer, my mom had a desmoid tumor, a type of very rare, benign growth. There are only about 1,000 cases of these tumors diagnosed in the US each year, mostly in women. Recent pregnancy is a risk factor — my mom was also diagnosed soon after giving birth.

Given the choice between colorectal cancer and a desmoid tumor, I found myself hoping the mass was "just" a desmoid. You hear the word "benign," and it gives you a sense of security. I had no idea just how serious the tumor would be.

The tumor was benign, but I still needed chemo

After I was officially diagnosed with a desmoid tumor, my doctor explained that specialized oncologists would be handling my care. That was terrifying. It was even more scary when the doctors told me I had two choices: watch and wait or undergo chemotherapy that could shrink or soften the tumor.

Until then, I hadn't realized that the tumor was already impacting my health. It was wrapped tightly around my bowel, which eventually led to an obstruction. It was also causing fluid to back up into my lungs.

Despite that, I didn't want to do chemo. But after ruminating on my options, I couldn't sit back and do nothing. I was in the best shape of my life, and I knew that doing chemo now, rather than in the future, was the best choice for me.

I was determined to keep living life despite treatments

Before I could start treatment, doctors recommended that I freeze my eggs. The chemotherapy would likely leave me infertile, and I knew I wanted to grow our family. I did two cycles of egg retrievals in December and January. Then, I started chemo in February.

While I was in treatment, I was determined to keep living my life as much as I could. I did treatments at home, where I could be around my 7-month-old. I got married days after losing my hair. I kept training for the Twin Cities Marathon, which I completed while undergoing chemotherapy.

The treatments shrunk my tumor slightly. More importantly, they softened it so that I wasn't having the same symptoms, including pain, bowel obstructions, and fluid in my lungs. For me, that was good enough. Today, I get scans every six months to monitor the tumor. I still take it very seriously: I know it's a sleeping giant that I might need to face again in the future.

I got pregnant using a donor egg

With the treatment stable, I wanted to have another baby. My egg retrievals had resulted in 19 eggs, a great amount. However after undergoing IVF, we only had one fertilized embryo, and it was abnormal, meaning it likely would have resulted in miscarriage. My husband and I turned to donor eggs, and I'm pregnant now, just out of the first trimester.

Being a mom to a bonus son, a biological daughter, and (soon) a child who is donor-conceived is complex. I was heartbroken to learn I wouldn't have any more biological children. I'm still processing it, but I know for sure that biology doesn't make a family; love does.

I feel great about the future. My family is growing, and I'm able to go longer between my tumor scans. I pack as much life as possible into every day. I know there's progress being made on treating rare diseases like mine. This pregnancy could result in more tumor growth, but whatever happens, I know the options. My decisions will not be based in fear, but based in knowledge, and I have a lot of confidence in that.