An excerpt from Held Together: A Shared Memoir of Motherhood, Medicine, and Imperfect Love.

Scott and I held hands as the last few minutes of waiting expanded to rival the anticipation of the days that had already passed. Two weeks ago at this same medical center, our perinatologist had performed a chorionic villus sampling, the procedure to collect the fragment of placenta that would determine our course. I had been tested for Huntington’s disease myself almost 10 years earlier, and, after an equally long two-week wait, my results had been confirmed: positive. I was a carrier of the genetic mutation that would almost certainly lead me to develop this incurable and fatal disorder. Now I was waiting to learn if my baby had the mutation too.

At fourteen weeks pregnant and 35 years old, I was not invested in this baby, or, more honestly, I had been using every emotional reserve I could summon to avoid becoming invested. The blandness of the beige walls in the geneticist’s office and the nondescript mountain sunset painting hanging over her desk matched the attitude I had been striving for.

It was unsettling to be looking at mountains in this context, with such detachment. The mountains had always been a place of comfort for me. When I first received my Huntington’s diagnosis, I was splitting my time between San Francisco’s urban bustle and Northern California’s untamable wilderness. During the week, I balanced an uninspiring day job in the hotel industry with rewarding volunteer work advocating for health care for HIV-positive people. But my true home was in the backcountry. I spent many evenings climbing at local crags and nearly every weekend on expeditions in Yosemite with an incredible group of mountaineering friends, challenging ourselves and supporting each other as we explored the world. I was in the best physical and mental shape I had ever been in. I loved my life.

Still, when I had learned about a nearby clinic that offered anonymous Huntington’s testing, I felt compelled to find out what might lie ahead for me. In her late forties, my mother’s mother had started suffering from a constellation of mysterious symptoms, including repeated episodes of stumbling on flat ground, sudden swings between rage and depression that were completely out of character, and gradually worsening memory loss after having always been renowned for keeping track of every birthday and every anniversary in our family. Countless lab tests and clinic visits finally led her doctors to diagnose what was causing her deteriorating health after more than a decade of observation. I had witnessed the insidious progression of my grandmother’s disease since I was 6 years old, and I had had a name for it since I was 17.

Huntington’s is a scary disorder precisely because it disrupts brain function in otherwise healthy young people, progressively eating away at the abilities that make us human. It causes uncontrolled muscle movements, disorienting emotional problems, and loss of the ability to think clearly, typically starting in a person’s thirties or forties. Some have compared it to having Parkinson’s, Alzheimer’s, and amyotrophic lateral sclerosis (also known as ALS or Lou Gehrig’s disease) all at the same time. In its late stages, typically ten to twenty-five years after the onset of symptoms, a person with Huntington’s becomes trapped inside her body, unable to walk or speak. Although she still understands much of what is going on around her, she is completely dependent on others for care.

The explanation for my grandmother’s condition probably eluded her doctors for so long because most of her twelve siblings had lived into their seventies with minimal medical problems. Huntington’s disease is a classic genetic condition. It is passed down through families in an autosomal dominant pattern, meaning that its inheritance has nothing to do with being male or female and that each child of a parent with Huntington’s has a fifty percent chance of inheriting the mutation. Because of the dominance of the gene, those who carry it have a 100 percent chance of developing the disorder, assuming they live long enough to do so. The decision about whether to undergo testing for Huntington’s is complex and difficult and intensely personal. Family members often disagree strongly about how to handle the situation, and whether to be tested themselves. Some people prefer to find peace with the ambiguity of not knowing.

I am not one of those people. Even if I did not get the answer I wanted, I believed that having knowledge was always preferable to living in fear of the unknown. I had been worrying enough already, convinced that the test would be positive. If I took the test, at least there was a chance I could be proven wrong. Throughout my life, I had tended to plan for the worst even while hoping for the best. I called the neurology clinic and enrolled in their Huntington’s program.

At my first visit, I sat in the waiting room wondering what to expect. To my left, a tired-looking woman was tending to a freckled, dark-haired boy. I guessed that he was her son and that he was about 13 years old. As I filled out questionnaires about my family and health history, the writhing movements of the teenager’s slender body brought him into and out of my peripheral vision. He furrowed his brow in concentration, trying to contain himself in his narrow chair, but he began to slide down when his abdominal muscles went involuntarily rigid. His right arm jerked at the shoulder. The back of his hand wiped his chin then grazed upward to hit the tip of his nose. His mother repositioned him gently, chatting casually about where they might stop for lunch after his appointment. He leaned sideways against her and smiled. His trembling fingers reached for her hand in a movement both painfully erratic and eerily fluid, as he mumbled something I could not understand. I averted my eyes, pressing my pen hard against the stack of clinic paperwork. At 26 years old, I swore to myself that I would never knowingly bring a child into this world who would have to endure what I was witnessing that morning.

Rebecca Thompson is a family physician and author of Held Together: A Shared Memoir of Motherhood, Medicine, and Imperfect Love.