When 45-year-old Mari Sarkisian Wyatt, a freelance copy editor, decided to have a third child, she had no idea what she was getting into—except that a woman her age had a success rate of less than 5% without help.

When Mari Wyatt’s first child was born in 1988, she had never heard of autism. But when her son was diagnosed at age three, she recognized that her older brother had probably been on the spectrum, too. After her daughter was born, Mari wanted to spare her second child from the fate that she’d endured growing up with only one troubled sibling. Her solution was to have a third child. What started as a modest attempt to conceive through IVF soon became an all-consuming, often heartbreaking quest, but with a surprise ending she never saw coming.