“We’re living longer, and this new middle age is becoming a time when people start to think about what they want to do with the rest of their lives. For many who haven’t had kids, they decide to reinvent themselves as parents.”

The path to parenthood comes in many ways. Beyond adoption and surrogacy, some choose in-vitro fertilization, either with donor eggs or eggs they have frozen in the past. None of this is cheap. Mr. Campanella, for example, paid about $120,000, which included legal and medical fees, and costs for the surrogate mother.

“People are so much healthier today,” said Dr. Philip Chenette, a reproductive endocrinologist at the Pacific Fertility Center in San Francisco. “I see 55-year-olds routinely mountain biking in Marin County, and if you keep a good diet and keep your weight down, you can do a lot of things with your body that you couldn’t do before. If your life expectancy is longer, why wouldn’t you want to fill that time with your kid?”

Some fertility clinics have extended the age of the patients they will accept. The cutoff at Pacific Reproductive is 55 for women (The combined age for a couple is 110). There is none at the New York Fertility Institute, in Manhattan. “We’ve had patient’s first baby delivered to 57,” said Dr. Majid Fateh, the founder and medical director.

Steve Klein, a family formation lawyer in San Diego, is also seeing older people coming through his doors. “As surrogacy has become more mainstream, people see it as a viable way to have a child, especially for people who are beyond the optimum reproductive ages,” he said. “They have money, they can provide a comfortable life, a private education. They can have nannies assist them, or one of them could be a stay-at-home parent, and they’re older and wiser and more mature. They can be a better parent than if they were younger.”

Sometimes no one is more surprised by the desire to have a child in later life than the soon-to-be-parent. Merle Hoffman, the founder and chief executive of Choices Women’s Medical Center, in Queens, said she had never wanted children.