When I told my husband we were going to adopt, he looked at me as if I were crazy. We had always wanted to do it, but somehow the years had slipped away while we were busy with work and family.

We are blessed with two biological sons, but through adoption we wanted to offer a child born into difficult circumstances a better home. My husband is a New York City firefighter and I am a paediatric physical therapist. Helping others is central to who we are.

Adoption is a huge business in the US, and the demand for babies is especially great in the New York area. Commercial agencies charge up to $30,000 upfront and you still barely stand a chance of being matched with a baby. What’s more, many agencies pressure women into giving up their children for adoption. We wanted no part in this, so last year we hired an attorney and an adoption consultant to help with what’s known as a private adoption. This simply means that no agency is involved, with the “match” arranged directly between a birth mother and the adoptive parents. It’s completely legal.

For six months, we bought adverts in local newspapers across the US, which cost about $500 a month. When our consultant suggested we also try the classified ad website Craigslist, I was stunned, but she told us it had produced successful matches in the past, so we gave it a go. Our Craigslist post had a picture of my husband and me, and a toll-free number so that prospective mothers could call us free of charge.

After a number of calls that went nowhere, a Pennsylvania woman contacted us via email. She liked our ad on Craigslist and was considering adoption for her unborn son but was still exploring her options. I wanted her to feel as safe as possible, so I suggested she start by speaking to our attorney.

It was our son Darien’s ninth birthday in June when she first phoned me. I was excited and nervous. Our conversation lasted over two hours and by the end she told me: “I want you to have my baby. I feel most comfortable with you.” She liked that we already had two boys who would be older brothers to her son. She warmed to me when I said that while my husband and I have stable jobs, we’re not rich. She didn’t want her son to be dropped off at summer camp by a nanny while his adoptive parents were too busy to raise him.

We paid some of her costs, such as attorney fees and living expenses during pregnancy, but that’s legal and typical for private adoptions.

We were open to any kind of adoption – but she wanted to have a closed adoption, where there is no contact at all between the birth mother and the child and adoptive parents. “Come straight to the hospital to pick him up,” she told me. “I don’t want to see him. I want him to go right into your arms.”

We were lucky that she was having a caesarean section, so we could schedule our trip to the hospital. But we didn’t name him or buy him a car seat, because we knew that there was still a chance she would change her mind after he was born.

Luckily, for us, that moment never came. When we saw him for the first time, minutes after he was born, lying in a nursery crib, we just stood there looking at this beautiful, tiny human being whom a complete stranger had just entrusted to us.

Pennsylvania, where Cayden was born, requires a 72-hour waiting period before a new mother can legally sign the consent forms for adoption. We stayed at a hotel next to the hospital, going back and forth, until they released both mother and son three days after her caesarean. That day, our attorney came to the hospital and we signed the custody papers. We then had to wait another week for permission to transport Cayden across state borders, but we eventually all made it home to Long Island in time for the 4 July holiday.

Cayden is now three months old. I worry sometimes about what will happen when he gets older and starts asking questions. I plan to tell him his story right away and just say: before you were born, you grew in another woman’s belly and she chose me to be your mommy, and now we are your family. It’s that simple.

• As told to Solvej Krause

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