A woman in her 50s walked down Main Street carrying a doll-sized baby on her shoulder. I was waiting for my husband and toddler outside the store she was about to enter.

"Your baby’s so beautiful" I said, looking into her scrunched up face as she lay, exhausted, on her mom’s shoulder. "She’s so tiny."

"She’s my foster daughter," the woman told me, and I could feel tears starting in my eyes. I was pregnant with my second and the sight of such a tiny, helpless baby (along with MacDonald’s commercials and billboards advertising long-distance telephone companies) made my throat close with emotion. "She’s three months old but she’s a crack baby, which is why she’s so small."

"May I hold her?" I’m always hesitant to ask. Some people are happy to hand over a newborn but I had a lot of trouble feeling comfortable letting anyone hold my daughter when she was so small. Still, this baby was so vulnerable and sweet looking, my arms ached to have her in them.

"You can try," the woman didn’t seem taken aback at all. "She might cry. I think that’s a good sign, actually. I think she might be attaching to me."

She handed over the tiny baby who clung to her shirt and howled as soon as I took her. "I’m so sorry," I said to both the woman and the baby. "She wants to be with you."

It turned out this woman had four grown children of her own. She had decided to become a foster mom to infants to fill her empty nest after her children left home, and to help otherwise disenfranchised babies get some kind of start in life.

"I don’t want to keep them," she admitted. "But it’s perfect for me. I take them for as long as needed until they find an adoptive family."

I felt filled with admiration and respect for the stranger in front of me. I’ve always thought one of the worst things about having children is that they grow up and leave you. Maybe when my children were older, I could do the same thing.

"Do you think anyone will want to adopt her?"

"We don’t know the extent of the crack damage yet," the woman said, stroking the fine black hair on her daughter’s head. "But I hope so."

I know people give their babies up for adoption for all sorts of reasons and that sometimes — maybe often — it’s the most responsible thing to do. My friend C. got pregnant at age 18. A devout Catholic, she couldn’t consider abortion. But C. was young and immature, one of eight children in her own house. Her parents had their hands full with her younger brothers and sisters and did not want to take the baby. So they encouraged her to give it up for adoption, which she did, to an older couple who had long wanted a child of their own. In some ways it was an ideal situation for everyone. The couple got the baby they had always wanted and C. was able to go to college without the financial burden and social stigma of being an unwed mother.

But to be unwanted, to be rejected by the woman who carried you in her womb for nine months and by the man whose genetic makeup you share, seems so sad. It’s hard enough for some of us to feel wanted and loved when we have a biological mother and father who do their best. I can only imagine how much harder it is for someone whose biological parents give them up for adoption.

I’ve always wanted to adopt. But I’ve been scared too — caring for a child is such a huge responsibility. What if I’m not good at it? What if my adopted son or daughter hates me? What if I mess things up?

"When they find a family for her, will you be able to let her go?" I asked the woman before we said goodbye. Fostering children seems like such a good idea. But my heart hurts thinking about when it would be time for them go.

She kissed her baby on the cheek. "It will be hard," she whispered. "But I’ll know that I gave her the best start I could."