Watching my sister unpack her double stroller from her SUV always fills me with a mix of admiration and relief. I love the fact that she’s given me multiple nephews, but I also love that she’s only getting one from me.

My son is an only child, and it’s gonna stay that way. That may sound sad to some, but for my family it’s perfect.

Before becoming pregnant with our son, I always imagined my husband and I would have at least two kids. But pregnancy has a way of changing our bodies, and sometimes, our minds, too.

After trying to conceive for some time, I was elated to get that positive test, but almost immediately I started feeling sick, which kind of robbed me of some of the joy I’d expected. By other people’s standards my pregnancy wasn’t a hard one—I wasn’t considered high risk and I wasn’t hospitalized—but being pregnant was really hard on me.

By the halfway point in my pregnancy, my husband and I decided that we were only going to do this once. It made sense not only when we considered how horrible I was feeling, but when we ran the numbers, too (as somebody who’s felt the crushing weight of student loans upon graduation, saving for college is a priority in my household). Financially and physically, having just one child felt like the perfect fit for us.

We were happy with our decision, but even before my son was born people began asking when we would have another, and most didn’t like the answer.

“Oh, you’ll change your mind,” was the common (and condescending) response.

Even my own doctor fell into that camp.

“When are you going to start trying again?” she asked shortly after my son was born.

“We’re not,” I told her.

“Why not? He’s so perfect?” she said. “Give it time, you’ll want another.”

Colleagues, friends, family members—hardly anyone trusted that we’d thought this through, and everyone had an opinion.

“It’s not right, he needs a brother or sister. He’s going to be lonely.”

“What if something happens to him? You’ll have no other children.”

“Two kids are not that much more expensive than one.”

“Couples like you who only have one child should have to pay higher taxes because you’re not contributing enough future workers to society.” (Yes, someone actually said that.)

I’d grown so accustomed to the negative reactions that when a nurse ended our newborn’s wellness appointment by asking when we were going to start trying again, I braced myself for another negative comment, but her response was perfect.

“That’s great,” she said. “I love it when people recognize what’s right for them.”

Her comment lifted me up and became my motto.

Whenever I felt like someone was judging me for our decision to stop at one, I remembered what that nurse said: I’m recognizing what’s right for us.

I love being a mom of one, but I think I would be overwhelmed and unhappy with two or three. In fact, I know I would be. We stopped at one because we recognized my limits. These days, when people tell me I should have another, I don’t take it personally (I can’t, I’m too busy chasing a 2-year-old). I also have two year’s worth of comebacks saved up for every argument.

Yes, my son will have a different experience than children who have siblings, but he won’t be lonely. He’ll have cousins and classmates and friends.

Yes, something could happen to him, but children aren’t tires—a sibling isn’t a spare.

Yes, having two kids is significantly more expensive than one, especially if you’re putting hundreds of dollars into an education savings account each month.

No, I should not have to pay higher taxes.

Knowing all this, and knowing that my son is my only baby, watching him leave babyhood behind has been hard. When he was 19 months old I took him for his last evening walk in the baby carrier that he was almost too big for.

He fell asleep as I walked, and as I stood at an intersection waiting for the light to change, I felt his warm, heavy little body on my chest and felt a sense of loss, too. I will never feel another baby of mine sleeping on me like that.

For the briefest moment I thought about having another baby to fill up that carrier, but by the time the light changed I was over it. Baby cuddles are great, I thought, but there’s a lifetime of parenting that comes after the cuddles.

“You can put the dog in the Ergo if you miss this. You don’t need another baby,” I thought.

When I watch my sister unload her double stroller and strap everybody in I’m in awe of her ability to do so much at once. She is an amazing mom to multiple children, but I know myself well enough to know that I would be overwhelmed in her place. I’m a great mom to one boy, but I can’t see my body handling another pregnancy or myself handling the stress of parenting two or three kids.

The second seat in my double stroller is reserved for my little dog, and I like it that way.