At breakfast one morning, my three-year-old stopped slurping her Cheerios and asked, "Mommy, when are we going to get a baby?"

The question wasn't a complete surprise. For weeks, Stella had been announcing the impending arrival of her imaginary sister. "My mommy has a baby in her tummy," she told neighbors and playmates while I simply shook my head. But this was the first time she asked me for a time frame.

I told her, once again, that there was no baby. Then, as disappointment clouded her big, brown eyes, I added, "not yet."

She returned to her Cheerios, and I returned to that troublesome word, "when?"

Stella couldn't have known it, but I have been pondering having a second baby since before the birth of my first. For reasons I can't logically defend, I've always imagined myself with two children. But then Stella's first years were tougher than expected – day care at 13 weeks, ear tubes at 9 months, sleeping habits that still send me to work bleary-eyed on a regular basis. There was the new job, the new house and the new day care. Life keeps getting fuller and more complicated, and I keep putting off another pregnancy.

My husband married me with a similar two-kid plan, but now he says he's happy with one. Like many couples who have left the city for smooth sidewalks and suburban schools, we've become two busy, career-focused people dependant on two incomes. If we had only one child, we could go on vacations. Stella could have any hobby, engage in almost any activity and have every opportunity her parents, both products of cash-strapped multi-child households, missed out on.

Why complicate things with another child?

I ask myself this question frequently. The answer I keep returning to is the image, still in my mind after all these years: A husband, two kids and me.

Why is the pressure to have more than one child so intense? We've got global warming and ballooning college costs, endless work and decreasing net worth. Another baby seems downright irresponsible, globally and personally. Sociology researchers at Penn recently found that one baby adds to the happiness of both parents, while the second baby doesn't affect the happiness of the father but decreases that of the mother. It makes sense to me. For my family, having another baby certainly would lead to less free time, less money and more worry.

But then I remember the advice of my father, who only lectured me about three things in my entire life: securing a good career, going to church and having more than one child. You'd think he's known a shocking number of one-child couples who lost their only child. But this is not the case. His old-fashioned way of thinking about family size hails from a time when infant- and child-mortality rates were much higher, a time when more kids equaled more breadwinners. Now kids are a liability financially. Parents are supporting them beyond the college years and even into their married years when they become parents themselves.

I have argued with my father about career choices and church but never about family size, and now, in my mid-30s, I still can't. I am torn between two future selves, the two-child self and the one-child self. I can see the bank accounts and calendars of each, but I can't see how each one feels. Overwhelmed or overjoyed? Fulfilled or frustrated? All I know is that the window for choosing is closing.

For now, Stella is one of the only 3 year olds she knows without a sibling. At playdates, she follows around crawling babies and tries to hold them on her lap. We can't leave her day-care center until we stop by the nursery to wave to her friends' brothers and sisters.

A fixation with other people's babies is fine. But why does she want one of her own? She's the princess of the family right now. Why would she want to share her plastic dress-up pumps?

Dr. Spock wrote about why three-year-olds are baby-crazy. It's called identification – they want to be like their parents in everything they do, including work and play and looking after tiny babies. Even though they can't be too much help with young siblings at this age, they still have bragging rights as big brothers and sisters.

Though I am reluctant to admit it, the second-child pressure I get from my small daughter is harder to discount than that from my father and society. It's not that I spoil her. I rarely have a problem telling her "no" when she asks for a toy at the grocery store or a piece of chocolate for breakfast. But denying her the lifelong relationship of a sibling seems especially cruel given my own background. I often joke that I would not have reached adulthood if it were not for my sister, who would fix whatever I broke before my parents found out and be my sworn ally against the sadistic, worm-hurling boys in the neighborhood. She listens, even now, to me bellyache endlessly, forgives my tendency toward introversion and transforms into the aunt version of Mary Poppins whenever she's with my daughter. When we fight, it's heartfelt. When we make up, it's a true healing.

I do not have that sort of relationship with anyone else. Not my best friends. Not my parents. Not my husband.

The next time Stella asks about a baby, I tell her she can get a fish, and that answer satisfies her temporarily. Meanwhile, I am looking at the calendar, counting the days until I can try for another baby, whose arrival will mean so much more than the surface struggles of increasing day-care costs, scheduling snafus and medical bills. Another baby, if we can have one, will be a gift beyond quantification. We'll figure out how to pay for music lessons and get to Disneyland some other time.

Jacqueline Marino's nonfiction stories and essays have been published by Cleveland Magazine, The Christian Science Monitor, River Teeth: a Journal of Narrative Nonfiction and other publications. She is an assistant professor of journalism at Kent State University. Her daughter Stella was thrilled when her sister, Charlotte, was born in March, though she still gets teary-eyed when Charlotte gets to ride in the stroller and she has to walk.