Riding home in a taxi at 9:30 on a Wednesday night, I knew I was in trouble when I heard a voicemail message from Emily saying she'd forgotten her keys and would be waiting for me at the Starbucks near our apartment. What I didn't know was how much trouble.

Sweeping into the coffee shop, I offered the breeziest of apologies. Emily was not charmed.

"I've been waiting here for two hours," she fumed.

"It's not my fault you forgot your keys," I retorted—reasonably enough, I thought.

On the walk home, I rolled out the excuses. I'd been at a work party, a networking thing. The music was loud, and I didn't hear the phone ring. I was on my way out when I ran into someone I knew. And so on. She wasn't having any of it. "You smell like liquor," she groused.

Back at our apartment, the argument continued, to my astonishment. If it had only been the one time, it would be one thing, Emily informed me. But I'd been out every night in the previous two weeks (this was only a mild exaggeration). Then came the punch line: "How are we supposed to have a baby in a few months if you never even come home after work?"

Aha! I thought. So that's what this is about.

I should have known. When you're 30 years old, like we are, and when you've been married three years, like we have, everything becomes about having a baby. No matter what we're talking about—our jobs, our friends, an upcoming vacation—reproduction is always just a free association away. It has even infiltrated our sex life: Yesterday, Emily confessed that her dirty thoughts about me now trigger a fantasy of me knocking her up.

And when we manage to avoid talking or thinking about it for a few hours, we can always be sure someone will remind us—if not our families, then our friends. (The other day, I got a call at work from my friend Nina. "Do you have something to tell me?" she demanded. I told her no, and asked why she thought I did. "I had a dream that Emily was pregnant!" she squealed.)

It's not as though the obsession is unwarranted. On the subject of procreation, you could say that Emily and I are like two companies that have reached an agreement in principle but are still negotiating over the details. For starters, we both know we do want to have kids, preferably two of them, ideally one of each sex. We also both want to be young parents, a desire that is, for me, rooted in my own childhood. My father was almost 40 by the time I was born. As a 12-year-old, I remember being faintly embarrassed by his bad back and outdated sense of humor, and envying the kids whose dads could throw a spiral and tolerate popular music. Emily had the opposite experience: Her parents had her when they were in their twenties, and the relatively small generation gap shows in her close relationship with them.