We're having a baby!

Well, my friend group is.

I've been part of a tight group of six girlfriends since we were in sixth grade, and now the first of us is pregnant.

I am beyond excited.

I can't sleep for thinking of baby names. I scour Sephora reviews for the best stretch-mark cream, I study Us Weekly's slide show of celebrity strollers, and I hunt for the best doesn't-look-like-maternity maternity clothes.

I preordered a children's book titled Feminist Baby to stake my claim as that aunt.

I'll never forget the time I first saw her tiny bump. Some of us had met for dinner, and the moment she slipped off her coat, I girl-squealed.

I never girl-squeal.

I found myself making sure she sat out of the way of the passing busboys, wanting to pull the chair out for her, then wanting the waiter to bring water faster, and bread, lots of bread! I wanted to order everything on the menu and watch her eat it.

When the waiter brought the wine list, we waved him off. It went without saying that we were abstaining in solidarity.

We chatted for two minutes before I caved: "So, what is it like?" And that unleashed a torrent of questions.

Pregnancy is simultaneously a universal female experience and an unfathomable one. You can't imagine what it's really like until you experience it.

Or, second best, until you see it up close.

Until this moment, I've gotten only as close as a sonogram photo on Facebook.

I'm an only child, and I have only one older cousin. Both sides of my family are bad at reproduction.

No one can stay married long enough.

I've cooed over babies but never held one.

Pip doesn't count.

When I've had an acquaintance announce a pregnancy, I don't feel comfortable asking questions. It feels too personal.

But nothing is too personal between friends of 20 years. So I had a million questions.

How do you feel? Are you nauseated? Are you starving?

Are your boobs awesome? Oh, no, they hurt?!

Does this mean we can order dessert?

She answered our questions and filled us in on all the things she did and didn't expect. She told us the best news ever:

It's a girl!

I tried not to burst into tears. I nearly succeeded.

It was at once surreal and fitting that I was again leaning over a table with these girlfriends to learn about the most momentous experience of a woman's life, just like we had around the lunch table in middle school.

These are the girls with whom I puzzled out puberty. Together, we figured out which razors wouldn't nick your knees and which tampons were the least scary. They reassured me I wasn't the only girl on earth to have slightly unequal-size breasts.

It was an unspoken rule that whoever did anything first reported back to the troops. We compared notes on what to do with your tongue when you kiss. When the first of us saw a guy naked, lunch became a Gray's Anatomy lesson, complete with crude diagrams on a napkin.

And it wasn't just boy stuff. We conferred on SAT prep, college essays - anything big and daunting was tackled as a team.

After college, we no longer hit life milestones in lockstep. That can be a source of jealousy in some friendships, but only if you reduce major life events like marriage or a child to merit badges of womanhood.

I've never felt competitive with these friends because we've always helped each other.

Childbearing is more complicated than shaving your legs. It will take all six of us to get a full sense of this remarkable, insane, beautiful female experience.

Friendship is a longitudinal study of how to be human. We're here to be one another's test subjects and to use our findings to tip the scales toward happiness.

Not that my pregnant friend is our unlucky guinea pig. Yes, she's running the diaper gauntlet first. But she has all of us unencumbered single ladies around to support her. Her baby girl will be the object of adoration of five happy aunties and last-minute babysitters.

Those of us who have children later won't need as much help, because we'll have cribbed notes for years. Plus, we'll get the mother lode of hand-me-downs.

And if any of us is unsure whether having kids is right for her, she'll have five of us living, breathing, spit-up-covered pros-and-cons lists to help her decide.

For the last 20 years, these girls, now women, have been my brain trust. Thanks to them, I haven't had to figure out anything alone.

And, Baby Girl, you'll always have a high chair at our table.

Look for Lisa and Francesca's new humor collection, "I've Got Sand in All the Wrong Places" and Lisa's novel "Damaged" in stores now.

Also look for Lisa's new domestic thriller, "One Perfect Lie," coming in April.