When I told people I was taking a course called Maternal Fitness, most assumed I was going to some sort of pregnant aerobics class. In fact, Maternal Fitness is a program that prepares women for labor by teaching them a unique set of abdominal exercises. The class, based in a studio in Union Square, has a zealous following that includes magazine editors, actresses, and models – Elle Macpherson is a fan.

The Maternal Fitness studio offers a pregnancy exercise program that, as founder Julie Tupler puts it, prepares women for the “marathon of labor.” The program consists of a series of exercises called the Tupler Technique, which strengthen the transverse abdominal muscles. Instructor, Ms. Tupler, who founded the studio in 1994, is also a registered nurse and certified childbirth educator. She claims that if a woman sticks to her regimen of very focused exercises for the abdominal muscles throughout her pregnancy, she will have a much easier labor and her abdominals will flatten soon after giving birth.

Clients attest to the results. There are stories of women leaving the hospital wearing their pre-maternity jeans. But what people really rave about is the effectiveness of their labor. “The exercises I learned really worked in labor,” Ms. Macpherson enthused in the Maternal Fitness brochure. “I don’t think Flynn could have been brought into the world with only 20 minutes of pushing without them.”

Forget the pre-maternity jeans – now that I’m entering my seventh month of pregnancy, words like “only 20 minutes of pushing” are the real music to my ears. So, with a mix of eagerness and curiosity, I called to sign up for a class.

Maternal Fitness, which is taught by registered nurses who are also certified physical trainers, offers classes in six-session workshops. Classes meet once a week for 90 minutes and cost $325. Only 12 women are admitted to each workshop. “You’re lucky,” Ms. Tupler said when I called. “Usually there’s a waiting list.”

I arrived at Maternal Fitness’s Union Square Studio to find the class filled with pregnant women and their partners (all husbands, in this case) seated on a classroom floor carpeted wall to wall in neutral-colored exercise mats. Partners are advised to attend the first two classes, which consist almost entirely of lectures.

“I want you guys here because I have a job for you,” the lithe, attractive Ms. Tupler explained, after likening herself to a drill sergeant. “I want you making sure these ladies are doing their exercises. You’re what I call the Fetus Police.” I suddenly felt less bad that my own partner couldn’t make it.

What followed was an hour and a half’s explanation of the Tupler Technique, complete with trial demonstrations of the foundational exercises, referred to as the BAKS – an acronym for Belly Breathing, Abdominals, Kegels, and Squatting. In addition to those exercises, we were taught how to get up and down without taxing our abdominal muscles (to go from lying to sitting, for example, it’s best to roll onto your side without lifting your head, then use your arms to bring yourself to a seated position). We were also instructed – sorry, folks – on the best way to take a bowel movement, a topic about which Ms. Tupler is passionate.

“Taking a bowel movement is the single best preparation for labor,” she told us. “My clients tell me they think of me on the toilet all the time,” she said, touching her heart. “And I think it’s the greatest compliment.”

Things to consider during this activity: keeping one’s feet elevated on a stool or some phonebooks to simulate a squatting position and, most importantly, using your abdominal muscles to push back, not down. “Think of it like squeezing a tube of toothpaste,” Ms. Tupler said.

I learned two main things from the lecture. Number one: The transverse muscle is important. “It’s my favorite muscle,” Ms. Tupler remarked more than once in what might be considered an understatement. Not only does her program call for 500 contractions of this muscle each day, but she expects it to be employed during every activity. “Are you working transverse?” she said when a class member coughed.

Number two: Diastasis – the separation of those six-pack abdominal muscles – is our greatest enemy. Diastasis can result from carrying a large child, from having done abdominal exercises incorrectly before pregnancy, or from the hormone relaxin, which is released during pregnancy to relax the joints in preparation for labor. “With diastasis, muscles can literally split apart like a broken zipper,” Ms. Tupler said ominously. Some women’s pregnancy diastasis never heals, leading to lower back pain and ill-protected internal organs, and, on the vainer side, pouchy “mommy tummies,” as Ms. Tupler called them.

The Maternal Fitness exercises seek to minimize the diastasis during pregnancy and eliminate it afterward. A 2001 study at Columbia University concluded that women who had done the Maternal Fitness program had smaller diastasis than a control group of women who did not exercise during their pregnancy.

After the second class, which consists of another lecture, this one focusing on episiotomies, the rest of the Maternal Fitness classes are more movement-based. The Tupler Technique moves are done to tango music (Ms. Tupler is a tango enthusiast; “tango is my passionate hobby,” she says).

Some participants leave the first class overwhelmed, however. “My head was swimming,” Mandy Hackett, a classmate due in early December, admitted to me. She’d heard about the class through a friend and hoped it would supplement her childbirth course but, after the first class, was tempted to throw in the towel. Two days later, however, she found she couldn’t. “My husband wouldn’t allow it,” she said. “He totally took his Fetus Police job seriously. He was like, ‘Do your exercises or I’m calling Julie Tupler.’ So I did them, and I love it now.”

And what about me? Knowing that Ms. Tupler will be reading this article, I’ll admit to not doing her exercises as often as she’d like me to. But I do think of her in the bathroom.