The room is quiet, save for soothing, meditative tunes, as a few women sitting cross-legged on yoga mats do slow neck rolls — first to the right and then to the left.

The neck rolls are followed by upper body circles, then, sitting upright, everyone takes a deep breath in through the nose, and exhales through the mouth with a sigh.

Welcome to prenatal yoga, which is not too entirely different from a regular yoga class except that the women here are in different stages of pregnancy.

"If a woman is able to become physically fit before giving labor, she may have an easier time with recovery," says prenatal yoga instructor Brynne Caleda. "If a woman embodies the tools of yoga while pregnant, not only will she benefit from yoga while pregnant but her body and mind will hold the memory of the physical and mental fitness when dealing with the joys and trials of being a new mother."

A minimum of 30 minutes of moderate exercise a day is recommended for women with normal pregnancies, according to the American Congress of Obstetricians and Gynecologists. Approved activities include yoga, walking, swimming and water aerobics.

While pregnant women may join a gentle yoga class and modify moves on their own, a growing number of prenatal yoga classes across the island cater to expectant moms.

Just like regular class, there’s an emphasis on the breath, on rooting "sits bones" — the part of the pelvis that a person sits on — to the ground, and poses that improve strength, flexibility and balance.

Yoga prepares the body for the physical demands of labor, according to Caleda, and is appropriate for beginners as well as experienced practitioners. Still, she recommends that women who did not practice yoga before pregnancy wait until the end of the first trimester, and that they first get approval from their physician.

Otherwise, pregnant women can practice yoga all the way up to the last minute before giving birth.

Carey Stanley of Kailua did just that; she was in yoga class even at a week overdue.

Stanley, an avid athlete who runs and swims, said she practiced yoga before becoming pregnant and felt it was even more essential during pregnancy, particularly for the hips and back.

For her, it was a way to remain relaxed and calm.

"I didn’t take any of the birthing classes — LaMaze, Bradley and hypnotherapy," she said. "I felt that what you could get out of it, I can get here."

It’s also nice to connect with other women who are going through the same changes in their bodies, she said, whereas, in a regular yoga class, she might be the only one with a big belly.

While some of the poses do have to be modified (avoid lying on the belly during a sunrise salutation sequence, for instance), the class does familiar poses such as downward dog, bridge (a gentle backbend), child’s pose and tree pose (one foot resting on the opposite leg while standing). Warrior II, with arms outstretched, gives the legs, chest and hip flexors a good stretch.

Moves to avoid include inversions (handstands and headstands), strong twisting postures, and lying on the right side of the body, which may restrict blood flow to the baby, according to Caleda.

In class, Caleda incorporates breathing exercises — the breath, after all, is the key to remaining calm.

The classes also include Kegels, those much-touted exercises to tighten the pelvic floor that doctors recommend before giving birth and for women in general.

To finish up in Caleda’s class, participants issue a resounding "ohm" chant to the child they are carrying.

After giving birth, new mothers can continue stretching routines at a growing number of mother-and-baby yoga classes around Oahu. These classes teach many of the same poses, but also include the baby (if awake and cooperative) by incorporating moves that allow mothers to lift, cradle or keep their infants on the mat in front of them during class.