When Nancy Redd was pregnant with her first child, her birth coach dropped some truth about labor’s dirty secret.

“She said, ‘You need to listen to (me) and listen good. You are going to feel like you need to poop, and you are going to poop … Just relax and act like you are on the can and you’ll be fine,’” Redd, 36, of New York City, told TODAY.

While women feel embarrassed about pooping during labor, it’s totally natural. And, it might even be healthier for both mom and baby.

“If women poop during the delivery they are using the right muscles,” said Dr. Christine Greves, a doctor at the Center for Obstetrics and Gynecology at Orland Health.

Redd was surprised, but she felt relieved someone told her about it.

“I was luckily prepared,” she said.

Redd — the author of “Pregnancy, O.M.G.!” — shares her story because she wants to destigmatize pooping during labor.

“You might poop, and I want you to know it is OK,” she said. “I would like to live in a world where we are confident and comfortable."

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Hospitals don’t track how many women poop during labor, Greves said, but added that it’s extremely common. That’s because the muscles used during labor are the same as used during defecation.

What's more — pooping during labor might help babies develop their microbiome, the bacteria that lives on and in people, which helps with everything from digestion to being able to fight off colds. Newborn babies do not have microbiomes.

“Babies are born with a sterile gut. They don’t have any bacteria in the large intestine,” Tracy Shafizadeh, director of scientific communication at Evolve BioSystems, told TODAY.

As the baby travels through the vaginal canal she’s exposed to mom’s bacteria. When mom poops, baby can pick up important gut bacteria, Shafizadeh said.

“We think ‘Oh god I don’t want people to see me poop,’” said Shafizadeh. “But that is how mom’s bacteria can be transferred to baby.”

One bacteria babies once received from their moms is B. infantis, which defends against harmful bacteria, such as E. coli, Staphylococcus or Streptococcus.

“(It) is really important for babies for the first six months of life and highly involved in developing the immune system for babies and helps with microbiome in baby’s gut,” said Shafizadeh.

Most babies born since 1980 lack B. infantis because of increased rates of Caesarian section births, as well as formula feeding and antibiotic use. Shafizadeh said restoring B. infantis in babies' guts, which makes for a more acidic environment, allows healthy bacteria to thrive.

“B. infantis is creating a protective environment,” Shafizadeh said.

So, there might be a good reason why women poop during labor. But, of course, don't worry if going No. 2 wasn't part of your childbirth experience.

Greves said that the American College of Obstetricians and Gynecologists does not recommend exposing babies to bacteria or "vaginal seeding." In vaginal seeding, moms swab their babies' faces with bacteria from their vaginas to share healthy bacteria with baby. There’s not enough research to show it works.

“Before changing things, I like to see good evidence to support it,” Greves said. (Before vaginal seeding can be done, patients need to be tested for staph and sexually transmitted infections, including chlamydia and gonorrhea, so mom doesn't transfer anything dangerous to baby.)

Still, Greves believes it is important for women feel comfortable about labor — no matter what happens.

“I don’t think a mom should to feeling guilty whether she poops or doesn’t poop,” she said. “Poop happens.” Read more: What baby poop reveals about the gut microbiome