The national body that certifies lactation consultants is investigating whether a consultant in Boise, Idaho, has been inappropriately pushing an unproven procedure on new mothers struggling to breastfeed, according to a letter reviewed by The New York Times.

The lactation consultant, Melanie Henstrom, was featured in an investigation by The Times that examined the explosion in “tongue-tie” procedures, which have become increasingly popular even though there is little evidence that the surgeries help babies breastfeed.

Ms. Henstrom is part of a booming industry of lactation consultants and dentists that aggressively markets the procedures, even for babies that have no signs of tongue-tie and despite a small risk of serious complications.

The procedures often involve a dentist using a laser to sever the bundle of tissues attaching the tip of the tongue to the floor of the mouth. Many tongue-ties are harmless, and there is little evidence that treating them improves feeding. As the procedures have accelerated, some lactation consultants and dentists have also recommended lasering the webbing that connects the lips and cheeks to the gums. Cutting all of these “oral ties” can cost parents hundreds of dollars.

Only three states license lactation consultants, and they face little oversight compared with other medical professionals like nurses, doctors and dentists. A professional body, the International Board of Lactation Consultant Examiners, issues credentials to 19,000 lactation consultants in the United States. The board’s guidance says that consultants should not diagnose tongue-ties or other oral ties in babies.

Since 2002, according to the board’s website, it has revoked the certifications of only three lactation consultants.

At least three people have complained to the board about Ms. Henstrom’s practices. They said that she diagnosed babies with tongue, lip and cheek ties despite not having the authority to do so, and that she pressured parents to get the procedures done, claiming that untreated tongue-ties could lead to migraines or speech problems. One complainant said that Ms. Henstrom forced open her baby’s wounds after the procedure, causing pain.

Ms. Henstrom did not respond to detailed questions about her practices. In a brief phone interview last fall, she said she had many satisfied clients who believed the procedures had helped their babies.

Since The New York Times published its article in December, the board has sent letters to three people who filed complaints, letting them know that their complaint was “valid and actionable,” and that the board had opened an investigation into Ms. Henstrom.

The board did not respond to questions about the investigation.