CHICAGO — After struggling to breast-feed her first two children, Nyssa Retter was determined to do better with her third.

She gave birth without painkillers, which may make newborns slightly drowsy. She chose a free-standing birth center staffed with lactation-savvy midwives. She had skin-to-skin contact with her daughter immediately after birth and consulted with midwives when her daughter cried and screamed between near-constant feedings.

But at the baby’s two-week weigh-in, Retter learned that, despite all her efforts, her daughter was still below her birth weight and would need formula supplementation.

It was only then that Retter verbally cornered a lactation consultant and finally received a diagnosis.

"I have IGT, don’t I?" said Retter, who had read online about insufficient glandular tissue, a breast condition strongly associated with the inability to produce enough milk for a baby.

"Yes," said the lactation consultant. "I think you do."

In an era when "breast is best" is trumpeted by the government, by the medical profession and even by baby formula companies, an estimated 1 to 5 percent of women are physically unable to produce enough milk to feed their babies.

These women are often ignored by doctors, given the brushoff by old-school lactation consultants, and essentially left to fend for themselves.

Women often see multiple health professionals without getting even a diagnosis, much less comprehensive care, says Retter, a co-administrator of the 1,300-member IGT and Low Milk Supply Support Group on Facebook.

"I would love for every obstetrician to actively acknowledge this and work with mothers to do everything they can to maximize their milk supply," Retter says. "I would just love for people to even know that it exists, just to acknowledge us. Just to know that we’re here and help take care of us and support us."

It’s a measure of how little attention chronic, primary or "true" low milk supply has received, that no one knows for sure how many women are affected.

"You cannot find a number for this," says Marianne Neifert, a clinical professor of pediatrics at the University of Colorado Denver School of Medicine who co-authored a 1990 study of 319 breast-feeding women that found 15 percent of the women were unable to produce sufficient milk by three weeks postpartum.

Neifert attributes most of the low supply to problems such as sore nipples and infant feeding difficulties, but she says 4 percent of the 319 women appeared to have chronic low milk supply.

Today, experts say that 1 to 5 percent of Western women are affected, Neifert says, but she hasn’t been able to find any additional studies that support those numbers.

"It think it’s a significant number of Western women," says Neifert. "I would say 4 percent or just under 5 percent."

The most commonly recognized causes of chronic low milk supply are IGT — in which it is believed that the milk-producing structures in the breast have failed to develop properly — and breast surgery, in which the ducts, or tubes, that carry milk to the nipple may be severed.

Research on IGT (also called breast hypoplasia and tuberous breasts) and its effect on lactation is almost nonexistent, with the most widely quoted study cobbled together in 2000 by enterprising nurses and lactation consultants who assembled 33 breast-feeding women with breast characteristics that they suspected were linked to low milk production.

The results were striking. Women with characteristics such as a wide space between the breasts, breasts with a pronounced lack of fullness, breasts with unusually small base circumferences, and breasts that didn’t grow during pregnancy, experienced very high rates of chronic low milk supply.

In the first month, 55 percent of the women in the study produced half or less than half of the milk their babies needed.

Other causes of low milk supply include thyroid disorders, pieces of retained placenta, which would likely be accompanied by abnormal postpartum bleeding, polycystic ovary syndrome, which involves an imbalance of sex hormones, and Sjogren’s syndrome, an autoimmune disease.

There’s currently no clear-cut test for IGT, and some women with very strong signs of it make enough milk. Similarly, surgery-related lactation problems are hard to predict.

So the only way for a woman with risk factors to really know if she has chronic low milk supply is to try breast-feeding with proper technique and pumping, and see if it works.

The process can be emotionally brutal.

"It was the most heartbreaking thing I’ve ever gone through," says Nichole Pool, 27, of Tehachapi, Calif., whose baby nursed and cried more or less continually for three days, despite help from a lactation consultant. "Here’s this tiny little person who literally depends on me and my husband for everything to keep her alive, and I don’t understand why she’s screaming. I just want to fix it. She wasn’t going to the bathroom or anything, and I was just like, ‘Is something wrong with her?’ I didn’t sleep for three days because I just wanted to hold her and make it better."

There are some good lactation consultants, according to Krystal Revai, a fellow of the Academy of Breastfeeding Medicine, but if a woman has chronic low milk supply, she should seek the help of an ABM physician, a doctor with breast-feeding expertise. If you’re choosing among lactation consultants, some low milk supply mothers suggest going with one who is board certified and more likely to be up-to-date in her knowledge.

Herbs such as fenugreek and the medications metoclopramide (Reglan) and domperidone are sometimes used to boost milk supply, but evidence that they work generally comes from poor-quality studies, according to the ABM. Reglan’s potential side effects include depression, and domperidone is not FDA-approved in the U.S. Herbs have allergic potential and may harbor contaminants.

Some women with low milk supply switch to formula feeding, saying that grueling pumping routines produce minimal milk and major stress.

Others breast-feed as much as they can, for months or even years.

"Dealing with low milk supply, it’s whatever keeps you sane — that’s the most important thing to do," says Retter, 28, who has been breast-feeding her daughter for two years, supplementing with formula and documenting her experience at her blog, Diary of a Lactation Failure. "If (breast-feeding) works for you, it’s worth it to pull through the really hard days, because once you get an older nursing baby, it’s a lot of fun."

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Dr. Corrine Kolka Welt says she gets calls all the time from women with low milk supply who want to try prolactin.

But Welt, an associate professor at Harvard Medical School and Massachusetts General Hospital who did a promising pilot study in which injections of prolactin, a hormone that triggers milk production, increased milk supply in mothers of pre-term babies and women with prolactin deficiencies, has nothing to offer the women who call. Genzyme, the company that produced the form of prolactin she used in her study, has since stopped making it, and no one else has stepped in.

Although many women suffer from chronic low milk supply, they only do so for a limited amount of time, Welt says. That makes medications less profitable than, say, insulin or Viagra, which patients use for years.

"If someone would take this up and make it, I think there would be a lot of women who would be interested in trying it," Welt says.