After undergoing hormone therapy, a 30-year-old transgender woman has been able to breastfeed her adopted baby. Her doctors believe it may be the first such instance reported in medical literature, according to a case study protocol in the journal Transgender Health.

Tamar Reisman, who co-authored the study, is an endocrinologist with the Center for Transgender Medicine and Surgery at Mount Sinai Hospital in New York. She says the case is important for two reasons. First, it proves that functional lactation—breastfeeding that provides nutrition—can be produced in transgender women. She also sees a broader trend: “Transgender healthcare, which has historically really been underground, is now moving to mainstream medicine,” she tells Tonic.

According to the study, the woman’s partner was pregnant, but didn’t want to breastfeed. The trans woman—who’d been taking feminizing hormones for six years and had developed fully grown breasts without augmentation surgery—wanted to be able to breastfeed. (Specifically, she was taking progesterone, a type of estrogen, and spironolactone, which blocks testosterone.) Reisman and her study co-author Zil Goldstein, they adapted an existing treatment protocol by using hormones to simulate pregnancy, the nausea drug domperidone, and a breast pump to stimulate the tissue to produce milk.

Reisman hesitated to speculate too deeply about the woman’s motivations, and the patient herself is not speaking to the media. But research shows that breastfeeding helps mother and child bond; it also has immune-system benefits for the baby. Formula-fed babies are more likely to experience certain kinds of infections than their breastfed counterparts, and women who have breastfed have lower rates of breast and ovarian cancer than those who’ve never nursed.

There are protocols for what’s called “non-puerperal induced lactation”—breastfeeding that occurs without a pregnancy. But, Reisman notes, “those protocols were meant to be applied to cisgender women,” like women who adopt infants and want to nurse.

Part of adapting the process meant blocking testosterone—a necessity for transgender women. Then there was an even more fundamental question: Are there functional differences between cisgender and transgender breast tissue, and would the modified protocols have the same effect?

“Part of the risk was of the unknown,” Reisman says. “What doesn’t exist in the literature is, for example, a nutritional breakdown of breast milk in transgender women.” Would it be the same as in cisgender breast milk? Would a transgender woman produce enough milk, with the right nutritional elements, to support a growing child?

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But Reisman says the actual drugs involved are well understood, with predictable effects; in other words, the risks there are manageable. For example, the patient needed to keep taking spironolactone, which was used to block testosterone, while breastfeeding. That could be a concern, but research suggests very little of it is excreted in breast milk, and the American Academy of Pediatrics sees no problem with its use. And while the nausea drug domperidone isn’t approved by the US Food and Drug Administration, it’s used internationally to increase lactation. (The woman obtained the drug from Canada.)

“Basically, our framework was this,” Reisman says. “We give hormones and medications to create a hormonal environment to mimic what pregnancy does to the body. We mimic delivery. Then we do whatever we can to keep prolactin levels high so breastfeeding can continue.” (Prolactin is a hormone that enables lactation but isn’t available as a drug.)

The patient began treatment about three months before her partner’s due date, essentially undergoing a quasi-pregnancy herself, hormonally. At the first follow-up visit, a month in, she produced droplets of milk; doctors increased her hormone dosages and told her to up her use of a breast pump, which also increases prolactin levels to stimulate lactation. Doctors continued to tweak the protocol as time went on. Three months after treatment began—two and a half weeks before the baby’s birth—she was producing 8 ounces of breast milk a day, and doctors began lowering her doses to mimic delivery.

She was able to breastfeed exclusively for six weeks until her milk production started to dip. Reisman says that’s fairly typical—many women see the same issue around the same time in the pregnancy. “It’s not really clear if that was something that just happened, that happens really frequently, or if we need to rethink her protocol,” she says. The only way to know is to gather more data, by having more people try it.

Either way, it was an easy problem to address: The parents simply supplemented breast milk with formula, as would many women in the same circumstance. The couple’s pediatrician, examining the baby at six weeks, said “the child's growth, feeding, and bowel habits were developmentally appropriate,” according to the case study. The woman continues to breastfeed alongside using formula.

Reisman says both mother and baby are healthy. “I last saw the baby around the six-month mark,” she says. “At that point, he was really cute. And everything was going well.”