Her partner was pregnant with their baby, but had no plans to breastfeed, The Washington Post reports.
The woman had already been on a hormone regime for six years, but had yet to undergo any gender-based surgeries.
Reisman, an endocrinologist with the Center for Transgender Medicine and Surgery at Mount Sinai Hospital in NY, said doctors used protocols for "non-puerperal induced lactation", in which a woman is stimulated to lactate.
"In some circumstances, modest but functional lactation can be induced in transgender women", authors of the study, Tamar Reisman and Zil Goldstein from the Mount Sinai Centre for Transgender Medicine and Surgery in NY, concluded in the results.
At the end of a year taking hormones, almost half of the transgender patients in the study had a bra cup size of less than AAA, roughly 8 centimeters.
However, the domperidone used in the case was obtained from Canada since it is not available in the United States due to the "FDA's concern about its association with cardiac arrhythmias, cardiac arrest, and sudden death when used intravenously", according to the case study.
What's also unclear are the long-term effects the breastmilk could have on children, such as subtle effects on cognitive development. Although this drug was originally developed to help treat stomach issues, it has been used to help increase milk production as well.
Women who breastfeed have lower rates of breast cancer and ovarian cancer than women who have never breastfed, the authors note in their study, but those rates would not transfer to breastfeeding in biological males who can not develop breast or ovarian cancer.
She later supplemented feedings with formula because she was not producing enough milk, the study said.
Her breasts were Tanner stage IV.
Over a three month period she gradually started to produce more and more milk, and two weeks before the baby arrived she was producing eight ounces a day. And during that time, the baby's paediatrician reported that the child's growth, feeding and bowel habits were developmentally appropriate.
The anonymous USA trans woman continued for at least six months, giving the baby a mixture of formula and breast milk.
After taking female hormones, medication to block male hormones, a drug to induce milk production and regular use of a breast pump the patient was able to feed the child herself. Also, the study didn't look into the nutritional quality of the breastmilk produced, which would be good to know.