A transgender woman from New York was successfully able to breastfeed her partner's newborn baby, in what's being touted as a medical first.

The unnamed woman, a 30-year-old assigned male at birth, told Dr. Tamar Reisman at the Mount Sinai Center for Transgender Medicine and Surgery her pregnant partner didn't want to breastfeed, but she felt it was important for the baby's wellbeing.

So Reisman helped the woman realize her goal, starting her on a regimen of testosterone-inhibiting hormones and lactation-inducing drugs.

Within three months (and two weeks before the baby was due), the patient had grown what appeared to be fully-developed breasts without surgical augmentation, and was producing eight ounces of milk per day.

Reisman and nurse practitioner Zil Goldstein's report on the case was published in the January 2018 issue of Transgender Health. Though trans woman have reportedly induced lactation by self-medicating, the duo wrote, "We believe that this is the first formal report in the medical literature of induced lactation in a transgender woman."

Breast milk is widely recognized as the best form of nutrition for newborns. However, the study's authors aren't sure if their trans patient's breast milk contains the same nutritional properties as milk from a cisgender mother. The patient did have to supplement the newborn's diet with formula after six weeks, Reisman and Goldstein reported.

Regardless, Boston Medical Center endocrinologist Joshua Safer told the New Scientist that the study is "a very big deal."