Case discussion

This case endorses that lactation induction protocols are also successful in transgender women. Our study is in line with published case reports, in which lactation induction was successful, but the production of milk was not sufficient for exclusive nursing [4, 5, 11]. Nevertheless, as the success of induced lactation is often attributed to parent-infant bonding, rather than the possibility of exclusive chestfeeding, this experience is valuable [25,26,27].

The success of non-puerperal lactation induction and the amount of milk produced depends on several factors [28, 29]. Physical stimulation of the breast tissue is an important factor in promoting lactation in non-puerperal breasts. In our case, due to a short lingual frenulum, the infant latched suboptimally, causing suckling problems. This caused our patient to discontinue lactation after two weeks. These suckling problems may have contributed to low milk production and a shorter period of lactation compared to cases described by prior reports [4, 5, 11]. Another contributory factor may be the time our patient used a breast pump to stimulate the breasts in comparison to other studies. Though our patient started manual stimulation and expression almost 20 weeks prior to delivery of her child, she only started using a breast pump three weeks before delivery, because labour was induced at approximately 38 weeks of gestation due to gestational diabetes. The period our patient was able to use a breast pump prior to the birth of her child was short compared to at least six weeks described in other reports and may have contributed to the low milk production [4, 5, 11]. Our participant refrained from visiting the lactation consultant provided by the hospital, but chose to be guided by a lactation consultant outside of our hospital, hence we did not discuss pumping advice.

Prenatal development of mammary tissue is similar in both males and females. In cisgender women breast development starts at puberty under influence of estrogen. Breast tissue composition changes during pregnancy and lactation [30]. In transgender women breast development occurs after initiation of gender affirming hormone therapy; typically combining estrogen with an anti-androgen. The breast of transgender women are indistinguishable from those of cisgender women on radiography [30, 31]. Nevertheless it is suggested that compared to cisgender women, transgender women have smaller breast and may not reach full breast maturity [30]. Successful lactation is independent of breast volume [32]. However, studies suggest that women with mammary hypoplasia and inadequate glandular tissue may be at risk for lactation failure [33,34,35,36,37,38].

In our case and the case presented by Wamboldt 2021, the breast size and maturation has not been described [5]. The cases presented by Reisman 2018 and Weimer 2023 do respectively describe degree of maturation and size [4, 11]. In Weimer’s report the patient also underwent mammogram with ultrasound for a medical reason, which was notable for extremely dense breast tissue [11]. Nevertheless, the breast tissue of lactating transgender women has not been analyzed yet and have not been uniformly described in previous published cases. Therefore, the effect of breast maturation on the success of induced lactation for transgender women is not known.

In our case report we did not analyze the nutritional value of milk produced by our patient. Only one previous report has assessed the milk produced by their patient. Weimer et al. assessed their participant’s milk and found values of fat, lactose, protein and calorie were comparable and even higher than those in term milk produced by cisgender women. They did not assess micronutrients and bioactive factors [11].

Recommendations for clinical practicePhysiology and methods for lactation induction

Increased levels of estrogen, progesterone and prolactin during pregnancy prepare the breast for lactation. Estrogen and progesterone inhibit lactation, but stimulate breast development, as proliferation of glandular tissue is stimulated by estrogen and the proliferation of ducts and lobules are stimulated by progesterone [39]. After childbirth and delivery of the placenta, the levels of estrogen and progesterone drop drastically, allowing prolactin to trigger lactation [40]. For non-puerperal induction of lactation, one has to mimic the physiological changes of breasts that occur due to pregnancy and childbirth. This may comprise both non-pharmacological and pharmacological methods [28]. Lactation induction is most effective if these methods are used in conjunction with one another.

Pharmacological methods rely on mimicking pregnancy by first increasing the estradiol and progesterone dose to optimize breast development and composition for lactation, as would naturally occur in pregnancy.

Subsequently, a galactogogue can be started to increase prolactin levels to eventually initiate and maintain milk production. Most galactogogues interact with dopamine receptors to increase prolactin levels. Different galactogogues are available and the choice for a galactogogue may be based on its side effects, and maternal and neonatal safety. First choice for a galactogogue may be domperidone or metoclopramide, as the efficacy of both these agents for lactation induction are well reported, and are safe for both the parent initiating lactation induction and infant [28, 29, 41,42,43]. It should be noted that both drugs may have notable side effects that have to be taken in account. Metoclopramide may cause extrapyramidal side effects such as bradykinesia, tremor and other dystonic reactions [41, 44]. These side effects are seldom seen in domperidone, since domperidone crosses the blood–brain barrier in minimal amounts compared to metoclopramide [45]. Domperidone and metoclopramide may cause QT prolongation [46, 47], however this effect is more often seen in domperidone than in metoclopramide [48]. Due to this effect it may be difficult to obtain domperidone in some countries [11]. A systematic review from 2021 reported no significant difference in maternal side effects between domperidone and metoclopramide [43], nevertheless a large observational study from 2018 did find that women reported 3.6 times more side effects using metoclopramide in comparison to domperidone [44],

As a final step, the estradiol and progesterone dose should be decreased to mimic the effects of delivery. This will revert the inhibition of prolactin, causing a rise in prolactin to initiate or enhance lactation.

Non-pharmacological methods may include using a breast pump to stimulate the breasts, manual stimulation of the breasts and optimal infant suckling. Successful lactation induction by solely applying non-pharmacological methods have been reported in cisgender women, however, often non-pharmacological and pharmacological methods are combined.

Considerations and recommendations

We suggest a thorough medical history taking prior to initiation of lactation medication. Medication used for lactation induction may have negative side effects and may be contraindicated based on the patient’s medical history. Even for patients who have previously taken estrogen, risks may be altered due to higher dosages for induced lactation. The most important patient factors to consider include: (family) history of thrombosis and smoking over the age of 35 years, as estrogen increases the risk of thrombosis [49], and cardiac irregularities, as both domperidone and metoclopramide may cause QT prolongation [46, 47].

We recommend conducting an electrocardiogram on patients with a (family) history of cardiac irregularities.

Care providers should explore the expectations of the parent desiring induced lactation, and manage these expectations by explaining that while exclusive nursing is often not achievable, it is not the sole purpose of lactation induction.

Some transgender women who desire to induce lactation may use anti-androgen agents. Spironolactone is often used, and though it crosses the placenta and into human milk, it is considered safe during chestfeeding [50,51,52]. Though these effects have not been described after birth in chestfeeding, it is important to inform and counsel patients using anti-androgen agents who wish to pursue lactation induction about the potential impact of these medications on the genital development of the newborn [50,51,52,53]. Taking into account that using anti-androgen agents may have a beneficial effect on gender dysphoria in transgender women and weighing this against the very small chance of it having impact on genital development.

Transgender women pursuing induced lactation should be referred to a lactation consultant to optimize breast stimulation techniques, develop pumping schedules, support in infant latching and chestfeeding positions and for adequate support.

Though the optimal dosage and route of administration of medication is not yet known, we suggest the following treatment regime:

Intake appointment in an outpatient clinic, preferably before conception or in first trimester. Analyse risk factors, allergies and blood-hormone levels.

At end of first trimester (12–13 weeks of gestation), after confirmation of viable intrauterine pregnancy, increase estrogen dosage to 150ug once daily and start progesterone 100 mg once daily. This should preferably be started three to five months prior to the expected due date. Start stimulation of breast tissue by massaging, nipple stimulation. Discuss referral to a lactation consultant.

At approximately 17–18 weeks of gestation, monitor blood hormone levels, and increase estrogen to 250ug once daily.

At 20 weeks of gestation, start domperidone 10 mg four times daily after two weeks.

At 21 weeks of gestation, double domperidone to 20 mg four times daily.

At 23–24 weeks of gestation monitor blood hormone levels, increase progesterone to 100 mg two times daily. Adjust estrogen dosage according to blood-hormone levels.

At 27–28 weeks of gestation monitor blood hormone levels, increase progesterone to 100 mg three times daily. Adjust estrogen dosage according to blood hormone levels.

At least six weeks before the expected due date, start manual breast pumping of breast to at least every three to four hours, at least once nightly.

Four to six weeks before the expected due date, decrease estrogen dose to 100ug once daily and discontinue progesterone.

At onset of milk production decrease estrogen dosage to 50ug once daily. When milk volume increases an electric pump may be used, preferably a hospital grade double electric breast pump.

After birth of the newborn continue pumping, including after feeds. Supplemental feedings with infant formula might be necessary if milk produced is not sufficient. If the gestational parent is also nursing, continue pumping at least every three hours.

Suggestions for future research

Scientific literature on lactation induction in transgender women remains scarce. Future research should focus on optimal treatment regime, the development of the infants that were chestfed by transgender women and the milk composition produced by transgender women. Furthermore, there should be a focus on if the extent of breast maturation has an influence on the success of induced lactation, as it would be beneficial to adequately counsel transgender women seeking help in lactation induction.