Taking oestrogen can suppress sperm production, but different people may be affected in different ways. While some people who take oestrogen do go on to have biological children, other people lose the ability to produce sperm. Unfortunately, it is not possible to predict exactly how oestrogen will affect your fertility.
Studies on the effects of oestrogen on sperm production have conflicting results. While sperm production stopped completely in some participants, sperm production continued as usual in other participants (Jindarak et al., 2018; Schneider et al., 2017).
One study has suggested that longer periods of treatment with oestrogen may be associated with lower sperm counts (Kent et al., 2018). However, this has not been shown in other studies.
Sperm production may come back if you stop taking oestrogen. In a recent study, trans women who had stopped taking oestrogen for an average period of 4.4 months were shown to have higher sperm counts than trans women who had continued to take oestrogen (Adeleye et al., 2019). However, the number of participants in the study was very small.
Given the uncertainty, it is best to assume that within a few months of commencing oestrogen you could permanently and irreversibly lose the ability to create sperm.
However, because feminising hormone treatment may not always lower sperm count, it is recommended to use a birth control method if you wish to avoid pregnancy and are sexually active with someone who is able to become pregnant.
Trans women and transfeminine people who have not undergone orchidectomy (removal of the testes) can store sperm at a specialist clinic by providing a semen sample through masturbation.
Sperm can be stored indefinitely and will not be negatively affected by the length of time it is frozen. Around 85% of sperm survive the freezing process (Huang et al., 2019).
Given that oestrogen can suppress sperm production, fertility preservation through sperm storage is more likely to be successful if the sample is produced before commencing feminising hormone treatment.
If you have already commenced feminising hormone treatment, then it may still be possible for you to produce sperm for fertility preservation, but the chance of success may be decreased.
As noted above, sperm production may come back if you stop taking oestrogen, and so your chance of producing sperm for fertility preservation may increase if you temporarily stop oestrogen for around four months before providing the sample for storage (Adeleye et al., 2019).
Your doctor or fertility clinic may be able to advise you about options for fertility preservation through sperm storage.
Taking testosterone can suppress egg production, but different people may be affected in different ways. Unfortunately, it is not possible to predict exactly how testosterone will affect your fertility.
Although we know that testosterone can stop menstruation and ovulation in the short-term, there is no consistent evidence about its long-term effects on fertility (Cheng et al., 2019).
While one study showed that ovaries of trans men who take testosterone exhibited changes in the tissues (Grynberg et al., 2010), another study showed that the ovaries of trans men who take testosterone remained healthy (de Roo et al., 2017).
Some people on testosterone do go on to conceive and give birth to children. However, given the uncertainty, it is best to consider the possibility that your fertility could be affected by testosterone.
Trans men and transmasculine people who have not undergone oopherectomy (removal of the ovaries) can store eggs at a specialist clinic. This is a medical procedure that requires hormonal stimulation for egg retrieval.
Given that testosterone can suppress egg production, fertility preservation through egg storage is more likely to be successful if the sample is produced before commencing masculinising hormone treatment.
If you have already commenced masculinising hormone treatment, then it may still be possible for you to produce eggs for fertility preservation, but there is a theoretical possibility that the chance of success may be decreased.
Hormonal stimulation for egg retrieval can take at least two weeks and results in temporarily increased estrogen during this period. We are aware that this may worsen gender dysphoria for some people.
After egg storage, pregnancy can be achieved through assisted reproduction if you have a uterus. If you do not have a uterus, then there may be the option of asking a gestational surrogate to carry the pregnancy.
It is important to note that egg storage does not guarantee a future pregnancy. A recent study of 543 people who received assisted reproduction with stored eggs found that 39% of participants achieved a live birth (Cascante et al., 2022).
There is evidence that egg quality declines with advancing age, which affects the success rate of fertility preservation through egg storage. In the aforementioned study on people who received assisted reproduction with stored eggs, the live birth rate was 51% for people aged under 38, 34% for people aged 38–40, 23% for people aged 41–44, and 0% for people aged over 44 (Cascante et al., 2022).
Your doctor or fertility clinic may be able to advise you about options for fertility preservation through egg storage.
It is important to remember that trans men can become pregnant while on testosterone, and so if you wish to avoid pregnancy and are sexually active with someone who is capable of producing sperm, it is advised that you use a method of contraception.
If you do become pregnant while on masculinising hormone treatment and wish to keep the baby, then it is advised that testosterone is stopped while you are pregnant. This is because testosterone can be associated with harm to the baby (Thornton and Mattatall, 2021).
We understand that stopping masculinising hormone treatment while pregnant can be very challenging and lead to increased dysphoria. If you feel like you need further support to make sense of these changes, we can offer help and support through counselling.
Puberty is usually a crucial stage for fertility, because this is when maturation of sperm or eggs usually occurs. However, in young people who take puberty suppressing medication or commence gender affirming hormone treatment before the completion of puberty, this maturation of sperm or eggs may not yet have occurred. This means that options for fertility preservation are much more limited for young people, because they may not have mature sperm or eggs to preserve.
While you are taking puberty suppressing medication, your ovaries or testes may not produce eggs or sperm that are required for fertility.
Although the effect of puberty suppressing medication on fertility is itself reversible, it is important to note that subsequent gender affirming hormone treatment may have a more prolonged impact on fertility.
If you commence puberty suppressing medication in early puberty (Tanner stages 2–3) but later stop taking the puberty suppressing medication without commencing gender affirming hormone treatment, then it is likely that your ovaries or testes will go on to produce eggs or sperm, which would allow you to have children (Krishna et al., 2019). However, the process of stopping puberty suppressing medication would also result in other secondary sexual characteristics developing, which may not desirable for gender affirmation.
If you commence puberty suppressing medication in early puberty (Tanner stages 2–3) and then begin gender affirming hormone treatment either at the same time or later, then there is a possibility that your fertility may not even recover after stopping the puberty suppressing medication. This is because your ovaries or testes may not have developed the capacity for mature egg or sperm production by the time you begin the gender affirming hormone treatment (Cheng et al., 2019).
If you commence puberty suppressing medication in late puberty (Tanner stages 4–5) and then begin gender affirming hormone treatment either at the same time or later, then there is a possibility that your fertility may recover after stopping the puberty suppressing medication and gender affirming hormone treatment. This is because your ovaries or testes may have already developed the capacity for mature egg or sperm production (Emmanuel and Bokor, 2021). However, the exact effect of the gender affirming hormone treatment on fertility cannot be predicted, and so it is best to consider the possibility that your fertility might be affected by the gender affirming hormone treatment.
As noted above, the options for fertility preservation are much more limited for young people, because maturation of sperm or eggs may not yet have occurred.
If sperm or egg storage is not possible, then currently the only other fertility preservation option for young people who have not completed puberty is cryopreservation of ovarian or testicular tissue. However, this procedure is currently experimental and may not be available under many healthcare services (Cheng et al., 2019).
Given the limited options that are available, it is best to consider the possibility that you may not be able to have biological children if you commence gender affirming hormone treatment before the completion of puberty.
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