Medical Oncologist
Fertility and family planning
Fertility, Pregnancy and — Contraception on Trastuzumab Deruxtecan
Trastuzumab deruxtecan is known to harm a developing baby. If you are of reproductive age, the contraception requirement starts on day one of treatment and continues for months after your last dose. This page sets out the exact durations, what to arrange before you start, and what to do if your situation changes.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed August 2026
- Contraception is required from dose one — For both women and men on this treatment — not something to arrange partway through.
- The washout period is specific — Seven months for women, four months for men with a female partner, after the last dose.
- Fertility preservation must happen first — Egg or embryo freezing has to be done before treatment begins, not after.
- Tell your team immediately — If you are pregnant, may be pregnant, or are breastfeeding when treatment is being planned.
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Trastuzumab deruxtecan is harmful to a developing baby and must not be used in pregnancy. According to the prescribing information approved by CDSCO and the FDA, women of reproductive potential must use contraception throughout treatment and for seven months after the last dose. Men must use contraception during treatment and for four months after. Tell your team immediately if you are pregnant or planning to conceive.
Why is trastuzumab deruxtecan dangerous in pregnancy?
Trastuzumab deruxtecan is an antibody-drug conjugate — an antibody that carries a chemotherapy payload directly to cancer cells. The payload is a topoisomerase I inhibitor, a type of drug that interferes with how cells copy their DNA. A developing baby's cells divide constantly, which makes them especially vulnerable to this kind of damage.
Animal studies have shown the drug causes harm to embryos and fetuses. Regulatory agencies including CDSCO and the FDA consider this risk applicable to humans, based on how the drug works.
The seven-month washout period after the last dose reflects how long the drug and its active payload are estimated to remain in the body at levels that could pose a risk to a pregnancy.
What contraception do women and men need during treatment?
| Female patients | Male patients with a female partner | |
|---|---|---|
| Contraception during treatment | Required throughout | Required throughout |
| Contraception after last dose | For 7 months | For 4 months |
| Pregnancy test before starting | Recommended | — |
| Breastfeeding | Not recommended during treatment or for 7 months after last dose | — |
What should you discuss with your team before your first dose?
If you want the option of a pregnancy after treatment, raise it before your first dose — not after. Egg or embryo freezing has to happen before chemotherapy begins, and arranging a fertility specialist appointment takes time your schedule may not have once treatment starts.
Tell your oncologist about the contraception you currently use. Your team will confirm whether it is appropriate to continue or whether a different method makes more sense during treatment.
If you become pregnant during treatment, tell your team the same day. The decision about how to proceed involves your oncologist and, if you wish, a specialist in high-risk pregnancy. There is no single right answer, but the conversation needs to happen urgently.
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What do you need to arrange before your first dose?
- Tell your team if you are pregnant, may be pregnant, or are breastfeeding
- Confirm you have effective contraception in place before the first dose
- Ask about a pregnancy test before starting if you are a woman of reproductive age
- Request an oncofertility referral if a future pregnancy matters to you
- Ensure a male partner receiving this drug knows about the four-month post-treatment requirement
- Ask your team when it would be safe to stop contraception after treatment ends
Did you know?
The payload released by trastuzumab deruxtecan can enter nearby cells that the antibody never directly targeted — a property called the bystander effect.
It is partly what makes the drug effective against tumours where not every cell carries HER2. It is also why the pregnancy risk does not disappear the moment the last dose is given.
Source: ESMO Clinical Practice Guidelines; FDA prescribing information for trastuzumab deruxtecan (Enhertu)
How does trastuzumab deruxtecan affect fertility and family planning?
Can I freeze my eggs or embryos before starting?
Yes, and if this matters to you, it is the most time-sensitive conversation to have. Egg or embryo freezing must be arranged before your first dose of trastuzumab deruxtecan. Ask your oncologist to refer you to an oncofertility or reproductive medicine specialist as soon as treatment is being discussed. These appointments can take weeks to arrange, and the ovarian stimulation cycle itself takes around two weeks, so the sooner you ask, the more options remain open to you.
How long after stopping treatment can I try to conceive?
The prescribing information specifies a minimum of seven months after the last dose for women before attempting pregnancy. This reflects the time for the drug and its payload to clear to levels no longer expected to pose a reproductive risk. Your oncologist may advise a longer interval depending on your overall treatment history, your response to therapy, and your general health at the time. The seven-month figure is a floor, not a signal that it is automatically the right moment for you once it passes.
What if I find out I am pregnant during treatment?
Tell your oncologist the same day — do not wait for your next scheduled appointment. The team will need to assess how far along the pregnancy is, discuss the potential risks to the baby from any doses already received, and go through your options with you. This may include pausing treatment, stopping it, or continuing with very close monitoring, depending on the clinical situation. It is a decision made with you, not for you, and input from a maternal-fetal medicine specialist is usually part of that conversation.
Does trastuzumab deruxtecan permanently affect fertility?
The drug may impair fertility in both women and men based on animal studies, but the extent of any long-term effect in humans is not yet fully established. Fertility recovers in many patients after cancer treatment, though the degree of recovery varies. This is one of the reasons why fertility preservation before treatment — freezing eggs, embryos, or sperm — is worth discussing proactively rather than waiting to see what happens. Your oncologist can refer you to a specialist who works specifically with cancer patients planning for future pregnancies.
Can I breastfeed after finishing trastuzumab deruxtecan?
Not until at least seven months after your last dose. The drug and its payload remain in the body for an extended period after the final infusion, and the risk of the baby being exposed through breast milk during that window is considered too high. If breastfeeding is important to you, discuss it with your oncologist and your baby's paediatrician as you approach the seven-month mark. Your milk supply and your baby's readiness for other feeds will also be part of the picture by then.
My male partner is on this treatment — what does that mean for us?
Men on trastuzumab deruxtecan must use effective contraception during treatment and for four months after the last dose, because the drug and its payload may be present in semen and could affect a developing embryo. If your partner is being treated and you are hoping to conceive, the four-month post-treatment period is the minimum waiting time. If sperm banking before treatment is something your partner wants, it needs to be arranged before the first dose — not after treatment has begun.
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Common questions
Frequently asked questions
What contraception is recommended while on trastuzumab deruxtecan?
Your oncology team will advise the most appropriate method for your situation, because the right choice depends on your cancer type, overall health, and any other medicines you are taking. The prescribing information requires effective contraception throughout treatment and for seven months after the last dose — it does not mandate a single method. Hormonal contraception may not suit every cancer type; an intrauterine device or barrier method may be more appropriate. The key point is that contraception must be in place before the first dose, not arranged partway through.
How long must I wait after treatment before trying to get pregnant?
The prescribing information specifies at least seven months after the last dose for women. Your oncologist may recommend a longer interval based on your treatment response and your health at the time. The seven-month figure is the regulatory minimum — it is not a signal that the moment it passes everything is straightforward. A pregnancy after cancer treatment benefits from careful planning and close medical support regardless of timing, so discuss the full picture with your team before stopping contraception.
Can I get a fertility preservation referral through CION?
Yes. If you tell your oncologist that future fertility matters to you, they can refer you to a reproductive medicine specialist before treatment begins. This conversation is most useful at the point of treatment planning, not after the first dose. CION manages your oncology care; the reproductive medicine team handles the fertility side alongside it. The two need to coordinate on timing so that any fertility procedure does not unnecessarily delay your cancer treatment.
What if I am already pregnant when I am diagnosed?
Tell your oncologist immediately. Being pregnant does not mean cancer treatment must be delayed indefinitely, but the plan has to be worked out carefully with maternal-fetal medicine involved alongside your oncology team. Trastuzumab deruxtecan specifically is not used in pregnancy given the known risk to the baby, so if this drug is the recommended treatment, the conversation will involve what alternatives exist for your situation and what the timing options are.
Does my male partner need to stop trying to conceive while he is on this drug?
Yes. Men on trastuzumab deruxtecan must use effective contraception during treatment and for four months after the last dose. If a future biological child matters to your partner, sperm banking before treatment is worth discussing — that conversation needs to happen before the first dose, not after. Ask your partner's oncologist for a referral to a reproductive medicine specialist at the point of treatment planning.
Will I go into early menopause from this treatment?
Trastuzumab deruxtecan does not target the ovaries the way some chemotherapy regimens do. However, depending on your age, your cancer type, and any other treatments you receive alongside it, treatment-related hormonal changes are possible and worth monitoring. If you notice changes to your menstrual cycle during treatment, tell your team. A fertility or menopause specialist can advise on monitoring and management alongside your cancer care.