Fertility, Pregnancy and — Contraception on Trastuzumab

No. Trastuzumab is contraindicated in pregnancy. If you become pregnant while on trastuzumab, tell your oncology team the same day — this needs urgent specialist review. The drug can cause serious harm to fetal kidney development, including cases of very low amniotic fluid and neonatal death recorded in clinical literature. EMA and ESMO guidance both classify pregnancy during trastuzumab treatment as a contraindication, not a warning to manage around.

EMA and ESMO guidance requires effective contraception for 7 months after your final trastuzumab infusion. The washout period runs from the date of your last trastuzumab dose — not from when chemotherapy ends, which is often earlier. Note the date of your final infusion and discuss with your oncologist when it is safe to stop contraception and begin trying for a pregnancy.

Trastuzumab alone is not known to directly damage ovarian reserve in the way that some chemotherapy agents do. However, most people receive trastuzumab alongside chemotherapy drugs that can affect fertility. The risk to your fertility depends on which chemotherapy agents are used, the doses given, and your age at the time of treatment. Ask your oncologist specifically about the fertility impact of the full treatment plan — not trastuzumab alone.

Breastfeeding is not recommended during trastuzumab treatment or within 7 months of your last dose. It is not fully established how much drug passes into breast milk, and the precautionary guidance from the EMA and ESMO is to avoid breastfeeding during this period. If you have recently given birth and are about to start treatment, raise this with your team before your first infusion so a plan is in place.

Fertility preservation means collecting and freezing eggs or embryos before treatment begins, so that options for pregnancy remain open afterwards. For women of childbearing age, this should be discussed before chemotherapy starts — the fertility-affecting agents are usually given in the early cycles, so the window is short. Trastuzumab continues longer, but it is the chemotherapy given alongside it that poses the greater risk to ovarian reserve, making the pre-treatment window the one that matters most.

Pregnancy after completing trastuzumab and waiting through the 7-month washout period may be possible. Registry data in oncology literature suggest that outcomes for women who conceive after completing HER2-positive breast cancer treatment can be favourable, though the evidence base is still growing. How long to wait beyond the washout, and whether pregnancy is appropriate given your individual situation, is a conversation for your oncologist — they will consider how your cancer responded to treatment and your overall health.