Can I become pregnant whilst on Cancer Treatment?

Although some breast cancer treatments can cause menstrual periods to stop, this does not necessarily mean that a woman cannot become pregnant during treatment.

It is important for women who are sexually active to continue to use contraception during, and after, breast cancer treatment. An unexpected, unplanned pregnancy may only complicate matters and add new and unwelcome ethical and treatment dilemmas.


There is no clear evidence to show that it is safe for breast cancer survivors to use hormone-based contraceptives. The following contraceptive options would constitute hormonal methods:

• Combined oral contraceptive pill, e.g. Triphasil,

Femodene and Yasmin

• Progesterone only pill, e.g. Microval

• Progestrone implants, e.g. Implanon

• Progestrone injections, e.g. Depo Provera, Nur-Isterate

As a general rule, non-hormonal contraception is recommended. These include:

• Natural family planning methods, e.g. cycle timing, cervical mucus and temperature checks; withdrawal before ejaculation in the vagina

• Condoms

• Diaphragm

• Copper intra-uterine device

• Male sterilisation (Vasectomy)

• Female sterilisation (Tubal Ligation)

Failure rates for all methods of contraception decrease as fertility drops with advancing age, this is natural and makes methods that may have an unacceptable failure rate for a younger woman, appropriate for a woman in her forties. Since fertility will be further decreased following chemotherapy, a contraceptive method with a higher failure rate may be acceptable in the small population of women who are still menstruating after treatment for breast cancer. So, for example, while condoms and natural family planning methods may not be effective enough in a 35 year old, they may be perfectly adequate for a 45 year old on chemotherapy.


The Mirena is an intra-uterine contraceptive device that releases a measured, low dose of progestin (levonorgestrel) on a daily basis for five years. The dosage is low enough to act within the uterus as a contraceptive but the theory is that the level of progestin in the blood stream should be too low to cause any hormonal effect on the breast. Basic scientific data however suggests that progestins can have an effect on the breast tissue that encourages growth of tissues as well as cell division.

This depends on the timing, type and amount of progestin used.

Women who have recently had Mirenas inserted will tell you, and studies have also shown, that one of the initial nuisance side effects of the Mirena is breast tenderness. So it would seem that there is some hormonal effect on the breast, at least in the first few months after insertion when levonorgestrel levels are highest. Accordingly, an effect of the Mirena on breast cancer risk cannot be dismissed at this time. More data on safety is needed before this device can be recommended as a first line contraceptive for breast cancer survivors. However, for some women, in special circumstances and in consultation with a specialist gynaecologist, it may be justified.

Written by Dr Sumayya Ebrahim

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