Do foetuses get cancer?

Hannah - Cancer is the unregulated growth of cells and during pregnancy, cells divide very rapidly. There are mechanisms in place to prevent cancer developing, but as Professor Graham Burton from Cambridge University points out.

Graham - About 1 in 10,000 babies when they're born will have some sort of tumour, a swelling in the body associated with abnormal growth. Thankfully, these are usually what we would call benign in that the cells do not invade into other parts of the body, and so, can be treated usually at the time of birth. In terms of true cancer, in terms of uncontrolled proliferation, the other way that a foetus could develop that is if it is transmitted from the mother. Fortunately again, this is very rare. Most maternal tumours will not cross the placenta. The placenta forms a pretty effective barrier to agents that would cause cancer in an adult so that the embryo is in a very protected environment, but will also stop cells from the mother crossing into the foetus. But occasionally, we know that there is mixing of the two circulations, the two blood systems, and if the mother has leukaemia or a similar condition, it has been reported that the foetus can develop the same problem.

Finally of course, the placenta itself can undergo a cancerous change. This again is very rare. It's associated with a very interesting, but curious condition known as hydatidiform mole. Normally, you would derive half of your chromosomes from the mother and half from the father, but in these cases, all of the chromosomes comes from the father, and this causes very rapid proliferation of the placental tissues, but interestingly, you get very, very small growth of the foetus itself. And so, often in these cases, there's no baby to be found at all, just a big mass of placenta. And because of this rapid proliferation, some of those placental cells can undergo a cancerous change.