My daughter turns 21 next year and my husband and I have decided to throw a bash not only to celebrate her birthday but also some milestone ones of our own which have gone by not properly celebrated.

I was chatting to my daughter the other day about the fact that my brother, who lives in Belgium, has declined the invitation. I explained to her that I felt really quite upset because the last time I had seen him was when we interred my mother’s ashes in April this year and before that, at her funeral in May last year.

My daughter is not one to get into emotional discussions, despite (or maybe because) she is studying for a psychology degree, and in response she informed me that I shouldn’t worry about not seeing him because he’s inside me. Inside me? Yes, she informed me as I tried to quell the rising tide of nausea – when he was born he left some of his DNA behind in the womb and that then ended up in me.

Microchimerism, it’s called – I looked it up. It means the presence of a small number of cells in an individual that have originated from another individual and are, therefore, genetically distinct.

As I understand it, on my very limited research, when a baby is in the womb the umbilical cord can act as a two-way street – the mother’s cells travel to the baby, and vice versa, so that some foetal cells can remain in the mother, even if the baby is not subsequently born. As they are effectively stem cells they can travel to parts of the mother’s body and grow as other cells eg cardiac cells (so the baby is forever part of the mother’s heart) or they can hang around and become part of future offspring. From what I can tell, the research has mainly been in terms of cells left by male babies, as it is easier to distinguish rogue Y chromosomes in the mother’s body, however, it is generally thought that it equally applies to female cells and that female babies may leave more cells behind than male babies. This process can play a part in autoimmune diseases and also the sex of the baby may influence the development of Parkinson’s and Alzheimer’s. All exciting stuff!

I was talking to my sister about it and the possibility of expressing this by making something akin to a set of Russian dolls with her as the outside one, and my brother and me on the inside – she wasn’t keen. I fear that our conversation may have been a contributing factor to her dream that night in which she was being chased by an artist who wanted to possess her body!