In My Heart forever: The science behind the sentiment

By Heather Carnaghan

          When my daughter was stillborn, friends and family reached out in countless thoughtful ways to show that they cared.  They brought meals to fill our bellies, sent cards to offer condolences, and gifted trinkets to help us remember Charlotte.   The overwhelming majority of those well-wishers suggested that she would "be in our hearts forever".   This metaphor is truly a beautiful one: I will hold my child in my heart by honoring her existence and she will live on as I revisit those few, but meaningful memories of her.  What they likely didn't realize, is that their kind sentiment actually has some pretty legitimate scientific backing.  

          Charlotte's stillbirth was a particularly rare one in which, after a battery of tests and review of all available medical files, there just wasn't an answer regarding the cause of her death.   I decided to read everything I could in the hopes of understanding those tests and identifying even a glimmer of an answer.   Most pre-labor stillbirths are caused by placental or cord issues, so this seemed like an important place to begin.   

The placenta is an organ that is shared by mother and baby during the pregnancy.    (Science nerd moment: Can you believe our bodies construct a whole new organ for each of our children?  Talk about the ultimate birthday gift!)    We typically think of the placenta and umbilical cord as providing nutrients to the baby, but it does so much more.  It actually allows cells to pass between the mother and her child.   In a study at Leiden University Medical Center, pathologists found cells with Y chromosomes in autopsies done on women who died during or shortly after pregnancy.  Why is this interesting?  Cells with Y chromosomes are male cells and should not exist in a female body.  Each of the 26 women had been carrying sons.  Scientists believe that this is evidence of fetal microchimerism, or the passage of fetal cells to the mother's body.  (History nerd moment: "microchimerism" is named after the chimera, an odd creature in Greek mythology with three heads, one of a goat, one of a lion, and one of a dragon.)  The finding that was most surprising to me in this study was where the cells were found.  

---

          The pathologists found these rogue little baby boy cells in every organ that they tested.   The cells had developed into functioning tissue in each of the organs.  Fetal cells in the brain developed into brain tissue, fetal cells in the kidneys became kidney tissue, and fetal cells in the heart became heart tissue.  The cells of these baby boys were, literally,  a part of their mothers' beating hearts.  Even more amazing yet: these cells have been found to be quick to spread and extremely long lasting.  They have been detected as early as seven weeks into a pregnancy and may last a lifetime.   One study found definitive evidence of fetal cells in a mother who had given birth to her son 27 years prior!  
​
            Dr. Nelson and her colleagues at the Fred Hutchinson Cancer Research Center believe that fetal microchimerism is "very common, if not universal" as they found these cells in 63% of subjects in a 2012 study.  The scientists theorize that the baby may be able to manipulate the mother to some degree in order to help them thrive (for example, sending messages to produce more milk, keep them warmer, or provide more resources for their growth).  

          So the next time you suggest to a grieving mother that her beloved little one will be in her heart forever, say it like you mean it.  Then tell her that he'll be in her lungs, kidneys, and brain too.  Science has your back.  

---