In 2013 there was a bit of excitement when a group out of Missouri U reported finding Y-chromosomal DNA in the blood dogs that had given birth to male pups. The first time fetal microchimerism (FMc) has been detected in dogs.
During pregnancy there is a small exchange of cells between mother and fetus, or among fetuses in multiple pregnancies. These small number of cells can take up permanent resident and in humans persist for over 43 years (2008).
The study in dogs also found male cells in females which had not been bred but came from a mother which had given birth to male pups; the authors posit the cells likely came from the previous pregnancy – a horrible thought to all of us who weren’t first-born. The hand-me downs begin before we are born. 😦
[Note: most of these studies on FMc focus on the presence of male cells in female proband because it’s easier, cheaper and faster to detect male cells in a female organism]
Interestingly fetal cells appear to cluster at sites of injury, possibly acting as stem cells and differentiating and aiding in tissue repair. As an editorial in Circulation Research put it, “Baby gives back”
Long after birth, mother and offspring may carry a little bit of each other. In some ways mother and child are never truly completely apart.
Axiak-Bechtel SM, Kumar SR, Hansen SA, & Bryan JN (2013). Y-chromosome DNA is present in the blood of female dogs suggesting the presence of fetal microchimerism. PloS one, 8 (7) PMID: 23861856
O’Donoghue K, Sultan HA, Al-Allaf FA, Anderson JR, Wyatt-Ashmead J, & Fisk NM (2008). Microchimeric fetal cells cluster at sites of tissue injury in lung decades after pregnancy. Reproductive biomedicine online, 16 (3), 382-90 PMID: 18339261