https://drjessesantiano.com/mothers-day-and-fetal-microchimerism
"Fetal microchimerism is when the fetal cells travel outside the fetus and embed in the mother’s body during pregnancy. Those fetal cells can stay with the mother for decades and affect her health."

"Wherever the mother has any inflammation and injury, fetal cells can be found. These fetal cells promote angiogenesis, or the growth of new blood vessels. They also supply necessary materials..."

See also:
• https://greenmedinfo.com/blog/baby-gives-back-fetus-capable-saving-moms-life
• https://biodesign.asu.edu/news/alien-within-fetal-cells-influence-maternal-health-during-pregnancy-and-long-after