Foetus helps pregnant women to repair organ damage by sending stem cells.

A study published in the journal Circulation Research point out the issue of fetal stem cells actually healing maternal organs.

Researchers mated female mice with transgenic male mice, tagged with a fluorescent protein, allowing the researchers to trace the flow of the stem cells of fetus from the mother’s placenta into its heart while they induced cardiac injury to the mother. They observed that fetal stem cells directly targeted the damaged cardiac cells and fully integrated themselves into the mother’s heart.

Points to the presence of precise signals sensed by cells of fetal origin that enable them to target diseased myocardium specifically and to differentiate into diverse cardiac lineages. Most notable is their differentiation into functional cardiomyocytes that are able to beat in syncytium with neighboring cardiomyocytes, thus potentially uncovering an evolutionary mechanism whereby the fetus assists in protecting the mother’s heart during and after pregnancy.

While this study was performed on mice, there is a wide body of research that suggests similar phenomena could occur in humans. There is still much research to be done, however, on the overall mechanisms behind this process and the totality of effects it may have on both fetus and mother.
Reference : https://www.snopes.com/fact-check/fetus-can-send-stem-cells-repair-mothers-damaged-organs/