Maresch the Midwife
There is a story in Michael Scott’s book Irish Folk and Fairy Tales Omnibus, of a Sidhe named Maresch who helps deliver the early arrival of a baby while the husband is absent having been caught in a storm. Once the baby is born, Maresch then burns a fire that makes the new mother groggy, and essentially convinces her to hand her the child. When the mother comes to, Maresch and the baby are gone.
The couple does, however, get their baby back. The employ the help of an old wise woman, who then performs a ritual at the foot of the fairy mound where the baby was taken. Nothing is the same though, after that. The wife dies during the birth of their second child, and the husband is later trampled under a horse. The baby, who was named Brigid, lives to her eighteenth year before she is found dead at the foot of the fairy mound (which is, in itself, part of another story).
It’s not clear why Maresch steals the child. It’s said that she had possibly lost her own baby. Another explanation given is that she is sterile, for the Sidhe are a dying race. This story is the only one I have ever seen mentioning the name Maresch, and any searching done for a “fairy midwife” brings up references to Shakespeare (for Mab, but her midwifing doesn’t seem to carry the same meaning as it does here). It is possible the name was made up by the author of the book, but even that indicates that fairies acting as midwife might be a common theme in Irish folklore. Though, it does go both ways. There’s another story of the same old woman—Nano Hayes—going to help deliver a child in the fairy realm. (The child of Brigid, incidentally. The plot thickens.)
Source: Scott, Michael, “The Fairy Midwife” and “… Into the Shadowland…”, Irish Folk and Fairy Tales Omnibus, Time Warner Paperbacks, 2002.