Babies switched at birth
Babies switched at birth are babies who, because of either error or malfeasance, are interchanged with each other at birth or very soon thereafter, leading them being unknowingly raised by parents who are not their biological parents.  In real life, the occurrence of such a thing is highly improbable, with it having occurred, or having been asserted to have occurred, in a few cases.  However, it is an idea that is a common staple in fiction.

# As a literary plot device
The plot device of babies who are switched at birth, or in their cradles, has been a common one in American fiction since the 18th century.  It is one of the several identifiable characteristics of melodrama that are plot devices dealing with situations that are highly improbable in real life.
The use of this common theme has continued ever since.  The device was used a number of times by W. S. Gilbert, including in the Gilbert and Sullivan comic operas H.M.S. Pinafore and The Gondoliers.  In both cases, well-born babies were switched with commoners.  Mark Twain, later used this plot device in The Tragedy of Pudd'nhead Wilson (1893), where two babies, one white and one black, are switched at birth, resulting in both passing for races that they are not.  It is one of the themes that made for TV movies regularly exploited in the 1970s and 1980s.  It continues to be a popular theme in the 1990s and 21st century with (for examples) it being employed as a plot device in Veronica Mars (the characters Cindy "Mac" Mackenzie and Madison Sinclair), in Neighbours (the characters Bree Timmins and Anne Baxter), and in The Young and the Restless (several times, including the characters Cane Ashby and Phillip Chancellor III, and the children of Lauren Fenmore Baldwin and Sheila Carter).
Although a common plot device in soap operas, it is not nearly as common as the theme of questionable paternity.  Mumford states that the reason for this is that the potential causes for questionable paternity are far more wide ranging and richer in scope than those for questionable maternity, and thus provide a greater vein for soap opera scriptwriters to mine.  Whereas questionable maternity can only be caused by error or malfeasance that causes babies to be switched at or after birth, questionable paternity can involve many aspects, ranging from a woman deliberately wishing to pin paternity on the wrong man, through unreported rape, to a clandestine love affair.  It is relatively simple, moreover, for writers to retrofit questions of paternity to characters years on, whereas it is difficult to introduce questions of maternity after the fact.
The device also occurs outside of American fiction, in stories such as The Little Michus.

# In real life
In real life, such a switch is highly improbable.  Cases that have occurred and made the newspaper headlines include:
- the case of a girl switched at birth as a result of a medical error in a hospital in Wauchula, Florida, the events surrounding whom were subsequently dramatized as the made-for-TV movie Switched at Birth
- the cases of the children of two South African women, Margaret Clinton-Parker and Sandra Dawkins, whose sons were accidentally switched at birth in 1989, and who sued in the High Court of South Africa in Johannesburg in 1995, demanding damages of ZAR120,000 each from the government of the province of Gauteng for the error, and who were later that year awarded damages to cover medical expenses and the future projected costs of visiting their biological children  Each family kept the child they had been living with, though, and raised them as their own even after learning of the switch.
- on December 9, 2006 two newborn girls were switched in the hospital in the Czech town of Trebic. The families haven't found out until September 2007 when a couple of friends of one of the fathers made fun of him that he is not the biological father of the baby. DNA test proved that the girl was indeed switched. After days of investigation, the other family was found. As of October 11, 2007 the families were in contact and figuring out ways to switch the children back.
Hospitals take fingerprints, foot prints, or palm prints of newborns in order to prevent babies being mixed up.  Nurses also double check with the mother, checking the identity of that person as well, in order to prevent errors.