The use of birth control and abortion have a long history, and a long history of being contentious. The idea that pregnancies can be prevented or stopped has raised ethical and moral issues, and, like today, in the Middle Ages you will find many opinions about what should or shouldn’t be done. However, the medieval period might be unique in that it is perhaps the only time when you can read the same author in one work condemning the use of birth control and in another giving directions on how to use it.
In the end, much of the knowledge about birth control practices in the Middle Ages is lost to history – these were issues that women had to deal with on their own, and they could usually only turn to other women for help and guidance. Some could try a medical treatment that had limited chances of success, but many would have realized that an unwanted pregnancy was something that had to be managed and/or hidden. The fate of children born in this way varied – some might have been placed in the care of another family or given to a monastery, but others might also be killed and disposed of. It may have been that in the Middle Ages the most dangerous time for an unwanted child was just after birth.
read entire article here @ Medievalist
read also "Abortion in the Middle Ages c500 - 900" by Zubin Mistry