What Causes It And Is It Something To Worry About?
Can you tell me why implantation bleeding occurs, and what it looks like? How common is it?
The expert answers
The cells that eventually form the placenta are called trophoblasts. Specialized trophoblasts, the syncitiotroblast, are responsible for developing an interface with the maternal circulatory system to provide nutrients and allow gas (oxygen [O2] and carbon dioxide [CO2]) exchange to occur.
Periodically, while this interface is developed, some of the maternal blood is lost. This implantation bleeding is typically short in duration and quite light.
Approximately one third of all pregnant women report bleeding that is associated with implantation. The presence of implantation bleeding does not increase the overall risk of miscarriage, however. Most pregnancies will continue until term without further bleeding.