There is a recently published book, Star Wars: Darth Plagueis, that supposedly answer this question. From Anakin Skywalker Wookipedia article

In addition, although Darth Plagueis did attempt to influence the midichlorians to create the ultimate Sith weapon alongside Darth Sidious, the experiment was ultimately a failure, and the midichlorians, sensing the Sith's inherent malevolent intention, not only refused to do so, but in retaliation, conceived Anakin Skywalker in order to destroy the Sith once and for all.

So, according to this, Darth Plagueis and Darth Sidious caused Anakin birth ... indirectly.

There is a recently published book, Star Wars: Darth Plagueis, that supposedly answer this question. From the Anakin Skywalker Wookieepedia article

In addition, although Darth Plagueis did attempt to influence the midichlorians to create the ultimate Sith weapon alongside Darth Sidious, the experiment was ultimately a failure, and the midichlorians, sensing the Sith's inherent malevolent intention, not only refused to do so, but in retaliation, conceived Anakin Skywalker in order to destroy the Sith once and for all.

So, according to this, Darth Plagueis and Darth Sidious caused Anakin's birth ... indirectly.