I drank castor oil with my daughter and went into labor a couple hours later. I do believe you have to have already started to dialate for it to work though.
@demetriecs21 no, it does not. The people that it induced labor for just got lucky. It doesnt hurt to try but its actually used to "tone" the uterus, soften the cervix, and to help make the second stage of labor shorter, along with pushing more productive. It really is most effective if you start early. I have been drinking it since the beginning of my third trimester