Does primrose oil induce labor?

According to HowStuffWorks, evening primrose oil contains GLA, a source of prostaglandin, which can help to soften the cervix and prepare it for opening. While evening primrose oil is used to induce labor naturally, experts suggest that it does not do anything that the body doesn't do naturally.

Due to the risk of possibly causing contractions, the oil should not be used until a woman has reached 34 weeks of pregnancy, according to HowStuffWorks. Evening primrose oil can be taken orally, or it can be manually applied to the cervix. In capsule form, it can also be inserted into the vagina.