Is it safe to use evening primrose oil vaginally at 34 weeks if already dilated 1cm?

Would not do because: Evening primrose oil is commonly advised by midwives to "ripen" the cervix but they usually recommend taking it orally & not vaginally until 39 weeks. See http://herbs.Lovetoknow.Com/evening_primrose_oil_for_cervical_dilation however, the one study done on this found that oral evening primrose oil did not help & might cause harm: http://www.Sciencedirect.Com/science/article/pii/s0091218299000555.