Evening Primrose Oil acts as a prostaglandin, which ripens or softens the cervix. It's also useful for softening scar tissue from abortions or IUD damage. This will soften/ripen the cervical tissues and increase the flexibility of the pelvic ligaments. This will help the baby to deeply engage in the pelvis. This early application of the baby's head will assist with dilation and should result in a relatively easy birth, even after multiple C-sections for "stalled" labor. Evening Primrose Oil may be helpful for women with borderline pelvises as well. The utilization of Evening Primrose Oil seems to enhance the complex set of biochemical messages that initiate labor.
You can take evening primrose oil, orally, in the last four weeks of your pregnancy. You should take three evening primrose oil capsules daily for the first week (36th week of gestation) and then one to two capsules a day for the last three weeks of pregnancy.
...Evening Primrose oil can soften the cervix. My midwife recommends taking 3 capsules per day for the last 4 to 6 weeks. However, it doesn't START labor, only prepares the cervix. It is not an emmenagogue or get more oxytocin into your system.
Another site on natural induction also mentions it:
Evening Primrose Oil and Red Raspberry Leaf Tea
Neither will actually induce labor. While some lay midwives will argue that statement about the Evening Primrose, which is the reason it is not recommended until 36 weeks or "full term", almost all sources with experience agree that it does nothing that the body was not ready to do on its own. I will repeat this at the end of this section, to make sure you understand this, as there is a lot of confusion and misconception surrounding these two substances.
Evening primrose oil is an excellent source of prostaglandins, which we already determined readies your cervix for labor. It can be taken orally as soon as 34 weeks, and can be applied directly to the cervix at full term (36 weeks). The general recommendation is two 500mg capsules per day until week 38, at which time you increase to 3-4 per day.
Any yet another site mentions the Evening Primrose next to Red Raspberry Leaf
After 38 weeks of pregnancy, a recommended dosage of 2,500 mg tablets per day of evening primrose oil is taken orally to systemically soften all tissues (including cervix and perineum, especially if cervical scarring or previous perineal injury exists) along with 1 cup of red raspberry leaf tea from 28 weeks, increasing red raspberry leaf tea to 2 cups from 32 weeks and then increasing the dosage of red raspberry leaf tea to 3 cups from 36 weeks gestation, then as needed in labor to strengthen and tone the uterus.
Aside from its use in pregnancy, it also aids in conceiving, according to the article,
Evening Primrose Oil (EPO) - Its Role In Trying to Conceive, and is good for rheumatoid arthritis (which I supposedly might have), according to a government funded site, along with many other ailments.
A girlfriend of mine wrote me to let me know she had used the oil during her pregnancy as well. Knowing that and who she's related to (our friend, doula/Bradley teacher), who'd never let her do anything unsafe in pregnancy, I have more confidence in using it. Maybe we'll start next week, when I'm 36 weeks. *;o)