Evening Primrose Oil for Cervical Ripening

Crestina L. Beites, PhD, and Lisa Morgan, RM, MAPhD(c)

Clinical Question:
Can evening primrose oil be used as a cervical ripening agent to avoid postdates pregnancy and shorten the length of labour?

BACKGROUND
Evening primrose (Oenothera biennis) is a native North American flower so named because it blooms in the evening. This plant is of special interest to midwives because of anecdotal evidence suggesting that the oil from its seeds can help soften the cervix, preventing postdate pregnancy and shortening the length of labour. Certified Nurse-Midwives in the United States felt that evening primrose oil was the most successful herbal extract preparation for promoting cervical ripening and the stimulation of labour, so it is not surprising that it scored high on their “comfort level in prescribing scale.”1 The oil extracted from evening primrose seeds contains an unusually high amount of gamma-linolenic acid (GLA), a very active essential fatty acid and a precursor of prostaglandin derivatives. Despite the lack of scientific evidence supporting its use in cervical ripening, In the past two decades, evening primrose oil has been popularized as an alternative remedy for rheumatoid arthritis and atopic dermatitis. Research in both animal and human models have discovered significant changes in serum lipid biosynthesis when evening primrose oil is consumed orally.2,3 Although the biological effects and biochemical changes that occur due to increases in fatty acids have not been precisely determined, evening primrose oil (theoretically, at least) holds promise for the treatment of some of these systemic diseases.