Is evening primrose oil safe during pregnancy?

What does the evidence say about evening primrose oil during pregnancy?

1. Evening primrose oil is generally regarded as possibly safe for most adults when taken by mouth, with gastrointestinal upset as the most common side effect, though the evidence specific to pregnancy is not conclusive. 1
2. Evening primrose oil holds generally recognized as safe (GRAS) status as a food with the FDA, and studies supplementing nursing mothers for extended periods found no adverse reactions in their breastfed infants. 2
3. A systematic review of evening primrose preparations used around childbirth found the evidence inconsistent and concluded the practice is not recommended, citing possible effects on bleeding and the absence of any endorsement from major obstetric guideline groups. 3
4. A separate meta-analysis of seven randomized trials found evening primrose oil improved cervical-ripening (Bishop) scores compared with no intervention, but adverse effects such as prolonged rupture of membranes and meconium-stained fluid appeared inconsistently across the studies reviewed. 4
5. Side effects reported from using evening primrose oil to try to start labor have mostly been mild, but the longer-term safety of that specific use has not been established. 1

Is evening primrose oil safe in each trimester?

• First trimester. Pregnancy-specific research on evening primrose oil is limited, and there's no established first-trimester use. If you're considering any new supplement this early, loop in your obstetric provider first.
• Second trimester. Little dedicated second-trimester data exists either. Most of the research on this supplement focuses on the weeks right before a due date, not routine use earlier in pregnancy.
• Third trimester. This is when evening primrose oil is most commonly tried, usually as capsules or a vaginal insert meant to help ripen the cervix before a due date. Evidence on whether it actually shortens labor is mixed, and a 2022 systematic review recommended against using it around delivery given possible effects on bleeding and the lack of backing from major obstetric guidelines.