Is rhubarb safe during pregnancy?

What does the evidence say about rhubarb during pregnancy?

1. Medicines containing rhubarb rhizome (the root) are not recommended for pregnant women according to the European Medicines Agency, and a Japanese database study of first-trimester exposure to Kampo medicines containing rhubarb rhizome found no significant association with major congenital malformations, though the researchers describe the overall evidence base as limited. 1
2. Researchers note that emodin, a compound found in rhubarb rhizome, may cause embryonic cytotoxicity in mouse blastocyst research, part of the reasoning behind grouping rhubarb-root products with other botanicals not recommended during pregnancy. 1
3. The rhubarb used medicinally is the root of Rheum officinale or Rheum palmatum, a different plant part from the stalk eaten as food. The root's anthraquinone compounds act as a stimulant laxative, and current reviewers advise against using it while breastfeeding because of possible effects on a nursing infant. 2
4. The edible rhubarb stalk is unusually high in oxalates, measured at roughly 987 to 1,235 mg of total oxalates per 100 g raw, and boiling reduces that content by close to a quarter. 3
5. Oxalic acid, the substance behind rhubarb's high-oxalate reputation, reacts with calcium in the blood to form insoluble calcium oxalate crystals. A case report on oxalic acid poisoning describes those crystals damaging kidney tubules and causing acute kidney injury at large, concentrated exposures, far beyond anything a food serving would deliver. 4

Is rhubarb safe in each trimester?

• First trimester. A normal serving of stewed or baked rhubarb stalk fits into typical prenatal eating without any special limit. If early nausea has you looking at herbal laxatives instead, mention any rhubarb-root product to your provider first, since that's the concentrated form the pregnancy caution applies to.
• Second trimester. Rhubarb stalk is unusually high in oxalates, so if you have a history of kidney stones, keep portions moderate and consider boiling it rather than eating it raw, which lowers the oxalate content somewhat.
• Third trimester. The same food-amount guidance holds through the third trimester. If you're planning to breastfeed afterward, know that reviewers currently advise against rhubarb-root laxative products while nursing, so this is a good window to sort out any fiber or constipation plan with your provider instead.