Cranberry in pregnancy and breastfeeding

What NCCIH says about safety

Cranberry taken orally (by mouth) is generally thought to be safe. However, if consumed in very large amounts, cranberry can cause stomach upset and diarrhea, particularly in young children. People who think they have a UTI should see a health care provider for diagnosis and treatment. Don’t use cranberry products instead of a proven treatment for a UTI. There is conflicting evidence about whether cranberry interacts with the anticoagulant (blood thinner) warfarin. If you take warfarin or any other medicine, talk with your health care provider before using cranberry or other herbal products; some herbs and medicines interact in harmful ways. Some studies of the use of cranberry during pregnancy or while breastfeeding suggest it is safe in amounts commonly found in food, but the evidence is not conclusive for use in larger amounts. If you’re considering using cranberry while pregnant or breastfeeding, consult your health care provider.

Quoted in full from NCCIH so nothing is lost in summarising. Where they say “little is known”, that means the studies do not exist — not that the herb is known to be safe, and not that it is known to be harmful.

How much is actually known

There have been many studies on cranberry for the prevention of UTIs, especially among women at increased risk for UTIs or recurrent UTIs. However, some research isn’t of high quality. There’s little research on cranberry for other conditions.

What the research has found

In general, cranberry products may decrease the overall risk of symptomatic, recurrent UTIs in women by 25 percent, and in some cases, by more than 30 percent. However, the effectiveness of cranberry is still in question because of inconsistent findings. While cranberry may assist in preventing symptomatic UTIs in some women, it isn’t recommended as a treatment for existing UTIs in any population. It’s thought that the proanthocyanidins (PACs) present in cranberries prevent bacteria from sticking to the bladder wall, thus preventing the start of a UTI. Processing cranberries into various products, like tablets or capsules, can reduce the concentration of PACs, which can reduce the potential effectiveness of a product. Studies in certain populations at increased risk for UTIs, such as elderly people in long-term care and pregnant women, have had inconsistent results. Studies in other high-risk populations, such as women undergoing gynecological surgeries or people with multiple sclerosis, have not found cranberry to be beneficial in reducing the risk for UTIs. Starting in 2020, the U.S. Food and Drug Administration has allowed manufacturers to claim on product labels that there is “limited” evidence that daily consumption of specified amounts of cranberry dietary supplements may reduce the risk of recurrent UTIs in healthy women.

Before you take this

Dose and form change the answer completely. A culinary amount of a spice, a cup of tea, and a concentrated supplement extract are three different things, and most research is done on the last of them.

Supplements are also not regulated like medicines, so strength and purity vary between products. Bring the actual bottle to your midwife, doctor or pharmacist — that conversation is worth more than any page, including this one.