Fact check: No evidence vitamin C prevents pregnancy, doctors say

The claim: Taking vitamin C after unprotected sex prevents pregnancy

A Feb. 4 Facebook video (direct link, archived link) shows a woman claiming to share information about natural remedies for pregnancy prevention. 

Taking 500 milligrams of vitamin C every two hours will “bring on” a woman’s menses and prevent pregnancy after unprotected sex, the woman says.

The caption says, “PUT THE PLAN B PILL DOWN- Vitamin C is a NATURAL day after remedy for slip ups."

The video was shared more than 100 tmes and viewed 300,000 times within two weeks.

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Our rating: False

There is no evidence taking high doses of vitamin C after unprotected sex will prevent pregnancy, according to multiple doctors. There is also no evidence taking the vitamin will induce an abortion once a pregnancy has occurred.

No evidence vitamin C prevents pregnancy

Vitamin C actually makes pregnancy more likely, said Dr. Shannon Clark, a professor at the University of Texas Medical Branch’s department of obstetrics and gynecology. It can increase progesterone levels, which thickens the lining of the uterus, thus potentially making it more receptive to a fertilized egg.

But alternative medicine promoters wrongly claim the vitamin prevents pregnancy after unprotected sex by interfering with the production of progesterone, Clark said.

Fact check: Tablets in pregnancy tests should not be ingested and are not Plan B pills

There is no evidence that taking high doses of vitamin C after unprotected sex will prevent pregnancy by inducing a menstrual cycle, nor will it induce an abortion after a pregnancy has occurred, Clark said.

Dr. Aaron Lazarwitz, a complex family planning subspecialist in the OB-GYN department at the University of Colorado, concurs.

“There are no vitamins or natural supplements that can prevent unintended pregnancies after unprotected sex, and people should be wary of taking high doses of any vitamin or supplement, as there very well might be health risks from doing so,” Lazarwitz said. 

USA TODAY reached out to the social media user who shared the claim for comment.

Our fact-check sources:

• Mitch Creinin, Feb. 13, Email interview with USA TODAY
• Clara Paik, Feb. 13, Email interview with USA TODAY
• Aaron Lazorwitz, Feb. 14, Email interview with USA TODAY
• Shannon Clark, Feb. 14, Email interview with USA TODAY
• Cleveland Clinic, accessed Feb. 14, Progesterone
• Mayo Clinic, accessed Feb. 14, Vitamin C
• Harvard Health Publishing, Dec. 13, 2011, Medical Dictionary of Health Terms: D-I
• National Library of Medicine, August 1966, Mechanism of abortion induced by ascorbic acid

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