Antihistamines For Hyperemesis: Risky Medication for Nausea

Babies who are born early often need extra help with breathing, eating, and other daily functions. Photo by:  Jeremykemp

Babies who are born early often need extra help with breathing, eating, and other daily functions. Photo by: Jeremykemp

Interview with Dr. Fejzo

Decoded Pregnancy had the opportunity to interview Dr. Marlena Fejzo, an assistant professor of research in obstetrics and gynecology at UCLA. She has also experienced hyperemesis first hand; she had undiagnosed hyperemesis with her first pregnancy – such a severe case that she nearly died, lost her baby at 15 weeks gestation. Dr. Fejzo talks to us about her recommendations for patients with hyperemesis and physicians, she says,

“For both women with HG and their doctors, I would recommend women with HG visit the HER Foundation for information and support, and get a thiamine shot if they are unable to tolerate vitamins and food to avoid Wernicke’s Encephalopathy, brain damage caused by thiamine (vitamin B1) deficiency in HG that is completely avoidable with a thiamine shot. I am hoping to post our table of medications, outcomes, and effectiveness from the manuscript on the HER website so that women and their doctors can make informed decisions about which medication they decide to take to treat their HG.

Clearly, antihistamines should be used with caution compared to other probably safer and more effective options in our table of 35 treatments/medication used by women in the study to treat HG.”

Decoded Pregnancy also asked Dr. Fejzo if the same results occurred when pregnant women took antihistamines for allergies and she explained,

“I have not done a study on antihistamine use for allergies. Many studies have been done to show that antihistamines are not a teratogen (cause major malformation) in pregnancy, but very few look at preterm birth. There is one large Swedish study on preterm birth with antihistamines and allergies vs antihistamines for nausea and vomiting, and their finding was that the outcomes were better for babies born to women that took antihistamines for nausea and vomiting than for allergies. They explain that this is likely due to the confounding factor that “normal” nausea/vomiting has a protective effect on the fetus. At this point I don’t know whether or not it is the combination of HG and antihistamines, the combo of HG, antihistamines and other medications given at the same time, or just antihistamines because I don’t know the mechanism. Overall, more studies need to be done on the safety and effectiveness of medication use in pregnancy.”

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Hyperemesis and Pregnancy Medication: Use Caution

Babies who are born before 37 weeks gestation are more likely to need help breathing, eating, and are more prone to infections, and more likely to suffer from developmental problems than babies who are born full term. Although researchers aren’t exactly sure why some women get hyperemesis, Dr. Fejzo suspects that it maybe genetic, and tells us that the greatest risk factor, other than having hyperemesis in a previous pregnancy, is having a sister who had hyperemesis, which increases the risk by 17-fold.

Dr. Fejzo reminds us that, “HG is the 2nd leading cause for hospitalization in pregnancy and yet very few research dollars are spent on it. Women with severe nausea and vomiting need to urge their government to invest in HG research.”


American Pregnancy Association. Hyperemesis gravidarum. (2011. Accessed June 12, 2013.

Fejzo, M., Magtira, A., Schoenberg, F., et al. Antihistamines and other prognostic factors for adverse outcome in hyperemesis gravidarum. (2013). European Journal of Obstetrics and Gynecology and Reproductive Biology. Accessed June 12, 2013.

UCLA. Pregnant Women with Severe Morning Sickness Who Take Antihistamines are Significantly More Likely to Experience Adverse Outcomes. (2013). Accessed June 12, 2013.

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  1. what are antihistamines for? says:

    Ok, antihistamines are like benadryl, right? So if mom can’t take it for nausea, can she take it for itchiness? Like, if she gets a bug bite or poison ivy or something? Isn’t that what antihistamines are actually for? Or are they some kind of anti-irritant?

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