Morning Sickness: Antihistamines Linked to Poor Outcomes

Steven Fox

June 14, 2013

Pregnant women who take antihistamines to help alleviate symptoms of hyperemesis gravidarum are significantly more likely to experience adverse outcomes, according to results from a new case-control study published online May 28 in the European Journal of Obstetrics & Gynecology.

"Hyperemesis gravidarum (HG), severe nausea and vomiting of pregnancy, accounts for over 285,000 hospital discharges in the US annually," write Marlena S. Fejzo, PhD, assistant professor of research in obstetrics and gynecology, University of California, Los Angeles, and colleagues.

Previous studies have shown a link between HG and adverse outcomes, and Dr. Fejzo and colleagues decided to investigate what the causes might be. They compared 2 cohorts of women: 254 women who experienced HG during their pregnancies and were treated with intravenous fluids and 308 women who had had normal pregnancies.

The researchers asked the women which of 35 different medications and other treatments they had used during pregnancy.

They found that women in the HG group were 4 times more likely to experience adverse outcomes, including preterm birth and lower birth weight, than women with normal pregnancies (P < .0001). They also found that both gestational hypertension and early-onset of HG symptoms were linked to poor outcomes.

Moreover, methylprednisolone and promethazine were both linked to adverse outcomes (P < .0217 and P < .0386, respectively). Other antihistamines, including diphenhy-dramine, dimenhydrinate, doxylamine, hydroxyzine, and doxylamine with pyridoxine, were also associated with adverse outcomes (P < 0.0151), regardless of efficacy.

The researchers say antihistamines also tended to be prescribed regardless of the severity of the symptoms. Nearly half of the women with HG who experienced adverse outcomes reported having taken antihistamines, yet the drugs were effective in less than 20% of cases.

In contrast, they report that women who were treated as outpatients and/or who made use of alternative treatments such as acupuncture, acupressure, and Bowen massage were more likely to have better outcomes.

The authors note that their findings are surprising, given the large body of evidence on the safety of antihistamine use during pregnancy.

"Given these results, there is an urgent need to address the safety and effectiveness of medications containing antihistamines in women with severe nausea of pregnancy," the authors conclude.

This study was funded by the Hyperemesis Education and Research Foundation. The authors have disclosed no relevant financial relationships.

Eur J Obstet Gynecol. Published online May 28, 2013. Abstract

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