Antihistamines may increase pregnancy risks for women with severe morning sickness

UCLA Health article
Women with a severe form of morning sickness who take antihistamines to help them sleep through their debilitating nausea are significantly more likely to experience premature births or have low–birth-weight babies, a UCLA study has found.
The findings, the first to link antihistamine use to adverse pregnancy outcomes, are important because babies born at 37 weeks or earlier often are hospitalized longer than full-term babies, can experience problems breathing and feeding, are more prone to infection and can suffer from developmental problems. Women with morning sickness who are considering taking such medications should know the risks, said Marlena Fejzo, the study's lead author an assistant professor of research in obstetrics and gynecology at UCLA.
The severe morning sickness, called hyperemesis gravidarum (HG), is the same condition that Kate Middleton, Duchess of Cambridge, recently experienced. Its cause is unknown and the symptoms are intense: The continuous nausea and vomiting can be so violent that women in the study reported suffering from detached retinas, blown eardrums, cracked ribs and torn esophagi, Fejzo said. The symptoms can last for several months or the entire pregnancy.
"It was surprising to find the link between antihistamines and adverse outcomes as these are over-the-counter medications that are used commonly by women with HG during pregnancy," said Fejzo, who had undiagnosed HG during her first pregnancy and nearly died during her second and lost the baby. "Women and their healthcare providers should be aware of the risk for adverse outcomes when deciding which medications to take to treat their HG symptoms."
The study appears June 10 in the European Journal of Obstetrics & Gynecology and Reproductive Biology.
The six-year study compared pregnancy outcomes in two groups of women. The first was composed of 254 women with HG who were sick enough to require treatment for dehydration with intravenous fluids. The second was made up of 308 women with normal or no morning sickness during pregnancy. The researchers found women with HG had four times the risk of adverse outcomes, confirming a link between HG and adverse outcomes that had been shown in several previous studies.
The study then compared women with HG who suffered adverse outcomes to women with HG who had good outcomes. Researchers looked at whether any of more than 35 medications and treatments that are commonly used by women with HG were linked to bad outcomes. They found that more than 50 percent of HG patients who experienced adverse outcomes took over-the-counter medications containing antihistamines.
Fejzo also found that the medications were reportedly effective in less than 20 percent of the women who took them.
"Some doctors will suggest that their HG patients take Unisom to help them sleep through their nausea," Fejzo said. "Our findings show not only that the use of antihistamines is linked with adverse outcomes, but also that they're not that effective. Women with HG should be aware of that so they can make educated decisions on how to treat their HG symptoms."
Adrienne Downs of Culver City, Calif., experienced some nausea and vomiting during her first two pregnancies, but nothing out of the ordinary. Her third pregnancy has not been so run-of-the-mill. Early in the pregnancy, she suffered from constant nausea, vomiting approximately every 20 minutes around the clock. She was hospitalized twice for five days each time, and had to get intravenous fluids to treat her severe dehydration and malnutrition.
"I literally could keep nothing down for months," Downs said. "I couldn't even get up out of bed and take care of my family. It was horrible. I was very scared for my baby. How would it get any nutrition if I couldn't eat or drink?"
Downs lost 12 pounds in three weeks. Her mother had to move in to take care of her and her sons, ages 4 and 2. 
Now that she is past 21 weeks gestation, Downs' symptoms have subsided somewhat, but she still can only keep down fluids. She has gained back some of the weight she lost. Although she did not take antihistamines to treat her HG symptoms, Downs said the findings are important.
"As pregnant moms, we want to be the best 'house' for our babies that we can," she said. "I had never heard of this condition before I got it, so I'm glad that UCLA researchers are studying HG and may one day find the cause."
HG is diagnosed in up to 2 percent of pregnant women, although rates are higher in China. Fejzo said much more work needs to be done to understand the short- and long-term effects of medication use during pregnancy. For example, she and her team are studying women with HG pregnancies to determine if the violent nausea and vomiting have any effects on the children later in life.
"We desperately need support for research into HG to determine its cause so that medications can be designed that are safe and effective," Fejzo said. "The greatest risk factor for HG other than a previous HG pregnancy is having a sister who had HG, which increases the risk by 17-fold. This suggests a genetic component is at work."
Fejzo and her team are collecting saliva from women with HG and women with normal pregnancies and are studying the DNA they extract for genes that may predispose women for HG. She hopes that once a cause is discovered, drugs can be developed to either prevent or more effectively treat the condition.
The study was funded by the Hyperemesis Education and Research Foundation.
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Media Contact:
Kim Irwin
(310) 794-2262
[email protected]

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Media Contact

Kim Irwin
(310) 794-2262
[email protected]