Nausea and vomiting in pregnancy- known as morning sickness- affects up to 80% of pregnant women. Doctors are increasingly turning to a prescription drug known as Zofran (generic name ondansetron) to solve this important problem. But- there is conflicting evidence in the media about the safety of Zofran in pregnancy. The May 2016 Green Journal provides as an analysis of the current safety studies on this helpful drug. So, is it safe?
Morning sickness affects the vast majority of pregnant women. Untreated, it can progress to severe nausea and vomiting, known as "hyperemesis gravidarum." 59,000 women are hospitalized every year because their nausea and vomiting becomes so severe. It can even cause malnutrition and increase the risk of preterm birth and infants who are born small for their age. This is not only a tremendous health problem; the costs of treating nausea and vomiting in pregnancy are astronomical. In 2012, hyperemesis gravidarum cost $2 billion. That's quite the bill.
The big OBGYN physician group ACOG recommends lifestyle changes as the first treatment for morning sickness- multivitamins and small meals. If this doesn't work, they recommend adding vitamin B6 and doxylamine, which is an anti-histamine (think: same family as Benadryl). The two drugs are combined in a pill known as Diclegis, which is FDA approved for this purpose. If that doesn't work, doctors may need to turn to IV treatments for unstoppable vomiting. Dramamine, Phenergan, and Reglan are all considered safe, but have side effects like drowsiness. If none of these works, Zofran is the next option.
However, real practice differs from this treatment plan. Because Zofran works better and has fewer side effects than the third-line treatments above, many doctors and patients prefer to use Zofran. In fact, you can't argue its popularity. It's the fifth most taken oral medication in pregnancy and the most commonly used prescription oral anti-nausea pill in pregnancy in the US. In the ER, about half of pregnant women with unstoppable vomiting receive IV Zofran.
The question, therefore, becomes even more urgent: is it safe? Rest assured, this review of the literature is reassuring. In 2013, the most scientifically sound study to date was published by Pasternak et al. They used the Danish National Birth Registry with about 441,500 pregnancies and over 1,200 women with a history of taking Zofran in the first trimester. The first trimester is key. Babies' organs are formed in the first trimester, so for a drug to cause birth defects, then it must have been taken before or during the formation of the organs. A little less than 3% of infants had a birth defect, regardless of whether or not mothers took Zofran.
In 2014, Danielsson et al published another study using data from Sweden. Their results raised concerns about Zofran causing heart defects. However, they did not take into account chromosomal abnormalities that cause heart defects or diabetes, which can also increase risk. A smaller 2012 study by Anderka et al revealed concern for an increased risk of cleft palate. However, this study was subject to recall bias and not as scientifically strong as the others, which showed no risk of cleft palate. Finally, Anderson et al in 2013 published an abstract using the Danish data, raising concern for heart defects. Unfortunately, they never published their findings in a peer-reviewed journal, so there is no way to know how or why they found those results, or if they are truly concerning. Finally, another study in 2013 from Australia provided reassuring results.
Taken all together, this is good news for pregnant women. Zofran can be a life saver for busy moms-to-be who are suffering from nausea and vomiting of pregnancy. As the authors of this review conclude, doctors can consider using Zofran when Diclegis fails, as the current evidence points to a good safety profile.