Pregnancy Nausea Drug Harmless for Fetuses

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Main Category: Pregnancy / Obstetrics
Also Included In: Pediatrics / Children's Health
Article Date: 01 Mar 2013 - 2:00 PST


A large study on the pregnancy nausea drug, Ondansetron, found that its use does not harm the developing embryo or fetus, researchers from the State Serum Institute in Copenhagen, Denmark reported in NEJM (New England Journal of Medicine).

The authors explained that Ondansetron, a drug used for vomiting and nausea, has been used increasingly in pregnancy over the last few years. There had been growing concern among pregnant mothers and health care professionals regarding its safety for the developing baby. Some wondered whether its usage might increase the risk of cleft palate.

The authors said pregnant mothers and their partners should feel reassured that they found no evidence of any detrimental effect on the fetus.

Lead researcher, Björn Pasternak, MD, PhD., said:

"We know that ondansetron (marketed in Denmark under the trade names Ondansetron and Zofran) is prescribed to pregnant women who experience nausea and vomiting in pregnancy ("morning sickness"), at least those with severe symptoms. We also know that the use of this drug in pregnancy has increased in recent years.

However, no one has looked into whether ondansetron is safe to use in pregnancy. That is, prior to our study, it was unknown whether this medication damages the fetus."

Registry-based study

Dr. Pasternak and team gathered nationwide registries and identified all pregnant mothers in Denmark from 2004 through 2011. Women who took Ondansetron were matched with females who did not take it, but were otherwise of the same age, had similar pregnancy histories, medical conditions and other characteristics.

They identified a total of 1,970 women who had used ondansetron while pregnant. 1,233 of them used ondansetron during the first three months of their pregnancy - during this period the embryo/fetus is most sensitive to insults that may result in congenital malformations.

No evidence of increased risk of adverse effects

Dr. Pasternak and team wrote that in the statistical analyses they could not find any evidence of adverse effects to the child from ondansetron. They found no link between the medication and:

• major birth defects
• preterm delivery
• miscarriages
• stillbirth
• any risk of fetal growth restriction

In the journal, the authors concluded:

"Although these results cannot definitively rule out the possibility of adverse effects in association with ondansetron, the results do provide reassurance regarding the use of this agent for nausea and vomiting in pregnancy."

The study was funded by the Danish Medical Research Council.

In January 1991 Ondansetron (Zofran) was approved by the FDA. GSK (GlaxoSmithKline), which at the time was called simply Glaxo, gained a patent extension and had US exclusivity until December 24th, 2006. In December 2006, the FDA approved the first generic versions of ondansetron.

In 2008, researchers from the University of North Carolina at Chapel Hill showed that ondansetron helps reduce vomiting and the need for intravenous fluids and hospitalizations in children with acute gastroenteritis.

What is morning sickness?

Morning sickness, which is also known as nausea gravidarum, emesis gravidarum, or pregnancy sickness, affects over half of all pregnant mothers. Symptoms may appear in the early hours of the morning and reduce as the day progresses, hence the name. In some cases, the symptoms of nausea and vomiting persist all day long.

Typically, most women start feeling better by about the 12th week of their pregnancy.

The symptoms of morning sickness are associated with increased estrogen levels, experts believe. Some women who use hormonal contraception or HRT (hormone replacement therapy) experience a similar kind of nausea.

In mild cases the mother feels slightly nauseous but manages to hold her food down. In moderate to severe cases there is also vomiting. Women with very severe morning sickness - hyperemesis gravidarum - can become dehydrated, lose weight, and develop alkalosis and hypokalemia. Hyperemesis gravidarum occurs in approximately 1% of all pregnancies.

Written by Christian Nordqvist


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