The scans are marketed as a way to catch cancer before symptoms begin, but the radiation from the scans themselves could cause cancer, the researchers said.

"Based on the findings from this study and other recent studies of ginger, there is evidence that ginger is helpful," Dr. Caroline Smith of the University of South Australia in Adelaide told Reuters Health.

"This increases the choices available to women on the management of their nausea and vomiting," Smith said.

Up to 80 percent of pregnant women experience morning sickness during the first trimester of pregnancy. Ginger has long been used to ease nausea, and there is some evidence that the botanical may relieve motion sickness and other types of queasiness. But the research on ginger's ability to ease morning sickness is limited. To investigate, Smith's team enrolled almost 300 women who were less than 16 weeks pregnant and suffered from nausea or vomiting.

Vitamin B6 has been shown to improve nausea and vomiting in some pregnant women, so the researchers compared the effects of ginger with the vitamin. The participants were randomly assigned to take a capsule containing 350-milligram (mg) of ginger or one containing 25 mg of vitamin B6 three times a day for three weeks. Ginger was equally effective as vitamin B6 at relieving nausea, vomiting and dry retching, Smith and her colleagues report in the April issue of the journal Obstetrics and Gynecology. Symptoms of morning sickness improved in a little more than half of the women in each group.

Neither ginger nor vitamin B6 caused any major side effects. However, women who took ginger were much more likely to experience belching after taking the capsules.

There have been some concerns that taking ginger during pregnancy may be harmful to babies, but there were no differences between the ginger and vitamin B6 groups in birth defects or pregnancy complications. But because of the small size of the study, Smith and her colleagues conclude that there is "insufficient data" on the safety of ginger during the first trimester.

"Firm evidence on the safety of ginger in pregnancy is essential and further systematic research on the risks and benefits of ginger during pregnancy would be of great clinical relevance," the authors conclude.

SOURCE: Obstetrics and Gynecology, April 2004.