BAKERSFIELD, Calif. -- Morning sickness is a natural part of pregnancy that affects about half of all pregnant women in their first trimester.

Despite the variety of treatments available to ease the discomfort, a new study from Cochrane researchers found that there are currently no reliable, safe and effective methods to relieve morning sickness.

The study included 27 clinical trials with more than 4,000 women and examined the effects of treatments such as acupuncture, vitamin B6, antihistamines and anti-vomiting drugs.

While some of the treatments appeared to have mild benefits, the results were inconsistent and it was difficult to draw firm conclusions.

In one study, some improvements were made from acustimulation, which is a mild electrical stimulation used on the body to control nausea and vomiting.

Ginger has long been a popular herbal remedy to treat nausea, but studies showed limited evidence that it actually curbed sickness, and it was shown to cause heartburn in some women.