There are currently no reliably safe and effective treatments for morning sickness, a team of researchers has stated.
Cochrane researchers conducted a systematic review of the available evidence and revealed that there was very limited evidence for all pharmaceutical and alternative medicines tested.
The review included 27 randomised controlled trials, which together involved 4,041 women who were up to 20 weeks pregnant.
Benefit was measured by various scales commonly used to gauge the severity of nausea at a time as close as possible to three days after treatment.
In six studies of acupressure and two of acupuncture there were no significant differences in benefit compared to control groups.
One study of acustimulation did, however, report some improvement over three weeks. There was limited evidence of an effect of ginger in relieving nausea, as there was for vitamin B6, antihistamines and antiemetic (anti-vomiting) drugs including the antenatal drug Debendox.
In addition, some of the treatments caused adverse effects including drowsiness in those taking antiemetics.
"A number of the studies we looked at appeared to show benefits, but in general the results were inconsistent and it was difficult to draw firm conclusions about any one treatment in particular," said lead researcher Anne Matthews of the University in Dublin.
"We were also unable to obtain much information about whether these treatments are actually making a difference to women's quality of life.
"Despite the wealth of different treatments available, it is not possible currently to identify with confidence any safe and effective interventions for nausea and vomiting in early pregnancy," she said.