Eight studies (702 women) were included: 2 placebo-controlled, double-blind, cross-over randomised controlled trials (RCTs; n=69), 3 crossover RCTs (n=196), 1 RCT (n=60), one controlled trial (n=350), and one pre-test post-test study (n=27).
Acupressure on nausea and vomiting (7 studies): 6 studies reported significant reductions with acupressure, compared with the control treatment. The study reporting no effect (crossover RCT with 157 women) showed a significant decrease in nausea and vomiting for both active treatment and placebo groups (p<0.0009).
Sensory afferant stimulation (1 randomised cross-over study, the sample size was unclear): 15 out of 25 women reported a significant reduction in nausea and vomiting.
Acupressure and affective state (1 crossover RCT with 16 women): acupressure reduced nausea, anxiety, depression, psychosocial dysfunction, and dysfunction in performing activities of daily living (p<0.05).
There were several methodological flaws associated with the primary studies. These included poor questionnaire response rates; small sample size; women unsure about positioning of self-applied bands; no differentiation between nausea and vomiting; no specification of uni- or bilateral application; lack of control group; inclusion and exclusion criteria were unclear; the estimation of gestational age was described generally, and only 2 studies confirmed gestational age using ultrasound; the pressure application time varied both between and within studies; and in some cases, the placebo control actually caused some surface pressure to the Neiguan point.