Objective: We review intervention trials that have used the State-Trait Anxiety inventory (STAI) as a measure of maternal anxiety in pregnancy in order to provide ranges in scores before and after participation in complementary therapy-based interventions to highlight the expected ranges of scores in pregnancy and determine whether anxiety in pregnancy is amenable to change when measured by the STAI. Methods: Combinations of the key words STAI, state anxiety, pregnancy, anxiety, maternal, stress, outcome and intervention were used to search publications between January 1970 and January 2011. Studies eligible for inclusion recruited low risk, adult women to a non-pharmacological intervention or a comparator group, and measured anxiety at baseline and post-intervention. Results: Ten studies were eligible. Scores were routinely high compared to expected ranges in non-pregnant populations. Studies examining the immediate effects of an intervention consistently reported significantly lowered STAI scores after a single session. Likewise, studies examining the effect of interventions consisting of multiple sessions over the course of pregnancy found that those in the intervention group were more likely to show an improvement in STAI scores. Limitations: Heterogeneity in type and duration of intervention prevent drawing conclusions on which were most effective in reducing anxiety. Conclusion: Scores on the STAI appear amenable to change during pregnancy, both after a single session and multiple sessions of interventions designed to reduce maternal anxiety. This review offers a guideline for the expected range of scores for future studies examining the efficacy of interventions in pregnancy when using the STAI.