A systematic review of studies investigating the impact of the menstrual cycle on the incidence of postoperative nausea and vomiting

Objective. Several studies suggest that the menstrual cycle has an impact on postoperative nausea and vomiting (PONV). However, many studies report inconsistent results. Thus, in this systematic review the results of all available studies are compared and statistically synthesised. Materials and methods. A systematic search of the literature was performed (Medline, the Cochrane-Library, reference lists of matching articles). The main end point in each study was defined as occurrence of PONV during an observation interval of at least 12 h postoperatively. These data were extracted from each article and the pooled incidences of PONV for each day of the menstrual cycle were calculated. These incidences were analysed using the chi(2)-test. Furthermore the pooled incidences of PONV during the following phases of the menstrual cycle were calculated: days 1-7,8-12, 13-15,16-24, and 25-end of cycle. Results. A total of 12 studies with 2625 patients containing informations on the incidence of PONV on different days or phases of the menstrual cycle were analysed. The total incidence of PONV was 37.3%. The incidence of PONV was lowest (26.9%) on day 20 and reached its maximum on day 5 (45.0%) with no statistically significant differences concerning the incidences of PONV between the different days (p=0,75). Furthermore there were no clinically relevant differences in the incidences of PONV during the phases of the menstrual cycle: day 1-7: 40,4%; day 8-12: 32,9%; day 13-15: 38,1%; day 16-24: 34,5%; day 25-end of cycle: 41,5%. Prophylactic administration of an antiemetic in some of the studies had no impact on these results. Conclusion. Studies investigating the influence of the menstrual cycle on the incidence of PONV show inconsistent results. Summarising the data of these studies suggests that the phase of the menstrual cycle has no impact on the occurrence of PONV.