Determining menstrual phase in human biobehavioral research: A review with recommendations

Given the volume and importance of research focusing on menstrual phase, a review of the strategies being used to identify menstrual phase and recommendations that will promote methodological uniformity in the field is needed. We conducted a literature review via Ovid Medline and PsycINFO. Our goal was to review methods used to identify menstrual phase and subphases in biobehavioral research studies with women who had physiologically natural menstrual cycles. Therefore, we excluded articles that focused on any of the following: use of exogenous hormones, the postpartum period, menstrual-related problems (e.g., polycystic ovarian syndrome, endometriosis), and infertility/anovulation. We also excluded articles on either younger (<18 years old) or older (>45 years old) study samples. We initially identified a total of 1,809 articles. After our exclusionary criteria were applied, 146 articles remained, within which our review identified 6 different methods used to identify menstrual phase and subphases. The most common method used was self-report of onset of menses (145/146 articles) followed by urine luteinizing hormone testing (50/146 articles) and measurement of hormones (estradiol and/or progesterone) in blood samples (49/146 articles). Overall, we found a lack of consistency in the methodology used to determine menstrual phase and subphases. We provide several options to improve accuracy of phase identification, as well as to minimize costs and burden. Adoption of these recommendations will decrease misclassification within individual studies, facilitate cross-study comparisons, and enhance the reproducibility of results.