Objective To assess the use of cervical mucus monitoring (CMM) in women trying to conceive and determine whether monitoring is associated with increased cycle-specific probability of conception (fecundability). Design Time-to-pregnancy cohort study. Setting Population-based cohort. Patient(s) Three hundred thirty-one women trying to conceive, ages 30 to 44 years, without known infertility. Intervention(s) None. Main Outcome Measure(s) CMM prevalence and fecundability. Result(s) During the first cycle of the study, CMM was performed consistently (checked on >66% of pertinent cycle days) by 20 women (6%), inconsistently (34% to 66% of days) by 60 women (18%), infrequently (≤33% of days) by 73 women (22%), and not performed by 178 women (54%). Cycles in which CMM was consistently performed were statistically significantly more likely to result in conception after adjusting for age, race, previous pregnancy, body mass index, intercourse frequency, and urinary luteinizing hormone (LH) monitoring. Fecundability also increased with increasing consistency of CMM. Conclusion(s) Among women trying to conceive, CMM is uncommon, but our study suggests that CMM - a free, self-directed method to determine the fertile window - is associated with increased fecundability independent of intercourse frequency or use of urinary LH monitoring. Copyright © 2013 American Society for Reproductive Medicine, Published by Elsevier Inc.