To help fulfil the objectives of prospective studies of pregnancy and human development, such as the National Children's Study, there is a need to pinpoint ovulation and conception in a cohort of women. This paper discusses the suitability of using natural and easily observed markers of ovulation for detection of the most likely day of ovulation and conception. Of the biomarkers supported by clinical data, the use of cervical mucus is emphasised as it appears most promising. A considerable amount of data suggests that observation of changes in vaginal discharge from cervical mucus can closely approximate the day of ovulation, is easy to learn and suitable for a large group of women. While this approach could also be cost-effective, a significant drawback may be the learning phase which may take 2-3 instructional sessions for women to fully identify recurring changes across the menstrual cycle.