In this guided inquiry, students explore the complex hormonal regulation of the female reproductive cycle using inexpensive ovulation and pregnancy detection hits that are readily available over the counter. This hands-on activity engages students in the practice of doing science as highlighted by the National Science Education Standards. The laboratory approach described is an effective alternative or complement to traditional lecture presentations of this challenging topic. The laboratory activities described are appropriate for both college and high school students, as reproductive physiology is covered in a wide variety of curricula.