The human reproductive system has received significant attention with respect to the outcome of pregnancy and caffeine intake during pregnancy. The nature of the biological mechanisms involved with any detrimental effect of caffeine on female infertility is uncertain. The studies of time to pregnancy can be useful provided that estimates of prepregnancy caffeine consumption are good; however, it is essential that several sources of bias are accounted for before making any conclusive statements based on the results obtained. The consumption of caffeine is a universally accepted habit; it is the most commonly consumed drug in the world. The primary sources of caffeine are tea and coffee, but it is also available through other dietary sources, including cola beverages and chocolate and nondietary sources via nonprescription drugs such as cold or flu remedies. Discrepancies can be attributed to differences in the measure of caffeine/coffee intake and time to conception data, both of which are imprecise in some studies.