During pregnancy it is important to cut down on your daily coffee. The word "caffeine" comes from the French term for coffee, café. Caffeine is found in varying quantities in the beans, leaves, and fruit of over 60 plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the
plants. Caffeine is most commonly consumed by humans in infusions extracted from the beans of the coffee plant and the leaves of the tea bush, as well as from various foods and drinks containing products derived from the kola nut or from cacao.
In humans, caffeine is a central nervous system (CNS) stimulant, having the effect of  temporarily warding off drowsiness and restoring alertness. Beverages containing caffeine, such as coffee, tea, soft drinks and energy drinks enjoy great popularity; caffeine is the world's most widely consumed psychoactive substance, but unlike most other psychoactive substances, it is legal and unregulated in nearly all jurisdictions.

The Food Standards Agency has recommended that pregnant women should limit their caffeine intake to less than 300 mg of caffeine a day - the equivalent of four cups of coffee a day. A higher intake may be associated with miscarriage. A study published in January 2008 concludes that an intake of 200 milligrams or more per day, representing two or more cups, "significantly increases the risk of miscarriage".
The only way to be 100% sure that you won't do any harm to the pregnancy is to completely abstain from drinking any caffeine when trying to conceive and in pregnancy.