Having a lot of caffeine increases your risk of having a miscarriage and a baby with low birth weight.

http://www.patient.co.uk/health/planning-to-become-pregnant

• Certain fish (as described earlier).
• Caffeine should be limited to no more than 200 mg per day. Caffeine is a substance that occurs naturally in foods such as tea, coffee and chocolate; is added to some drinks such as cola, and some energy drinks; and is an ingredient of some cough and cold remedies, and some painkillers which you can buy at pharmacies. Having a lot of caffeine increases your risk of having a miscarriage and a baby with low birth weight.