Since 2009, 5-Hour Energy has been mentioned in some 90 filings with the F.D.A., including more than 30 that involved serious or life-threatening injuries like heart attacks, convulsions and, in one case, a spontaneous abortion, a summary of F.D.A. records showed.NYT: Caffeinated Drink Cited in Reports of 13 Deaths
Because caffeine is a stimulant, it increases your blood pressure and heart rate, both of which are not recommended during pregnancy. Caffeine also increases the frequency of urination. This causes reduction in your body fluid levels and can lead to dehydration.
Caffeine crosses the placenta to your baby. Although you may be able to handle the amounts of caffeine you feed your body, your baby cannot.