High levels of caffeine have been linked to an increased risk of miscarriage and low birth weight. However, a moderate amount (roughly one 12oz cup) is considered safe by the ACOG.
A "Use Caution" rating means this food is generally fine during pregnancy but comes with a specific factor worth managing — a daily limit, a preparation requirement, or a moderation guideline — rather than a reason to avoid it outright. These ratings reflect general guidance from the FDA, ACOG, CDC, and USDA. The goal of the "caution" label is to flag what to pay attention to, not to suggest the food is unsafe when that factor is properly managed.