However, caffeine is not completely harmless. In fact, caffeine crosses the human placenta, rapidly reaching a similar concentration in the fetus and mother. The excessive intake of caffeine has been implicated as a cause of spontaneous abortion or impaired fetal growth.3 Caffeine intake for women who plan to become pregnant and for women during gestation should not exceed 300mg/day. In a variety of studies for caffeine ingestion, children can be defined as another risk group because altered behavior including nervousness or anxiety is found. It is judged that an intake of 2.5mg/kg body weight/day is an upper limit of caffeine consumption in children (Federal Department of Health, Ottawa, Ontario, Canada).