However, if a pregnant woman drinks too much or too strong tea, especially strong black tea, it can be harmful to the fetus. Tea leaves contain 2% to 5% caffeine, with approximately 0.06 mg of caffeine per 500 ml of strong black tea. Caffeine has a stimulating effect; excessive tea consumption can stimulate the fetus, increasing fetal movement, and may even endanger fetal growth and development. Surveys by Japanese experts have confirmed that pregnant women drinking five cups of black tea daily may reduce newborn weight. Tea contains tannic acid, which can combine with iron from the pregnant woman's diet to form a complex that the body cannot absorb. Excessive consumption of strong tea may lead to pregnancy anemia, and the fetus might develop congenital iron-deficiency anemia. Scientists conducted experiments using ferric chloride solution as an iron source and found that iron absorption was 21.7% in those who drank plain water, but only 6.2% in those who drank strong tea.
Drinking light green tea is beneficial for both the pregnant woman and the fetus, but green tea also contains tannic acid, which can hinder iron absorption. How can one drink green tea to benefit both the mother and fetus without affecting iron absorption? Pregnant women can resolve this issue by drinking light green tea one hour after meals.
Pregnant women without a tea habit are advised to consume beverages rich in vitamin C, as vitamin C aids iron absorption and enhances the body's resistance to disease.