Dutch experts have analyzed data on tea and coffee consumption as well as health conditions of 936 pregnant women (healthy, with uncomplicated pregnancy). The results of their study report the following.
In the course of this study, the experts found no associations between coffee or tea intake and birth weight or birth length (also with regard to gestational age). At the same time, they identified a significant association between high caffeine consumption (more than 300 mg per day) and a modest increase in gestational age at birth. And also a possible relation between high tea consumption and increased risk for pregnancy induced hypertension, which the scientists hope to further investigate in more detail.
By the way. In 2013, a Norwegian study on coffee, tea and chocolate consumption by pregnant women demonstrated that every additional 100 mg of coffee caffeine per day delayed labor for eight hours.
A thing to remember.