Research out [recently] may one day complicate the standard advice given to pregnant people about drinking coffee. The study found that people with higher levels of caffeine consumption during their first trimester of pregnancy went on to have slightly shorter children on average than those with less caffeine in their system. This association was seen even with modest amounts of caffeine below the maximum daily dose recommended by experts. But it’s not clear yet whether the connection raises the risk of relevant health problems, such as obesity.
The study was led by researchers from the National Institutes of Health. They analyzed data from two previous long-running observational studies of pregnant people that also kept track of their children’s health through age 8. As part of these studies, the mothers had their levels of caffeine and paraxanthine (a byproduct of caffeine) measured through blood samples collected in the first trimester of pregnancy. They then compared the height and weight outcomes of children born to these parents.
They also note that there is a biologically plausible explanation for this effect. Caffeine can cross over through the placenta and reach the fetus, and neither the placenta nor the fetus produce an enzyme that allows fully developed humans to break down caffeine, meaning that it could accumulate in fetal tissue. From there, the caffeine might be able to interfere with how fetuses respond to hormones that regulate their growth, the authors theorize.
