Pregnancy reminder: For the sake of the child, expectant mothers should limit caffeine intake

Whether or not you should drink coffee during pregnancy and how much coffee is safe to drink has been a major controversial topic in recent years.

According to the recommendation of the American College of Obstetrics and Gynecology in 2010, it is safe for expectant mothers to consume 200 mg of caffeine per day, and the World Health Organization later recommended an upper limit of 300 mg per day. However, a study last year believed that there is no safe upper limit for drinking coffee during pregnancy, so it is best not to drink it if you can.

Recently, a team from the National Institutes of Health (NIH) in the United States investigated the relationship between coffee drinking and the future health of their children among 2,055 pregnant women at 10-13 weeks of pregnancy between 2009 and 2013. In order to be objective, considering that caffeine is not only in coffee but also in tea, a blood test was used to assess the level of caffeine and its main metabolite, 1, 7-dimethylxanthine, in the body. [The analysis results show that if an average pregnant woman consumes 50 mg of caffeine per day, which is half a cup of coffee a day, it may lead to fetal growth retardation, lower baby weight, and thinner arms and thighs.]

Half a cup of coffee is not too much. Within one hour after consuming half a cup of coffee, the caffeine concentration in the body will reach 1859ng/mL, which is nearly three times the highest concentration in the current study (658.8ng/mL). In addition, expectant mothers who drink coffee do not drink much, with only 35.7% of the participants reporting a daily caffeine intake of ≥50 mg, and 41.6% saying they do not drink it at all.

But regardless of whether it is based on the caffeine concentration in the blood or the self-reported situation of expectant mothers, the statistical results show that excessive caffeine intake is related to a decrease in development-related indicators such as fetal weight, arm and thigh circumference. Among them, according to the analysis of caffeine concentration in the blood, the highest concentration group is also related to a decrease in head circumference and height after the fetus is born.

Although it seems that the baby's weight has dropped by dozens of grams, and indicators such as head circumference and height have dropped by less than 1 centimeter, and the fluctuation is not large, but these are fetal data, and the impact may be relatively large when converted into relative levels.

The reason is unknown!

The mechanism for this effect is still unclear. Caffeine may cause uterine and placental blood vessel constriction, affecting blood supply to the fetus and thus delaying development, or caffeine may disrupt the hormone levels in the expectant mother, which may have more profound effects on the fetus after birth.

It seems that expectant mothers may have to completely give up coffee, tea and other caffeinated beverages during pregnancy. Although the long-term effects of caffeine on the fetus cannot be confirmed at present, it is still prudent to limit caffeine intake during pregnancy.

JAMA Network Open, 2021, 4(3): e213238.