Caffeine in tea, coffee can be just as risky for the fetus

New research suggests that pregnant women who consume caffeine – be it coffee or tea – have babies who are smaller than those who do not take this stimulant during pregnancy.

Even women who consumed less than 200 milligrams of caffeine, safe threshold during pregnancy according to the American College of Obstetricians and Gynecologists (ACOG), had a significantly increased risk of premature labor or delivery. low birth weight.

"On the basis of the consistent associations we have observed and the fact that many pregnancies are unplanned, we recommend that pregnant women or women who wish to become pregnant should at least limit their consumption of coffee and tea containing caffeine", Ling-Wei Chen, lead author of the study researcher at University College Dublin in Ireland, said in an email.

The study can not prove the cause and effect, he warned. But several previous studies have associated exposure to caffeine in the uterus to negative effects, write Chen and colleagues in The American Journal of Clinical Nutrition.

In most of these studies, coffee was the main drink containing caffeine consumed.

For the current study, Chen's team studied 941 mother-child pairs born in Ireland, where people drink more tea than coffee. Nearly half of the mothers in the study drank tea, while 40% drank coffee.

Each additional 100 milligrams of caffeine consumed daily during the first trimester of pregnancy was associated with a birth weight of 2.5 ounces (72 grams) and a gestational age, length at birth and a much lower head circumference.

The researchers found that women who took the most caffeine had babies weighing about 170 grams (6 ounces) less than those who consumed the least. Whether caffeine comes from coffee or tea makes no difference in the results.

"High caffeine intake can cause limited blood flow to the placenta, which can affect fetal growth," said Chen. "Caffeine can also easily cross the placenta and, since caffeine clearance slows as pregnancy progresses, caffeine buildup can occur in fetal tissue."

A cup of brewed coffee (355 ml) contains about 200 mg of caffeine, but tea usually contains less caffeine and its amount may vary depending on the type of tea and the duration of its infusion. Lipton Tea, for example, says its black tea contains about 83 mg of caffeine in a 12-ounce cup.

The public does not seem to recognize the caffeine content of tea, said lead author of the study, Catherine Phillips, a researcher at University College Dublin. "Maternal intake of tea and coffee should be taken into account when trying to minimize the overall intake of caffeine during pregnancy. This is especially important when tea is the main source of caffeine, "she told Reuters Health by email.

According to the ACOG, consuming less than 200 milligrams of caffeine per day during pregnancy "does not appear to be a major contributor to miscarriage or premature birth." The World Health Organization recommends that women consume less than 300 mg of caffeine per day during pregnancy.

"This document and other documents show that this rate is probably too high," said Dr. De-Kun Li, principal investigator at the Kaiser Permanente Northern California Research Division in Oakland, who did not participated in the study. "Epidemiological findings based on self-reported caffeine use are generally not very accurate. Thus, the thresholds chosen by ACOG and WHO can only be considered as approximate reference points. Biologically, 300 mg is unlikely to be risky, while 299 mg is safe, "Li said in a phone interview.

"The message I would prefer to women would be:" The less there is, the better, "Li said." Then women can choose for themselves. "

Reports touting the health benefits of caffeine should also include a warning that it may be harmful during pregnancy, Li added, whose research has linked caffeine consumption during pregnancy. , miscarriage and childhood obesity. "My advice would be to try to reduce as much as possible.If you could totally stop smoking, it would be even better."

ACOG told Reuters Health that it reviewed all of its recommendations every 18 to 24 months, that it incorporated all new research into its reviews, and made the necessary adjustments, as appropriate. "Until then, current ACOG guidelines are still valid."

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