Caffeine is to be avoided during pregnancy as it is associated with adverse birth outcomes. 

This is the main conclusion of a new Irish study that examined the effects of maternal caffeine intake from both coffee and tea, Reuters reported.

Pregnant women who consume caffeine  have smaller babies than those who abstain from the stimulant during pregnancy, new research suggests.

Even women who took in less than 200 milligrams of caffeine, the safe cutoff during pregnancy according to the American College of Obstetricians and Gynecologists (ACOG), had a significantly increased risk of delivering prematurely or having a low-birthweight baby.

Planning a pregnancy? Limit your caffeine intake

Based on the consistent associations we observed, and because many pregnancies are unplanned, we would recommend women who are pregnant or seeking to become pregnant to at least limit their intakes of caffeinated coffee and tea,” lead study author Ling-Wei Chen, a researcher at University College Dublin in Ireland, commented to Reuters.

For the current study, Chen’s team looked at 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 about 40 percent drank coffee.

Results

Every additional 100 milligrams of caffeine consumed daily during the first trimester of pregnancy was associated with a 72-gram (2.5 ounce) lower birth weight, as well as significantly lower gestational age, birth length and head circumference.

High caffeine intake can result in restricted blood flow in the placenta which may subsequently affect fetal growth,” Chen explained. “Caffeine can also cross the placenta readily, and because caffeine clearance slows as pregnancy progresses, caffeine accumulation may occur in fetal tissues.”

Women who took in the most caffeine had babies weighing about 170 grams (6 ounces) less than those who consumed the least, the researchers found. Whether the caffeine came from coffee or tea made no difference to the results.

Cause and effect not proved

The study cannot prove cause and effect, Chen cautioned. But several previous studies have linked caffeine exposure in the womb to negative effects, Chen and his colleagues write in The American Journal of Clinical Nutrition.