Researchers Reveal How Drinking Tea, Coffee During Pregnancy Reduces Baby Size
New Research has suggested that pregnant women who consume caffeine – whether it’s from coffee or tea – have smaller babies than those who abstain from the stimulant during pregnancy.
Even women who drink less than the ‘safe’ cutoff of 200mg caffeine – about two mugs of instant coffee or three cups of tea – are more at risk of having low-birth weight or premature newborns.
The researchers, from University College Dublin, believe caffeine restricts blood flow to the placenta, affecting babies’ growth.
“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,”Reuters quoted the lead study author Ling-Wei Chen, a researcher at University College Dublin in Ireland, as saying via an email.
The study cannot prove cause and effect, 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.
In most of those studies, coffee was the main caffeinated beverage consumed.
During 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.
The results suggested that 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.
The researchers further found that women who took in the most caffeine had babies weighing about 170 grams (6 ounces) less than those who consumed the least. Whether the caffeine came from coffee or tea made no difference to the results
“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.”
The researchers worry people are unaware of how much caffeine their tea contains. Tea has less caffeine than a cup of coffee, but the exact amount depends on the brew time, water temperature and type of tea.
The Department of Nutritional Services reports a cup of black tea contains anywhere between 23 and 110mg of caffeine.
The World Health Organization recommends women consume less than 300mg of caffeine a day during pregnancy, while the NHS and American College of Obstetricians and Gynecologists advise no more than 200mg.