How much caffeine is too much?

pregnant woman coffee pregnancy

New observational research may provide further impetus for expectant mums to limit caffeine intake

In a prospective cohort study of 50,943 mothers and their children recruited from 2002 to 2008, Norwegian researchers looked at the potential association between caffeine intake during pregnancy and child weight gain/overweight risk.

Sources of caffeine in the study included coffee, black tea, caffeinated soft drinks, energy drinks, chocolate, chocolate milk, sandwich spreads; and desserts, cakes, and sweets.

The average espresso contains 63 mg of caffeine, while a 250 ml cup of normal white coffee contains 95 mg. Cola-based drinks and tea both contain 50 mg per standard serve.

According to results published in the BMJ this week, researchers found that compared with pregnant women with low caffeine intake (<50 mg/day, 46%), women with average (50–199 mg/day, 44%), high (≥200–299 mg/day, 7%) and very high (≥300 mg/day, 3%) caffeine intakes had an increased risk of their child experiencing excess growth in infancy.

In utero exposure to any caffeine was associated with higher risk of overweight at age three and five years, while the association persisted at eight years, only for very high exposures.

Any caffeine intake was associated with increased body mass index from infancy to childhood.

Children prenatally exposed to caffeine intake >200 mg/day had consistently higher weight. Very high caffeine exposures were associated with higher weight gain velocity from infancy to age eight years.

“Any caffeine consumption during pregnancy is associated with a higher risk of excess infant growth and of childhood overweight, mainly at preschool ages,” conclude the authors.

“Maternal caffeine intake may modify the overall weight growth trajectory of the child from birth to eight years.

“This study adds supporting evidence for the current advice to reduce caffeine intake during pregnancy.”

Most health authorities suggest that pregnant women limit their caffeine intake since, after ingestion, caffeine is readily absorbed into the bloodstream and distributed to the tissues.

“During pregnancy, elimination of caffeine is prolonged and it rapidly passes all biological membranes, including the blood-brain and placenta barriers, resulting in exposure of the fetus,” explain the authors.

“Not novel or unexpected”

While the study shows a link, “it may not all be as simple as it sounds,” according to Dr Gino Pecoraro, the Australian Medical Association spokesperson for obstetrics and gynaecology.

“We know that the higher the chances the mother having caffeine, the more likely she is to be older than 30 years, have had previous multiple children, have an increase daily calorie count herself, be a smoker during the pregnancy and not suffer nausea or vomiting during the pregnancy.

“In addition, women with very high (greater than 300 mg of caffeine per day) were also more likely to have low education levels, have been obese before pregnancy and have partners who are obese and smokers, compared with others.

“While interesting and worthy of discussion with would-be and pregnant women, the exact level of safe caffeine consumption in pregnancy is not clear, although whether doctors should just advise total abstinence as in alcohol where the safe level is unclear, remains to be seen.

“An interesting area for future research may well be does treating women with caffeine induce greater foetal growth in women at risk for small babies?”

The research provides no evidence of a causal link between prenatal exposure to caffeine and early childhood obesity, argues Dr Clovis Palmer, Senior Monash University Fellow and head of the Immunometabolism and Inflammation Laboratory at the Burnet Institute.

“In this study, the mothers with high caffeine intake were most likely to be heavy smokers, economically disadvantaged, have poor diet and be overweight. These factors may have had stronger influence on early childhood obesity than dietary caffeine intake itself.

“Indeed, previous work conducted at the University of New South Wales by Morris and colleagues have lent support to a direct link between cigarette smoking during pregnancy and abnormal metabolic outcomes in offspring.

“It has already been recommended that women should limit caffeine intake during pregnancy, therefore the overall conclusion of this work is not novel or unexpected.

“Notwithstanding, the work adds to a growing body of evidence that a break from a cuppa during pregnancy may be good for the health of the next generation.”

See the full study here

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