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EXPERT REACTION: High caffeine levels in womb linked to childhood weight gain

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Norwegian researchers are suggesting that pregnant women cut out caffeine altogether, after a new study found there may be a link between consuming mid to high levels of caffeine during pregnancy and your kids gaining weight in early childhood. They didn't just target coffee in their study, and none of your favourites were safe; black tea, caffeinated energy drinks, chocolate, desserts and cakes were all on the hit list. Existing guidelines in Australia and New Zealand recommend limiting caffeine intake while pregnant, but the authors are advocating for a complete cold-turkey stop. However, this type of study cannot prove cause and effect and those who had high caffeine intake were also more likely to smoke be less educated, have been obese before pregnancy and have partners who are obese and smokers, so other experts are suggesting the study be viewed with caution and to consider the wellbeing of mothers before changing guidelines.

Journal/conference: BMJ Open

DOI: 10.1136/ bmjopen-2017-018895

Organisation/s: Norwegian Institute of Public Health, Norway

Funder: The Norwegian Mother and Child Cohort Study is supported by the Norwegian Ministry of Health and Care Services and Ministry of Education and Research.

Media Release

From: The BMJ

Fetal exposure to moderate/high caffeine levels linked to excess childhood weight gain 

Should mums-to-be cut out caffeine altogether, ask the researchers?

Exposure to moderate to high caffeine levels while in the womb is linked to excess weight gain in early childhood, suggests a large observational study published in the online journal BMJ Open.

The findings, which back general advice to limit caffeine intake while pregnant, prompt the researchers to query whether mums-to-be should cut out the world’s most widely consumed central nervous system stimulant altogether.

Caffeine passes rapidly through tissues, including the placenta, and takes the body longer to get rid of during pregnancy. It has been linked to a heightened risk of miscarriage and restricted fetal growth.

The researchers wanted to try and find out if caffeine intake during pregnancy might also be associated with excess weight gain in the child’s early years.

They therefore drew on just under 51,000 mother and infant pairs, all of whom were part of the Norwegian Mother and Child Cohort Study between 2002 and 2008.

At 22 weeks of pregnancy, the mums-to-be were asked to quantify their food and drink intake from among 255 items, including caffeine, using a specially adapted Food Frequency Questionnaire.

Sources of caffeine included coffee, black tea, caffeinated soft/energy drinks, chocolate, chocolate milk, sandwich spreads; and desserts, cakes, and sweets. Daily intake was grouped into: 0-49 mg (low); 50-199 mg (average); 200-299 mg (high); and 300 + mg (very high).

Their children’s weight, height, and body length were subsequently measured at 11 time points: when they were 6 weeks old; at 3, 6, 8, and 12 months; and then at 1.5, 2, 3, 5, 7, and 8 years of age.

Excess weight gain was assessed using World Health Organization criteria, while overweight and obesity were assessed according to International Obesity Task Force criteria. Growth trajectories for weight and length/height were calculated from the age of 1 month to 8 years using a validated approach (Jenss-Bayley growth curve).

Just under half of the mums-to-be (46%) were classified as low caffeine intake; 44 percent as average intake; 7 percent as high; and 3 percent as very high.

The higher the intake, the greater was the likelihood that the mother was older than 30, had had more than one child, consumed more daily calories, and smoked during her pregnancy. And women with a very high caffeine intake during their pregnancy were more likely to be poorly educated, and to have been obese before they got pregnant.

Average, high, and very high caffeine intake during pregnancy were associated with a heightened risk—15, 30, and 66 percent, respectively—of faster excess growth during their child’s infancy than low intake, after taking account of potentially influential factors.

And exposure to any caffeine level while in the womb was associated with a heightened risk of overweight at the ages of 3 and 5 years, although this persisted only for those 8 year olds whose mums had had a very high caffeine intake during their pregnancy.

Children exposed to very high levels of caffeine before birth weighed 67-83 g more in infancy (3-12 months); 110-136 g more as toddlers; 213-320 g more as pre-schoolers (3-5 years); and 480 g more at the age of 8 than children who had been exposed to low levels.

This is an observational study, so it can't confirm causality, while questionnaires can only provide a snapshot in time of dietary behaviour.

Nevertheless, the researchers point to the large sample size, the consistency of their findings, and a plausible biological explanation—fetal programming.

“Maternal caffeine intake may modify the overall weight growth trajectory of the child from birth to 8 years,” they write.

“The results add supporting evidence for the current advice to reduce caffeine intake during pregnancy and indicate that complete avoidance might actually be advisable,” they add.

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Dr Gino Pecoraro is an obstetrician and gynaecologist, based in Queensland. He is the Federal Australian Medical Association Spokesperson for Obstetrics and Gynaecology

How much caffeine is too much?
 
The average espresso contains 63 mg of caffeine, while a 250ml cup of normal white coffee contains 95 mg. Cola-based drinks and tea both contain 50 mg per standard serve.
 
New research out today may provide further evidence that limiting caffeine intake during pregnancy may have beneficial effects for the developing child.
 
A Norwegian study looking at 50,000 mothers and children concluded that children exposed to more than 200 mg of caffeine per day (2 coffees or 4 teas) were more likely to have excess growth during infancy. There seem to be an increased risk with higher levels of caffeine intake, culminating in women ingesting more than 300 mg of caffeine a day having accelerated growth of their children from birth until eight years of age.
 
It may not all be as simple as it sounds, however, as 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?

Last updated: 23 Apr 2018 6:03pm
Dr Clovis Palmer is a Senior Monash University Fellow and head of the Immunometabolism and Inflammation Laboratory at the Burnet Institute

This is a large Norwegian-prospective observational cohort study, claiming that maternal caffeine intake during pregnancy is linked to being overweight in early childhood. They further suggested that a caffeine intake greater than 200mg/day during pregnancy is associated with increased growth rate during childhood.

The researchers provided no evidence of a causal link between prenatal exposure to caffeine and early childhood obesity. 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. 

Last updated: 23 Apr 2018 3:55pm

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