BMJ: 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,” the 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.
[Ends]
Maternal
caffeine intake during pregnancy and childhood growth and overweight:
results from a large Norwegian prospective observational cohort study
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