A new study has warned that women should avoid drinking any tea or coffee while they are pregnant.
Current guidelines say mums-to-be can enjoy about two cups of coffee a day without affecting their unborn baby’s health but researchers who analysed previous studies say there is no safe level of caffeine consumption for pregnant women.
They are now calling for a “radical revision” of health advice to warn women who are pregnant or trying to conceive that they should avoid caffeine completely.
The NHS currently sets the “safe” caffeine level at 200mg, which is the equivalent to around two cups of moderate-strength coffee per day.
But the new analysis of observational studies, published in BMJ Evidence Based Medicine, suggests there is no safe level of consumption during pregnancy.
Through database searches, Professor Jack James identified 1,261 English language peer-reviewed articles linking caffeine and caffeinated drinks to pregnancy outcomes. These were whittled down to 48 original observational studies and meta-analyses published in the past two decades reporting results for one or more of six major negative pregnancy outcomes.
The outcomes were miscarriage, stillbirth, low birth weight and/or small for gestational age, preterm birth, childhood acute leukaemia, and childhood obesity.
A total of 42 separate findings were reported in 37 observational studies; of these 32 found caffeine significantly increased risk of adverse pregnancy outcomes and 10 found no or inconclusive associations.
Prof James, of Reykjavik University, Iceland, said: “Caffeine-related risk was reported with moderate to high levels of consistency for all pregnancy outcomes except preterm birth.
“Eleven studies reported on the findings of 17 meta-analyses, and in 14 of these maternal caffeine consumption was associated with increased risk for four adverse outcomes: miscarriage, stillbirth, low birth weight and/or small for gestational age, and childhood acute leukaemia.
“The three remaining meta-analyses did not find an association between maternal caffeine consumption and preterm birth.”
Prof James said no meta-analyses looked at the association between maternal caffeine consumption and childhood obesity, but four of five observational studies reported significant associations.
He said that although it was an observational study, which can’t establish causation, the nature of the associations between caffeine and adverse pregnancy outcomes, and the fact some studies found no threshold below which negative outcomes were absent, “supports” likely causation rather than mere association.
Prof James concluded there is “substantial cumulative evidence” of an association between maternal caffeine consumption and diverse negative pregnancy outcomes.
As a result, he said, current health recommendations concerning caffeine consumption during pregnancy are in need of “radical revision”.
Prof James added: “Specifically, the cumulative scientific evidence supports pregnant women and women contemplating pregnancy being advised to avoid caffeine.”