London, Aug 25 (IANS): Women who are pregnant or trying to conceive should be advised to avoid caffeine because evidence suggests that maternal caffeine consumption is linked to negative pregnancy outcomes, say researchers.

The study, published in the journal BMJ Evidence Based Medicine, undertook a review of current evidence on caffeine-related pregnancy outcomes, to determine whether the recommended safe level of consumption for pregnant women is soundly based. Pregnant women have been advised that consuming a small amount of caffeine daily will not harm their baby.

The European Food Safety Authority (EFSA) set this level at 200 mg caffeine, which approximates to roughly two cups of moderate-strength coffee per day.

Through database searches, the research team from Reykjavik University in Iceland identified 1,261 English language peer-reviewed articles linking caffeine and caffeinated beverages 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 overweight and obesity.

A total of 42 separate findings were reported in 37 observational studies; of these 32 found that caffeine significantly increased risk of adverse pregnancy outcomes and 10 found no or inconclusive associations.

The 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 this 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.

The author pointed out that the results could be impacted by other confounding factors, such as the recall of caffeine consumption, maternal cigarette smoking and most importantly pregnancy symptoms.

Pregnancy symptoms such as nausea and vomiting in early pregnancy are predictive of a healthy pregnancy and women who experience them are likely to reduce their caffeine intake.

"The cumulative scientific evidence supports pregnant women and women contemplating pregnancy being advised to avoid caffeine," the study authors wrote.