Coffee linked to birth of smaller babies: Study
London: Mothers-to-be who have a couple of mugs of coffee a day risk having an underweight baby, a new study has warned.
Researchers also found that coffee may make pregnancy last longer – by a matter of hours.
The observations come from researchers who studied detailed records of almost 60,000 pregnancies from a ten-year period in Norway.
New research published in the journal BMC Medicine shows that along with nutrients and oxygen, caffeine freely passes the placental barrier, but the developing embryo does not express the enzymes required to inactivate it efficiently.
The World Health Organisation (WHO) currently suggests a limit of 300mg of caffeine per day during pregnancy but some countries recommend a limit of 200mg, which can be less than a single cup of coffee from some high street cafes.
Researchers from the Norwegian Institute for Public Health used information about mother's diet and birth details collected over ten years.
All sources of caffeine were monitored in the study: coffee, tea, fizzy drinks, as well as food including cocoa-containing cakes and deserts and chocolate.
"Although caffeine consumption is strongly correlated with smoking which is known to increase the risk for both preterm delivery and the baby being small for gestational age at birth (SGA)," Dr Verena Sengpiel, from Sahlgrenska University Hospital, Sweden, who led the project said.
"In this study we found no association between either total caffeine or coffee caffeine and preterm delivery but we did find an association between caffeine and SGA.
"This association remained even when we looked only at non-smoking mothers which implies that the caffeine itself is also having an effect on birth weight," Sengpiel said in a statement.
Researchers found that caffeine from all sources reduced birth weight. For a child of expected average weight (3.6kg) this equates to 21-28g lost per 100mg caffeine per day.
Caffeine also increased the length of the pregnancy by 5hr per 100mg caffeine per day, but caffeine intake from coffee was associated with an even longer gestational length – 8hr extra for every 100mg caffeine per day.