Drinking too much coffee can put pregnant women at risk of delivering a low birth weight baby

A recent research suggests that pregnant women who consume caffeine are at higher risks of delivering a low birth weight baby who is also more likely to be small for gestational age. Maternal coffee intake was also associated with a longer pregnancy.

Caffeine consumption during pregnancy

The existing guidelines on safe amounts of caffeine intake during pregnancy are conflicting because of inconsistent research findings. For instance, the World Health Organisation currently recommends a limit of 300mg of caffeine a day — the equivalent of two 250ml cups of medium-strength coffee — whereas the American College of Obstetricians and Gynecologists reported in 2010 that expecting mothers could safely consume up to 200mg of caffeine a day. In the UK, the Department of Health recommends that pregnant women do not consume more than 200mg of caffeine.

Just like nutrients and oxygen, caffeine can cross the placental barrier freely. However, since the immature foetus does not yet have the necessary enzymes to metabolise the caffeine, the baby is therefore exposed to high levels of caffeine for a long period of time — this could have detrimental effects on the developing baby.

Study details

In order to better understand the effects of caffeine on a growing foetus, scientists from the Norwegian Institute for Public Health analysed data from the 10-year long Norwegian Mother and Child Cohort Study. They selected a total of 59,123 women who had uncomplicated pregnancies, gave birth to a single live baby and had completed three questionnaires: one assessing their general health status, a second one focusing on lifestyle behaviour and a third one investigating their diet intake at gestational weeks 17, 22 and 30. Since there exists no consensus, small for gestational age (SGA) was defined according to ultrasound-based, population-based and growth curves.

Study findings

“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). 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,” said study lead author Verena Sengpiel, MD, from Sahlgrenska University Hospital in Sweden in a news release.

The researchers found that women who consumed over 200mg or caffeine per day had 20 to 60 percent higher risks of delivering a SGA baby. They also reported that for every 100mg of daily caffeine consumption — irrespective of the source (that is coffee, tea, soft drinks, chocolate or cocoa-containing foods) — the birth weight was reduced by 21 to 28 grams while gestation period increased by 5 hours. And if coffee was the source of caffeine, the gestation period augmented by a significant 8 hours for every 100mg consumed per day.

The authors explain that since caffeine is processed more slowly during pregnancy and can cross the placental barrier, it decreases placental blood flow which could hinder foetal growth.

Since SGA babies may be more vulnerable to a host of both short-term and long-term complications, the authors suggest that actual recommendations should be re-evaluated.