If you are pregnant, you may want to put that cup of coffee down. Researchers now say that women who have a few cups of coffee may run the risk of having smaller babies. Not only that, but coffee may actually make your pregnancy last a few hours longer. According to the Daily Mail, researchers studied close to 60,000 cases.

Mothers-to-be who have a couple of mugs of coffee a day risk having an underweight baby, research suggests.

Coffee may also make pregnancy last longer - but only 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.

The records included information about how often the women had foods or drinks containing caffeine, from tea and coffee to chocolate sandwich spread and bars of chocolate.

Comparing this with details of their baby revealed a clear link with caffeine and birth weight, with 200 to 300mg a day raising the odds of the child being classed as small for the length of the pregnancy by up to 62 per cent.

A mug of instant coffee contains around 100mg of caffeine, and a mug of filter coffee, around 140mg of caffeine.

However, some drinks sold in high street coffee shops contain as much as 300mg per cup.

In Britain, as in Scandinavia, pregnant women are advised to limit their caffeine intake to 200mg a day.

Coffee, specifically, was found to be linked with increasing the length of pregnancy, with a daily mug of instant coffee lengthening the time the baby is in the womb by eight hours.

Unlike some previous studies, the research did not make a link between caffeine and premature birth.

Researcher Dr Verena Sengpiel, of the Sahlgrenska University Hospital in Sweden, said that caffeine may hurt the growth of the unborn baby by slowing the vital passage of nutrients from mother to baby via the placenta.

Moderation may be key in this story.