London, July 24 (IANS) Pregnant women now can enjoy their morning coffee as researchers in the US claim that one cup a day is unlikely to cause any harm at all.

They say that 200 mg of caffeine - the equivalent of two cups of instant or one of filter - will not increase the risk of miscarriage or premature birth, Mail Online reported Friday.

In the past, mothers-to-be have been advised not to drink coffee at all because it was thought to substantially increase the risk of harm to the foetus and of reduced birth weight.

The US research by the American College of Obstetricians and Gynaecologists, looked at two previous studies on the effects of coffee consumption on 1,000 pregnant women.

One study found no increased rate of miscarriage for women who consumed low, moderate, or high levels of caffeine at different points in their pregnancy.

The other found a higher risk of miscarriage in women who consumed more than 200mg of caffeine per day, but no extra risk at lower levels.

However, scientists still warn that expectant mothers should not have more than two cups a day as this increases the chance of miscarriage or premature birth.

Dr William Barth, chairman of the American College of Obstetricians and Gynaecologists committee on Obstetric Practice, said: 'I think it's time to comfortably say that it's OK to have a cup of coffee during pregnancy.'