Expecting mothers have one more reason to ban coffee altogether from their diets after a Swedish study found that caffeine intake is linked to longer pregnancies and low birth weights in babies.

According to new research published in BioMed Central’s open access journal BMC Medicine, for every 100 mg of caffeine consumed a day, babies of average expected size -– 3.6 kg –- lost 21 to 28 g in weight among the 60,000 Norwegian women studied.

Babies who are termed small for gestational age at birth, or SGA, are at higher risk of short-term and lifelong health problems, points out the study out of Sahlgrenska University Hospital in Sweden.

Consumption of caffeine from all sources was also found to lengthen pregnancy terms by a rate of five hours per 100 mg of caffeine a day.

Moreover, that figure spiked to an even longer gestational length when caffeine intake came specifically from coffee: eight extra hours for every 100 mg of caffeine a day.

The findings suggest that there’s an additional ingredient in coffee responsible for increasing gestational length, or an additional behavioral habit associated with the consumption of coffee that’s not present among women who drink only tea, for example, authors point out.

Researchers monitored all sources of dietary caffeine, including coffee, tea, fizzy drinks, chocolate, and cocoa-based cakes and desserts.

Meanwhile, the World Health Organization’s daily recommended caffeine intake for pregnant women is 300 mg a day. The average cup of 8 oz coffee in the U.S. contains between 100 to 200 mg of caffeine.

Another study published last year in the Journal of Caffeine Research likewise found that mothers who drink caffeine and breastfeed may find themselves with sleepless, irritable babies given that infants are unable to metabolize or excrete caffeine efficiently.