If the normal health consequences of drinking diet soda weren’t bad enough, now pregnant mothers need to watch their intake in addition to all of the other foods and substances they are told to abstain from.

Researchers studied over 59,000 Danish pregnant women from 1996 to 2002. The women were evaluated during their pregnancy via a written exam, one of the questions gauging their diet soda intake. The expectant mothers who consumed at least one diet soft drink per day were found to have an increased likelihood, 38% more likely, of pre-term birth than the non-diet soda drinking mothers. If they drank four or more drinks per day they were 78% more likely. Those are some pretty scary numbers.

The study was authored by Halldorsson TI, Strøm M, Petersen SB and Olsen SF and is titled Intake of artificially sweetened soft drinks and preterm delivery: a prospective cohort study of 59,334 Danish pregnant women. It was published in the American Journal of Clinical Nutrition in 2010.

Read more: Midwives Magazine