A clinical trial that involved giving sildenafil, a drug typically used to treat erectile dysfunction, to expecting mothers has been been immediately halted after 11 newborn babies died.

The Dutch study was examining the possible benefits of the medication, which increases blood flow, on improving the growth of fetuses in mothers with poorly developed placentas, Reuters reports. But the drug may have resulted in lethal damage to the babies' lungs.

The trial, which began in 2015, involved 11 hospitals and 183 women.

Among the treatment group, 17 babies developed lung conditions that reportedly caused high blood pressure in the lungs and may have been the result of reduced oxygen levels. Eleven of these newborns died.

In the control group, three newborns developed lung conditions, and none died.

The researchers found no positive effect of the drug, the Amsterdam University’s Academic Medical Center (AMC) said.

Sildenafil is the active ingredient in popular erectile dysfunction medications like Viagra, but the study did not involve Viagra nor a generic form authorized by Viagra’s creator, Pfizer.

Underdeveloped placentas can led to fetal growth restriction, a serious condition that can result in premature births, low birth weights and death. There is currently no treatment.

Previous studies in the U.K., Australia and New Zealand also examined whether sildenafil could assist these babies. No evidence of harm, or benefit, was observed in these trials.

“There have been other studies in this area, both involving preliminary work using animals and using pregnant women, and there was no indication that the treatment was dangerous based on previous research,” Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, told Reuters.

At the time the Dutch trial was halted on Monday, approximately half of the 183 pregnant women participating were taking sildenafil, according to the AMC. More than a dozen have yet to give birth.

Correction July 25

The original version of this story misstated the drug involved in the study. It was sildenafil, the active ingredient in many erectile dysfunction drugs. It was not Viagra or the generic form made by Viagra ’s creator, Pfizer.