Previous research in rats suggested the drug might boost blood flow in the placenta and promote a baby's growth, The Guardian reported. Half the subjects are given sildenafil and half are given a placebo, three times daily. "The researchers expect that the use of sildenafil for this application will stop worldwide".
The Dutch study began in 2015 and involved 183 women.
It sometimes occurs because the mother has high blood pressure, uncontrolled diabetes or a condition called preeclampsia, he added. But the drug may have resulted in lethal damage to the babies' lungs.
Out of the placebo group, nine babies died, none of them from lung disease. Some were then born with lung conditions.
The Queensland trial has had no adverse effects so far.
The research, led by Amsterdam University Medical Center, focused on improving the flow of blood through the placentas of 93 pregnant women.
During the study, another 90 women took a placebo pill with no active ingredients. Out of 93 babies born in the trial, 19 died, including 11 possibly from a lung condition linked to the medicine that resulted in reduced oxygen levels. It can lead to stillbirth or neonatal death, and babies that survive are still at higher risk for infections and often suffer from long-term problems such as obesity and cardiovascular disease. Women participated in a medical experiment. One of the first things we heard was that they were doing this research and they said it might benefit us.
It was hoped the drug would increase the size of the placenta and encourage their development.
The trial has now been cancelled and an investigation is ongoing.
The company also issued a statement Wednesday noting that it did not fund or provide medication for the trial.
In a statement, Pfizer, the makers of Viagra, said they were not involved in the trial, "and neither funded nor provided product for the trial". A study by a team in the United Kingdom, published online in The Lancet Child & Adolescent Health in December 2017, found sildenafil didn't improve the duration of pregnancy, birth weight, or fetal and neonatal survival. That poses a hard dilemma for doctors: Inducing birth too early increases the risk of complications, but waiting too long could lead to developmental anomalies or stillbirth.
She has no concerns for the participants of a New Zealand and Australian trial. A large number of newborn deaths has caused the trial to be halted.
A second trial with the same drug in Canada has also been paused, though there is no indication anyone there has been harmed.
Between 10 and 15 women are still waiting to find out if their baby has been affected.
"We have already notified Canadian researchers who are conducting a similar study", Ganzevoort said. One possible explanation is a "rebound effect", Groom says. The drug dilates the blood vessels.