Amsterdam’s UMC teaching hospital has halted trials of a drug to help pregnant women whose babies are not growing well in the womb after finding a possible link with lung problems and neonatal death, according to news show Hart van Nederland.

The research was being carried out at hospitals across the country and involved giving women with a poorly-performing placenta the drug siddenafil, which is better known as viagra. Hart van Nederland has a copy of the letter sent to women who were taking part.

Chief researcher Wessel Ganzevoort told RTL Nieuws that more babies than expected were born with lung problems. In addition, 11 babies with the lung problem died shortly after birth, he said.

In total, 93 women were given the drug and 17 babies developed lung problems, 11 of which have since died. However, of the 90 women in a control group, who took a placebo, just three developed the same lung issues and none died, RTL Nieuws said.

In addition, 19 babies which were born prematurely died in the trial group, compared with nine in the control group, Hart van Nederland said.

The researchers have now pulled the plug on the trials and alerted health service inspectors.

According to Hart van Nederland, research in other countries indicated that viagra would improve the functioning of the placenta and boost the growth of the baby.