Dutch doctors and researchers announced Monday that a study involving Viagra and pregnant women had been halted with immediate effect after 11 infants died due to lung conditions possibly linked to the drug.

The study, carried out at the Amsterdam University's Academic Medical Center (AMC) in conjunction with 11 Dutch hospitals, involved administering the drug sildenafil, more commonly known by its brand name Viagra, to pregnant mothers whose babies were severely undeveloped in the womb.

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Viagra increases blood flow, and previous studies had showed the drug to improve the functioning of the placenta, the AMC said in a statement.

Doctors wanted to see whether the drug could "stimulate the growth of the unborn child" who faced a negative prognosis.

"The first results of the current study showed that there may be adverse effects for the baby after birth," the center's statement continued.

It added that the side effects revealed in the study had not been seen before.

The women in the drug-trial study had babies that were highly underdeveloped in the womb. Some were then born with lung conditions.

Lung disease possibly linked to sildenafil

Starting in 2015, the study involved 183 pregnant women, roughly half of whom received sildenafil while the others received a placebo.

Out of the 93 women who took the drug, 19 saw their babies die after birth, with 11 deaths possibly due to high blood pressure in the lungs that may be linked to the drug. Six other babies also had the same lung condition but survived.

Nine babies from the placebo group of 90 women died. None of the placebo deaths were due to the lung condition. Three babies from the placebo group developed the same lung condition as those in the sildenafil group. All three survived. The drug was shown to have no effect on the mothers. About 15 mothers in the drug trial group have yet to give birth.

The AMC said that sildenafil is sometimes prescribed to pregnant women in other countries whose babies face developmental delays in the womb, though this rarely occurs in the Netherlands. It said researchers expect all such usage of the drug to be stopped and that further research should examine the effects and safety of the substance when used in pregnancy.

The center's researchers will analyze the currently available data.

Viagra was originally developed by pharmaceutical company Pfizer and is commonly used to treat erectile dysfunction in men. It is now available as a generic drug.

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cmb/se (AFP, Reuters)

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