The anti-impotence drug Viagra could be used to treat a pregnancy disorder which can prove fatal for mothers and babies, researchers suggest.
Experts say Viagra could aid blood flow to the foetus
Pre-eclampsia affects about one in 10 pregnancies, and kills up to five women and 600 babies a year in the UK.
Tests on rats by a team at University of Vermont College of Medicine showed no offspring died in the pregnancies where mother rats were given Viagra.
UK experts said the finding gave hope for future treatment of the condition.
The US research is to be presented to the International Union of Physiological Sciences meeting in San Diego, US this week.
The scientists studied rats with induced high blood pressure.
Half were given Viagra, while the rest were left untreated.
There were no deaths of foetuses in the pregnancies treated with Viagra, but 11% of foetuses were lost in pregnancies in untreated rats.
Pre-eclampsia occurs in pregnancies where the arteries which cross through the placenta do not widen as much as they should be to take the necessary amount of blood and nutrients from the mother to the developing foetus.
If this happens, the mother's body works harder to pump enough blood and nutrients through - and her blood pressure goes up.
Viagra works by inhibiting the action of an enzyme called PDE-5, which prevents the expansion of arteries.
The researchers found the drug did not lower blood pressure, in the rats, but it did have beneficial effects.
The arteries in treated rats were much wider than those in untreated animals, allowing better circulation of blood and nutrients.
The offspring from these pregnancies were also of a normal weight. Surviving offspring from untreated rats were around 20% smaller.
Professor George Osol, who led the research, said more work was needed to confirm his findings.
But he added: "These findings are exciting because they suggest that Viagra may have beneficial effects in hypertensive pregnancy and possibly, pre-eclampsia."
Mike Rich, chief executive of the charity Action on Pre-eclampsia, said: "Using Viagra would not cure the pre-eclampsia, but you could potentially get to a point where you could prolong a pregnancy by enabling better blood flow."