Scientists have discovered that a species of parasitic worm increases fertility in women.

Researchers studying 986 indigenous women in Bolivia discovered evidence that an infection of Ascaris lumbricoides, a type of roundworm, can lead to women having an extra two children over their lifetime.

For Tsimane in Bolivia, around 70 per cent of the population are infected with the worm,where the average number of children per woman is nine.

The study, publish in the journal Science, indicates that the parasite has the ability to alter the immune system so that it is easier to fall pregnant.

Experts say that this discovery could one day be used to create new fertility enhancing drugs.

Researcher Prof Aaron Blackwell, of the University of California Santa Barara, told the BBC News that changes to the immune system would make a woman’s body less like to reject a foetus.

He said: “We think the effects we see are probably due to these infections altering women’s immune systems, such that they become more or less friendly towards a pregnancy.”

He added that a lot of work would need to be done “before we would recommend anyone try this.”

On the other hand, it was also found that an infection of Ascaris lumbricoides hookworms had the opposite effect, resulting in three fewer children over a lifetime.

Prof Rick Maizels, a specialist in parasitic worms and the immune system, told the BBC News: “It’s horrifying that the hookworm effects are so profound, half of women by 26 or 28 have yet to fall pregnant and that’s a huge effect on life.”

He suggested that anaemia caused by hookworm may be one explanation behind its effect on fertility.

Source: BBC News/James Gallagher