Roundworm infections found to increase fertility in women

A Tsimane family

This finding, according to experts, might lead to the formulation of new fertility enhancing drugs. Hookworms - bloodsucking parasites about the length of a grain of rice - seemed to postpone women's first pregnancies.

Scientists have - slightly improbably - discovered that infection by the roundworm Ascaris lumbricoides increases fertility in women belonging to Bolivia's Tsimane ethnic group.

Parasitic worms can live inside humans gaining nourishment from the food we ingest (roundworms) or from our blood (hook worms), whilst being safe from predators. The age-old concept may need a rethinking if the findings of a study on the linkage between parasitic worms and female fertility are firmly established.

Tsimane women often are unaware they've been infected because there often are no symptoms, however these women show levels of increased immune response, and being infected with either of the worms has an effect on the chances of infection with other parasites or diseases.

The researchers also noted that the women infected with the roundworm species have shortened intervals between births and have earlier first pregnancies. On the flip side, researchers found that women with hookworm had three fewer children during their lifetime.

Professor Aaron Blackwell, one of the authors of the study and a researcher at the University of California, Santa Barbara, told BBC News website the worm's effects were unexpectedly significant. However, a few of these parasites actually have a lot in common with a fetus in the womb-triggering a few of the same immune changes that occur during pregnancy. This means they double in size every 17 or so years. On the contrary, the infection with roundworms makes the immune system to produce more type 2 T cells, which definitely helps pregnant women by creating a sort of defense mechanism which protects the embryo from being harmed.

Overall, women infected with roundworm were more likely to get pregnant, and those with hookworm were less likely. 

Using worms as a fertility treatment was an "intriguing possibility", he said, but warned more studies needed to be carried out before he could recommend trying this.