Parasitic worm boosts human fertility.

The BBC has me wondering just how many worm-babies there are out there (like blackout babies or blizzard babies). Because being infected with this parasitic worm increases your chance of getting pregnant:

A study of 986 indigenous women in Bolivia indicated a lifetime of Ascaris lumbricoides, a type of roundworm, infection led to an extra two children.

Researchers, writing in the journal Science, suggest the worm is altering the immune system to make it easier to become pregnant.

Experts said the findings could lead to “novel fertility enhancing drugs”.

Nine children is the average family size for Tsimane women in Bolivia. And about 70% of the population has a parasitic worm infection.

But while Ascaris lumbricoides increased fertility in the nine-year study, hookworms had the opposite effect, leading to three fewer children across a lifetime.

Prof Aaron Blackwell, one of the researchers , from the University of California Santa Barara, told the BBC News website: “The effects are unexpectedly large.”