A study by researchers from University of California, Santa Barbara (UCSB), has linked a parasitic worm to high fertility rate in women in Bolivia. The species of parasitic worm found in study is Ascaris lumbricoides, which is a giant roundworm of humans.

The study published in journal Science examined more than 900 Tsimane women. Aaron Blackwell, a researcher in the study, and other researchers from UCSB examined those women who have been infected by Ascaris lumbricoides for most of their lives.

On average, a Tsimane woman has up to nine children, but women infected by Ascaris lumbricoides were able to have two additional children, as per the researchers. They also found that more than two-third of Tsimane has been infected with the parasitic worm, while about 33% individuals in the world are having some form of parasitic infection.

The researchers found that roundworm has been increasing fertility rate in women, while an infection of hookworms is reducing the average number of children in the indigenous women. Blackwell said lifetime of hookworm infection could result in three fewer babies for Tsimane women.

“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”, as per Blackwell. It is important to study the effects of parasitic worms to find fertility enhancing treatments, he said.

Blackwell also said that the researchers are not recommending the procedure to anyone as more research is still needed.