--- title: Parasitic Worm May Increase Women's Fertility: Study description: The researchers studied 986 Tsimane women in Bolivia for nine years. canonical: https://time.com/4121861/parasitic-worm-fertility-study/ author: Julia Zorthian article:opinion: false article:content_tier: free article:published_time: 2015-11-20T14:18:51.000Z article:modified_time: 2026-08-04T07:57:06.985Z article:section: Health og:title: Parasitic Worm May Increase Women's Fertility, Study Suggests og:description: The infection may have an effect on the immune system og:url: https://time.com/4121861/parasitic-worm-fertility-study/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltbcbbc1c7153a17b5/6988721c5f570f3519b1e72a/ascaris-lumbricoides.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 4625 og:image:height: 2602 og:image:alt: 158680049 og:type: article twitter:card: summary_large_image twitter:title: Parasitic Worm May Increase Women's Fertility, Study Suggests twitter:description: The infection may have an effect on the immune system twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltbcbbc1c7153a17b5/6988721c5f570f3519b1e72a/ascaris-lumbricoides.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Parasitic Worm May Increase Women's Fertility, Study Suggests > Sponsored content. 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But it's been a long and controversial process._  by [Julia Zorthian](https://time.com/author/julia-zorthian/)  ## Julia Zorthian Nov 20, 2015 2:18 PM UTC  Ascaris Lumbricoides unfertilized eggs under a microscope. Ascaris Lumbricoides unfertilized eggs under a microscope. Getty Images  by [Julia Zorthian](https://time.com/author/julia-zorthian/)  ## Julia Zorthian Nov 20, 2015 2:18 PM UTC Women who are infected with a certain parasitic worm may be more likely to become pregnant, according to a new study. The study, [published in ](http://www.sciencemag.org/content/350/6263/970)[_Science_](http://www.sciencemag.org/content/350/6263/970)on Friday, studied 986 Tsimane women in Bolivia for nine years, and found that women infected with the roundworm species _scaris lumbricoides_ had about two more children than women without the worm (Tsimane women have an average of 10 children in general). The researchers noted that the infection is associated with shortened intervals between births, and with earlier first pregnancies. “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,” University of California Santa Barbara professor Aaron Blackwell, one of the study’s authors, [told the BBC](http://www.bbc.com/news/health-34857022). The researchers suggested that a suppressed immune system due to the infection may make the body less likely to reject a fetus. Blackwell added that further research is necessary before there could be any practical use of this potential link between the roundworm infection and fertility. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/4121861/parasitic-worm-fertility-study/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/4121861/parasitic-worm-fertility-study/"},"headline":"Parasitic Worm May Increase Women's Fertility, Study Suggests","datePublished":"2015-11-20T14:18:51.000Z","dateModified":"2026-08-04T07:57:06.985Z","description":"The infection may have an effect on the immune system","url":"https://time.com/4121861/parasitic-worm-fertility-study/","keywords":["Research"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltbcbbc1c7153a17b5/6988721c5f570f3519b1e72a/ascaris-lumbricoides.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Julia Zorthian","jobTitle":null,"url":"https://time.com/author/julia-zorthian/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltbcbbc1c7153a17b5/6988721c5f570f3519b1e72a/ascaris-lumbricoides.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"158680049","caption":"158680049","creditText":"Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/research/","name":"Research"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/4121861/parasitic-worm-fertility-study/","name":"Parasitic Worm May Increase Women's Fertility, Study Suggests"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"After 2 Rejections, FDA Approves Drug Dubbed 'Female Viagra'","description":"The FDA approved Addyi, a drug whose maker claims it helps raise sexual desire in women. 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