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©2013 UpToDate ® Print Email Ascaris lumbricoides life cycle Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces (2) . Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3) , depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4) , the larvae hatch (5) , invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs (6) . The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7) . Upon reaching the small intestine, they develop into adult worms (1) . Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years. Reproduced from: Centers for Disease Control and Prevention. Available at: file://www.dpd.cdc.gov/dpdx/html/ascariasis.htm .