free style: The Chinook salmon swam from the Pacific Ocean to the South Atlantic Ocean where they don't naturally occur, says a study. The study projected that the silvery predators with a "healthy appetite' threaten to deprive penguins and sea mammals of food. Chinook salmon are a Pacific species that has recently been established in the Santa Cruz River system in the Patagonia region of Argentina. The cooler waters of southern Argentina make the region most vulnerable to invasion, a researcher said.

39 weeks: Babies delivered by elective caesarean (before labour begins) are more likely to have respiratory problems than those delivered vaginally or emergency surgery. Researchers studied 34,458 births at a hospital in Denmark, of which 2,687 were elective caesareans. At 37 weeks, they were four times as likely as others of the same gestational age to have respiratory problems, at 38 weeks, three times, and at 39 weeks, two times. Researchers say it would be a good idea to postpone elective caesareans until 39 weeks.