Facebook is aggressively being used by anti-vaccination advocates to target pregnant women with sponsored advertisements to spread false information and conspiracy theories as the US battles a climbing measles outbreak.

A sponsored ad found by Quartz journalist Jeremy Merrill shows the anti-vaccination organisation Stop Mandatory Vaccination targeting women ages 20 to 60 who have expressed interest in pregnancy living in the state of Washington – where the governor recently declared a state of emergency over the measles outbreak.

Nearly 50 children and young adults in Clark County, Washington have become sickened by the disease since January.