There is currently a lot of chatter about the study by Pål Surén and colleagues* (open-access) reporting that "Use of prenatal folic acid supplements around the time of conception was associated with a lower risk of autistic disorder".
Since the paper is open-access and opinions already abound about the findings (see here and here and here), there is little point in me adding to the column inches. So instead, I'll direct you to a previous post on the topic of maternal folic acid use during pregnancy being linked to offspring autism risk and some words of caution....
* Surén P. et al. Association Between Maternal Use of Folic Acid Supplements and Risk of Autism Spectrum Disorders in Children. JAMA. February 2013.
Pål Surén, Christine Roth, Michaeline Bresnahan, Margaretha Haugen, Mady Hornig, Deborah Hirtz, Kari Kveim Lie, W. Ian Lipkin, Per Magnus, Ted Reichborn-Kjennerud, Synnve Schjølberg, George Davey Smith, Anne-Siri Øyen, Ezra Susser, & Camilla Stoltenberg (2013). Association Between Maternal Use of Folic Acid Supplements and Risk of Autism Spectrum Disorders in Children JAMA : doi:10.1001/jama.2012.155925