Last June, high-school English teacher Jaimie Dorn found herself facing down an unexpected challenge: how to make an Instagram profile that would convince a pregnant stranger that she and her husband, Brian, would make good parents. The 39-year-old from West Islip, NY, created the account, @JaimieAndBrianAdopt, then began uploading cheery photos of herself, Brian and her two stepchildren (from her husband’s previous marriage) engaged in fun, family-friendly activities such as