Michael Nordine authorYou’d be forgiven for not being inclined to laugh at anything pregnancy-related at the moment. Kudos to “Doula” for trying, though, as director Cheryl Nichols’ lighthearted pregnancy comedy arrives at a time when the “laughter is the best medicine” theory is being stress-tested like never before for women across the country. To call its brand of comedy “niche” might be an understatement — for one thing, its central plot development hinges on knowing the difference between a midwife and a doula — but the film’s insights ultimately outnumber its laughs.That wouldn’t appear to be the case early on, as the funniest scene is also the first.