It's a boy! 17 year-old Bristol Palin gave birth to "Tripp," making mom Sarah a 44-year-old grandmother. Menstruating grannies are a phenomenon most commonly found in Appalachia or the ghetto. It was a busy month for the Palins. Last week, the baby's other grandmother, Sherry Johnston, was arrested on six felony counts involving the Rush Limbaugh's weakness, oxycontin.