I think it's an interesting question to study but I don't think much of their "research" to date. They're not at all clear about why each group did or didn't have pain management and their statistics clearly show that they aren't pulling from homogenous or equivalently diverse groups (vastly different rates of pre-natal classes and also breastfeeding rates). I'm left wondering how many of the group of "no epi" women chose that route and how many didn't have prenatal care or insurance or had fast labors where things were out of their control.