A topic most pregnant women are afraid about Evidence-Based Birth had a public webinar on how to prevent tears. The most influential factor is the provider!
In short
:-Avoiding episiotomies prevents tears.
-Being in an upright position without an epidural is overall helpful (more 2nd-degree tears, but less severe tears, also shorter pushing stage).
-With an epidural, being in an upright position doesn’t seem to be helpful, but side-lying and delayed pushing is helpful to increase the intact perineum rate
.-Warm cloth compress decreases the risk of severe tears and has a higher rate of the intact perineum rate, it also might increase comfort.
-Having Hands-On (hands of the provider are pressing on the perineum) or Hands-Off (hands of the provider are not touching the perineum) makes no difference in the risk of the severe tear. Hands-Off has a lower episiotomy rate, might have more 1st degree tears, less pain, and a higher rate of intact perineum.
-Perineum massage during (not before) by the provider. Gentle massage seems to decrease severe tears rate, a lower episiotomy, and has no benefits of the provider already has a low severe tear rate.
-A slow birth of the head and shoulders is very efficient (breathing, no breath-holding pushing).