Hi asset1 - I would never recommend an elective episiotomy, as there are many factors which cause 3rd degree tear, but in your case it is almost certainly the ventouse, which doesnt give the perineum time to stretch naturally, and possibly the doctor not lifting babys head up as it came out, or tearing the peri with the shoulders. Ive seen this happen many times
From my experience (and there may be many who disagree), the best results after having had a 3rd degree with the first baby, is to deliver sitting up at 45 degrees, (as this will slow down the delivery of the head) and if it looks like a bad tear is happening, then a small episiotomy to direct it away from the anus, (and its very unusual to have to do this.)
Most of the time the peri is intact or a small tear - never had a repeat 3rd degree in over 20 years of delivering babies!
What I find is not so good are the more upright positions, such as squatting, standing, all fours etc, as the birth is quicker and much less controlled, also, its virtually impossible to do an epis in a squatting position!
Water is also a good option, as it helps the skin to stretch, but again, its not easy to slow down the birth, and impossible to do an epis.
But Im sure your midwife will help guide you and please discuss your fears with her when you go into labour.
Good luck!