Risks of faecal incontinence and pelvic organ prolapse both straight after birth and later on in life are common after ventouse and forceps.
You're probably going to check your pregnancy book and find nothing on this. I suggest checking the following pages:
forcepsthefollowonblog.wordpress.com/2014/10/28/what-i-wish-id-known-before-giving-birth/
www.patient.co.uk/doctor/faecal-incontinence (Scroll down to Aetiology-childbirth)
www.patient.co.uk/doctor/delay-in-second-stage-of-labour-and-use-of-forceps (Scroll down to Outcome)
www.patient.co.uk/health/genitourinary-prolapse-leaflet (Scroll down to What causes genitourinary prolapse? Childbirth)
The NHS Choices website does not mention any risks at the moment. This is wrong. They have assured me the page will be updated in February 2015.