What is a perineal birth tear?
A tear that occurs along the perineum during childbirth. It is graded by depth, depending on which tissues are torn. The diagram below explains the varying degrees.
Image from: Sydney Pelvic Floor Health,
The tearing occurs when there is too much pressure exerted on to surrounding tissues, at the time of the baby descending through the birth canal. It can happen spontaneously or during assisted births such as with episiotomies and/or forceps/ventouse.
3rd degree tears are categorised into three: 3a, 3b and 3c.
3a = where less than 50% of the external anal sphincter is torn (internal sphincter unaffected)
3b = where more than 50% of the external anal sphincter is torn (internal sphincter unaffected)
3c = where both the external and internal anal sphincters have both been damaged.
The severity does increase which each grade, 3c being the most severe.
4th degree tears involve all of the above, and the rectal mucosa.
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