Single-nucleotide polymorphisms (SNP's) in connective tissue components are associated with increased risk of pelvic organ prolapse (POP). The investigators expect to find a difference in SNP's frequency between women who had Obstetric anal sphincter injuries (OASIS) and in the healthy population. The fact that pelvic organ prolapse (POP) and OASIS occurs in the same anatomic region and the well-known association between few SNP's and the risk for POP, suggests for a common pathophysiology.

The perineum consists of skin, muscles and connective tissue. A connective tissue disorder related to POP has been reported in biochemical and molecular studies. OASIS are considered a severe complication of vaginal delivery that may lead to a great deal of morbidity. Familial history is known as a risk factor for OASIS. Currently, there is no established genetic link between connective tissue components and OASIS. Therefore, the investigators assume that studying the genetic predisposition factors of women who experience OASIS, might generate a stronger tool to predict severe occurrence of vaginal laceration. It may also help to consult women before vaginal delivery about the risk of OASIS.

The aim of this study is to find an association between genetic variation and increased risk for OASIS.

Inclusion Criteria:

• Women with severe external anal sphincter injury during first vaginal delivery
• Healthy women undergoing vaginal delivery without any clinically apparent perineal laceration

Exclusion Criteria:

• Women with known metabolic or connective-tissue disorder (e.g., Ehlers-Danlos syndrome).
• Women with known neurologic disorder
• Women undergoing episiotomy cut or assisted delivery (e.g., vacuum or forceps delivery)