Obstetric perineal tears: risk factors, wound infection and dehiscence: a prospective cohort study

To assess risk factors for perineal tears, wound infection and dehiscence among primiparous women.

A prospective cohort study at four Danish hospitals (Odense, Esbjerg, Aarhus and Kolding) among 603 primiparous women sampled in three groups: 203 with none/labia/1st degree, 200 with 2nd degree, and 200 with 3rd/4th degree tears included between July 2015 and January 2018. Baseline data were obtained and a clinical examination of perineal wound healing was performed 11-21 days postpartum. Main outcome measurements were as follows: degree of perineal tear, 1st to 4th, analyzed with a case-control approach, infection (purulent drainage or wound abscess), and wound dehiscence (a gap between wound edges > 0.5 cm).

Instrumental delivery and birthweight > 4000 g increased the risk of 3rd/4th degree tears (adjusted Odds Ratio [aOR] 13.7, 95% confidence interval [CI] 5.48-34.1 and aOR 3.27, 95% CI 1.52-7.04, respectively). BMI > 35 kg/m² increased the risk of wound infection and dehiscence (aOR 7.66, 95% CI 2.13-27.5 and aOR 3.46, 95% CI 1.10-10.9, respectively). Episiotomy tripled the risk of infection (aOR 2.97, 95% CI 1.05-8.41). Treatment with antibiotics during delivery and postpartum seemed to decrease the risk of dehiscence (aOR 0.32, 95% CI 0.15-0.70).

Instrumental delivery and high birth weight increased the risk of perineal tears. Severe obesity and episiotomy increased the risk of perineal wound complications. More focus on these women may be warranted postpartum. The use of prophylactic antibiotics among women in high risk of wound complications should be further investigated in interventional studies.