Antibiotic prophylaxis for third- and fourth-degree perineal tear during vaginal birth

One to eight per cent of women suffer third-degree perineal tear (anal sphincter injury) and fourth-degree perineal tear (rectal mucosa injury) during vaginal birth, and these tears are more common after forceps delivery (28%) and midline episiotomies. Third- and fourth-degree tears can become contaminated with bacteria from the rectum and this significantly increases in the chance of perineal wound infection. Prophylactic antibiotics might have a role in preventing this infection.

To assess the effectiveness of antibiotic prophylaxis for reducing maternal morbidity and side effects in third- and fourth-degree perineal tear during vaginal birth.

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 August 2010) and the reference lists of retrieved articles.

Randomised controlled trials comparing outcomes of prophylactic antibiotics versus placebo or no antibiotics in third- and fourth-degree perineal tear during vaginal birth.

Two review authors independently assessed the reports and extracted data.

We identified and included one trial (147 participants) that compared the effect of prophylactic antibiotic (single-dose, second generation cephalosporin, intravenously) on postpartum perineal wound complications in third- or fourth-degree perineal tears. Perineal wound complications (wound disruption and purulent discharge) at the two-week postpartum check up were 8.20% and 24.10% in the treatment and the control groups respectively (risk ratio 0.34, 95% confidence interval 0.12 to 0.96).

Although the data suggest that prophylactic antibiotics help to prevent perineal wound complications following third- or fourth-degree perineal tear, loss to follow-up was very high. The results should be interpreted with caution as they are based on one small trial.