What are the risk factors for infection following vaginal delivery?

The risk of developing infection following operative vaginal birth is high when episiotomy is performed, forceps are used, and among women who are primiparous and overweight, a study has found. As such, timely prophylactic antibiotics should be given.

Researchers performed a secondary analysis of the ANODE randomized controlled trial, which showed that women who received prophylactic intravenous amoxicillin and clavulanic acid had a significantly lower risk of developing confirmed or suspected infection within 6 weeks of operative vaginal birth.

This current analysis involved 3,225 women. They were grouped according to the perineal trauma experienced (episiotomy and/or perineal tear). Log binomial regression and the likelihood ratio test were used to assess the consistency of the prophylactic antibiotics in preventing infection across the subgroups, while multivariable log binomial regression facilitated the identification of factors associated with infection.

Of the women, 2,144 (66.5 percent) had an episiotomy alone, 726 (22.5 percent) had an episiotomy and a tear, 277 (8.6 percent) had a tear alone, and 78 (2.4 percent) had neither episiotomy nor tear. Compared with placebo, amoxicillin and clavulanic acid conferred some protection across all subgroups, with no significant interaction between subgroup and trial allocation (p=0.17).

The risk factors for infection were episiotomy (adjusted risk ratio [aRR], 2.94, 95 percent confidence interval [CI], 1.62–5.31), forceps use (vs vacuum extraction: aRR, 1.37, 95 percent CI, 1.12–1.69), primiparity (aRR, 1.34, 95 percent CI, 1.05–1.70), and higher body mass index (25–29.9 vs <25 kg/m²: aRR, 1.21, 95 percent CI, 1.00–1.47; ≥30 vs <25 kg/m²: aRR, 1.22, 95 percent CI, 0.98–1.52).

Amoxicillin and clavulanic acid administration was confirmed to be associated with a lower risk of infection (aRR, 0.60, 95 percent CI, 0.51–0.72), with timing of administration factoring in. Specifically, each 15-minute increment between birth and antibiotic administration upped the risk of infection by 3 percent (aRR, 1.03, 95 percent CI, 1.01–1.06).