Obstetric anal sphincter injury after episiotomy in vacuum extraction: an epidemiological study using an emulated randomised trial approach.

OBJECTIVE: To emulate a randomised controlled trial investigating whether lateral or mediolateral episiotomy compared with no episiotomy reduces the prevalence of obstetric anal sphincter injury (OASIS) in nulliparous women delivered with vacuum extraction. DESIGN: A population-based observational study. SETTING: Sweden. POPULATION: 63 654 nulliparous women delivered with vacuum extraction derived from the Swedish Medical Birth Register 2000-2011, with a live singleton baby with no known malformations in cephalic presentation in gestational week ≥34+0 , and subject to lateral or mediolateral episiotomy or no episiotomy. METHODS: The effect of episiotomy was calculated using a causal doubly robust estimation method based on propensity scores. Results are presented as the average treatment effect and numbers needed to treat (NNT). MAIN OUTCOME MEASURES: OASIS (third- and fourth-degree perineal injury) in nulliparous women delivered with vacuum extraction. RESULTS: Episiotomy was associated with a reduction in OASIS from 15.5% to 11.8%, average treatment effect of -3.66% (95% CI -4.31 to -3.01) and NNT 27. Third-degree perineal injuries were reduced from 14.0% to 10.9% (-3.08, 95% CI -3.71 to -2.42) with NNT 32. Fourth-degree perineal injuries were reduced from 1.6% to 1.0 % (-0.58%, 95% CI -0.79 to -0.37) with NNT 172. CONCLUSIONS: Lateral or mediolateral episiotomy reduced the prevalence of OASIS in nulliparous women delivered with vacuum extraction, compared to women with no episiotomy. TWEETABLE ABSTRACT: To prevent one case of OASIS in first-time mothers delivered with vacuum, 27 episiotomies had to be performed.

Age-specific prevalence of HPV genotypes in cervical cytology samples with equivocal or low-grade lesions.

BACKGROUND: To define the spectrum of human papillomavirus (HPV) types and establish an age limit for triage HPV testing in atypical squamous cells of undetermined significance (ASCUS) and low-grade squamous intraepithelial lesion (LSIL). MATERIALS AND METHODS: 343 liquid-based cytological samples from the population-based screening programme with minor abnormalities were subjected to HPV genotyping (Linear Array, Roche, Basel, Switzerland). RESULTS: High-risk human papillomavirus (HR-HPV) was found in 71% of LSIL and 49% of ASCUS cases (P<0.001). High-risk human papillomavirus prevalence was age-dependent in LSIL (P=0.01), with decreasing prevalence until the age of 50 years, followed by a slight increase. Human papillomavirus type 16 was the most common HR-HPV, found in 23% of HPV-positive women. Human papillomavirus type 18 was the sixth most common, found in 9.9% (P<0.001). An age-dependent quadratic trend was observed for multiple infections (P=0.01) with a trough at about 42 years. The most common HR-HPV types to show a coinfection with HPV16 (clade 9) were HPV39 (28%), 45 (38%), and 59 (46%), belonging to HPV18 clade 7. The frequency of low-risk (LR) vs probable HR and HR-HPV also followed an age-dependent quadratic trend. CONCLUSIONS: After the age of 25 years, HR-HPV prevalence is similar in LSIL and ASCUS cases, motivating a low age limit for triage HPV testing. Multiple infections and LR/HR-HPV dominance are age-dependent. Genotyping in longitudinal design is needed to elucidate the importance of multiple infections in cancer progression and in cross-protection from vaccination.