Defining risks of instrumental delivery in a large UK cohort

Abstract

Background Instrumental delivery accounts for approximately 10-15% of UK deliveries. It is increasingly scrutinised for complication rates, yet there is variable data in the literature describing complication rates in the UK, with, for example, third degree tear rates for forceps deliveries of 8-12% being reported (RCOG 2010). This study sought to describe complication rates in a large UK cohort, which could subsequently be used to generate audit standards. Methods Data was collected from all instrumental deliveries conducted at a large tertiary referral centre from October 2008- June 2011, using an electronic audit proforma that also served as the medical record. Results Data was available for 1985 deliveries; 688 (35%) ventouse, 905 (46%) forceps, 178 (9%) kiellands, 51 (2%) rotational ventouse, 163 (8%) 2 instruments. Forceps was associated with an increased risk of third degree tears (p<0.01 Mann-Whitney) of 6.3% compared to 2.6% for ventouse delivery. Forceps were also associated with an increased estimated blood loss (EBL) of median 500mls (interquartile range 300-700mls) compared to 300mls (200-500mls) for ventouse (p<0.01). Babies born using forceps had a higher median birthweight of 3452g (IQR 3100-3835) compared to 3250g (IQR 2948-3600g) for ventouse, (p<0.01, Mann-whitney). Conclusions This cohort represents one of the largest published UK cohorts of women undergoing instrumental deliveries, and can be used to set audit standards. Forceps is associated with increased blood loss and third degree perineal trauma. However, the risks of the latter were less than those suggested in the RCOG consent advice, suggesting this guidance may require adjustment.

Assisted Vaginal Birth

“…Symptoms associated with pelvic floor trauma include pain, dyspareunia, and urinary and bowel incontinence. [94][95][96][97][98][99][100] However, a longitudinal prospective cohort study nested with a two-centre RCT of routine versus restrictive episiotomy for assisted vaginal birth reported that pelvic floor morbidities associated with assisted vaginal birth are often as prevalent, if not more prevalent, in the third trimester of pregnancy than postpartum. 101 This suggests that much of the pelvic floor morbidity reported by women in the weeks and months after an assisted vaginal birth may not be causally related to the procedure.…”

“…Vacuum and forceps birth are associated with a higher incidence of episiotomy, pelvic floor tearing, levator ani avulsion and obstetric anal sphincter injury (OASI) than spontaneous vaginal birth. Symptoms associated with pelvic floor trauma include pain, dyspareunia, and urinary and bowel incontinence . However, a longitudinal prospective cohort study nested with a two‐centre RCT of routine versus restrictive episiotomy for assisted vaginal birth reported that pelvic floor morbidities associated with assisted vaginal birth are often as prevalent, if not more prevalent, in the third trimester of pregnancy than postpartum .…”

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“…ŞƂƇźƆƟƑƇƂƃ źƇźƅƟƁ ƋƌƊƍƄƌƍƊƂ ƈƋƇƈżƇƂƏ ƋƄƅź-žƈżƂƏ ƁźŽźƅƖƇƈŽƈ ƊƟżƇƙ ƊſƉƊƈžƍƄƌƂżƇƂƏ żƌƊźƌ ƍƉƊƈžƈżƀ ƉſƊƟƈžƍ žƈƋƅƟžƀſƇƇƙ ƁźƋżƟžƑƂż ƠƏ ƊƟƁ-ƇƈƋƉƊƙƆƈżźƇƍ ƇźƉƊźżƅſƇƟƋƌƖ. ũƈƁƂƌƂżƇƟ ƌſƇ-žſƇƐƟƠ ŻƍƅƂ ƁźŻſƁƉſƑſƇƟ Ƈź ƒƅƙƏƍ ƉƊſƇźƌźƅƖƇƈƠ ƋƄƅźžƈżƈƠ -żƂƆƍƒſƇƂƏ źŻƈƊƌƟż Ɓ 79,9% ƍ 2000 Ɗ. žƈ 74,7% ƍ 2021 Ɗ., ŜŲ Ɓ 95% Şő 0,93 (0,89-0,97), Ɗ<0,0001, ƌƟƅƖƄƂ Ɓź ƊźƏƍƇƈƄ żƂƉſƊſžƀźƘƑƈŽƈ ƁƇƂƀſƇƇƙ, ƆſžƂƑƇƂƏ ƅſŽźƅƖƇƂƏ źŻƈƊƌƟż ƍ ƌſƊƆƟƇƟ żƟž 12 žƈ 22 ƌƂƀƇƟż żźŽƟƌƇƈƋƌƟ Ɓ 27,9% žƈ 8,3%, ŜŲ Ɓ 95% Şő 0,23 (0,22-0,25), Ɗ<0,0001, ƉƊƂ ƈž-ƇƈƑźƋƇƈƆƍ ƁŻƟƅƖƒſƇƇƟ žƈƅƟ (ƋƉƈƇƌźƇƇƂƏ) źŻƈƊƌƟż ƟƁ 52,0% žƈ 67,4%, ŜŲ Ɓ 95% Şő 1,90 (1,98), Ɗ<0,0001. šź Ɛſƃ ƉſƊƟƈž ƍ ƋƌƊƍƄƌƍƊƟ ƊſƉƊƈžƍƄ-ƌƂżƇƂƏ żƌƊźƌ ƁŻƟƅƖƒƂƅźƋƙ žƈƅƙ ƎſƌƈƟƇƎźƇƌƂƅƖ-ƇƂƏ żƌƊźƌ Ɓ 20,0% žƈ 24,4%, ŜŲ Ɓ 95% Şő 1,24 (1,13-1,3), Ɗ<0,0001, Ɓź ƊźƏƍƇƈƄ ƁƇźƑƇƈŽƈ ƁŻƟƅƖ-ƒſƇƇƙ ƑźƋƌƈƌƂ ƇźƊƈžƀſƇƂƏ ƆſƊƌżƂƆƂ Ɓ 6,2% žƈ 11,6%, ŜŲ Ɓ 95% Şő 1,98 (1,86-2,1), Ɗ<0,0001, ƉƊƂ ƉƈƁƂƌƂżƇƟƃ ƌſƇžſƇƐƟƠ ƉƈƆſƊƅƂƏ žƟƌſƃ Ƈź ƉſƊƒƈƆƍ ƊƈƐƟ ƀƂƌƌƙ -13,8% Ɵ 12,8%, ŜŲ Ɓ 95% Şő 0,91 (0,86-0,96), Ɗ<0,0001 (ƌźŻƅ. 3) ŜƂƙżƅſƇƈ, Ɠƈ ƉƈƁƂƌƂżƇź žƂƇźƆƟƄź ƁźŽźƅƖ-ƇƂƏ ƊſƉƊƈžƍƄƌƂżƇƂƏ żƌƊźƌ żƟžŻƍƅźƋƙ Ɓź ƊźƏƍ-ƇƈƄ ƁƆſƇƒſƇƇƙ żƂƆƍƒſƇƂƏ ƋźƆƈżƟƅƖƇƂƏ (ƋƉƈƇ-ƌźƇƇƂƏ) Ɵ ƆſžƂƑƇƂƏ ƅſŽźƅƖƇƂƏ źŻƈƊƌƟż ƍ ƌſƊƆƟƇƟ żƟž 12 žƈ 22 ƌƂƀƇƟż żźŽƟƌƇƈƋƌƟ, ƄƟƅƖƄƟƋƌƖ ƙƄƂƏ ƁƆſƇƒƂƅźƋƙ Ɓ 68,8 Ƈź 1000 ƇźƊƈžƀſƇƂƏ ƀƂżƂƆƂ ƍ 2000 Ɗ. žƈ 43,2‰ ƍ 2021 Ɗ., ŜŲ Ɓ 95% Şő 0,63 (0,59-0,67), Ɗ<0,0001, ƌź ƉƈƆſƊƅƂƏ Ƈź ƉſƊƒƈ-Ɔƍ ƊƈƐƟ ƀƂƌƌƙ -Ɓ 11,9‰ žƈ 7,2‰ żƟžƉƈżƟžƇƈ, ŜŲ Ɓ 95% Şő 0,7 (0,66-0,74), Ɗ<0,0001.…”

“…Vacuum and forceps birth are associated with a higher incidence of episiotomy, pelvic ʶ oor tearing, levator ani avulsion and obstetric anal sphincter injury (OASI) than spontaneous vaginal birth. Symptoms associated with pelvic ʶ oor trauma include pain, dyspareunia, and urinary and bowel incontinence [94][95][96][97][98][99][100]. However, a longitudinal prospective cohort study nested with a two-centre RCT of routine versus restrictive episiotomy for assisted vaginal birth reported that pelvic ʶ oor morbidities associated with assisted vaginal birth are often as prevalent, if not more prevalent, in the third trimester of pregnancy than postpartum [101].…”