Factors Influencing the Likelihood of Instrumental Delivery Success

pOBJECTIVE: To evaluate risk factors for unsuccessfulnbsp;instrumental delivery when variability between individualnbsp;obstetricians is taken into account.br / METHODS: We conducted a retrospective cohort studynbsp;of attempted instrumental deliveries over a 5-year periodnbsp;(2008ndash;2012 inclusive) in a tertiary United Kingdom center.nbsp;To account for interobstetrician variability, we matchednbsp;unsuccessful deliveries (case group) with successful deliveriesnbsp;(control group) by the same operators.nbsp;Multivariatenbsp;logistic regression was used to compare successful andnbsp;unsuccessful instrumental deliveries.br / RESULTS: Three thousand seven hundred ninety-eightnbsp;instrumental deliveries of vertex-presenting, single, termnbsp;newborns were attempted, of which 246 were unsuccessfulbr / (6.5%). Increased birth weight (odds ratio [OR]nbsp;1.11; P,.001), second-stage labor duration (OR 1.01;nbsp;P,.001), rotational delivery (OR 1.52; P,.05), and usenbsp;of ventouse compared with forceps (OR 1.33; P,.05)nbsp;were associated with unsuccessful outcome. When interobstetriciannbsp;variability was controlled for, instrumentnbsp;selection and decision to rotate were no longer associatednbsp;with instrumental delivery success. More seniornbsp;obstetricians had higher rates of unsuccessful deliveriesnbsp;(12% compared with 5%; P,.05) but were used to undertakenbsp;more complicated cases. Cesarean delivery duringnbsp;the second stage of labor without previous attempt atnbsp;instrumental delivery was associated with higher birthnbsp;weight (OR 1.07; P,.001), increased maternal age (ORnbsp;1.03; P,.01), and epidural analgesia (OR 1.46; P,.001).br / CONCLUSION: Results suggest that birth weight andnbsp;head position are the most important factors in successfulnbsp;instrumental delivery, whereas the influence ofnbsp;instrument selection and rotational delivery appear tonbsp;be operator-dependent. Risk factors for lack of instrumentalnbsp;delivery success are distinct from risk factors fornbsp;requiring instrumental delivery, and these should not benbsp;conflated in clinical practice./p