Factors influencing the likelihood of vacuum delivery success
Keywords:Birth trauma, Instrumental delivery, Perineal tear, Still births, Vacuum delivery, Ventouse
Background: Instrumental or assisted vaginal birth is commonly used to expedite birth, for the benefit of either mother, baby or both. Objective of present study was to evaluate risk factors for unsuccessful vacuum delivery when variability between individual accoucheurs is taken into account.
Methods: We conducted a retrospective cohort study of attempted 687 vacuum deliveries over a 10-year period (2008–2017 inclusive) in a tertiary care center at Smt. Kashibai Navale Medical College and General Hospital, Narhe to account for inter-accoucheur variability, we matched unsuccessful deliveries (cases) with successful deliveries (controls) by the same operators. Multivariate logistic regression was used to compare successful and unsuccessful vacuum deliveries.
Results: During the study period of 10 years, there were 29861 deliveries, of which 19831 (66.4%) were vaginal deliveries. 8802 (29.47%) were cesarean deliveries and 1228 (4.1%) were instrumental deliveries. Among instrumental deliveries, 687 (56%) were vacuum deliveries and 541 (44%) were forceps deliveries. Six hundred and eighty-seven ventouse deliveries of vertex presenting, single, term infants were attempted, of which 38 were unsuccessful (5.5%). Increased birth weight (OR=1.11 p<0.001), second-stage duration (OR=1.01 p<0.001), rotational delivery (OR=1.52 p<0.05) and use of ventouse versus forceps (OR=1.33 p<0.05) were associated with unsuccessful outcome. When inter-accoucheur variability was controlled for, instrument selection and decision to rotate were no longer associated with vacuum delivery success. More senior accoucheurs had higher rates of unsuccessful deliveries (12% v. 5%, p<0.05), but undertook more complicated cases. Cesarean delivery in the second stage without prior attempt at ventouse delivery was associated with higher birth weight (OR=1.07 p<0.001), increased maternal age (OR=1.03 p<0.01), and epidural analgesia (OR=1.46 p<0.001).
Conclusions: Careful selection of cases and adequate training of post graduate students during residency under direct supervision of senior experienced obstetrician can reduce the rate of failed vacuum delivery and related complications Results suggest that birth weight and head position are the most important factors in successful vacuum delivery, whereas the influence of patient selection and rotational delivery appear to be operator-dependent. Risk factors for lack of vacuum delivery success are distinct from risk factors for requiring vacuum delivery, and these should not be conflated in clinical practice.
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