Abstract
Objective
To evaluate whether the number of vacuum pop-offs, the number of forceps pulls, or the duration of operative vaginal delivery (OVD) is associated with adverse maternal and perinatal outcomes.
Study Design
This is a secondary analysis of a multicenter observational cohort of women who underwent an attempted OVD. Women were stratified by the duration of OVD and the number of pop-offs (vacuum) or pulls (forceps) attempted. Severe perineal lacerations, failed OVD, and a composite adverse neonatal outcome were compared by the duration of OVD and number of pop-offs or pulls.
Results
Of the 115,502 women in the primary cohort, 5,325 (4.6%) underwent an attempt at OVD: 3,594 (67.5%) with vacuum and 1,731 (32.5%) with forceps. After adjusting for potential confounders, an increasing number of pop-offs was associated with an increased odds of the composite adverse neonatal outcome. However, an increasing duration of vacuum exhibited a stronger association with the composite adverse neonatal outcome. Similarly, the number of forceps pulls was less strongly associated with the composite adverse neonatal outcome compared with the duration of forceps application.
Conclusion
The duration of OVD may be more associated with adverse neonatal outcomes than the number of pop-offs or pulls.
Keywords: operative vaginal delivery, forceps, vacuum, pop-offs, pulls, duration
Operative vaginal deliveries (OVDs) are endorsed by American College of Obstetricians and Gynecologists (ACOG) as a means to achieve a vaginal delivery, and avoid unnecessary cesarean delivery, in this setting.1 However, evidence delineating best practices for both vacuum and forceps are limited and often conflicting. For example, some existing data suggest that an extended application-to-delivery interval for the vacuum incurs a higher risk of cephalohematoma.2 This conclusion is in contrast to that of a randomized study demonstrating that continuous application of vacuum traction is not associated with an increased risk of adverse fetal outcomes compared with intermittent application.3 For forceps-assisted deliveries, more than three pulls have been associated with increased neonatal trauma in one small cohort from two teaching centers in the United Kingdom, but, to the best of our knowledge, this finding has not been replicated.4 Given the sparse and at times conflicting data, there is no consensus on the maximum duration of attempted operative delivery, number of pulls, or number of vacuum pop-offs that is acceptable.
Thus, our objective was to determine whether the number of vacuum pop-offs, the number of forceps pulls, or the duration of OVD is associated with failed OVD, severe perineal lacerations, or adverse neonatal outcomes.
Materials and Methods
This is a secondary analysis of a multicenter observational cohort designed to develop quality measures for labor management. A total of 115,502 women who delivered at 25 hospitals over a 3-year period were included in the primary study. Details of the methodology have been previously published.5 In brief, data were abstracted by trained and certified research personnel from the medical records of women who delivered on randomly selected days between 2008 and 2011 after 23 weeks’ gestation at one of the Maternal-Fetal Medicine Units Network hospitals. Women with a nonanomalous vertex singleton gestation at term who underwent an attempted OVDs with a single instrument type (i.e., vacuum or forceps) were included in the analysis. Women with an antenatal stillbirth were excluded. Given the known increased risks of adverse neonatal outcomes seen in women who deliver via a combination of forceps and vacuum, these women were also excluded.
The OVD duration variables examined included (1) the number of vacuum pop-offs, (2) the number of forceps pulls, and (3) the duration of OVD (defined as the time from first application of the vacuum or forceps to either time of vaginal birth or time of decision to convert to cesarean, divided into 3-minute intervals). Three minutes was used as a clinically translatable duration given the intermittent frequency of contractions and, therefore, active use of the vacuum or forceps. Outcomes examined included failed OVD (i.e., cesarean delivery), severe perineal laceration (i.e., third or fourth degree), and a composite adverse neonatal outcome that was defined to be present if any of the following occurred: brachial plexus injury, facial nerve palsy, clavicular fracture, skull fracture, other skeletal fracture, skin laceration, intracranial hemorrhage (including subgaleal), seizure requiring treatment, or neonatal death. Potential confounders, which were identified prior to analysis, were those that have been associated with any of the outcomes examined and included: maternal age, race/ethnicity, body mass index at delivery, station at placement of vacuum or forceps, indication for OVD, orientation of the vertex, chorioamnionitis, prior cesarean delivery, and prior vaginal delivery. Birth weight was not included as a covariate as it was felt to be on the causal pathway between the duration of OVD and adverse outcome (i.e., a fetus with a larger birth weight would potentially be expected to require more pulls or a longer duration of application until delivery).
Women were stratified by the type of OVD (i.e., vacuum or forceps) performed. Rates of failed OVD, severe perineal lacerations, and composite adverse neonatal outcomes were calculated and compared according to each of the OVD variables (i.e., number of vacuum pop-offs, duration of vacuum OVD, number of forceps pulls, and duration of forceps OVD). Tests of trend were performed as appropriate between each outcome and OVD duration variable. Multivariable logistic regressions were performed to adjust for potential confoun-ders and, as there are no statistical tests to compare trends in odds ratios, visual comparisons were made to describe the persistence of trends after controlling for potential confoun-ders. The presence of interaction of the OVD variables with fetal station, orientation of the vertex, and indication for OVD also were assessed. A sensitivity analysis was performed, excluding skin lacerations, to examine associations with more severe composite adverse neonatal outcomes.
All analyses were performed using SAS (SAS Institute, Cary, NC). All tests were two-tailed and an a of 0.05 was used to define statistical significance. No imputation for missing data was performed. The primary study was approved by the Institutional Review Board at each participating institution under a waiver of informed consent.
Results
Of the 5,325 women who met inclusion criteria, 3,594 (67.5%) underwent an attempted vacuum-assisted delivery and 1,731 (32.5%) underwent an attempted forceps-assisted delivery ( ► Fig. 1 ). For vacuum-assisted deliveries, 559 (15.6%) had missing data on the number of pop-offs. Of those with complete data, 1,823 (60.1%), 674 (22.2%), 372 (12.3%), and 166 (5.5%) had zero, one, two, or at least three pop-offs. For forceps-assisted deliveries, 403 (23.3%) had missing data on the number of pulls. Of those with complete data, 817 (61.5%), 306 (23.0%), and 205 (15.4%) had one, two, or at least three pulls. Finally, there was missing OVD duration data for 1,226 (34.1%) of vacuum deliveries and 588 (34.0%) of forceps deliveries. The median duration for vacuum and forceps deliveries was 4 minutes (interquartile range: 2–7 minutes) and 4 minutes (interquartile range: 2–6 minutes), respectively. Baseline characteristics of the study population are shown in ►Table 1. Two-hundred and ninety-two women (5.5%) had a failed OVD (5.8% of vacuums vs. 4.9% of forceps, p = 0.20), 987 women (18.6%) experienced a severe perineal laceration (14.4% of vacuums vs. 27.1% of forceps, p < 0.001), and in 166 women (3.1%), the composite neonatal outcome occurred (3.0% of vacuums vs. 3.5% of forceps, p = 0.31).
Fig. 1.
Flow chart of women eligible for analyses.
Table 1.
Characteristics of study population
Age (y) | 27.8 ± 6.1 |
---|---|
Race | |
Hispanic | 860 (16.1%) |
Non-Hispanic black | 873 (16.4%) |
Non-Hispanic white | 2,873 (54.0%) |
Asian | 414 (7.8%) |
Other | 305 (5.7%) |
BMI at delivery (kg/m2) | 29.9 ± 5.6 |
Prior vaginal delivery | 1,403 (26.4%) |
Prior cesarean delivery | 257 (4.8%) |
Suspected chorioamnionitis | 511 (9.6%) |
Station at operative vaginal delivery placement | |
Low | 2,323 (43.6%) |
Outlet | 1,385 (26.0%) |
Mid | 267 (5.0%) |
Unknown/undocumented | 1,350 (25.4%) |
Indication for operative vaginal delivery (n = 4,983) | |
Nonreassuring fetal status | 2,281 (45.8%) |
Failure to descend | 637 (12.8%) |
Maternal medical complication | 71 (1.4%) |
Maternal exhaustion | 1,178 (23.6%) |
Unknown/undocumented | 816 (16.4%) |
Fetal position at operative vaginal delivery placement | |
OA | 2,825 (53.9%) |
OT | 111 (2.1%) |
OP | 634 (12.1%) |
Unknown/undocumented | 1,671 (31.9%) |
Abbreviations: BMI, body mass index; OA, occiput anterior; OT, occiput transverse; OP, occiput posterior.
Note: Data presented as mean ± standard deviation or n (%).
For attempted vacuum-assisted deliveries, both the number of pop-offs and the duration of OVD were associated with failed OVD, severe perineal lacerations, and adverse neonatal outcomes with tests of trend for each exposure and outcome dyad each with p < 0.05 (►Table 2). The frequency of each individual component of the composite neonatal outcome stratified by vacuum duration is shown in ►Table 3.
Table 2.
Association of number of vacuum pop-offs orduration of attempted vacuum-assisted delivery with maternal and neonatal morbidities
Number of pop-offs | ||||||
0 | 1 | 2 | 3 or more | p-Valuea | ||
n = 1,823 | n = 674 | n = 372 | n = 166 | |||
Failed operative vaginal delivery (n = 3,035) | 51 (2.8%) | 39 (5.8%) | 44 (11.8%) | 42 (25.3%) | <0.0001 | |
Severe perineal laceration (n = 3,032) | 248 (13.6%) | 100 (14.8%) | 61 (16.4%) | 37 (22.3%) | 0.004 | |
Composite adverse neonatal outcome (n = 3,031) | 44 (2.4%) | 24 (3.6%) | 17 (4.6%) | 8 (4.8%) | 0.006 | |
Duration of operative vaginal delivery (min) | ||||||
0–2 | 3–5 | 6–8 | 9–11 | 12 or more | p-Valuea | |
n = 850 | n = 694 | n = 363 | n = 163 | n = 298 | ||
Failed operative vaginal delivery (n = 2,368) | 20 (2.4%) | 22 (3.2%) | 26 (7.2%) | 15 (9.2%) | 55 (18.5%) | <0.0001 |
Severe degree perineal laceration (n = 2,364) | 103 (12.1%) | 113 (16.4%) | 61 (16.8%) | 29 (17.8%) | 51 (17.2%) | 0.013 |
Composite adverse neonatal outcome (n = 2,364) | 9 (1.1%) | 19 (2.8%) | 13 (3.6%) | 6 (3.7%) | 15 (5.0%) | <0.0001 |
p-Value is for test of trend.
Table 3.
Individual adverse neonatal outcomes, stratified by duration of vacuum
Number of pop-offs | |||||
0 | 1 | 2 | 3 or more | ||
n = 1,823 | n = 674 | n = 372 | n = 166 | ||
Brachial plexus injury (n = 3,035) | 5 (0.3%) | 1 (0.2%) | 1 (0.3%) | 0 | |
Facial nerve palsy (n = 3,035) | 0 | 0 | 0 | 0 | |
Clavicular fracture (n = 3,035) | 9 (0.5%) | 5 (0.7%) | 4 (1.1%) | 0 | |
Skull/other skeletal fracture (n = 3,035) | 4 (0.2%) | 1 (0.2%) | 1 (0.3%) | 1 (0.6%) | |
Skin laceration (n = 3,035) | 21 (1.2%) | 13 (1.9%) | 9 (2.4%) | 4 (2.4%) | |
Intracranial hemorrhage (n = 3,035) | 6 (0.3%) | 5 (0.7%) | 6 (1.6%) | 3 (1.8%) | |
Seizure requiring treatment (n = 3,035) | 3 (0.2%) | 1 (0.2%) | 1 (0.3%) | 0 | |
Neonatal death (n = 3,029) | 0 | 1 (0.2%) | 0 | 0 | |
Duration of operative vaginal delivery (min) | |||||
0–2 | 3–5 | 6–8 | 9–11 | 12 or more | |
n = 850 | n = 694 | n = 363 | n = 163 | n = 298 | |
Brachial plexus injury (n = 2,368) | 1 (0.1%) | 3 (0.4%) | 3 (0.8%) | 0 | 0 |
Facial nerve palsy (n = 2,368) | 0 | 0 | 0 | 0 | 0 |
Clavicular fracture (n = 2,368) | 2 (0.2%) | 5 (0.7%) | 3 (0.8%) | 1 (0.6%) | 1 (0.3%) |
Skull/other skeletal fracture (n = 2,368) | 1 (0.1%) | 2 (0.3%) | 0 | 1 (0.6%) | 2 (0.7%) |
Skin laceration (n = 2,368) | 4 (0.5%) | 6 (0.9%) | 5 (1.4%) | 4 (2.5%) | 10 (3.4%) |
Intracranial hemorrhage (n = 2,368) | 1 (0.1%) | 4 (0.6%) | 3 (0.8%) | 1 (0.6%) | 5 (1.7%) |
Seizure requiring treatment (n = 2,368) | 0 | 1 (0.1%) | 1 (0.3%) | 0 | 1 (0.3%) |
Neonatal death (n = 2,362) | 0 | 0 | 0 | 0 | 0 |
For attempted forceps-assisted deliveries, the number of pulls was associated with failed OVD and severe perineal lacerations (p < 0.05 for each) but was not associated with the composite neonatal adverse outcome (p = 0.58) (►Table 4). Conversely, the duration of forceps was associated with failed OVD, severe perineal lacerations, and adverse neonatal outcomes (p < 0.05 for each). The frequency of each individual component of the composite neonatal outcome stratified by forceps duration is shown in ►Table 5.
Table 4.
Association of number of forceps pulls or duration of attempted forceps-assisted delivery with maternal and neonatal morbidities
Number of pulls | ||||||
1 | 2 | 3 or more | p-Valuea | |||
n = 817 | n = 306 | n = 205 | ||||
Failed operative vaginal delivery (n = 1,328) | 19 (2.3%) | 22 (7.2%) | 19 (9.3%) | <0.0001 | ||
Severe perineal laceration (n = 1,328) | 181 (22.2%) | 110 (36.0%) | 72 (35.1%) | <0.0001 | ||
Composite adverse neonatal outcome (n = 1,327) | 32 (3.9%) | 9 (2.9%) | 11 (5.4%) | 0.577 | ||
Duration of operative vaginal delivery (min) | ||||||
0–2 | 3–5 | 6–8 | 9–11 | 12 or more | p-Valuea | |
n = 300 | n = 478 | n = 195 | n = 76 | n = 94 | ||
Failed operative vaginal delivery (n = 1,143) | 8 (2.7%) | 14 (2.9%) | 14 (7.2%) | 8 (10.5%) | 10 (10.6%) | <0.0001 |
Severe perineal laceration (n = 1,143) | 68 (22.7%) | 139 (29.1%) | 56 (28.7%) | 24 (31.6%) | 34 (36.2%) | 0.010 |
Composite adverse neonatal outcome (n = 1,141) | 4 (1.3%) | 12 (2.5%) | 6 (3.1%) | 5 (6.6%) | 9 (9.6%) | <0.0001 |
p-Value is for test of trend.
Table 5.
Individual adverse neonatal outcomes, stratified by duration of forceps
Number of pulls | |||||
1 | 2 | 3 or more | |||
n = 817 | n = 306 | n = 205 | |||
Brachial plexus injury (n = 1,328) | 2 (0.2%) | 0 | 0 | ||
Facial nerve palsy (n = 1,328) | 3 (0.4%) | 2 (0.7%) | 2 (1.0%) | ||
Clavicular fracture (n = 1,328) | 7 (0.9%) | 0 | 1 (0.5%) | ||
Skull/other skeletal fracture (n = 1,328) | 1 (0.1%) | 0 | 2 (1.0%) | ||
Skin lacerations (n = 1,328) | 17 (2.1%) | 5 (1.6%) | 5 (2.4%) | ||
Intracranial hemorrhage (n = 1,328) | 1 (0.1%) | 1 (0.3%) | 2 (1.0%) | ||
Seizure requiring treatment (n = 1,327) | 1 (0.1%) | 1 (0.3%) | 1 (0.5%) | ||
Neonatal death (n = 1,325) | 0 | 0 | 1 (0.5%) | ||
Duration of operative vaginal delivery (min) | |||||
0–2 | 3–5 | 6–8 | 9–11 | 12 or more | |
n = 300 | n = 478 | n = 195 | n = 76 | n = 94 | |
Brachial plexus injury (n = 1,143) | 0 | 0 | 1 (0.5%) | 1 (1.3%) | 0 |
Facial nerve palsy (n = 1,143) | 0 | 0 | 2 (1.0%) | 0 | 3 (3.2%) |
Clavicular fracture (n = 1,143) | 0 | 3 (0.6%) | 0 | 0 | 1 (1.1%) |
Skull/other skeletal fracture (n = 1,143) | 0 | 1 (0.2%) | 0 | 0 | 0 |
Skin lacerations (n = 1,143) | 4 (1.3%) | 7 (1.5%) | 3 (1.5%) | 3 (4.0%) | 4 (4.3%) |
Intracranial hemorrhage (n = 1,143) | 0 | 1 (0.2%) | 0 | 1 (1.3%) | 1 (1.1%) |
Seizure requiring treatment (n = 1,143) | 0 | 1 (0.2%) | 0 | 0 | 1 (1.1%) |
Neonatal death (n = 1,141) | 0 | 0 | 0 | 0 | 0 |
Multivariable regressions adjusting for confounders generally demonstrated similar findings (►Table 6). Of note, as the duration of the attempted vacuum-assisted or forceps-assisted delivery increased, the odds ratios for the composite adverse neonatal outcomes increased as well. When duration was analyzed as an ordinal variable, an increasing number of minutes of OVD was associated with an increased odds of composite adverse neonatal outcomes for both vacuum (adjusted odds ratio [aOR]: 1.09, 95% confidence interval [Cl]: 1.03–1.16) and forceps (aOR: 1.13, 95% Cl: 1.03–1.24). No interaction was observed (p-values > 0.05) between duration of OVD (with either vacuum or forceps) and fetal station orientation of the vertex, and indication for the procedure indicating that any adverse associations of the duration of OVD were not particularly pronounced by these second-stage characteristics.
Table 6.
Multivariable analysis of duration of operative vaginal delivery for adverse outcomes
Failed operative vaginal delivery |
Severe perineal laceration |
Composite adverse neonatal outcomes |
||
---|---|---|---|---|
Vacuum (n = 3,594) |
Number of pop-offs | |||
0 | Referent | Referent | Referent | |
1 | 2.08 (1.31, 3.30) | 0.95 (0.72, 1.25) | 1.49 (0.88, 2.52) | |
2 | 3.57 (2.21, 5.77) | 1.10 (0.79, 1.52) | 1.89 (1.03, 3.45) | |
3+ | 11.27 (6.82, 18.63) | 1.61 (1.06, 2.43) | 2.00 (0.90, 4.45) | |
Duration (min) | ||||
0–2 | Referent | Referent | Referent | |
3–5 | 1.15 (0.59, 2.22) | 1.21 (0.89, 1.65) | 2.36 (1.04, 5.36) | |
6–8 | 2.43 (1.26, 4.68) | 1.06 (0.73, 1.54) | 2.70 (1.10, 6.64) | |
9–11 | 2.83 (1.33, 6.06) | 1.08 (0.66, 1.77) | 3.17 (1.08, 9.32) | |
12+ | 6.52 (3.59, 11.85) | 1.03 (0.70, 1.53) | 3.70 (1.50, 9.13) | |
Forceps (n = 1,731) |
Number of pulls | |||
1 | Referent | Referent | Referent | |
2 | 2.45 (1.22, 4.90) | 1.70 (1.24, 2.33) | 0.62 (0.27, 1.43) | |
3+ | 3.07 (1.49, 6.33) | 1.36 (0.94, 1.97) | 1.15 (0.52, 2.55) | |
Duration (min) | ||||
0–2 | Referent | Referent | Referent | |
3–5 | 1.14 (0.44, 2.96) | 1.10 (0.76, 1.58) | 1.63 (0.51, 5.25) | |
6–8 | 2.49 (0.93, 6.66) | 0.95 (0.61, 1.49) | 1.79 (0.47, 6.75) | |
9–11 | 2.90 (0.91, 9.29) | 1.09 (0.59, 2.02) | 2.46 (0.51, 11.88) | |
12+ | 2.57 (0.84, 7.85) | 1.41 (0.81, 2.44) | 4.98 (1.38, 17.98) |
Note: Data are reported as aOR (95% CI) after adjusting for indication for operative vaginal delivery, fetal station, and position, maternal age and race/ethnicity, chorioamnionitis, prior vaginal deliveries, prior cesareans, and maternal BMI. Emboldened text represents statistical significance.
A sensitivity analysis was performed, excluding skin lacerations from the composite adverse neonatal outcomes. This severe composite adverse neonatal outcomes variable occurred in 89 women (1.7% of vacuums vs. 1.7% of forceps, p = 0.99). Similar to the primary analyses, there was an increasing trend in the incidence of the severe composite adverse neonatal outcome in bivariable analyses (p-value for test of trend for pop-offs = 0.043 and for duration = 0.019). The same held true for forceps; there was no significant association between the number of pulls and the severe composite adverse neonatal outcome (p-value for test of trend = 0.292); however, forceps duration was associated with an increasing risk (p-value for test of trend < 0.001). Given the small number of cases of severe adverse neonatal outcomes, the multivariable analyses did not converge and thus could not be reported.
Given the number of women with missing information on indication for the OVD as well as fetal station, a post hoc sensitivity analysis was performed excluding those women who did not change the overall results.
Discussion
OVD is endorsed by ACOG as an alternative to cesarean when vaginal delivery is unlikely to occur spontaneously,2 but the literature to inform best practice of OVD is limited. These data, derived from a large cohort assembled at multiple hospitals in the United States, suggest that an increasing duration of the vacuum or forceps assistance is more strongly associated with adverse neonatal outcomes compared with an increasing number of pop-offs or pulls. Nevertheless, it should be noted that, even in the cohort with the longest duration of OVD, the overwhelming majority of neonates did not experience an adverse neonatal outcome.
In terms of pop-offs, while limiting vacuum assistance to a maximum of three pop-offs is often cited as best practice,6 this recommendation is without a clear evidence base. Our data demonstrated that after controlling for potential con- founders, an increasing number of pop-offs was not consistently associated with a significant increase in the frequency of adverse neonatal outcomes. This finding has biological plausibility: a pop-off may signify that too much force is being exerted in the wrong direction leaving to incorrect and ineffective vectors, not necessarily that too much traction is being placed on the fetal scalp.7
Prior data on duration of vacuum-assisted delivery and neonatal outcomes are conflicting. One prospective observational study demonstrated the duration of vacuum cup application wasstatisticallysignificantlylongerininfants whoexperienced a subgaleal hematoma compared with those without a sub-galeal hematoma.8 However, after controlling for potential confounders, including characteristics of vacuum placement, this association did not persist. In contrast, a population-based study using Swedish registry data demonstrated that a longer duration of vacuum assistance was associated with an increased risk of brachial plexus injury.9 Another study demon-strated an increased risk of scalp trauma with longer durations of vacuum assistance.10 Our data support a possible association between a longer duration of vacuum assistance and an increased frequency of the composite adverse neonatal outcome. Yet, itshouldbe stressed that the data cannot confirm causality of this association or that the alternative strategy of converting to a cesarean would lead to better outcomes. When deciding to perform a cesarean, additional time is required to accomplish a neonatal delivery. Thereby the alternative to an ongoing OVD attempt, a cesarean, may in fact lead to an increased frequency of adverse neonatal outcomes compared with the additional minutes required to achieve an OVD.
The number of forceps pulls and duration of forceps assistance have received less attention. One prior study identified an increased risk of neonatal trauma associated with more than three pulls; however, they were unable to control for significant potential confounders such as indication for OVD, fetal position, and prior obstetric history (i.e., prior vaginal delivery or cesarean).4 Accordingly, there are limited data otherwise to guide safe parameters of forceps use. Our data demonstrate that the overall duration of forceps assistance, as opposed to the number of pulls, may be associated with increased adverse neonatal outcomes.
This study has several strengths. First, the quality of the data abstracted for the primary study was ensured by (1) completion of an initial pilot study to review the data collection process, (2) planned randomly assigned data reabstraction and review, and (3) ongoing data audits throughout the data collection process.11 Second, the external generalizability is enhanced by its observational design— the OVDs that occurred during the study period represent standard practice at the 25 hospitals included in the study. However, all participating hospitals had an academic affiliation and thus may not reflect practice patterns in a community-based setting.
Despite these strengths, there are limitations that must be noted. First, as the number of pop-offs, pulls, and duration of OVD attempt are related to ongoing second-stage characteristics, causal attribution is limited. Other statistical limitations that should also be noted include (1) unmeasured confoun-ders, such as the specific type of vacuum used or obstetrician experience, that could mediate the observed relationships, (2) an inability to statistically assess trends across odds ratios in multivariable analyses, and (3) a not insignificant amount of missing data for pop-offs, pulls, and duration. In addition, based on the design of this study, we could only evaluate risk factors associated with OVD duration and were not able to evaluate whether the alternative to OVD—a cesarean delivery or spontaneous vaginal delivery—would have averted adverse outcomes. Furthermore, while the quality of data abstracted was ensured through multiple quality control mechanisms, the OVD duration is limited to what was documented in the medical record and did not include specific devices used or involvement of trainees. Finally, given the rarity of serious adverse neonatal outcomes and the relatively limited sample size, we utilized a composite adverse neonatal outcome for analyses. It is worth noting that skin lacerations were the most common of these adverse outcomes and likely drive the observed associations. While sensitivity analyses were performed excluding skin lacerations, the lack of convergence precludes drawing definitive conclusions.
In summary, these data demonstrate that, compared with the number of pop-offs or pulls, the duration of OVD, whether vacuum or forceps, may be more strongly associated with adverse neonatal outcomes. Future studies directed at quality improvement could include implementation of time notifications to maintain physician awareness of the duration of OVD attempts.
Acknowledgments
The authors thank Cynthia Milluzzi, RN, and Joan Moss, RNC, MSN, for protocol development and coordination between clinical research centers, and Elizabeth Thom, PhD, Madeline M. Rice, PhD, William A. Grobman, MD, MBA, Brian M. Mercer, MD, and Catherine Y. Spong, MD, for protocol development and oversight.
Funding
The project described was supported by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (HD21410, HD27869, HD27915, HD27917, HD34116, HD34208, HD36801, HD40500, HD40512, HD40544, HD40545, HD40560, HD40485, HD53097, HD53118) and the National Center for Research Resources (UL1 RR024989; 5UL1 RR025764). Comments and views of the authors do not necessarily represent views of the NIH.
Appendix A
In addition to the authors, other members of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network are as follows:
Northwestern University, Chicago, IL—W. Grobman, G. Mal- lett, M. Ramos-Brinson, A. Roy, L. Stein, P. Campbell, C. Collins, N. Jackson, M. Dinsmoor (NorthShore University HealthSys- tem), J. Senka (NorthShore University HealthSystem), K. Pay- chek (NorthShore University HealthSystem), A. Peaceman.
Columbia University, New York, NY—M. Talucci, M. Zylfijaj, Z. Reid (Drexel U.), R. Leed (Drexel U.), J. Benson (Christiana H.), S. Forester (Christiana H.), C. Kitto (Christiana H.), S. Davis (St. Peter’s UH.), M. Falk (St. Peter’s UH.), C. Perez (St. Peter”s UH.).
University of Utah Health Sciences Center, Salt Lake City, UT— K. Hill, A. Sowles, J. Postma (LDS Hospital), S. Alexander (LDS Hospital), G. Andersen (LDS Hospital), V. Scott (McKay-Dee), V. Morby (McKay-Dee), K. Jolley (UVRMC), J. Miller (UVRMC), B. Berg (UVRMC).
University of North Carolina at Chapel Hill, Chapel Hill, NC—K. Dorman, J. Mitchell, E. Kaluta, K. Clark (WakeMed), K. Spicer (WakeMed), S. Timlin (Rex), K. Wilson (Rex).
University of Texas Southwestern Medical Center, Dallas, TX —L. Moseley, M. Santillan, J. Price, K. Buentipo, V. Bludau, T. Thomas, L. Fay, C. Melton, J. Kingsbery, R. Benezue.
University of Pittsburgh, Pittsburgh, PA—H. Simhan, M. Bickus, D. Fischer, T. Kamon (deceased), D. DeAngelis.
MetroHealth Medical Center, Case Western Reserve University, Cleveland, OH—B. Mercer, C. Milluzzi, W. Dalton, T. Dotson, P. McDonald, C. Brezine, A. McGrail.
The Ohio State University, Columbus, OH—C. Latimer, L. Guzzo (St. Ann’s), F. Johnson, L. Gerwig (St. Ann’s), S. Fyffe, D. Loux (St. Ann’s), S. Frantz, D. Cline, S. Wylie, J. lams.
University of Alabama at Birmingham, Birmingham, AL— M. Wallace, A. Northen, J. Grant, C. Colquitt, D. Rouse, W. Andrews.
The University of Texas Medical Branch, Galveston, TX—J. Moss, A. Salazar, A. Acosta, G. Hankins.
Wayne State University, Detroit, MI— N. Hauff, L. Palmer, P. Lockhart, D. Driscoll, L. Wynn, C. Sudz, D. Dengate, C. Girard, S. Field.
Brown University, Providence, RI—P. Breault, F. Smith, N. Annunziata, D. Allard, J. Silva, M. Gamage, J. Hunt, J. Tillin- ghast, N. Corcoran, M. Jimenez.
Children’s Memorial Hermann Hospital, The University of Texas Health Science Center at Houston, Houston, TX—F. Ortiz, P. Givens, B. Rech, C. Moran, M. Hutchinson, Z. Spears, C. Carreno, B. Heaps, G. Zamora.
Oregon Health & Science University, Portland, OR—J. Seguin, M. Rincon, J. Snyder, C. Farrar, E. Lairson, C. Bonino, W. Smith (Kaiser Permanente), K. Beach (Kaiser Permanente), S. Van Dyke (Kaiser Permanente), S. Butcher (Kaiser Permanente).
Biostatistics Center, The George Washington University, Washington, DC—E. Thom, M. Rice, Y. Zhao, P. McGee, V. Momirova, R. Palugod, B. Reamer, M. Larsen.
Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD—C. Spong, S. Tolivaisa.
MFMU Network Steering Committee Chair (Medical University of South Carolina, Charleston, SC)—J. P. VanDorsten, MD.
Footnotes
Note
These findings were presented at the Society for Maternal-Fetal Medicine annual meeting in Atlanta, GA, 2016.
See Appendix A for a list of other members of the NICHD MFMU Network.
Conflict of Interest
None declared.
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