Operative vaginal delivery rates have declined significantly over the past several decades. By 2013, the cesarean delivery rate rose to 32.7% from a nadir of 4.5% in 1965.1 In contrast, by 2013 the use of operative vaginal delivery had decreased to 3.3% of all deliveries as compared with 9.0% in 1990. Currently 0.6% of all births are accomplished with the use of forceps and 2.7% with vacuum devices.2
Although the literature has delineated benefits of spontaneous vaginal birth over cesarean delivery with respect to maternal and neonatal morbidity, shorter recovery, and decreased costs, less clear is the question of operative vaginal delivery as compared with cesarean delivery in the second stage of labor, particularly from a low station.3 Additionally, prior studies have been limited to actual mode of delivery, not attempted mode of delivery, and thus are prone to selection bias. Furthermore, in 2012 the Cochrane Collaborative endeavored to perform a meta-analysis of randomized trials to investigate outcomes of attempted operative vaginal delivery compared with immediate cesarean delivery but was not able to identify any suitable studies for inclusion.4Therefore, we evaluated maternal and neonatal adverse outcomes by attempted mode of operative delivery from a low station in the second stage of labor.
MATERIALS AND METHODS
The Consortium on Safe Labor was a retrospective cohort study of electronic medical records from 228,562 deliveries, including 12 clinical centers with 19 hospitals across nine American College of Obstetricians and Gynecologists districts between 2002 and 2008.5 All participating institutions obtained institutional review board approval. Institutional review board approval also was obtained for the present analysis.
Women with singleton pregnancies who delivered at 37 weeks of gestation or greater, in cephalic presentation, achieved 10 cm dilation, attained at least low fetal station (+2/3 or greater or +3/5 or greater depending on the scale used by each institution), and underwent either attempted operative vaginal delivery through forceps or vacuum or cesarean delivery without an attempt of operative vaginal delivery were included (Fig. 1). Women with pregnancies complicated by severe anomalies, antepartum or intrapartum stillbirth, prolonged second stage of labor more than 12 hours, and sequential procedures (eg, forceps followed by vacuum or vice versa; n=12) were excluded. Intrapartum stillbirths were excluded because timing of stillbirth in labor was unknown, so it could not be determined whether it occurred during the first or second stage of labor. The number of individual exclusions may exceed the total at each point as a result of patients being excluded for multiple reasons (Fig. 1).
Data were collected from electronic antenatal, obstetric, and neonatal records, including maternal demographics, labor and delivery characteristics, gravidity, parity, insurance status, body mass index (BMI, calculated as weight [kg]/[height (m)]2), chronic hypertension, gestational hypertensive disease (inclusive of gestational hypertension and preeclampsia), pregestational diabetes mellitus, gestational diabetes mellitus, prior uterine scar, gestational age at delivery, oxytocin use, duration of the first and second stages of labor, birth weight, and hospital type.
Primary study outcomes were separate maternal and neonatal adverse outcome composites from diagnoses or interventions as recorded in the medical record. The maternal adverse outcome composite was defined as any of the following: postpartum hemorrhage, blood transfusion, endometritis, peripartum hysterectomy, intensive care unit admission, and mortality. The neonatal adverse outcome composite consisted of the following: 5-minute Apgar score less than 4, respiratory morbidity (defined as the use of any supplemental oxygen), neonatal intensive care unit (NICU) admission, shoulder dystocia, birth trauma, sepsis, and mortality. Secondary outcomes included the individual outcomes from the each composite as well as maternal venous thromboembolism, wound complications (infection or separation), episiotomy, third-degree and fourth-degree lacerations, cervical or sulcal lacerations, and length of stay in days (median, 10th, 90th percentile). Analyses were performed by attempted mode of delivery stratified by parity.
Bivariate analyses were performed to determine associations between maternal demographics and the type of delivery. Student's t or Mann-Whitney U tests were used to evaluate continuous variables as appropriate. χ2 and Fisher's exact test were used for the analysis of categorical variables. Multivariable logistic regression models were performed to calculate adjusted odds ratios (ORs) with corresponding 95% confidence intervals (CIs) of maternal and neonatal outcomes for attempted forceps or vacuum compared with cesarean delivery (referent group). Models were stratified by parity status and controlled for maternal race, diabetes (pregestational and gestational), BMI, insurance status, and hospital type. Statistical analysis was performed using SAS 9.3.
There were 2,518 deliveries that met inclusion criteria for this analysis. These occurred among 1,974 nulliparous and 544 parous women (Fig. 1). The overall rate of operative delivery by any method (forceps, vacuum, or cesarean) in the second stage of labor within the entire Consortium on Safe Labor cohort was 20.5%.
Women who attempted operative vaginal delivery were slightly younger, more likely to be non-Hispanic white, have private insurance, have a lower BMI, be less likely to have pregestational diabetes, and deliver at a community teaching or nonteaching hospital (Table 1). Among women who attempted operative vaginal birth, the gestational age at delivery was 3 days earlier and neonates weighed 119 g less on average (Table 1).
In nulliparous women, the maternal adverse outcome composite was not significantly different by attempted mode of delivery (Table 2). Attempted forceps was associated with a decreased risk of endometritis (0.7% compared with 3.0%; adjusted OR 0.20, 95% CI 0.05–0.86) and wound complications (0.5% compared with 2.0%; adjusted OR 0.16, 95% CI 0.03–0.78), but an increased risk of episiotomy use (69.5% compared with 1.5%; adjusted OR 104.4, 95% CI 31.5–320.3) and cervical or sulcal lacerations (9.0% compared with 1.0%; adjusted OR 8.74, 95% CI 2.07–37.02). Attempted vacuum was associated with a decreased risk of endometritis (0.3% compared with 3.0%; adjusted OR 0.10, 95% CI 0.02–0.44) and wound complications (0.3% compared with 2.0%; adjusted OR 0.13, 95% CI 0.03–0.55). Similar to forceps, vacuum was associated with increased episiotomy use (52.0% compared with 1.5%; adjusted OR 63.30, 95% CI 20.00–200.00) (Table 2).
In parous women, the maternal adverse outcome composite was not significantly different with either attempted forceps or vacuum. Blood transfusion occurred less frequently with vacuum use (8.9% compared with 18.8%; adjusted OR 0.20, 95% CI 0.04–0.95) (Table 3).
Among neonates born to nulliparous women, the neonatal adverse outcome composite was significantly lower with attempted forceps (9.4% compared with 16.7%; adjusted OR 0.44, 95% CI 0.27–0.72); it was not significantly different in women with attempted vacuum. Attempted forceps delivery was associated with significantly less NICU admission (5.6% compared with 13.6%; adjusted OR 0.35, 95% CI 0.20–0.63), respiratory morbidity (1.7% compared with 6.6%; adjusted OR 0.28, 95% CI 0.11–0.69), and sepsis (0.4% compared with 2.5%; adjusted OR 0.18, 95% CI 0.03–0.99). Attempted vacuum was associated with reduced NICU admission (6.5% compared with 13.6%; adjusted OR 0.49, 95% CI 0.30–0.80) and respiratory morbidity (2.8% compared with 6.6%; adjusted OR 0.48, 95% CI 0.24–0.95), similar to forceps (Table 4).
Among neonates born to parous women, the neonatal adverse outcome composite was not significantly different between groups. Birth trauma was significantly less for both forceps (0.8% compared with 8.3%; adjusted OR 0.03, 95% CI 0.002–0.40) and vacuum (2.8% compared with 8.3%; adjusted OR 0.15, 95% CI 0.03–0.95) (Table 5).
Actual mode of delivery correlated with attempted mode of delivery in 99.3% of nulliparous women who attempted forceps delivery and 99.25% of nulliparous women who attempted vacuum use. The actual mode of delivery matched the attempted route in all parous women (Table 6).
In our large, diverse cohort, attempted forceps or vacuum delivery compared with cesarean delivery from a low station in the second stage was associated with decreased maternal and neonatal risks, specifically blood transfusion, endometritis, neonatal infectious, and respiratory morbidities as well as NICU admission. These improvements should be balanced with increased incidences of episiotomy and cervical or sulcal lacerations in nulliparous women.
Early literature reported increased operative vaginal delivery-related retinal hemorrhage, cephalohematoma, facial injury, or maternal lacerations.6,76,7 Studies that followed found increased intracranial hemorrhage rates with forceps or vacuum use compared with prelabor cesarean delivery.8–128–128–128–128–12 Recently, epidemiologic cohorts have found either no associations or benefits of operative vaginal birth over cesarean delivery in terms of umbilical cord gas parameters, encephalopathy, neonatal death, or composite outcomes.13–1513–1513–15 Other literature has delineated the results of patients undergoing cesarean delivery after a failed operative vaginal attempt with conflicting findings as to the potential associated risks.16–1816–1816–18 Previous literature compared operative vaginal delivery against cesarean delivery from disparate stations as well (eg, midlabor cesarean delivery compared with operative vaginal delivery from an unknown station), diminishing applicability.8–158–158–158–158–158–158–158–15
Blood transfusion was lower in parous women attempting vacuum-assisted birth, likely as a result of avoidance of increased blood loss with second-stage cesarean delivery (greater than 1,000 mL in 10% of such patients).12 Wound complications were diminished in nulliparous women attempting operative vaginal birth, likely attributable to avoidance of a laparotomy incision. This is in contrast to a Maternal-Fetal Medicine Units Network study that reported increased incision site infections, seroma, or hematoma with forceps or vacuum use compared with cesarean delivery.16 Decreased endometritis with both forceps and vacuum in nulliparous women demonstrates the potential benefit of reducing infectious risks associated with second-stage cesarean delivery (over 10% in some cohorts).16 Decreased respiratory morbidity may be explained by the known lower incidence in this with vaginal delivery compared with cesarean delivery as well.3 Our findings are in agreement with a study of 122,000 birth records that found forceps use was associated with lower composite morbidity than either vacuum or cesarean delivery.14
In a seminal report of 580,000 neonates, intracranial hemorrhage occurred in one of 664, one of 860, and one of 907 births for forceps-assisted, vacuum-assisted, and intrapartum cesarean delivery, respectively.8 Another publication noted no differences in peripartum death or encephalopathy between either vacuum or forceps compared with cesarean delivery in the second stage for nearly 65,000 neonates.13 Our investigation is similarly reassuring in regard to attempted operative vaginal delivery compared with cesarean delivery overall and in agreement with other literature reporting improved outcomes with completed operative vaginal birth as compared with cesarean delivery in the second stage.12–14,1812–14,1812–14,1812–14,18
The rate of operative delivery by any method (forceps, vacuum, or cesarean) in the second stage overall has been reported at 18%, similar to 20.5% in our cohort.11 Episiotomy use increased with attempted operative vaginal delivery in our cohort (up to 69%), in keeping with the reported incidence in such circumstances (88%).19 Cervical or sulcal lacerations were elevated in nulliparous women undergoing operative vaginal birth, although overall occurred in less than one in 10 with attempted forceps and one in 20 patients with attempted vacuum use.
The strength of our study is the comparison of attempted mode of delivery at equivalent low station as opposed to the limitation of prior investigations that included all second-stage cesarean deliveries as a referent. Weaknesses are the retrospective nature, inability to adjust for nonuniformly abstracted variables, including estimated fetal weight and indication for delivery, and possible selection bias of patients undergoing attempted operative vaginal birth. It is likely that women thought to be better candidates were offered forceps or vacuum, because the attempted operative vaginal delivery group had lower birth weight, incidence of diabetes, BMI, and shorter labors, and this must be considered when interpreting our results. Because this cohort was retrospective and noninterventional, these differences are likely the result of health care provider judgment and therefore similar to usual clinical practice. The high success rates for operative vaginal birth attempts may be the result of such bias as well. Regardless, our findings are reassuringly consistent with those of others that have assessed outcomes by completed route of delivery.12–1412–1412–14 Some outcomes occurred rarely (eg, mortality), limiting the ability to detect a significant result. Lastly, analyses with multiple comparisons may experience a significant finding as a result of chance.
The results of our study can be used in counseling women who achieve full dilation and a low station but are unable to complete a spontaneous vaginal delivery. For both mother and neonate, attempted forceps or vacuum delivery demonstrates potential benefits without clinically significant excess harms compared with the risks of a second-stage cesarean delivery. Moreover, this information can be used to support the practice of operative vaginal delivery as an alternative to immediate cesarean delivery from a low station and thus may help lower the rate of primary cesarean delivery.
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