The cesarean delivery rate in the United States was 32.8% in 2012, representing a 58% increase since 1996.1 In contrast, the operative vaginal delivery rate has continued to decline; the rate in 2012 was 3.4% of all deliveries (2.8% vacuum and 0.6% forceps). This rate represents a 64% decline from the rate of 9.4% in 1996.2
Investigators have reported that a longer second stage is associated with an increased likelihood of maternal complications including puerperal infection, severe perineal lacerations, and postpartum hemorrhage as well as neonatal morbidities including admission to the intensive care unit, sepsis, and low 5-minute Apgar scores.3–9 Despite these associations, it has been suggested that the second stage of labor does not need to be terminated based on duration alone.9 The objective of our study was to compare outcomes between a contemporary cohort of nulliparous women and an analogous group delivered at the same institution approximately 10 years before to evaluate changes in mode of delivery as well as maternal and neonatal complications.
MATERIALS AND METHODS
We conducted a retrospective cohort study of all nulliparous women delivered at the University of Alabama at Birmingham from January 1, 2011, to December 31, 2012, and compared our findings with those from a prior prospectively assembled cohort at the same institution from July 28, 2000, to February 28, 2003. University of Alabama at Birmingham institutional review board approval was obtained.
For the current cohort, electronic medical records were reviewed, and data were transferred to detailed abstraction forms by three of the authors (J.L.F., N.-A.A., and S.B.C.) and then entered into a relational database by trained data entry staff. Trained data management staff confirmed data integrity. We included all women with singleton gestations at 36 weeks or greater who had a documented examination confirming complete cervical dilation. We excluded pregnancies with prenatally diagnosed fetal anomalies or missing data from the medical record. The data from the prior cohort were abstracted onto data forms designed specifically for the study by trained research nurses using medical record review and then entered into a dedicated electronic research database by a single author (J.O.) who was responsible for confirming data integrity. These data were archived in a deidentified database.
The primary outcome was the rate of cesarean delivery. Secondary outcomes included second-stage duration, operative vaginal delivery (forceps and vacuum collectively), and indications for cesarean delivery and operative vaginal delivery. Although operative vaginal delivery was an outcome in the prior cohort, the specific mode of operative vaginal delivery (forceps or vacuum) was not included in that database. To approximate those proportions for the women in the prior cohort, we used historical institutional percentages (obtained from our validated obstetric database, restricting the query to patients meeting our study enrollment criteria) to report the relative proportion of forceps compared with vacuum. For the current cohort, the specific type of operative vaginal delivery was recorded during record review.
We examined maternal puerperal infections (including chorioamnionitis, endometritis, and cesarean wound infection). These infections were defined as diagnosis documented in the clinical record or maternal fever with intravenous antibiotic administration without another documented source of infection. We also evaluated whether the cohorts differed in terms of mean umbilical artery pH and composite neonatal morbidity. This composite included neonatal death, intrapartum fetal death, 5-minute Apgar score less than 4, umbilical artery pH less than 7.00, mechanical ventilation, necrotizing enterocolitis, culture-confirmed sepsis, grade III or IV intraventricular hemorrhage, skull fracture, subgaleal bleed, seizures, or brachial plexus injury. These outcomes were stratified by mode of delivery. Finally, we compared the durations of the second stage between these two cohorts overall as well as stratified by mode of delivery.
Multivariable analyses were used for comparative statistics between modes of delivery, complications, and durations of the second stage. Covariates considered included maternal age, body mass index, gestational age, diabetes, hypertension, duration of membrane rupture, chorioamnionitis, and epidural use. We included covariates in the multivariable regression models that were both statistically significantly associated with the outcome of interest and significantly different between cohorts.
Categorical variables were analyzed using χ2 and Fisher's exact tests, as appropriate. Continuous variables were analyzed with the Student's t test and Wilcoxon rank-sum test. The mean second-stage durations were adjusted using multivariable analysis of covariance. Distributional assumptions were investigated before statistical analysis, and the only outcome for which skewness (to the right) was noted was second-stage duration. Therefore, we reported medians (25th, 75th percentile) for that variable and means for all others. Multivariable logistic regression was used to estimate covariate-adjusted odds ratios for cesarean delivery and operative vaginal delivery. We considered a P value <.05 to be statistically significant. Analyses were conducted using SAS 9.3. Assuming equal sizes of the prior and current cohorts, to evaluate a relative 100% increase in the cesarean delivery rate from 2% to 4% (α=0.05 and β=0.2), we calculated a sample size of 1,239 participants needed in each cohort. In addition, that same sample size would yield more than 95% power to detect a relative 30% decrease in operative vaginal delivery (from 20% to 14%).
From January 1, 2011, to December 31, 2012, there were 7,729 deliveries at our institution. Of these, 1,546 met our enrollment criteria. An additional 70 were excluded for missing data (eg, timing of start of second stage) or prenatally diagnosed fetal anomalies. The remaining 1,476 women were included in the analysis. Figure 1 is a flow diagram showing details of patients excluded to arrive at the analyzed current cohort. The prior cohort included 1,059 nulliparous women who delivered between July 28, 2000, and February 28, 2003. Of these, 36 were excluded for missing data. The remaining 1,023 were included in our analysis.
Demographic data comparing women in these two cohorts are presented in Table 1. When comparing the two cohorts, women in the current cohort were older, were less likely to have a self-reported race–ethnicity of black, delivered at a slightly earlier mean gestational age, and were more likely to undergo induction of labor. In addition, women in the current cohort were more likely to have hypertension and diabetes (class A2 or higher). Mean neonatal birth weight was similar between the cohorts.
Table 2 shows the unadjusted comparison of modes of delivery between the prior and current cohorts. The prevalence of both spontaneous vaginal delivery and cesarean delivery increased significantly, whereas the prevalence of operative vaginal delivery decreased significantly. In addition, the proportion of operative vaginal delivery performed using vacuum has significantly increased, whereas the proportion of operative vaginal delivery performed using forceps has significantly decreased (all P<.01).
Indications for operative deliveries, both cesarean delivery and operative vaginal delivery, are shown in Table 3. Indications for cesarean delivery did not differ significantly between cohorts, but operative vaginal delivery indications did differ; maternal exhaustion was more frequent and elective less often the indication for operative vaginal delivery in the current cohort (P<.01).
Among several possible confounders (including sociodemographic variables, body mass index, diabetes, hypertension, duration of membrane rupture, chorioamnionitis, and epidural use), maternal age, gestational age, duration of membrane rupture, and diabetes were significantly associated with cesarean delivery and differed significantly between the cohorts. When adjusting for these factors, compared with women in the prior cohort, women in the current cohort were more likely to have a cesarean delivery (compared with operative vaginal delivery or spontaneous vaginal delivery) (adjusted odds ratio [OR] 1.74, 95% confidence interval [CI] 1.04–2.91). Also, compared with women in the prior cohort, women in the current cohort were less likely to have an operative vaginal delivery (compared with cesarean delivery or spontaneous vaginal delivery) (adjusted OR 0.42, 95% CI 0.33–0.54). Compared with women in the prior cohort, women in the current cohort were more likely to have a spontaneous vaginal delivery (adjusted OR 1.92, 95% CI 1.54–2.40) (separate regression models using the same covariates as the cesarean delivery model).
We examined the duration of the second stage overall between cohorts as well as by mode of delivery. Median duration of the second stage was 4 minutes longer for the current cohort (42 compared with 38 minutes; P<.01). However, this difference became null after multivariable adjustment (Table 4).
The incidence of maternal infections was similar between the prior and current cohorts; composite puerperal infection (chorioamnionitis, endometritis, or cesarean wound infection) rates were 13% compared with 14%, respectively (P=.57). There also were no differences in rates of individual infections; in the prior and current cohorts, respectively, chorioamnionitis occurred in 9% compared with 9% (P=.68), endometritis occurred in 3% compared with 5% (P=.09), and cesarean wound infection occurred in 0.3% compared with 0% (P=.08). Conversely, the prevalence of postpartum hemorrhage was higher in the current cohort (1% compared with 6%; P<.01).
Finally, mean umbilical artery pH was similar between the cohorts (7.237 compared with 7.242 for the prior and current cohorts, respectively; P=.07) and also was not significantly different when stratified by mode of delivery. Likewise, an umbilical artery pH less than 7.00 was infrequent in both cohorts and not significantly different (0.2% compared with 0.6% for prior and current cohorts, respectively; P=.21). However, composite neonatal morbidity occurred more often in the current cohort, even after multivariable adjustment (Table 5). This composite outcome in the current cohort was primarily driven by brachial plexus injury (n=12) and mechanical ventilation (n=11), whereas in the old cohort this was driven by 5-minute Apgar score less than 4 (n=4), mechanical ventilation (n=3), and seizures (n=3). There was one neonatal death in the current cohort. This neonate encountered a shoulder dystocia at delivery that lasted 6 minutes, had severe metabolic acidemia, and died on the fifth day of life from multiorgan system failure. No intrapartum deaths occurred in either cohort. In regard to brachial plexus injuries, the difference between cohorts was statistically significant (12/1,476 compared with 0/1,023; P=.002). One of these neonates was delivered by cesarean, three were delivered by operative vaginal delivery, and the remaining eight were delivered through spontaneous vaginal delivery. Four of these cases resolved and three were improving by the time of hospital discharge.
We demonstrated that, over a 10-year period at our institution, rates of spontaneous vaginal deliveries and cesarean deliveries have increased for nulliparous women reaching the second stage of labor, whereas operative vaginal delivery rates have decreased. Also, the proportion of operative vaginal delivery using forceps has decreased. Changes in patient population do not explain these results, because rate differences persisted after adjustment.
Rouse and colleagues9 evaluated 4,126 nulliparous women from 14 centers who reached the second stage between 2002 and 2005, reporting rates of spontaneous vaginal delivery (74%), operative vaginal delivery (18.5%), and cesarean delivery (7.4%). Bleich and colleagues4 reviewed 21,991 nulliparous women reaching the second stage between 2003 and 2008 at Parkland Hospital with the rate of spontaneous vaginal delivery (87.9%), operative vaginal delivery (6.2%), and cesarean delivery (5.9%). Both Parkland and the University of Alabama at Birmingham were in the 14 centers contributing data to the study by Rouse, et al.9 Like our data, these two studies support a trend toward higher cesarean delivery and lower operative vaginal delivery rates for nulliparous women reaching the second stage.
Increasing cesarean delivery and decreasing operative vaginal delivery (particularly forceps) rates in the second stage are concerning. Not only is there a large body of literature demonstrating an increased risk of complications associated with previous cesarean delivery,10–19 but the risk of hysterotomy extension, uterine atony, and incidental cystotomy is higher when cesarean delivery is performed in the second stage compared with the active phase of the first stage.20 Furthermore, our data suggest that this increasing cesarean delivery rate does not improve neonatal outcome. However, it would be unrealistic to expect a reversal of the trend of decreasing operative vaginal delivery rates. In our opinion, obstetric training is approaching or may even have passed a critical threshold below which teaching obstetric forceps deliveries will become unfeasible. During the study period, reported case volume of operative vaginal delivery for residents at our center perennially was in the top half of programs in the United States (Alice Goepfert, MD, residency program director, personal communication). Therefore, we speculate that many residents elsewhere have even less training in operative vaginal delivery.
Our study has several strengths. We described changes in practice at a single institution over time. In addition, we used high-quality data collected by trained obstetricians from the intrapartum and postpartum records. Finally, our center's physicians practice in a relatively uniform manner according to clinical guidelines maintained by the Division of Maternal-Fetal Medicine.
Weaknesses include the retrospective nature of the study. We designed our study for comparison to a previously collected cohort and could only include variables in that prior database. Therefore, some comparisons are limited; third- and fourth-degree perineal laceration was not recorded for the prior cohort, and although we saw a difference in postpartum hemorrhage rate, the definition of postpartum hemorrhage in the two cohorts probably differed. Because the rate of transfusion in the current cohort was 0.9%, the rates may actually have been similar. Also, excluding mother–neonate pairs with missing data may have altered our results; those with missing start time of the second stage likely had shorter second stages and perhaps fewer complications than the patients we included. Although composite neonatal morbidity was significantly different between groups, individual neonatal outcomes were infrequent. A larger cohort would be necessary to evaluate individual neonatal outcomes. Although one individual outcome was significantly different between groups (brachial plexus injury), we speculate that the difference was the result of increased attentiveness of pediatricians to the diagnosis, because most were resolved or resolving by hospital discharge. We were unable to compare the rate of failed operative vaginal delivery, especially by subtype, leading to cesarean delivery. This information was not included in the prior cohort database. Also, we collected cesarean wound infection as an outcome, but this was restricted to diagnoses before hospital discharge or in women who returned to the hospital after discharge. Opøien and colleagues21 showed that the rate of postcesarean surgical site infections increases approximately fivefold from hospital discharge until 30 days after delivery. Therefore, we almost certainly underestimated the true incidence of cesarean wound infection. Finally, because this study was performed at a single center, this limits the generalizability.
Despite these limitations, we think that our study confirms a shift in management of the second stage of labor with fewer operative vaginal deliveries and more cesarean deliveries. Although the exact reasons for these changes are uncertain, they have not resulted in improved outcome. We anticipate additional analyses from the current cohort to evaluate the effect of duration of labor on maternal and neonatal complications as well as the mode of delivery.
1. Martin JA, Hamilton BE, Osterman MJ, Curtain SC, Matthews TJ. Births: final data for 2012. Natl Vital Stat Rep 2013;62:1–68.
2. Curtin SC, Park MM. Trends in the attendant, place, and timing of births, and in the use of obstetric interventions: United States, 1989–97. Natl Vital Stat Rep 1999;47:1–12.
3. Allen VM, Baskett TF, O'Connell CM, McKeen D, Allen AC. Maternal and perinatal outcomes with increasing duration of the second stage of labor. Obstet Gynecol 2009;113:1248–58.
4. Bleich AT, Alexander JM, McIntire DD, Leveno KJ. An analysis of second-stage labor beyond 3 hours in nulliparous women. Am J Perinatol 2012;29:717–22.
5. Cheng YW, Hopkins LM, Laros RK Jr, Caughey AB. Duration of the second stage of labor in multiparous women: maternal and neonatal outcomes. Am J Obstet Gynecol 2007;196:585.e1–6.
6. Cohen WR. Influence of the duration of second stage labor on perinatal outcome and puerperal morbidity. Obstet Gynecol 1977;49:266–9.
7. Laughon SK, Berghella V, Reddy UM, Sundaram R, Lu Z, Hoffman MK. Neonatal and maternal outcomes with prolonged second stage of labor. Obstet Gynecol 2014;124:57–67.
8. Myles TD, Santolaya J. Maternal and neonatal outcomes in patients with a prolonged second stage of labor. Obstet Gynecol 2003;102:52–8.
9. Rouse DJ, Weiner SJ, Bloom SL, Varner MW, Spong CY, Ramin SM, et al.. Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes. Am J Obstet Gynecol 2009;201:357.e1–7.
10. Clark EA, Silver RM. Long-term maternal morbidity associated with repeat cesarean delivery. Am J Obstet Gynecol 2011;205(suppl):S2–10.
11. Shellhaas CS, Gilbert S, Landon MB, Varner MW, Leveno KJ, Hauth JC, et al.. The frequency and complication rates of hysterectomy accompanying cesarean delivery. Obstet Gynecol 2009;114:224–9.
12. Getahun D, Oyelese Y, Salihu HM, Ananth CV. Previous cesarean delivery and risks of placenta previa and placental abruption. Obstet Gynecol 2006;107:771–8.
13. Grobman WA, Gersnoviez R, Landon MB, Spong CY, Leveno KJ, Rouse DJ, et al.. Pregnancy outcomes for women with placenta previa in relation to the number of prior cesarean deliveries. Obstet Gynecol 2007;110:1249–55.
14. Kennare R, Tucker G, Heard A, Chan A. Risks of adverse outcomes in the next birth after a first cesarean delivery. Obstet Gynecol 2007;109:270–6.
15. Lydon-Rochelle M, Holt VL, Easterling TR, Martin DP. First-birth cesarean and placental abruption or previa at second birth(1). Obstet Gynecol 2001;97:765–9.
16. Nisenblat V, Barak S, Griness OB, Degani S, Ohel G, Gonen R. Maternal complications associated with multiple cesarean deliveries. Obstet Gynecol 2006;108:21–6.
17. Silver RM, Landon MB, Rouse DJ, Leveno KJ, Spong CY, Thom EA, et al.. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstet Gynecol 2006;107:1226–32.
18. Wood SL, Chen S, Ross S, Sauve R. The risk of unexplained antepartum stillbirth in second pregnancies following caesarean section in the first pregnancy. BJOG 2008;115:726–31.
19. Wu S, Kocherginsky M, Hibbard JU. Abnormal placentation: twenty-year analysis. Am J Obstet Gynecol 2005;192:1458–61.
20. Alexander JM, Leveno KJ, Rouse DJ, Landon MB, Gilbert S, Spong CY, et al.. Comparison of maternal and infant outcomes from primary cesarean delivery during the second compared with first stage of labor. Obstet Gynecol 2007;109:917–21.
21. Opøien HK, Valbø A, Grinde-Andersen A, Walberg M. Post-cesarean surgical site infections according to CDC standards: rates and risk factors. A prospective cohort study. Acta Obstet Gynecol Scand 2007;86:1097–102.