Abstract
BACKGROUND:
Although the neonatal morbidity associated with shoulder dystocia are well known, the maternal morbidity caused by this obstetrical emergency is infrequently reported.
OBJECTIVE:
This study aimed to assess the composite adverse maternal and neonatal outcomes among vaginal deliveries (at 34 weeks or later) with and without shoulder dystocia.
STUDY DESIGN:
This is a secondary analysis of the Consortium of Safe Labor, an observational obstetrical cohort of all vaginal deliveries occurring at 19 hospitals (from 2002–2008) and for which data on the occurrence of shoulder dystocia were available. The composite adverse maternal outcome included third- or fourth-degree perineal laceration, postpartum hemorrhage (>500 cc blood loss for a vaginal delivery and >1000 cc blood loss for cesarean delivery), blood transfusion, chorioamnionitis, endometritis, thromboembolism, admission to intensive care unit, or maternal death. The composite adverse neonatal outcome included an Apgar score of <7 at 5 minutes, a birth injury, neonatal seizure, hypoxic ischemic encephalopathy, or neonatal death. A multivariable Poisson regression was used to estimate the adjusted relative risks with 95% confidence intervals. The area under the receiver operating characteristic curve was constructed to determine if clinical factors would identify shoulder dystocia.
RESULTS:
Of the 228,438 women in the overall cohort, 130,008 (59.6%) met the inclusion criteria, and among them, shoulder dystocia was documented in 2159 (1.7%) cases. The rate of composite maternal morbidity was significantly higher among deliveries with shoulder dystocia (14.7%) than without (8.6%; adjusted relative risk, 1.71; 95% confidence interval, 1.64–2.01). The most common maternal morbidity with shoulder dystocia was a third- or fourth-degree laceration (adjusted relative risk, 2.82; 95% confidence interval, 2.39–3.31). The risk of composite neonatal morbidity with shoulder dystocia (12.2%) was also significantly higher than without shoulder dystocia (2.4%) (adjusted relative risk, 5.18; 95% confidence interval, 4.60–5.84). The most common neonatal morbidity was birth injury (adjusted relative risk, 5.39; 95% confidence interval, 4.71–6.17). The area under the curve for maternal characteristics to identify shoulder dystocia was 0.66 and it was 0.67 for intrapartum factors.
CONCLUSION:
Although shoulder dystocia is unpredictable, the associated morbidity affects both mothers and newborns. The focus should be on concurrently averting the composite morbidity for the maternal-neonatal dyad with shoulder dystocia.
Keywords: birth injury, postpartum hemorrhage, third- or fourth-degree perineal injury
Introduction
Shoulder dystocia, defined as the inability to deliver the fetal shoulder with gentle downward traction of the fetal head, prompting supplementary maneuvers to effectuate delivery, complicates up to 3% of vaginal deliveries.1 Although the risk factors for this obstetrical emergency are known, the majority of the clinicians surveyed across the country and national guidelines on the topic characterize shoulder dystocia as “unpredictable and unpreventable1–3.” Irrespective of this characterization, the neonatal morbidities— fracture, brachial plexus palsy, or hypoxic ischemic injury—with shoulder dystocia are well acknowledged.1,4,5 Most publications about the topic focused on identifying risk factors, management strategies, and interventions to mitigate the neonatal morbidity associated with the impacted shoulder.6–21
The maternal morbidities with shoulder dystocia, however, are inadequately emphasized as evidenced by the few reports that focused on the adverse outcomes of the parturient. The American College of Obstetricians and Gynecologists’ (ACOG) practice bulletins on the topic, for example, published in 2002 and 2017, noted that maternal complications with shoulder dystocia include a postpartum hemorrhage rate of 11% and a third- and fourth-degree perineal laceration in 4% of cases.1,22 In both practice bulletins, ACOG referenced the same publication, which involved a single center, had a small sample size, was published decades ago, and is the only reference cited from the United States, that reported on frequently encountered complications.23 Thus, the benchmark rate of frequent maternal complications with shoulder dystocia may not be applicable in contemporary practice in the United States.
To rectify the knowledge gap about maternal morbidities associated with shoulder dystocia, we undertook this secondary analysis of the Consortium of Safe Labor data.4 The primary objective of our analysis was to compare the composite maternal morbidity among vaginal deliveries complicated with vs without shoulder dystocia; the secondary objective was to compare the composite neonatal morbidity between the 2 groups. We also sought to ascertain if the risk factors associated with shoulder dystocia can predict if the delivery will be complicated by an impacted shoulder.
Materials and Methods
For this analysis, we utilized a retrospective observational obstetrical cohort, the Consortium for Safe Labor. This study collected information about all deliveries from 19 hospitals within 12 clinical centers across 9 different ACOG districts from 2002 to 2008. Previous publications have described the details of this study.4,24,25 The maternal characteristics, peripartum outcomes, and neonatal morbidities were collected from electronic medical records at all participating sites. The participants included women delivering at 23 weeks of gestation or later. Newborn intensive care unit admission information was linked to the newborn records. The institutional review board at each participating center approved the study.
Women were included in our secondary analysis if they vaginally delivered a nonanomalous singleton at 34 weeks of gestation or later with documentation of whether shoulder dystocia occurred or not.4 Women were excluded if they delivered a fetus with a congenital anomaly or had a stillbirth before the onset of labor. For women with more than 1 delivery in the database, we selected the first delivery from each study subject.
The maternal and neonatal outcomes were extracted from the electronic medical records and supplemented with International Classification of Diseases, ninth revision, codes. The prespecified primary outcome was a composite maternal morbidity, which included any of the following: third- or fourth-degree perineal laceration, postpartum hemorrhage (>500 cc blood loss for a vaginal delivery and >1000 cc blood loss for cesarean delivery), blood transfusion, chorioamnionitis, endometritis, or thromboembolism. Hypertensive disease of pregnancy was defined as any case of gestational hypertension or preeclampsia. The secondary outcome was a composite adverse neonatal outcome, which included any of the following: an Apgar score of <7 at 5 minutes, birth injury (defined as brachial plexus, skull fracture, facial nerve injury, laceration, clavicular fracture, or shoulder dislocation), neonatal seizure, hypoxic ischemic encephalopathy, or perinatal death. Rates of maternal death were also reported for each group.
Descriptive statistics were used to report all variables of interest. A multivariable Poisson regression model was utilized to examine the association between shoulder dystocia and adverse outcomes, reported as the adjusted relative risk (aRR) with 95% confidence interval (CI). The analysis was adjusted for possible confounders, revealed by the univariate analysis, including maternal age (<20, 20–34, or ≥35 years), maternal race and ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, other), nulliparous (yes, no), prepregnancy body mass index [BMI] (group 1 BMI, 0–29.9 kg/m2; group 2 BMI, ≥30.0 kg/m2; group 3, missing), insurance status (private, nonprivate), and enrollment site. As an additional analysis, a second multivariable Poisson regression model was employed using the same confounders as listed above and additionally also included the diabetes status (yes, no). STATA statistical software version 16 (StataCorp LP, College Station, TX) was utilized for the analyses. All tests were 2-tailed, and p<.05 was used to define statistical significance. No imputation for missing data was performed.
Using the final regression model, a receiver operating characteristic curve analysis was also performed. The predictive capacity of the logistic regression was assessed using the area under the curve (AUC); an AUC of 0.80 was considered clinically significant.26 The sensitivity, specificity, and positive and negative likelihood ratios, along with their corresponding 95% CIs, were estimated for the several risk factors included in the final predictive model. In addition, the risk of both composite adverse maternal and neonatal outcomes for the beginning of the second stage of labor to delivery were assessed using a Kaplan-Meier analysis, in which the length of the second stage (in minutes) was the time scale and composite adverse outcome was the event. Hazard ratios (HRs) were estimated with the use of a Cox proportional hazards model.
This analysis qualified for exempt status by the institutional review board at the McGovern Medical School at the University of Texas Health Science Center at Houston, TX (HSC-MS-20-0041). The Strengthening the Reporting of Observational Studies in Epidemiology guidelines for reporting observational studies were followed.27
Results
From 2002 to 2008, of the 228,438 births within the Consortium of Safe Labor, 130,008 (59.6%) delivered vaginally and met the inclusion criteria (Figure 1). The 3 most common reasons for exclusions were cesarean delivery, multiple gestation, and delivering more than once during the study period. The rate of shoulder dystocia among vaginal deliveries at 34 weeks or later was 1.7% (n=2159). Seventy-one cases (3.4%) of shoulder dystocia occurred among newborns delivered before 37 weeks.
FIGURE 1. The flowchart of participants in the study.
CSL, Consortium on Safe Labor.
Several maternal characteristics differed between vaginal deliveries with shoulder dystocia and those without. Deliveries complicated by shoulder dystocia were more likely to be associated with advanced maternal age, Hispanic or African American race or ethnicity, less likely to be associated with nulliparity, more likely to be associated with maternal obesity, less likely to be associated with private insurance use or a high school education, and more likely to be associated with a diagnosis of pregestational or gestational diabetes. Hypertensive disease of pregnancy occurred with a similar frequency in the 2 groups (Table 1). The AUC for the maternal characteristics to identify a case of shoulder dystocia was 0.66, suggesting that the known variables before labor are not useful in identifying women whose delivery would be complicated by shoulder dystocia (Figure 2).
TABLE 1.
Baseline maternal characteristics
| Characteristic | SD (n=2159) | No SD n=127,849) | P value |
|---|---|---|---|
| Maternal age (y), mean (SD) | 27.1 (6.0) | 27.8 (6.17) | .01a |
| ≤19 y, n (%) | 190 (8.8) | 12,898 (10.1) | <.01a |
| 20–34 y, n (%) | 1622 (75.1) | 98,686 (75.1) | |
| 35 y or older, n (%) | 344 (16.0) | 16,088 (12.6) | |
| Missing, n (%) | 3 (0.1) | 177 (0.1) | |
| Race or ethnicity | |||
| African American, n (%) | 487 (22.6) | 25,637 (20.1) | .04a |
| White, n (%) | 1048 (48.5) | 66,260 (51.8) | |
| Hispanic, n (%) | 413 (19.1) | 21,939 (17.2) | |
| Others, n (%) | 211 (9.8) | 14,013 (11.0) | |
| Nulliparous, n (%) | 801 (37.1) | 54,110 (42.3) | <.01a |
| Prepregnancy BMI (kg/m2), mean (SD) | 26.4 (6.23) | 24.6 (5.62) | <.01a |
| <30, n (%) | 1064 (49.3) | 73,056 (57.1) | <.01a |
| ≥30, n (%) | 344 (15.9) | 12,639 (9.9) | |
| Missing, n (%) | 751 (34.8) | 42,154 (33.0) | |
| Private insurance, n (%) | 1196 (55.4) | 74,060 (57.9) | .02a |
| High school education, n (%) | 200 (10.8) | 12,994 (12.6) | .02a |
| <High school, n (%) | 362 (19.5) | 22,523 (21.8) | .02a |
| Hypertensive disease of pregnancy, n (%) | 85 (3.9) | 5447 (4.3) | .46 |
| Diabetes—gestational or pregestational, n (%) | 196 (9.6) | 4970 (4.2) | <.01a |
Data are presented as mean (standard deviation) or n (%). Hypertensive disease of pregnancy includes all cases of gestational hypertension and preeclampsia.
SD, shoulder dystocia.
Significant difference.
FIGURE 2. ROC curve for antepartum risk factors for identification of newborn with shoulder dystocia and injury.
The following antepartum factors were evaluated: maternal age, race or ethnicity, nulliparity, prepregnancy body mass index, insurance status, education level, and diagnosis of diabetes complicating pregnancy.
ROC, receiver operating characteristic.
Several intrapartum characteristics among deliveries with and those without shoulder dystocia differed. Specifically, cases affected by shoulder dystocia were more likely to be delivered at or after 40 weeks, have a suspicion for a large for gestational age fetus (clinically or sonographically), undergo induction and artificial rupture of membranes, have a longer duration of the second stage of labor, require an operative vaginal delivery, and have a birthweight of over 4000 g. An episiotomy was done more frequently among those with shoulder dystocia than those without (Table 2). The AUC for risk factors during the labor course to identify shoulder dystocia was 0.67, indicating that intrapartum variables are poor predictors of an impacted shoulder (Figure 3).
TABLE 2.
Intrapartum characteristics
| Characteristic | SD (n=2159) | No SD (n= 127,849) | P value |
|---|---|---|---|
| History of cerclage, n (%) | 8 (0.4) | 341 (0.3) | .39 |
| Previous cesarean delivery or uterine scar, n (%) | 107 (5.0) | 4394 (3.4) | <.01a |
| Gestational age at delivery (wk), mean (standard deviation) | 39.4 (1.2) | 39.0 (1.4) | <.01a |
| 34.0–36.6, n (%) | 71 (3.3) | 9044 (7.1) | <.01a |
| 37.0–39.6, n (%) | 1236 (57.3) | 79,827 (62.4) | |
| ≥40.0, n (%) | 852 (39.5) | 38,978 (30.5) | |
| LGA suspected prenatally, n (%) | 38 (2.8) | 552 (0.7) | <.01a |
| Regional anesthesia, n (%) | 1277 (59.2) | 72,327 (56.6) | .02a |
| Induction, n (%) | 921 (42.7) | 50,391 (39.4) | <.01a |
| Augmentation, n (%) | 587 (31.7) | 33,357 (32.3) | .59 |
| Artificial rupture of membranes, n (%) | 350 (18.7) | 16,588 (14.8) | <.01a |
| Duration of second stage of labor (min), mean (standard deviation) | 64.3 (77.2) | 53.7 (73.7) | <.01a |
| <60 min, n (%) | 1169 (63.3) | 74,259 (70.9) | <.01a |
| 60–119 min, n (%) | 389 (21.1) | 18,304 (17.5) | |
| 120–179 min, n (%) | 170 (9.2) | 7351 (7.0) | |
| ≥180 min, n (%) | 118 (6.4) | 4901 (4.7) | |
| Operative vaginal delivery, n (%) | 258 (12.0) | 8960 (7.0) | <.01a |
| Episiotomy, n (%) | 514 (25.3) | 24,967 (21.0) | <.01a |
| Birthweight (g), mean (standard deviation) | 3809.4 (468.4) | 3292.7 (456.5) | <.01a |
| ≥4000, n (%) | 731 (34.1) | 7474 (5.9) | <.01a |
| ≥4500, n (%) | 145 (6.7) | 608 (0.5) | <.01a |
Data are presented as n (%) or mean (standard deviation).
LGA, large for gestation age; SD, shoulder dystocia.
Significantly difference.
FIGURE 3. ROC curve for intrapartum risk factors for identification of newborn with shoulder dystocia and injury.
The following antepartum factors were evaluated: gestational age at delivery, induction, use of regional anesthesia, operative vaginal delivery, duration of second stage, prior cesarean delivery, and suspected large for gestational age.
The maternal composite morbidity was more common among deliveries complicated by shoulder dystocia (14.7%) than without (8.6%) (aRR, 1.71; 95% CI, 1.64–2.01). Several components—postpartum hemorrhage (5.0% vs 2.8%; aRR, 1.77; 95% CI, 1.47–2.15), third- or fourth-degree laceration (6.5% vs 2.7%; aRR, 2.82; 95% CI, 2.39–3.31), and chorioamnionitis (1.8% vs 1.0%; aRR, 1.69; 95% CI, 1.22–2.34)—of the composite were more common with shoulder dystocia than without. Blood transfusion, endometritis, deep venous thrombosis or pulmonary embolism, and death did not differ between the groups (Table 3).
TABLE 3.
Maternal outcomes
| Outcome | SD (n=2159) | No SD (n=127,849) | RR (95% CI) | aRRa (95% CI) |
|---|---|---|---|---|
|
|
||||
| Composite maternal morbidity, n (%) | 318 (14.7) | 11,015 (8.6) | 1.71 (1.54–1.89)b | 1.71 (1.64–2.01)b |
|
| ||||
| Third- or fourth-degree perineal laceration, n (%) | 141 (6.5) | 3449 (2.7) | 2.42 (2.06–2.85)b | 2.82 (2.39–3.31)b |
|
| ||||
| Postpartum hemorrhage, | 107 (5.0) | 3516 (2.8) | 1.80 (1.49–2.17)b | 1.77 (1.47–2.15)b |
|
| ||||
| n (%) | ||||
|
| ||||
| Blood transfusion, n (%) | 61 (4.5) | 3159 (3.8) | 1.20 (0.94–1.54) | 1.25 (0.97–1.59) |
|
| ||||
| Chorioamnionitis, n (%) | 38 (1.8) | 1384 (1.0) | 1.63 (1.18–2.24)b | 1.69 (1.22–2.34)b |
|
| ||||
| Endometritis, n (%) | 2 (0.2) | 81 (0.1) | 1.30 (0.32–5.27) | –– |
|
| ||||
| Deep venous thrombosis or PE, n (%) | 4 (0.2) | 169 (0.2) | 1.40 (0.52–3.77) | –– |
|
| ||||
| Death, n (%) | 0 | 2 (0.01) | –– | –– |
|
| ||||
| Major lacerations other than third- or fourth-degree, n (%)c | 81 (3.8) | 5091 (4.0) | 1.00 (0.99–1.01) | 1.00 (0.99–1.01) |
Data are presented as n (%).
aRR, adjusted relative risk; CI, confidence intervals; PE, pulmonary embolism; PPH, postpartum hemorrhage; SD, shoulder dystocia.
Poisson regression with robust error variance adjusted for maternal age, race or ethnicity, nulliparity, body mass index, insurance status;
XXX;
Major lacerations defined as perineal, vaginal, cervical, labial, or periurethral.
The neonatal outcomes subsequent to the resolution of the shoulder dystocia was significantly worse than those without an impacted shoulder. The composite neonatal morbidity was higher with shoulder dystocia (7.4%) than without (1.5%) (aRR, 4.80; 95% CI, 3.91–5.88). The following 2 components of the composite morbidity were also significantly higher with than without shoulder dystocia: Apgar score of <7 at 5 min and birth injury (Table 4). The rate of admission to the neonatal intensive care unit for at least 24 hours was also higher in deliveries complicated by shoulder dystocia than those without (8.3% vs 4.5%; aRR, 1.96; 95% CI, 1.60–2.32).
TABLE 4.
Neonatal outcomes
| Outcome | SD(n=2159) | No SD(n=127,849) | RR (95% CI) | aRRa (95% CI) |
|---|---|---|---|---|
| Admission to NICU ≥24 h, n (%) | 204 (9.5) | 6380 (5.0) | 0.98 (0.96–1.00) | 0.98 (0.95–1.01) |
| Neonatal asphyxia, n (%) | 5 (0.2) | 116 (0.1) | 2.55 (1.04–6.25) | –– |
| Composite neonatal morbidity, n (%) | 263 (12.2) | 3085 (2.4) | 5.04 (4.48–5.68)b | 5.18 (4.60–5.84)b |
| Apgar score <7 at 5 min, n (%) | 68 (3.2) | 688 (0.5) | 5.85 (4.58–7.48)b | 6.03 (4.71–7.71)b |
| Birth injury, n (%) | 213 (9.9) | 2402 (1.8) | 5.25 (4.59–6.00)b | 5.39 (4.71–6.17)b |
| Neonatal seizure, n (%) | 6 (0.3) | 67 (0.1) | 5.30 (2.30–12.2) | –– |
| Hypoxic ischemic encephalopathy, n (%) | 1 (0.01) | 4 (0.01) | 14.8 (1.66–132.4) | –– |
| Neonatal death, n (%) | 0 | 28 (0.02) | –– | –– |
Data are presented as n (%).
aRR, adjusted relative risk; CI, confidence intervals; NICU, neonatal intensive care unit; SD, shoulder dystocia.
Poisson regression with robust error variance adjusted for maternal age, race and ethnicity, nulliparity, body mass index, insurance status;
XXX.
The sensitivity, specificity, positive, and negative likelihood ratios for the number of antepartum risk factors to identify a delivery that will be complicated by shoulder dystocia are noted in Table 5. The positive likelihood ratio was below 6, irrespective of whether 1 or 5 risk factors were present.
TABLE 5.
Sensitivity, specificity, positive, and negative likelihood ratios for antepartum risk factors
| Antepartum risk factor | Number of cohorts | Cases of SD | Sensitivity | Specificity | Positive LR | Negative LR |
|---|---|---|---|---|---|---|
| At least 1 risk factor (AMA) | 16,088 | 344 | 2.1 (1.9–2.3) | 98.4 (98.3–98.5) | 1.31 (1.17–1.47) | 0.99 (0.99–1.00) |
| At least 2 risk factors (AMA or nulliparity) | 2033 | 35 | 1.7 (1.2–2.4) | 98.3 (98.2–98.4) | 1.04 (0.74–1.44) | 1.0 (0.99–1.01) |
| At least 3 risk factors (AMA or nulliparity or obesity) | 127 | 6 | 4.7 (1.8–10.0) | 98.3 (98.2–98.4) | 2.85 (1.30–6.23) | 0.97 (0.93–1.01) |
| At least 4 risk factors (AMA or nulliparity or obesity or AA or Hispanic) | 38 | 3 | 7.9 (1.7–21.4) | 98.3 (98.2–98.5) | 4.76 (1.61–14.1) | 0.94 (0.85–1.03) |
| At least 5 risk factors (AMA or nulliparity or Obesity or AA or Hispanic or private insurance) | 20 | 2 | 10.0 (1.2–31.7) | 98.3 (98.2–98.4) | 6.03 (1.62–22.5) | 0.92 (0.79–1.06) |
The following risk factors were assessed: maternal age ≥35, nulliparity, prepregnancy body mass index ≥30, African American or Hispanic race or ethnicity, and private insurance.
AA, African American; AMA, advanced maternal age; LR, likelihood ratio; SD, shoulder dystocia.
The Kaplan-Meier analysis indicated that the cumulative percentage of women suffering composite maternal morbidity was significantly higher in women with shoulder dystocia during delivery given the same length of the second stage of labor (HR, 1.3; 95% CI, 1.19–1.52; P<.01) (Figure 4). Likewise, the cumulative percentage of women with neonates suffering composite neonatal morbidity was significantly higher in deliveries with shoulder dystocia given the same length of second stage of labor (HR, 3.86; 95% CI, 3.22–4.63; P<.01) (Figure 5).
FIGURE 4.
Length of second stage of labor and composite maternal morbidity
FIGURE 5.
Length of second stage of labor and composite neonatal morbidity
Discussion
Principal findings
Both the composite adverse maternal and neonatal outcomes were significantly higher following deliveries with shoulder dystocia than those without it. The receiver operating characteristic curves indicated that neither the antepartum maternal characteristics nor the intrapartum course were clinically useful in identifying which vaginal birth would be complicated by shoulder dystocia. Although the duration of the second stage of labor differed among those with composite maternal and neonatal morbidity, its clinical utility and application remain uncertain.
Results
It is unknown whether the impaction of a shoulder per se is the etiology of the increased maternal morbidity with shoulder dystocia or if the antecedent characteristics are the cause. Risk factors associated with shoulder dystocia —diabetes, macrosomia, prolonged labor, and operative vaginal deliveries— by themselves are linked with postpartum hemorrhage and obstetrical anal sphincter injuries.28–30 Thus, it is difficult to differentiate whether the antecedent factors alone or in conjunction with shoulder dystocia precipitate or exacerbate the maternal complications. In addition, despite a lack of evidence that episiotomy improves the neonatal outcomes with shoulder dystocia, clinicians utilized it to effectuate delivery.5,31 Hence, the management of shoulder dystocia may contribute to the maternal complications.
The high rate of adverse maternal outcomes associated with shoulder dystocia should be addressed. Extreme examples of complications with shoulder dystocia include maternal or neonatal death.5,32 Uncommon complications of shoulder dystocia for the mother include urethral injury33 and for the newborn, neonatal brachial plexus palsy, hypoxic ischemic encephalopathy, or death.4,19 Because of these increased complications associated with shoulder dystocia, shared decision making should involve discussions about the complications to the dyad.32
The baseline risk factors for shoulder dystocia (eg, maternal age, nulliparity, BMI, and diabetes) and additional intrapartum risk factors (eg, advancing gestational age, large for gestational age, induction, duration of second stage, operative vaginal delivery, and birth-weight of at least 4000 g) were identified in our analysis. Of note, several studies have previously reported these same factors.5,6,8,10,11,14–18 Characteristics that are infrequently reported as risk factors for shoulder dystocia, such as maternal education, insurance status, and a previous cesarean delivery,34 were identified in this analysis.
Irrespective of the acknowledged risk factors, clinical utility is determined by whether shoulder dystocia can be predicted before birth. From data based on practice in 1982 to 1983, Gross et al10 reported that a combination of maternal characteristics and labor abnormalities was insufficient to identify which newborn with macrosomia would suffer a shoulder dystocia. From more recent data (2005–2014), Palatnik et al8 reported that risk factors, which are associated with shoulder dystocia, that are present before an operative vaginal delivery were inadequate to identify which delivery would be complicated by impaction of the shoulder. With a larger sample size, we confirm that neither the maternal characteristics nor intrapartum events could differentiate between deliveries complicated with shoulder dystocia and those that were not.
Clinical implications
These findings have potential implications for the management of shoulder dystocia. Currently, ACOG recommends simulation exercises and shoulder dystocia protocols to decrease the incidence of brachial plexus palsy.1 Multiple publications35–40 on simulation have focused on neonatal morbidity, irrespective of the fact that maternal complications occur more frequently with shoulder dystocia than neonatal morbidity. We suggest that simulation exercises should also focus on the steps to mitigate maternal complications like postpartum hemorrhage and third- and fourth-degree lacerations, which are associated with long-term sequelae.29,30,41
Research implications
Although shoulder dystocia is uncommon and unpredictable, there is recent evidence that with machine learning models, which incorporate maternal characteristics and sonographic measurements of biometric parameters, hold promise for the identification of vaginal deliveries that could be complicated by shoulder dystocia.42 Such models, however, have not been used in daily clinical practice to assess the potential for shoulder dystocia as well as a concomitant increase in interventions like cesarean delivery and prevention of maternal-neonatal morbidity.
Strengths and limitations
The major strength of our analysis that differs from previous studies is that the current data were derived from 19 hospitals stemming from 12 unique and geographically dispersed centers.24,25 Unlike previous studies, which focused primarily on neonatal complications, we were able to analyze both maternal and neonatal complications associated with shoulder dystocia.23 The large sample size also permitted us to adjust for several potential confounders.
The limitations of the analysis should be acknowledged. Despite our sample size of more than 130,000 vaginal deliveries, it may be limited to assess the differences in low frequency outcomes such as symphyseal separation, hypoxic ischemic injury, and neonatal mortality.1,4 We cannot comment on if a suspicion of macrosomia influenced intrapartum management.43 We could not correlate the duration of the shoulder dystocia to the type or total number of maneuvers used to resolve the impacted shoulder with the complications.4,5,44 Putatively, the utilization of a shoulder dystocia protocol, which would include identification of the risk factors and management of the impacted shoulder, may lower the morbidity associated with this obstetrical emergency. Bailit et al,45 however, reported on a cohort study of deliveries at 25 hospitals over 3 years. They noted that there were no differences in the odds of a shoulder dystocia occurring or the severity of the shoulder dystocia in hospitals with vs without a shoulder dystocia protocol. Data on long-term follow-up was unavailable for this cohort and therefore we are unable to comment on the long-term sequelae of complications of shoulder dystocia.7,46,47
Conclusions
Shoulder dystocia, although unpredictable, is associated with adverse outcomes to the maternal-neonatal dyad. Providers caring for women in labor need to be aware of the increased rate of maternal complications associated with shoulder dystocia and be prepared to manage these. Our findings should be nidus for additional research on the identification of deliveries likely to be complicated by shoulder dystocia as well as pre- and postintervention trials of simulation exercises on shoulder dystocia that could mitigate both the maternal and neonatal complications42,48
AJOG MFM at a Glance.
Why was this study conducted?
There is a paucity of publications on the composite adverse maternal and neonatal outcomes among deliveries complicated by shoulder dystocia vs those without.
Key findings
The composite maternal morbidity among deliveries complicated by shoulder dystocia was almost 2-fold higher (adjusted relative risk [aRR], 1.71; 95% confidence interval [CI], 1.64–2.01) than those without the complication; the composite neonatal morbidity was 5-fold higher (aRR 5.18; 95% CI, 4.60–5.84) with shoulder dystocia than without.
What does this add to what is known?
With shoulder dystocia, both the mother and the newborn are at an increased risk for morbidity.
ACKNOWLEDGMENTS
Institutions involved in the consortium include the following, in alphabetical order: Baystate Medical Center, Springfield, MA; Cedars-Sinai Medical Center Burnes Allen Research Center, Los Angeles, CA; Christiana Care Health System, Newark, DE; Georgetown University Hospital, MedStar Health, Washington, DC; Indiana University Clarian Health, Indianapolis, IN; Intermountain Healthcare and the University of Utah, Salt Lake City, UT; Maimonides Medical Center, Brooklyn, NY; MetroHealth Medical Center, Cleveland, OH; Summa Health System, Akron City Hospital, Akron, OH; The EMMES Corporation, Rockville, MD (Data Coordinating Center); University of Illinois at Chicago, Chicago, IL; University of Miami, Miami, FL; and University of Texas Health Science Center at Houston, Houston, TX.
The Consortium on Safe Labor was funded by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, under contract number HHSN267200603425C.
Footnotes
The authors report no conflict of interest.
Contributor Information
Hector Mendez-Figueroa, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX.
Mathew K. Hoffman, Department of Obstetrics and Gynecology, Christiana Care, Newark, DE.
Katherine L. Grantz, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD.
Sean C. Blackwell, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX.
Uma M. Reddy, Department of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Medicine, New Haven, CT.
Suneet P. Chauhan, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX.
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