International Journal of Gynecology and Obstetrics 104 (2009) 25–27
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International Journal of Gynecology and Obstetrics j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i j g o
CLINICAL ARTICLE
Shoulder dystocia in a Jamaican cohort Loxley R. Christie ⁎, John A. Harriott, Sharmaine Y. Mitchell, Horace M. Fletcher, Ian G. Bambury Department of Obstetrics and Gynecology, University Hospital of the West Indies, Kingston, Jamaica
a r t i c l e
i n f o
Article history: Received 29 May 2008 Received in revised form 27 August 2008 Accepted 28 August 2008 Keywords: Jamaica Parity Retrospective cohort analysis Risk factor Shoulder dystocia
a b s t r a c t Objective: To assess the risk factors for shoulder dystocia in Jamaica. Methods: A retrospective cohort analysis of all cases of shoulder dystocia, and birth weight-matched controls identified from January 1, 2000 to December 31, 2004. Multiple factors were analyzed individually and in combination to identify risk factors. Results: The incidence of shoulder dystocia was 0.83%. Nulliparity, a first stage of labor greater than 7 hours, a second stage lasting more than 1 hour, and use of oxytocin augmentation were found to be statistically significant factors with unadjusted odds ratios (95% confidence interval) of 1.78 (0.86–3.34), 1.89 (0.91–3.94), 2.78 (0.24–31.47), and 1.56 (0.77–3.15), respectively. The incidence of shoulder dystocia decreased as parity increased when adjusted for age. Conclusion: Individual risk factors for shoulder dystocia remain obscure. The nulliparous pelvis, when controlled for neonatal weight, was associated with a statistically increased risk of shoulder dystocia; this risk decreased with increasing parity. © 2008 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.
1. Introduction Shoulder dystocia (SD) is an obstetric emergency with potentially devastating effects on the neonate, mother, and the delivery attendant from both emotional and medico-legal standpoints. Definitions have included “tight shoulders” [1], “any difficulty in extracting the shoulders after delivering the head” [2,3], clinical judgment [4], and failure of shoulder delivery after downward traction [5]. The following definition is used in this series: the failure of spontaneous delivery of the fetal shoulder after the delivery of the fetal head, requiring additional obstetric maneuvers other than routine downward traction [6–10]. SD is associated with maternal complications such as postpartum hemorrhage (11%), unintentional extension of the episiotomy or laceration into the rectum (fourth degree laceration) (3.8%), and vaginal lacerations (19.3%) [9]. Other maternal complications include cervical tears, bladder atony, and uterine rupture. In a review of 285 cases of SD, the fetal injury rate was 24.9%, including 48 (16.8%) brachial plexus palsy injuries, 27 (9.5%) clavicular fractures, and 12 (4.2%) humeral fractures [11]. Approximately 50% of cases of SD are associated with macrosomia. Nesbitt reviewed over 175 000 pregnancies not complicated by diabetes, and the percentage of births complicated by SD was 5.25%, 9.1%, 14.3%, and 21.1% for birth weights from 3500–3999 g, 4000–4449 g, 4500– 4749 g, and 4750–5000 g, respectively [12].
At the University Hospital of the West Indies (UHWI) each case of fetal macrosomia, defined by an estimated fetal weight greater than 4 kg using ultrasound is reviewed individually. In the absence of documented evidence of a previously uncomplicated delivery of a macrosomic infant or unless clinical pelvimetry is favorable, cesarean delivery is generally recommended. The purpose of this study was to assess the factors other than neonatal weight that influence the development of SD at this institution. 2. Materials and methods Permission for this retrospective cohort analysis was obtained from the Departmental Review Board. Labor ward records were reviewed from January 1,2000 to December 31, 2004 and all cases of SD were identified. The records were reviewed to confirm the diagnosis of SD by the use of additional maneuvers. For each case of SD, a control was chosen by selecting the next neonate, delivered vaginally and of birth weight within 100 g of the case. Prenatal, intrapartum, and fetal factors were reviewed for cases and their controls. Univariate logistic regression analysis was used and crude odds ratios (ORs) were calculated as an estimation of the strength of association between the individual risk factors and SD. Multiple variable regression analysis was utilized to determine the effect of confounding variables where applicable. Analysis was performed using STATA 8.0 (College Station, TX, USA). 3. Results
⁎ Corresponding author. Department of Obstetrics and Gynecology, University Hospital of the West Indies, Mona, Kingston 7, Jamaica. Tel.: +1 876 927 1145; fax: +1 876 927 0100. E-mail address:
[email protected] (L.R. Christie).
During this 5-year period, of the 8267 cephalic vaginal deliveries performed at UHWI, 69 were complicated by SD giving an incidence of 0.83%. In the SD group, there were 3 stillbirths, only 1 of which occurred
0020-7292/$ – see front matter © 2008 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijgo.2008.08.025
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L.R. Christie et al. / International Journal of Gynecology and Obstetrics 104 (2009) 25–27
Table 1 Maternal, parturition, and neonatal characteristics
Table 3 Multiple logistic regression analysis of risk factors for shoulder dystocia
Factors
SD
Control
Age, y Height, cm Weight, kg BMI Change in weight, kg First stage, h Second stage, min Birth weight, kg Males (%) Apgar score, 1 mina 0–3 4–6 7–10 Apgar score, 5 mina 0–3 4–6 7–10 Paritya 0 1 2 ≥3
29.0 ± 6.2 162.9 ± 6.4 73.1 ± 13.4 28.2 ± 5.7 12.2 ± 5.7 8.3 ± 4.1 25.9 ± 7.5 3.8 ± 0.4 47.8
28.34 ± 5.7 165.75 ± 8.1 75.72 ± 16.2 28.19 ± 5.6 12.1 ± 5.3 6.9 ± 4.5 21.0 ± 13.8 3.72 ± 0.2 50.7
a
P value 0.51 0.99 0.33 0.99 0.95 0.09 0.11 0.21 –
22 21 23
0 6 63
b 0.001
6 5 55
0 0 69
b 0.01
36 19 11 3
27 21 14 7
0.55
The Fisher exact test was used for categorical data.
during the second stage of labor. There were no neonatal deaths in the SD group and no stillbirths or neonatal deaths in the control group. During this period, the hospital’s cesarean delivery rate was 28.9%; macrosomia was the second most common indication for elective cesarean delivery accounting for 12% of elective abdominal deliveries. Of the 69 cases of SD, 24 (34.8%) neonates weighed more than 4.0 kg. Compared with the controls, women with pregnancies complicated by SD had no statistically significant differences regarding age, height, weight, body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters), or change in weight. Using the Fisher exact test, significant differences existed between the 1- and 5-min Apgar scores of the neonates (Table 1). The Apgar scores of the stillbirths were not included in the comparison between the cases and controls. Univariate analysis was done and the crude OR calculated (Table 2). SD had a greater chance of occurring with nulliparity, if the first stage of labor exceeded 7 hours, the second stage exceeded 1 hour, or if labor was augmented by oxytocin. These findings were more pronounced when adjusted for age; however, only nulliparity and prolonged first stage were statistically significant. Of the 69 cases of SD, 29 (42%) were nulliparous. Due to the increased adjusted OR for nulliparity, models were designed and multiple logistic regression analysis applied to determine if other confounding variables influenced the role of nulliparity (Table 3). The most likely patient to develop SD was the younger nulliparous woman with increased fetal
Table 2 Results of univariate analysis of risk factors for shoulder dystocia Factors
Unadjusted OR (95% CI)
Age adjusted OR (95% CI)
Age, y Nulliparity Height, cm Weight, kg BMI BMI N30 Change in weight, kg Change in weight N 20 kg First stage First stage N7 h Second stage Second stage N60 min Oxytocin use Gender
1.02 (0.96–1.07) 1.78 (0.86–3.34) 0.95 (0.89–1.01) 0.99 (0.96–1.01) 1.00 (0.92–1.08) 0.78 (0.31–1.89) 1.00 (0.94–1.07) 1.17 (0.51–2.65) 1.07 (0.99–1.17) 1.89 (0.91–3.94) 1.02 (1.00–1.05) 2.78 (0.24–31.47) 1.56 (0.77–3.15) 0.94 (0.48–40)
– 2.72 (1.15–6.43) 0.94 (0.89–1.01) 0.98 (0.95–1.08) 0.99 (0.90–1.08) 0.68 (0.26–1.74) 1.01 (0.94–1.09) 1.44 (0.58–3.59) 1.09 (1.00–1.20) 2.08 (0.97–4.44) 1.02 (1.00–1.05) 3.51 (0.29–41.99) 1.60 (0.79–3.25) 0.96 (0.49–1.90)
Model
OR (95% CI)
Nulliparity Nulliparity + age Nulliparity + age + fetal weight Nulliparity + age + use of oxytocin Nulliparity + age + duration, first stage Nulliparity + age + duration, second stage
1.78 (0.86–3.34) 2.72 (1.15–6.43) 3.15 (1.04–9.62) 1.53 (0.74–3.17) 1.10 (1.00–1.20) 1.02 (099–1.04)
size (OR 3.15, 95% CI, 1.04–9.62). Logistic regression analysis was used to assess the risk of SD with increasing parity. The results were: nulliparity, OR 1.00; para 1, OR 0.45 (95% CI, 0.18–1.12, P = 0.08); para 2, OR 0.30 (95% CI, 0.10–0.97, P = 0.04); para ≥3, OR 0.23 (95% CI, 0.04–1.20, P = 0.03). There was 1 mother with pregestational diabetes in the SD group but no cases of gestational diabetes, thus the incidence of infants of mothers with diabetes was 1.45%. SD occurred after operative delivery in 5 of the 69 cases (7.2%); 4 (5.7%) of these were vacuum deliveries. None of the controls required an operative delivery, therefore this could not be subjected to statistical analysis. Injuries to the infants included 2 fractured clavicles (2.90%) and 2 brachial plexus injuries (2.90%); there were no permanent injuries. Postpartum hemorrhage complicated 4 deliveries (5.80%), 1 of which was an episiotomy with a third degree extension (1.45%). Of the 69 cases identified, 51 (74%) of the case records were located. This impacted on the data for the maternal factors of weight, BMI, and change in weight and BMI. Comparing the neonates of the SD cases whose records were found with those missing, there were no differences with respect to 1- or 5-min Apgar score, neonatal weight, duration of first or second stage of labor, or neonatal sex. However, the neonates in the missing record group were more likely to be male. 4. Discussion Over the period 2000–2004, the incidence of SD at UHWI was 0.83%, which is comparable to the rate reported worldwide, ranging from 0.6% to 2.8% [13]. Currently, the American College of Obstetricians and Gynecologists (ACOG) guidelines recommend consideration of cesarean delivery for an estimated fetal weight of 5.0 kg for nondiabetic mothers [14]. Although there are no data to support this recommendation (level IV evidence) directly, larger infants are more likely to suffer permanent brachial plexus injury [15]. A decision cost analysis of a policy of cesarean deliveries for suspected fetal weight exceeding 4.5 kg found that it would necessitate 2345 surgeries at a cost of US $4.9 million to prevent one permanent brachial plexus injury [16] (level III). In a previously unpublished departmental audit done at the UHWI in 1993 by Charoo et al., 48.4% of cases of SD occurred when the birth weight was between 4.0 kg and 4.49 kg in nondiabetic mothers. The fact that SD occurred with a mean birth weight of 3.82 kg underscores that birth weight alone as the determinant of route of delivery is unsound. A local decision cost analysis is desirable to evaluate current UHWI practice in view of the international literature and the local cesarean delivery rate. A statistically significant difference in 1- and 5-minute Apgar scores between the cases and the controls was found, suggesting that the cases were potentially subjected to an increased degree of hypoxia. The frequency with which hypoxia occurs during deliveries complicated by SD has not been thoroughly addressed in the literature. The results from Table 1 demonstrate that individual prenatal predictors of SD were imprecise as reported in other studies. Langer et al. [8], in a review of 75 979 women, and Lewis et al. [17] observed no relationship with maternal age. Robinson et al. [18] reviewed 413 women and found that maternal weight had no significant predictive value. The cutoff limit for BMI in this study was based on the World Health Organization's definition of obesity [19]. The limit for change in
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the development of SD when controlled for neonatal weight; this risk decreased with increasing parity.
Table 4 The incidence of nulliparity in published studies Author(s)
Year
Study type
No. of cases
% nullipara
Benedetti et al. [5] Baskett and Allen [22] Sandmire [7] McFarland [24]
1978 1995 1988 1995
Retrospective review Retrospective review Case–control Case–control
33 254 73 276
68 52 31.5 22
weight was based on the recommendations of the Institute of Medicine [20]. These results are not uniform, however; in a case– control review of 65 cases, Mehta et al. [21] found a statistically significant difference with maternal age and BMI. In the population in this study, the duration of the first and second stages of labor was similarly imprecise in predicting SD. However, there was a statistically significant difference in the risk of shoulder dystocia for prolonged labor in both the first and second stages. The confidence interval for both parameters makes recommendations based on these results difficult. These findings are in keeping with those of Baskett and Allen [22] who reported a 3-fold increase in SD in pregnancies complicated by prolonged second stage of labor. The disproportionate representation of male fetuses (55%–68%) in cases of SD [12,23] was not noted in this series. The use of oxytocin in the cases compared to the controls was associated with a statistically significant increased risk of SD, corroborating the findings of Acker et al. [13] and Mehta et al. [21]. Nulliparity was found to be a significant risk factor in this series. The reduction in OR for SD after adjusting for augmentation with oxytocin suggests that nulliparas are more likely to require oxytocin augmentation during labor. The reduction of OR when controlled for nulliparity and duration of either first or second stage of labor is in keeping with the findings of Mehta et al. [21] and McFarland et al. [23]. These facts can be explained by increased resistance to parturition due to reduced pliability of the untried pelvis compared to the multiparous pelvis. This is supported by the finding of decreasing OR for SD with increasing parity. The combination of these factors should be considered in determining route of delivery, and indicate that senior obstetric staff should be present at vaginal delivery, especially in the nulliparous patient with macrosomia and protracted, augmented labor. The finding of increased risk of SD with nulliparity is in direct contradiction to the findings of Parks and Ziel [25]. However, multiparity, as shown in this series, is not necessarily an independent risk factor, but is likely to be linked to increased risk of gestational diabetes with increasing parity, as well as the trend of increasing neonatal weight with increasing parity. The incidence of nulliparity in studies on SD is highly variable ranging from 22% to 68% in some series (Table 4). Due to the low incidence of SD, large reviews are retrospective. Thus, retrieval of records was a limiting factor as only 51 (73.9%) of the records for cases of SD were located. This impacted on data for the maternal factors of weight and BMI, and change in weight and BMI, as the labor ward records document all other intrapartum and prenatal information required for analysis. In conclusion, individual risk factors for SD remain obscure suggesting a multifactorial etiology. At UHWI, the incidence of SD is 0.83%. Nulliparity was found to confer a statistically significant risk for
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