Shoulder dystocia: Definitions and incidence

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Shoulder dystocia: Definitions and incidence Alexandra Hansen, MDa, and Suneet P. Chauhan, MDn,b a

Department of Obstetrics and Gynecology, Eastern Virginia Medical School, Norfolk, VA Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, UT Health Science Center at Houston, Houston, Texas b

article info

abstract

Keywords:

Though subjective in nature, both the American College of Obstetricians and Gynecologists

Shoulder dystocia

practice bulletin and the Royal College of Obstetricians and Gynaecologists green guideline

Diabetes

are in agreement on the descriptor of shoulder dystocia: requirement of additional

Operative vaginal delivery

obstetric maneuvers when gentle downward traction has failed to affect the delivery of

Guidelines

the shoulders. The rate of shoulder dystocia is about 1.4% of all deliveries and 0.7% for vaginal births. Compared to non-diabetics (0.6%), among diabetics, the rate of impacted shoulders is 201% higher (1.9%); newborns delivered by vacuum or forceps have 254% higher likelihood of shoulder dystocia than those born spontaneously (2.0% vs. 0.6%, respectively). When the birthweight is categorized as o4000, 4000–4449, and 44500 g, the likelihood of shoulder dystocia in the US vs. other countries varies significantly. Future studies should focus on lowering the rate of shoulder dystocia and its associated morbidities, without concomitantly increasing the rate of cesarean delivery. & 2014 Elsevier Inc. All rights reserved.

Shoulder dystocia has been described as unpreventable, unpredictable, and an undeniably uncommon1 obstetric emergency.2 The potential complications for impacted shoulder include maternal hemorrhage, fourth-degree laceration, fracture of the clavicle or humerus, temporary or permanent brachial plexus injury, hypoxic ischemic encephalopathy, and neonatal death.3,4 If the brachial plexus palsy persists beyond 1 year, there is potential for microsurgical reconstruction with financial and quality-of-life implications5 and, consequently, litigation.6 Thus, there is a need for understanding of the fundamentals of shoulder dystocia—definitions and incidence—so clinicians and researchers alike can ensure that they are discussing the same morbidity and plan studies, which can reduce the associated sequela. The purpose of this review is to ascertain the various definitions utilized for shoulder dystocia and determine the incidence of this obstetric emergency. n

Definitions According to the American College of Obstetrician and Gynecologists (ACOG) practice bulletin on the topic, the turtle sign, which is retraction of the fetal head against the perineum, may assist in the diagnosis of shoulder dystocia.3 The Royal College of Obstetricians and Gynaecologists (RCOG) in the guideline on the topic suggests that to anticipate dystocia, with each vaginal delivery, the clinicians should routinely observe for one of the following things: difficulty with delivery of the face and chin, head either tightly applied to the vulva or retracting, failure of restitution of the fetal head, and failure of the shoulders to descend.7 Neither of these documents provides evidence that by observing any one of these phenomena, clinicians can do anything to mitigate the morbidity linked with shoulder dystocia. Gherman et al.,2 in their review article on the uncommon obstetric emergency, noted that it is characterized as the failure of delivery of the fetal shoulder(s), whether it is the anterior,

Correspondence to: 825 Fairfax Ave, Suite 544, Norfolk, VA 23507-1914. E-mail address: [email protected] (S.P. Chauhan).

http://dx.doi.org/10.1053/j.semperi.2014.04.002 0146-0005/& 2014 Elsevier Inc. All rights reserved.

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Table 1 – Definitions of shoulder dystocia.

1 2 3 4 5 6

Definitions

ACOG PB

RCOG GG

Tight shoulders Any difficulty in extracting the shoulders after delivering the head Clinical judgment Failure of shoulder delivery after downward traction Deliveries requiring maneuvers in addition to gentle downward traction on the fetal head to affect delivery Time interval of Z60 s from delivery of the head to the delivery of the body

No No No Yes Yes No

No No No Yes Yes No

ACOG PB, American College of Obstetricians and Gynecologists practice bulletin3; RCOG GG, Royal College of Obstetricians and Gynaecologists Green guideline.7 Adapted with permission from Gherman et al.2

posterior, or both fetal shoulders. They culled the literature and provided 6 definitions that researchers have used. We examined the ACOG and RCOG guidelines3,7 on the topic and noted that they acknowledge only 2 of the 6 definitions. Among these 6 definitions of shoulder dystocia, only 1 is objective: time interval of Z60 s from delivery of the head to delivery of the body.8 Though, objective definitions should be preferred over subjective descriptors, neither of the national guidelines accepted it. Thus, based on the fact that ACOG and RCOG concur, we suggest that clinicians and researchers alike use the following definition: shoulder dystocia is requirement of “additional obstetric maneuvers” when “gentle downward traction” has “failed” to affect the delivery of the shoulders (Table 1).

Incidence The practice bulletin notes that shoulder dystocia may complicate up to 1.4% of vaginal births.3 The incidence of this obstetric emergency, according to RCOG, is 0.6% among an unselected population in the United Kingdom and in North America.7 Gherman et al.2 summarized 18 articles that published on the incidence and noted that it ranged from 0.2% to 16%, a relative difference of 7900%. Thus, to better gauge the incidence, we reviewed the literature for this review. We included publications in English language that were cited in PubMed and published between 1985 and 2012 (Table 2). While this search may not be

Table 2 – Incidence of shoulder dystocia with total births. Ref 9

Soni et al. Jennett et al.10 Nocon et al.11 Gonen et al.12 Bahar13 Gherman et al.14 Ecker et al.15 Gherman et al.16 Turrentine and Ramirez17 Olugbile and Mascarenhas18 Kees et al.19 Gudmundsson et al.20 Mollberg et al.21 Gurewitsch et al.22 Chauhan et al.1 MacKenzie et al.23 Ford et al.24 Backe et al.25 Draycott et al.26 Foad et al.27 Melendez et al.28 Grobman et al.29 Inglis et al.30 Walsh et al.31 Paris et al.32 Ouzounian et al.33 Tsuret et al.34 Overland et al.35

Country

Published

Study period

Total births

SD

SD/total births (%)

Libya USA USA Israel Kuwait USA USA USA USA United Kingdom Israel Sweden Sweden USA USA United Kingdom USA Norway United Kingdom USA United Kingdom USA USA Ireland USA USA

1985 1992 1993 1996 1996 1997 1997 1998 1999 2000 2001 2005 2005 2006 2007 2007 2007 2008 2008 2008 2009 2011 2011 2011 2011 2012

1983 1977–1990 1986–1990 1994–1995 1989 1991–1995 1985–1993 1991–1995 1996–1998 1991–1995 1996–1999 1990–1996 1987–1997 1993–2004 2000–2004 1991–2005 1998–2002 1991–2000 1996–1999; 2001–2004 1997, 2000, and 2003 2000–2006 2205–2006 2003–2009 2004–2008; 1994–1998 1998–2009 1995–2004

7829 57,597 14,297 4480 13,756 58,565 77,616 58,565 3008 28,932 24,000 16,743 1,213,987 20,478 41,200 95,321 299,130 30,574 39,220 11,555,823 21,376 14,812 18,677 77,624 94,842 16,071

11 472 185 92 160 303 919 303 45 134 56 56 1577 385 624 514 4626 178 586 30,814 182 254 158 451 953 221

0.1 0.8 1.5 2.3 1.2 0.5 1.2 0.5 1.5 0.6 0.2 0.4 0.1 2.4 2.1 0.6 1.5 0.6 2.0 0.3 0.9 1.7 1.3 0.7 1.4 1.6

Israel Norway

2012 2012

1988–2010 1967–2006

240,189 1,914,544 16,059,256

451 13,109 57,819

0.2 0.7 0.4

Ref, reference; SD, shoulder dystocia.

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exhaustive, it should provide better granularity than done thus far. We identified 28 articles that provided the rate of total births and the incidence of shoulder dystocia.1,9–35 With over

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16 million births, the rate of impacted shoulder was 0.4% (57,819/16,059,256; Table 2). When these 28 publications were segregated by whether published in the United States1,10,11,14– 17,22,24,27,29,30,32,33 vs. other countries,9,12,13,18–21,23,25,26,28,31,34,35

Table 3 – Incidence of shoulder dystocia with vaginal births.

Ref

Country

Published

Study period

Vaginal births

Chauhan et al.1 Nocon et al.11 Gonen et al.12 Gherman et al.16 Olugbile and Mascarenhas18 Gudmundsson et al.20 Gurewitsch et al.22 MacKenzie et al.23 Draycott et al.26 Inglis et al.30 Walsh et al.31 Paris et al.32 Ouzounian et al.33 Tsur et al.34 Overland et al.35

USA USA Israel USA United Kingdom Sweden USA United Kingdom United Kingdom USA Ireland USA USA

2007 1993 1996 1998 2000 2005 2006 2007 2008 2011 2011 2011 2012

2000–2004 1986–1990 1994–1995 1991–1995 1991–1995 1990–1996 1993–2004 1991–2005 1996–1999; 2001–2004 2003–2009 2004–2008; 1994–1998 1998–2009 1995–2004

Israel Norway

2012 2012

1988–2010 1967–2006

SD

SD/vaginal births (%)

29,621 12,532 3985 50,114 24,100 15,594 15,891 79,781 29,025 11,862 66,098 67,949 13,998

624 185 92 303 134 56 385 514 586 158 451 953 221

2.1 1.5 2.3 0.5 0.6 0.4 2.4 0.6 2.0 1.3 0.7 1.4 1.6

240,189 1,914,544 2,575,283

451 13,109 18,222

0.2 0.7 0.7

Ref, reference; SD, shoulder dystocia.

Table 4 – Shoulder dystocia among non-diabetics and diabetics. Ref

Country

Published

SD

Non-DM and SD

DM and SD

Chauhan et al.1 Nocon et al.11 Gherman et al.16 Draycott et al.26 Grobman et al.29 Ouzounian et al.33 Tsur et al.34 Overland et al.35

USA USA USA United Kingdom USA USA Israel Norway

2007 1993 1998 2008 2011 2012 2012 2012

624 185 285 586 254 221 451 13,109 15,715

90% 94% 65% 99% 92% 80% 85% 97% 96%

10% 6% 35% 1% 8% 20% 15% 3% 4%

(562) (174) (185) (579) (233) (176) (383) (12,767) (15,059)

(62) (11) (100) (7) (21) (45) (68) (342) (656)

Ref, reference; SD, shoulder dystocia; DM, diabetes mellitus (gestational and pre-gestational).

Table 5 – Shoulder dystocia with spontaneous vs. operative vaginal delivery. Ref

Country

Published

SD

Chauhan et al.1 Gherman et al.16 Kees et al.19 Gurewitsch et al.22 MacKenzie et al.23 Draycott et al.26 Grobman et al.29 Inglis et al.30 Ouzounian et al.33 Tsur et al.34 Overland et al.35

USA USA Israel USA United Kingdom United Kingdom USA USA USA

2007 1998 2001 2006 2007 2008 2011 2011 2012

624 303 56 385 514 586 254 158 221

Israel Norway

2012 2012

451 13,109 16,661

SD with SVD

SD with OVD

84% 90% 59% 69% 65% 75% 75% 92% 92% 88% 79% 79%

16% 10% 41% 31% 35% 25% 25% 8% 8% 12% 21% 21%

(523) (272) (33) (265) (332) (442) (191) (145) (203) (395) (10,391) (13,192)

Ref, reference; SD, shoulder dystocia; SVD, spontaneous vaginal delivery; OVD, operative (vacuum or forceps) vaginal delivery.

(101) (31) (23) (120) (182) (144) (63) (13) (18) (56) (2718) (3469)

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Fig – Birthweight of newborns with shoulder dystocia. the rates were 0.3% (40,262/12,330,681) and 0.5% (17,557/ 3,728,575), respectively. To assess the contemporary rate of shoulder dystocia in the United States, we focused on 8 publications1,24,27,29,30,32,33 after 2000, and in these reports, the incidence was 0.3% (38,035/12,061,033) of total births. But this rate is substantially influenced by a publication by Foad et al.,27 with over 11 million births and based on a database of ICD codes, with inherent shortcomings.36 Thus, excluding this singular publication, the rate of shoulder dystocia, based on 7 publications since 2000 in the US, is 1.4% (7,221/505,210) of all births and is consistent with the ACOG bulletin.3 We also ascertained the rate of shoulder dystocia with vaginal births because, by definition, it does not occur with cesarean delivery (Table 3). Among the 15 publications1,11,12,16,18,20,22,23,26,30–35 that provided the incidence of shoulder dystocia, the rate was 0.7% (18,222/2,575,283) of vaginal births. When these publications were segregated into those done in the US vs. other countries, the rate was substantially different. Among the 7 publications1,11,16,22,30,32,33 from the US, the rate was 1.4% (2,829/201,967) and for the 8 articles12,18,20,23,26,31,34,35 from

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other countries (Ireland, Israel, Norway, Sweden, and United Kingdom), it was 0.6% (15,393/2,373,316) (Table 3). Both gestational and pre-gestational diabetes are considered to be risk factors for shoulder dystocia.3 Thus, we ascertained the likelihood of dystocia among non-diabetics and diabetics. Four studies26,33–35 reported on the incidence among these 2 groups and the combined results indicate that the rate is 0.6% (13,905/2,173,795) for non-diabetics and 1.9% (462/ 23,961) among diabetics, a relative difference of 201%. Eight publications1,11,16,26,29,33–35 provided data on what proportion of newborns with an impacted shoulder were born of diabetics vs. non-diabetic parturients. Overall, 96% of shoulder dystocia occurred among non-diabetic women (Table 4). Since operative vaginal delivery is also considered a risk factor for shoulder dystocia,3 we ascertained the likelihood of impacted shoulders when vacuum or forceps are used, as well as what proportion of dystocias occur with assisted vaginal births. Of the 6 publications22,23,26,33–35 that provided data on dystocia with spontaneous vs. operative vaginal deliveries, the likelihoods were 0.6% (12,028/2,131,475) and 2.0% (3,238/161,953), respectively, a relative difference of 254%. Overall, 11 publications1,16,19,22,23,26,29,30,33–35 provided data on the proportion of newborns with shoulder dystocia who were delivered spontaneously vs. with assistance of forceps or vacuum. Overall, 21% of newborns with shoulder dystocia had operative vaginal deliveries (Table 5). With shoulder dystocia, it is often assumed that the newborns are macrosomic (birthweight of 4000 g or more). We identified 6 publications1,12,21,23,33,35 that categorized the birthweight as o4000, 4000–4449, or 44500 g. There were over 16,000 cases of shoulder dystocia in these 6 articles and while 27% were not macrosomic, 39% of the newborns weighed between 4000 and 4449 g and the remaining 34% weighed at least 4500 g (Table 5). Surprisingly, the birthweight distribution of newborns with dystocia varied significantly (p o 0.0001) for the 2 publications1,33 from the US vs. 4 reports12,21,23,35 from other countries (Fig.). The possible explanations for this finding include variation in the definition of shoulder dystocia, indications and threshold for doing cesarean delivery or trial of labor after cesarean, and publication bias (Table 6).

Conclusions Two national guidelines—ACOG and RCOG—define shoulder dystocia similarly, albeit subjectively. The rate of shoulder

Table 6 – Birthweight of newborns with shoulder dystocia. Ref 1

Chauhan et al. Gonen et al.12 Mollberg et al.21 MacKenzie et al.23 Ouzounian et al.33 Overland et al.35

Country

Published

USA Israel Sweden United Kingdom USA

2007 1996 2005 2007 2012

624 92 1,577 514 221

Norway

2012

13,109 16,137

Ref, reference; SD, shoulder dystocia; BW, birthweight.

SD

BW o 4.0 kg and SD

BW 4–4.5 kg and SD

BW 4 4.5 kg and SD

65% 50% 19% 38% 51%

26% 43% 39% 39% 35%

8% 7% 43% 23% 14%

(407) (46) (295) (197) (112)

26% (3344) 27% (4401)

(164) (40) (611) (200) (77)

39% (5155) 39% (6247)

(53) (6) (671) (117) (32)

35% (4610) 34% (5489)

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dystocia is about 1.4% of all deliveries and 0.7% of all vaginal births. The likelihood of shoulder dystocia is 201% higher among diabetics (1.9%) vs. non-diabetics (0.6%) and 254% higher with operative (2.0%) vs. spontaneous vaginal delivery (0.6%). For inexplicable reasons at present, compared to other countries, shoulder dystocia is significantly more likely to occur among non-macrosomic newborns in the US. Future studies should focus on innovative ways to decrease the rate of shoulder dystocia and its associated morbidities, without concomitantly increasing the cesarean delivery rate.

r e f e r e n c e s

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