Risk of shoulder dystocia: associations with parity and offspring birthweight. A population study of 1 914 544 deliveries

Shoulder dystocia in babies born to Aboriginal mothers with diabetes: a population-based cohort study, 1998-2015

BACKGROUND

Australian Aboriginal and Torres Strait Islander women with diabetes in pregnancy (DIP) are more likely to have glycaemic levels above the target range, and their babies are thus at higher risk of excessive fetal growth. Shoulder dystocia, defined by failure of spontaneous birth of fetal shoulder after birth of the head requiring obstetric maneuvers, is an obstetric emergency that is strongly associated with DIP and fetal size. The aim of this study was to investigate the epidemiology of shoulder dystocia in Aboriginal babies born to mothers with DIP.

METHODS

Stratifying by Aboriginal status, characteristics of births complicated by shoulder dystocia in women with and without DIP were compared and incidence and time-trends of shoulder dystocia were described. Compliance with guidelines aiming at preventing shoulder dystocia in women with DIP were compared. Post-logistic regression estimation was used to calculate the population attributable fractions (PAFs) for shoulder dystocia associated with DIP and to estimate probabilities of shoulder dystocia in babies born to mothers with DIP at birthweights > 3 kg.

RESULTS

Rates of shoulder dystocia from vaginal births in Aboriginal babies born to mothers with DIP were double that of their non-Aboriginal counterparts (6.3% vs 3.2%, p < 0.001), with no improvement over time. Aboriginal mothers with diabetes whose pregnancies were complicated by shoulder dystocia were more likely to have a history of shoulder dystocia (13.1% vs 6.3%, p = 0.032). Rates of guideline-recommended elective caesarean section in pregnancies with diabetes and birthweight > 4.5 kg were lower in the Aboriginal women (28.6% vs 43.1%, p = 0.004). PAFs indicated that 13.4% (95% CI: 9.7%-16.9%) of shoulder dystocia cases in Aboriginal (2.7% (95% CI: 2.1%-3.4%) in non-Aboriginal) women were attributable to DIP. Probability of shoulder dystocia among babies born to Aboriginal mothers with DIP was higher at birthweights > 3 kg.

CONCLUSIONS

Aboriginal mothers with DIP had a higher risk of shoulder dystocia and a stronger association between birthweight and shoulder dystocia. Many cases were recurrent. These factors should be considered in clinical practice and when counselling women.

A Trial of Labor after Cesarean Section with a Macrosomic Neonate. Is It Safe?

OBJECTIVE

 This study aimed to determine whether a trial of labor after cesarean section (TOLAC) with a macrosomic neonate is associated with adverse outcomes.

STUDY DESIGN

 A retrospective cohort study was conducted in a population motivated for TOLAC. Women attempting TOLAC with a neonatal birth weight >4,000 g were compared with women attempting TOLAC with neonatal birth weights between 3,500 and 4,000 g. The primary outcome was TOLAC success. Secondary outcomes included mode of delivery, uterine rupture, postpartum hemorrhage (PPH), shoulder dystocia, obstetric anal sphincter injury (OASI), Apgar's score <7 at 5 minutes, and umbilical artery pH <7.1. Data were analyzed using Fisher's exact test and Chi-square test.

RESULTS

 Overall, 375 women who underwent TOLAC with a neonate weighing >4,000 g comprised the study group. One thousand seven hundred and eighty-three women attempting TOLAC with a neonate weighing 3,500 to 4,000 g comprised the control group. There were no clinically significant differences between the groups for maternal age, gestational age, parity, and vaginal birth after cesarean (VBAC) rate. There were no significant differences in the rates of successful TOLAC (94 vs. 92.3%, p = 0.2, odds ratio [OR] = 0.8, 95% confidence interval [CI]: 0.5, 1.2), operative vaginal delivery (7.4 vs. 5.3%, p = 0.18, OR = 0.7, 95% CI: 0.4, 1.1), uterine rupture (0.4 vs. 0%, p = 0.6), PPH (3.2 vs. 2.3%, p = 0.36, OR = 1.4, 95% CI: 0.7, 2.7), OASI (0.8 vs. 0.2%, p = 0.1, OR = 3.6, 95% CI: 0.8, 1.6), Apgar's score <7 at 5 minutes (0 vs. 0.4%, p = 0.37), and umbilical artery pH <7.1 (0.5 vs. 0.7%, p = 1.0, OR = 0.73, 95% CI: 0.2, 3.2). Women with a neonate weighing >4,000 g had a significantly increased risk of shoulder dystocia (4 vs. 0.4%, p < 0.05, OR = 9.2 95% CI: 3.9, 22) CONCLUSION:  Women attempting TOLAC with a macrosomic neonate are not at increased risk for failed TOLAC, operative vaginal delivery, uterine rupture, PPH, or OASI but are at risk of shoulder dystocia. This information may aid in prenatal counseling for women considering TOLAC with a macrosomic fetus.

KEY POINTS

· TOLAC with fetal macrosomia does not increase the risk of uterine rupture.. · TOLAC with fetal macrosomia is associated with high chances of VBAC.. · TOLAC with fetal macrosomia is not associated with adverse neonatal outcomes..

Trends and characteristics of multiple births in Baoan Shenzhen: A retrospective study over a decade

Background

Shenzhen has the largest and youngest foreign population among all cities in China. The reproductive health of pregnant women from different backgrounds is a social issue that deserves attention. In the past decade, China has liberalized its population policies to stimulate population growth, and the proportion of multiple births has continued to increase.

Method

This retrospective cohort included 526,654 newborns born in Baoan, Shenzhen, from January 1, 2009, to December 31, 2019, including 515,016 singletons and 11,638 twins or triplets. Univariate regression models were used to analyze the effects of maternal sociodemographic characteristics, physiological characteristics, medical history, antenatal care and other factors associated with single vs. multiple births and to elucidate the changing trends of different factors affecting multiple births in the past 11 years. Additionally, fetal development in multiple births was analyzed by generalized linear mixed models.

Results

The rates of pregnancy complications, preterm birth, and advanced-age pregnancy were significantly higher in the multiple birth mothers than in single birth mothers, and more multiple pregnancies were achieved through assisted reproductive technologies. The rates of adverse outcomes such as stillbirth, malformation, hypoxia, and ultralow body weight in multiple fetuses were significantly higher than that in singleton fetuses. The trend analysis from 2009 to 2019 showed that the socioeconomic status and health level of mothers with multiple births improved over time, and the risk during pregnancy generally decreased. Simultaneously, the development indicators of multiple fetuses have improved year by year, and the proportion of adverse outcomes has also decreased significantly. A low pre-natal care utilization rate was shown to be detrimental to the development of multiple fetuses. Independent risk factors for hypoxia and very low birth weight were also identified. The differences in secular trends between two birth groups were further revealed by time series models.

Conclusion

This study presented a comprehensive survey of multiple pregnancies in the area with the largest population inflow in China. This study identified the factors that affect the health of multiple birth mothers and their fetuses, particularly suggesting that preterm birth rates and the use of assisted reproduction remain high. The findings provide a basis for the formulation of individualized pre-natal care, assisted reproductive guidance and healthcare policies for multiple births.

Human shoulder development is adapted to obstetrical constraints

SignificanceDuring human birth, the risk of complications is relatively high because of the comparatively large dimensions of the fetal head and shoulders relative to the maternal birth canal. Here we show that humans exhibit a developmental mode of the shoulders that likely contributes to mitigating obstetrical problems. Human shoulder growth is decelerated before birth but accelerated after birth, which stands in contrast to the more uniform shoulder growth trajectories of chimpanzees and macaques. This indicates that fetal developmental modifications were required during human evolution not only in the head but also in the shoulders to compensate obstetrical constraints.

Intrauterine fetal death followed by shoulder dystocia and birth by modified posterior axillary sling method: a case report

Background

Various manoeuvres such as McRoberts position, suprapubic pressure, rotational methods, posterior arm extraction and all-four position (HELPERR) have been proposed for relieving shoulder dystocia with variable success. Posterior axillary sling method using a rubber catheter was proposed in 2009 but has not been widely used. We modified this method using ribbon gauzes and a long right-angle forceps and report a successful case.

Case presentation

A 44 years old parity one Chinese woman with a history of a caesarean delivery and poorly controlled type 2 diabetes mellitus was admitted to the Accident and Emergency Department for advanced stage of labour at term. Upon arrival, intrauterine fetal demise was diagnosed with severe asynclitism causing obstruction at the perineum. Episiotomy resulted in birth of the fetal head. The fetal posterior right shoulder, however, remained very high up in the pelvis and HELPERR methods failed to extract the shoulders. We then tied two long ribbon gauzes together, and guided its knot to the anterior aspect of the posterior axilla. By using a long right-angle forceps (24 cm long) to grasp the knot on the posterior side of the axilla and pulling it through, a sling was formed. Traction was then applied through the sling to simultaneously pull and rotate the posterior shoulder. A stillbirth of 3488 g was finally extracted.

Conclusions

We modified the sling method by using two ribbon gauzes, tied together and a right-angle forceps with several advantages. Compared to a rubber catheter, ribbon gauze with a knot can be easily held between the fingers for easy guidance past the fetal axilla. It is also thin, non-elastic and stiff enough to ensure a good grip for traction. The long and slim design of the right-angle forceps makes it easy to pass through a narrow space and reach the axilla high up in the pelvis. We emphasize simultaneous traction and rotation, so that the shoulders are delivered through the wider oblique pelvic outlet dimension.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04126-4.

Offspring birthweight and placental weight-does the type of maternal diabetes matter? A population-based study of 319 076 pregnancies

INTRODUCTION

Our aim was to estimate the difference in birthweight and in placental weight in pregnancies with type 1 diabetes, type 2 diabetes, and gestational diabetes compared with pregnancies without diabetes.

MATERIAL AND METHODS

By using data from the Medical Birth Registry of Norway during the years 2009-2017, we included 319 076 singleton pregnancies with delivery after the 21st week of pregnancy. We used linear regression analyses to estimate the difference in birthweight and in placental weight in grams (g) in pregnancies with type 1 diabetes, type 2 diabetes, and gestational diabetes, using pregnancies without diabetes as the reference. Adjustments were made for pregnancy duration and pre-pregnancy body mass index.

RESULTS

In pregnancies without diabetes, mean crude birthweight was 3527 g (SD 552 g). The adjusted mean birthweight was 525 g (95% CI 502-548 g) higher in pregnancies with type 1 diabetes compared with pregnancies without diabetes. In pregnancies with type 2 diabetes, and pregnancies with gestational diabetes, birthweights were 192 g (95% CI 160-223 g) and 102 g (95% CI 93-110 g) higher, respectively. Mean crude placental weight was 664 g (SD 147 g) in pregnancies without diabetes. Compared with pregnancies without diabetes, the adjusted mean placental weight was 109 g (95% CI 101-116 g) higher in pregnancies with type 1 diabetes, 50 g (95% CI 39-60 g) higher in pregnancies with type 2 diabetes, and 31 g (95% CI 28-34 g) higher in pregnancies with gestational diabetes.

CONCLUSIONS

The increase in birthweight and in placental weight associated with maternal diabetes was most pronounced for type 1 diabetes, followed by type 2 diabetes, and gestational diabetes.

The association of vacuum-assisted delivery and shoulder dystocia among macrosomic newborns: a retrospective study

PURPOSE

Although shoulder dystocia (ShD) is associated with fetal macrosomia and vacuum-assisted delivery (VAD), the independent role of the latter in the occurrence of ShD is yet to be completely elucidated, as it is difficult to study its true independent contribution to ShD formation in the presence of many confounding factors. Therefore, we aimed to study whether VAD is independently associated with an increased risk for ShD among macrosomic newborns.

METHODS

A retrospective cohort study from a single tertiary medical center including all women who delivered vaginally a macrosomic infant during 2011-2020. We allocated the study cohort into two groups: (1) VAD (2) spontaneous vaginal deliverys, and analyzed risk factors for ShD. A multivariate regression analysis was performed to identify determinants independently associated with ShD occurrence.

RESULTS

Of 2,664 deliveries who met the study inclusion criteria, 118 (4.4%) were VAD. The rate of ShD in the entire cohort was 108/2664 (4.1%). The following factors were more frequent among the VAD group: no previous vaginal delivery [odds ratio (OR) 2.4 (95% confidence interval (CI) 1.4-4.0, p < 0.001)], prolonged second stage (OR 11.9; 95% CI 8.1-17.6, p < 0.01), induction of labor (OR 2.4; 95% CI 1.5-3.8, p < 0.01) and ShD (OR 2.0; 95% CI 1.0-4.1, p = 0.04). ShD was associated with higher rates of maternal height < 160 cm (OR 2.0; 95% CI 1.3-3.1, p < 0.01), pregestational diabetes (OR 7.2; 95% CI 2.0-26.8, p = 0.01), hypertensive disorder (OR 2.6; 95% CI 1.1-6.2, p = 0.02) and higher birthweight (mean 4,124 vs. 4,167 g, p < 0.01). On multivariate regression analysis, the following factors remained independently associated with ShD occurrence: increased birthweight (aOR 1.0; 95% CI 1.0-1.0, p < 0.01), pregestational diabetes (aOR 5.3; 95% CI 1.1-25.0, p = 0.03), while maternal height was negatively associated with ShD (aOR 0.9; 95% CI 0.9-0.9, p < 0.01).

CONCLUSION

In deliveries of neonates above 4000 g, VAD did not independently increase the risk of ShD occurrence. Therefore, when expeditious delivery of a macrosomic infant is required, VAD is a viable option.

Population-Based Risk Factors for Shoulder Dystocia

OBJECTIVE

To re-examine the risk factors for shoulder dystocia given the increasing rates of obesity and diabetes in pregnant women.

DESIGN

Retrospective observational study.

SETTING

Five hospitals located in Wisconsin, Florida, Maryland, Michigan, and Alabama.

PARTICIPANTS

We evaluated 19,236 births that occurred between April 1, 2011, and July 25, 2013.

METHODS

Data were collected from electronic medical records and used to evaluate the risk of shoulder dystocia. Data were analyzed using a generalized linear mixed model, which controlled for clustering due to site.

RESULTS

When insulin was prescribed, gestational diabetes was associated with an increased risk of shoulder dystocia (odds ratio = 2.10, 95% confidence interval [1.01, 4.37]); however, no similar association was found with regard to gestational diabetes treated with glycemic agents or through diet. Use of epidural anesthesia was associated with an increased risk for shoulder dystocia (odds ratio = 3.47, 95% confidence interval [2.72, 4.42]). Being Black or Hispanic, being covered by Medicaid or having no insurance, infant gestational age of 41 weeks or greater, and chronic diabetes were other significant risk factors.

CONCLUSION

With the changing characteristics of pregnant women, labor and birth clinicians care for more pregnant women who have an increased risk for shoulder dystocia. Our findings may help prospectively identify women with the greatest risk.

Risk Factors for Shoulder Dystocia: the Impact of Mother's Race and Ethnicity

Shoulder dystocia is a rare but severe birth trauma where the neonate's shoulders fail to deliver after delivery of the head. Failure to deliver the shoulders quickly can lead to severe, long-term injury to the infant, including nerve injury, skeletal fractures, and potentially death. This observational study examined shoulder dystocia risk factors by race and ethnicity using a sample of 19,236 pregnant women who presented for labor and delivery from July 1, 2010 until June 30, 2013 at five locations. Multivariate analyses were used to identify risk factors associated with shoulder dystocia occurrence in racial/ethnic groups with high incidence rates. For White non-Hispanic mothers, the strongest risk factors were delivering past 40 weeks' gestation (odds ratio [OR] = 2.4; 95% confidence interval [CI] = 1.5, 3.9; p < .01) and use of epidural anesthesia during delivery (OR = 4.4; 95% CI = 3.0, 6.4; p < .01). Among Black non-Hispanic mothers, the risk factors with the greatest impact were use of epidural (OR = 5.3; 95% CI = 3.2, 8.7; p < .01) and having gestational diabetes and controlling the condition with insulin (OR = 4.6; 95% CI = 1.5, 13.8; p < .01). Additionally, among Hispanic mothers, having Spanish as primary language increased shoulder dystocia likelihood compared to those who did not cite it as their primary language (OR = 2.3; 95% CI = 1.1, 4.6; p < .05). This study provides evidence that risk factors for a labor and delivery condition can vary significantly across racial and ethnic subgroups. These differences emphasize the importance of evaluating risk by population subgroups and might provide a basis for labor and delivery clinicians to enhance personalized medicine to reduce adverse events.

Intrauterine fetal death and risk of shoulder dystocia at delivery

INTRODUCTION

Vaginal delivery is recommended after intrauterine fetal death. However, little is known about the risk of shoulder dystocia in these deliveries. We studied whether intrauterine fetal death increases the risk of shoulder dystocia at delivery.

MATERIAL AND METHODS

In this population-based register study using the Medical Birth Registry of Norway, we included all singleton pregnancies with vaginal delivery of offspring in cephalic presentation in Norway during the period 1967-2012 (n = 2 266 118). Risk of shoulder dystocia was estimated as absolute risk (%) and odds ratio with 95% confidence interval. Adjustment was made for offspring birthweight (in grams). We performed sub-analyses within categories of birthweight (<4000 and ≥4000 g) and in pregnancies with maternal diabetes.

RESULTS

Shoulder dystocia occurred in 1.1% of pregnancies with intrauterine fetal death and in 0.8% of pregnancies without intrauterine fetal death (p < 0.0001) (crude odds ratio 1.5, 95% confidence interval 1.2-4.9). After adjustment for birthweight, the odds ratio was 5.9 (95% confidence interval 4.7-7.4). In pregnancies with birthweight ≥4000 g, shoulder dystocia occurred in 14.6% of pregnancies with intrauterine fetal death and in 2.8% of pregnancies without intrauterine fetal death (p < 0.001) (crude odds ratio 5.9, 95% confidence interval 4.5-7.9). In pregnancies with birthweight ≥4000 g and concurrent maternal diabetes, shoulder dystocia occurred in 57.1% of pregnancies with intrauterine fetal death and 9.6% of pregnancies without intrauterine fetal death (p < 0.001) (crude odds ratio 12.6, 95% confidence interval 5.9-26.9).

CONCLUSIONS

Intrauterine fetal death increased the risk of shoulder dystocia at delivery, and the absolute risk of shoulder dystocia was particularly high if offspring birthweight was high and the mother had diabetes.

The associations of maternal body mass index with birthweight and placental weight. Does maternal diabetes matter? A population study of 106 191 pregnancies

INTRODUCTION

The aim of this study was to study whether the associations of maternal body mass index with offspring birthweight and placental weight differ by maternal diabetes status.

MATERIAL AND METHODS

We performed a population study of 106 191 singleton pregnancies by using data from the years 2009-2012 in the Medical Birth Registry of Norway. We estimated changes in birthweight and in placental weight (in grams) by maternal body mass index by linear regression analysis.

RESULTS

In pregnancies of women without diabetes, birthweight increased by 14.7 g (95% confidence interval 14.1-15.2) per unit increase in maternal body mass index, and the increase in placental weight was 4.2 g (95% confidence interval 4.0-4.4). In pregnancies of women with gestational diabetes, the corresponding figures were 11.8 g (95% confidence interval 8.3-15.4) and 2.9 g (95% confidence interval 1.7-4.0). In pregnancies of women with type 1 diabetes we found no significant changes in birthweight or in placental weight by maternal body mass index. Overall, mean birthweight was 513.9 g (95% confidence interval 475.6-552.1) higher in pregnancies involving type 1 diabetes than in pregnancies of women without diabetes. Mean placental weight was 102.1 g (95% confidence interval 89.3-114.9) higher. Also, in pregnancies of women with gestational diabetes, both birthweight and placental weight were higher than in women without diabetes (168.2 g and 46.5 g, respectively). Adjustments were made for maternal body mass index and gestational age at birth.

CONCLUSIONS

Birthweight and placental weight increased with increasing maternal body mass index in pregnancies of women without diabetes and in pregnancies of women with gestational diabetes, but not in pregnancies of women with type 1 diabetes. Independent of body mass index, mean birthweight and mean placental weight were highest in pregnancies of women with type 1 diabetes.

Metformin in women with type 2 diabetes in pregnancy (MiTy): a multi-center randomized controlled trial

Background

The incidence of type 2 diabetes in pregnancy is rising and rates of serious adverse maternal and fetal outcomes remain high. Metformin is a biguanide that is used as first-line treatment for non-pregnant patients with type 2 diabetes. We hypothesize that metformin use in pregnancy, as an adjunct to insulin, will decrease adverse outcomes by reducing maternal hyperglycemia, maternal insulin doses, maternal weight gain and gestational hypertension/pre-eclampsia. In addition, since metformin crosses the placenta, metformin treatment of the fetus may have a direct beneficial effect on neonatal outcomes. Our aim is to compare the effectiveness of the addition of metformin to insulin, to standard care (insulin plus placebo) in women with type 2 diabetes in pregnancy.

Methods

The MiTy trial is a multi-centre randomized trial currently enrolling pregnant women with type 2 diabetes, who are on insulin, between the ages of 18–45, with a gestational age of 6 weeks 0 days to 22 weeks 6 days. In this randomized, double-masked, parallel placebo-controlled trial, after giving informed consent, women are randomized to receive either metformin 1,000 mg twice daily or placebo twice daily. A web-based block randomization system is used to assign women to metformin or placebo in a 1:1 ratio, stratified for site and body mass index. The primary outcome is a composite neonatal outcome of pregnancy loss, preterm birth, birth injury, moderate/severe respiratory distress, neonatal hypoglycemia, or neonatal intensive care unit admission longer than 24 h. Secondary outcomes are large for gestational age, cord blood gas pH < 7.0, congenital anomalies, hyperbilirubinemia, sepsis, hyperinsulinemia, shoulder dystocia, fetal fat mass, as well as maternal outcomes: maternal weight gain, maternal insulin doses, maternal glycemic control, maternal hypoglycemia, gestational hypertension, preeclampsia, cesarean section, number of hospitalizations during pregnancy, and duration of hospital stays. The trial aims to enroll 500 participants.

Discussion

The results of this trial will inform endocrinologists, obstetricians, family doctors, and other healthcare professionals caring for women with type 2 diabetes in pregnancy, as to the benefits of adding metformin to insulin in this high risk population.

Trial registration

ClinicalTrials.gov Identifier: no. NCT01353391. Registered February 6, 2009.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-016-0954-4) contains supplementary material, which is available to authorized users.

Shoulder dystocia in primary midwifery care in the Netherlands

INTRODUCTION

In the Netherlands, low-risk pregnancies are managed by midwives in primary care. Despite strict definitions of low risk, obstetric complications can occur. Midwives seldom encounter uncommon labour complications, but are sufficiently trained to manage these. We assessed neonatal and maternal outcome after management of shoulder dystocia in primary midwifery care.

MATERIALS AND METHODS

In this 2-year prospective cohort study from April 2008 to April 2010, primary-care midwives, who participated in an obstetric emergency course, reported all obstetric complications. Main outcome was neonatal and maternal outcome.

RESULTS

In sixty-four cases of shoulder dystocia McRoberts was the first maneuver in 42/64 (65.6%) cases with a success rate of 23.8%. All-fours maneuver was most frequently used as the second maneuver (24/45; 53.3%). No neonatal mortality occurred, none of the infants suffered from hypoxic ischemic injury, two (3.1%) had transient brachial plexus injuries, two (3.1%) had fractured clavicles and one (1.6%) had a fractured humerus. Eight (12.5%) neonates were successfully resuscitated because of birth asphyxia. All infants fully recovered. In neonates with immediate adverse outcome significantly more maneuvers were used compared with those without adverse neonatal outcome (p = 0.02). Postpartum hemorrhage occurred in 2/64 (3.1%) women, deep vaginal lacerations in 2/64 (3.1%), perineal tears in 23/64 (35.9%). No anal sphincter injuries occurred.

CONCLUSIONS

McRoberts and all-fours maneuvers are widely used by primary-care midwives in the management of shoulder dystocia. Low rates of adverse neonatal and maternal outcomes were observed in cases of shoulder dystocia up to 6 weeks postpartum.

[Epidemiology of shoulder dystocia]

OBJECTIVES

To synthetize the available evidence regarding the incidence and risk factors of shoulder dystocia (SD).

METHODS

Consultation of the Medline database, and of national guidelines.

RESULTS

Shoulder dystocia is defined as a vaginal delivery that requires additional obstetric manoeuvres to deliver the foetus after the head has delivered and gentle traction has failed. With this definition, the incidence of SD in population-based studies is about 0.5-1% of vaginal deliveries. Many risk factors have been described but most associations are not independent, or have not been constantly found. The 2 characteristics consistently found as independent risk factors for SD in the literature are previous SD (incidence of SD of about 10% in parturients with previous SD) and foetal macrosomia. Maternal diabetes and obesity also are associated with a higher risk of SD (2 to 4 folds) but these associations may be completely explained by foetal macrosomia. However, even factors independently and constantly associated with SD do not allow a valid prediction of SD because they are not discriminant; 50 to 70% of SD cases occur in their absence, and the great majority of deliveries when they are present is not associated with SD.

CONCLUSION

Shoulder dystocia is defined by the need for additional obstetric manoeuvres to deliver the foetus after the head has delivered and gentle traction has failed, and complicates 0.5-1% of vaginal deliveries. Its main risk factors are previous SD and macrosomia, but they are poorly predictive. SD remains a non-predictable obstetrics emergency. Knowledge of SD risk factors should increase the vigilance of clinicians in at-risk contexts.

Risk Factors for Macrosomia

OBJECTIVE

To identify risk factors for macrosomic babies.

METHODS

This cross-sectional analytical study was carried out in the University Teaching Hospital and the Central Hospital of Yaoundé (Cameroon) from October 1st, 2012 to March 31st, 2013. Women who gave birth to ≥4,000 or 3,000-3,499 g babies were recruited. Variables recorded were fetal sex and birth weight, gestational age, maternal age, parity, mother's body mass index (BMI), weight gain during pregnancy, previous macrosomia, and father's BMI. Fisher exact test and student t-test were used for comparison. Level of significance was P < 0.05.

RESULTS

Main risk factors for macrosomia are delivery of a previous macrosomic baby (OR 13.1), maternal weight gain ≥16 kg (OR 10.2), parity ≥3 (OR 4.8), father's BMI ≥30 (OR 3.7), male sex (OR 2.2), and post-term (OR 1.9).

CONCLUSION

Father's obesity should be added among the known risk factors for macrosomia.

Prevention of shoulder dystocia related birth injuries: Myths and facts

Traditionally, brachial plexus damage was attributed to excessive traction applied on the fetal head at delivery. Recently, it was proposed that most injuries occur spontaneously in utero. The author has studied the mechanism of neurological birth injuries based on 338 actual cases with special attention to (1) fetal macrosomia; (2) maternal diabetes; and (3) methods of delivery. There was a high coincidence between use of traction and brachial plexus injuries. Instrumental extractions increased the risk exponentially. Erb’s palsy following cesarean section was exceedingly rare. These facts imply that spontaneous neurological injury in utero is extremely rare phenomenon. Literary reports show that shoulder dystocia and its associated injuries increased in the United States several-fold since the introduction of active management of delivery in the 1970’s. Such a dramatic change in a stable population is unlikely to be caused by incidental spontaneous events unrelated to external factors. The cited investigations indicate that brachial plexus damage typically is traction related. The traditional technique which precludes traction is the optimal method for avoiding arrest of the shoulders and its associated neurological birth injuries. Effective prevention also requires meticulous prenatal care and elective abdominal delivery of macrosomic fetuses in carefully selected cases.

Maternal and neonatal complications of macrosomia

This case control study, aimed at identifying complications of macrosomia, was conducted in two major hospitals of Yaoundé, Cameroon over a 6-month period from 1 October 2012. Maternity records were compared of births weighing ≥4000 g with those weighing between 3000 g and 3500 g. The main outcome variables were mode of delivery, low genital lacerations, Apgar score, birth injuries, postpartum haemorrhage and early neonatal death. Data were analysed using SPSS 18.0. Chi-square test or Fisher’s exact test and t-test were used for comparison. P < 0.05 was considered statistically significant. Maternal complications observed were poor uterine contractions during labour, second-degree perineal tears, Caesarean section, instrumental delivery and postpartum haemorrhage. Neonatal complications were birth injuries, poor 5-minute Apgar score and early neonatal death. In our setting, macrosomia is associated with increased maternal and neonatal complications.

Shoulder dystocia: definitions and incidence

Though subjective in nature, both the American College of Obstetricians and Gynecologists practice bulletin and the Royal College of Obstetricians and Gynaecologists green guideline are in agreement on the descriptor of shoulder dystocia: requirement of additional obstetric maneuvers when gentle downward traction has failed to affect the delivery of 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 <4000, 4000-4449, and >4500 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.

Timing of delivery in women with diabetes in pregnancy

The incidence of both gestational and pre-gestational diabetes is increasing worldwide. The main cause of this increase is likely the concomitant increase in the incidence of global obesity, but in the case of gestational diabetes, changes in the diagnostic criteria are also a contributing factor. The adverse outcomes associated with pre-gestational diabetes are well known and have led clinicians to implement various strategies that include increased fetal surveillance and induction of labour at various gestational ages. In many cases these same strategies have been applied in clinical practice also to women with gestational diabetes despite there being differences in the type and magnitude of perinatal complications associated with this diagnosis. Despite the widespread application of these clinical practices, there is a paucity of quality data in the medical literature to guide the clinician in choosing a strategy for fetal surveillance and timing of delivery in both gestational diabetes and pre-gestational diabetes pregnancies. In the following review, we will discuss the rationale and consequences of planned delivery in gestational diabetes and pre-gestational diabetes, the evidence supporting different strategies for delivery and finally highlight future targets for research in this area.

The impact of maternal obesity on intrapartum outcomes in otherwise low risk women: secondary analysis of the Birthplace national prospective cohort study

OBJECTIVES

To evaluate the impact of maternal BMI on intrapartum interventions and adverse outcomes that may influence choice of planned birth setting in healthy women without additional risk factors.

DESIGN

Prospective cohort study.

SETTING

Stratified random sample of English obstetric units.

SAMPLE

17,230 women without medical or obstetric risk factors other than obesity.

METHODS

Multivariable log Poisson regression was used to evaluate the effect of BMI on risk of intrapartum interventions and adverse maternal and perinatal outcomes adjusted for maternal characteristics.

MAIN OUTCOME MEASURES

Maternal intervention or adverse outcomes requiring obstetric care (composite of: augmentation, instrumental delivery, intrapartum caesarean section, general anaesthesia, blood transfusion, 3rd/4th degree perineal tear); neonatal unit admission or perinatal death.

RESULTS

In otherwise healthy women, obesity was associated with an increased risk of augmentation, intrapartum caesarean section and some adverse maternal outcomes but when interventions and outcomes requiring obstetric care were considered together, the magnitude of the increased risk was modest (adjusted RR 1.12, 95% CI 1.02-1.23, for BMI > 35 kg/m(2) relative to low risk women of normal weight). Nulliparous low risk women of normal weight had higher absolute risks and were more likely to require obstetric intervention or care than otherwise healthy multiparous women with BMI > 35 kg/m(2) (maternal composite outcome: 53% versus 21%). The perinatal composite outcome exhibited a similar pattern.

CONCLUSIONS

Otherwise healthy multiparous obese women may have lower intrapartum risks than previously appreciated. BMI should be considered in conjunction with parity when assessing the potential risks associated with birth in non-obstetric unit settings.

Gestational diabetes and macrosomia by race/ethnicity in Hawaii

Background

Gestational diabetes (GDM) has been shown to have long-term sequelae for both the mother and infant. Women with GDM are at increased risk of macrosomia, which predisposes the infant to birth injuries. Previous studies noted increased rates of GDM in Asian and Pacific Islander (API) women; however, the rate of macrosomia in API women with GDM is unclear. The objective of this study was to examine the relationship between ethnicity, gestational diabetes (GDM), and macrosomia in Hawaii.

Methods

A retrospective cohort study was performed using Hawaii Pregnancy Risk Assessment Monitoring System (PRAMS) data. Data from 2009–2011, linked with selected items from birth certificates, were used to examine GDM and macrosomia by ethnicity. SAS-callable SUDAAN 10.0 was used to generate odds ratios, point estimates and standard errors.

Results

Data from 4735 respondents were weighted to represent all pregnancies resulting in live births in Hawaii from 2009–2011. The overall prevalence of GDM in Hawaii was 10.9%. The highest prevalence of GDM was in Filipina (13.1%) and Hawaiian/Pacific Islander (12.1%) women. The lowest prevalence was in white women (7.4%). Hawaiian/Pacific Islander, Filipina, and other Asian women all had an increased risk of GDM compared to white women using bivariate analysis. Adjusting for obesity, age, maternal nativity, and smoking, Asian Pacific Islander (API) women, which includes Hawaiian/Pacific Islander, Filipina, and other Asian women, had a 50% increased odds of having GDM compared to white women when compared using multivariate analysis. Among women with GDM, the highest prevalence of macrosomia was in white women (14.5%) while the lowest was in Filipina (5.3%) women.

Conclusions

API women in Hawaii have increased rates of GDM compared to white women. Paradoxically, this elevated GDM risk in API women is not associated with an increased rate of macrosomia. This suggests the relationship between GDM and macrosomia is more complex in this population.

Identification of pregnancies at increased risk of brachial plexus birth palsy - the construction of a weighted risk score

OBJECTIVE

Since it is difficult to identify women at increased risk of fetal brachial plexus birth palsy (BPBP) during labor and delivery, we aimed to construct and validate a risk score.

METHODS

A retrospective case-control study was undertaken in 2001 and 2006 in an urban context in Malmö, Sweden. A risk score was constructed for all women who had received routine municipal maternal health care at Skåne University Hospital (n = 10 459). The model was validated among all pregnant women with BPBP and controls in Sweden between 2006 and 2007.

RESULTS

The likelihood of BPBP increased as the risk score rose: 3.1% of the women studied had a risk score ≥5, including 32.1% of the BPBP cases, where the risk showed a 38-fold increase, as compared to those with a risk score ≤1 (2/3 of the population).

CONCLUSION

Our findings indicate that it is possible to identify women at increased risk of having a child with BPBP by using variables observable in advance of delivery.

Fetal macrosomia and shoulder dystocia in women with gestational diabetes: risks amenable to treatment?

Fetal macrosomia and maternal diabetes are independent risk factors for shoulder dystocia, an obstetrical emergency that may cause permanent neonatal injury. Randomized trials of glycemic control in pregnancies complicated by gestational diabetes reveal decreased rates of macrosomia and shoulder dystocia among those treated. However, definitions of gestational diabetes vary and a specific glycemic threshold for clinically significant risk reduction remains to be delineated. This review discusses risks associated with gestational diabetes including macrosomia (birth weight above 4000-4500 g) and delivery-related morbidity, specifically, shoulder dystocia. Subsequently, we will review recent randomized trials assessing the impact of glycemic control on these delivery-related morbidities. Finally, we will examine a large observational study that found associations with delivery-related morbidity and hyperglycemia below current diabetic thresholds, observations which may suggest reexamination of current diagnosis guidelines for gestational diabetes.

Objective structured assessment of technical skills evaluation of theoretical compared with hands-on training of shoulder dystocia management: a randomized controlled trial

OBJECTIVE

To compare the skills of performing a shoulder dystocia management algorithm after hands-on training compared with demonstration.

METHODS

We randomized medical students to a 30-minute hands-on (group 1) and a 30-minute demonstration (group 2) training session teaching a standardized shoulder dystocia management scheme on a pelvic training model. Participants were tested with a 22-item Objective Structured Assessment of Technical Skills scoring system after training and 72 hours thereafter. Objective Structured Assessment of Technical Skills scores were the primary outcome. Performance time, self-assessment, confidence, and global rating scale were the secondary outcomes. Statistics were performed using Mann-Whitney U test, χ test, and multiple linear regression analysis.

RESULTS

Two hundred three participants were randomized. Objective Structured Assessment of Technical Skills scores were significantly higher in group 1 (n=103) compared with group 2 (n=100) (17.95±3.14 compared with 15.67±3.18, respectively; P<.001). The secondary outcomes global rating scale (GRS; 10.94±2.71 compared with 8.57±2.61, respectively; P<.001), self-assessment (3.15±0.94 compared with 2.72±1.01; P=.002), and confidence (3.72±0.98 compared with 3.34±0.90, respectively; P=.005), but not performance time (3:19±0:48 minutes compared with 3:31±1:05 minutes; P=.1), were also significantly different, favoring group 1. After 72 hours, Objective Structured Assessment of Technical Skills scores were still significantly higher in group 1 (n=67) compared with group 2 (n=60) (18.17±2.76 compared with 14.98±3.03, respectively; P<.001) as were GRS (10.80±2.62 compared with 8.15±2.59; P<.001) and self assessment (SA; 3.44±0.87 compared with 2.95±0.94; P=.003). In a multiple linear regression analysis, group assignment (group 1 compared with 2; P<.001) and sex (P=.002) independently influenced Objective Structured Assessment of Technical Skills scores.

CONCLUSION

Hands-on training helps to achieve a significant improvement of shoulder dystocia management on a pelvic training model.

CLINICAL TRIAL REGISTRATION

www.ClinicalTrials.gov, NCT01618565.

LEVEL OF EVIDENCE

I.

Use of birth weight threshold for macrosomia to identify fetuses at risk of shoulder dystocia among Chinese populations

OBJECTIVE

To assess the incidence of macrosomia and the influence of birth weight on shoulder dystocia risk among a cohort of Chinese women.

METHODS

A retrospective analysis was conducted of 80953 singleton deliveries recorded at the Prince of Wales Hospital, Hong Kong, between 1995 and 2009. The incidences of macrosomia (birth weight ≥ 4000 g) and shoulder dystocia were assessed by birth weight; risk factors for shoulder dystocia were examined by multiple logistic regression analysis.

RESULTS

The incidence of macrosomia was 3.4%. The overall incidence of shoulder dystocia was 0.3%; however, the incidence rose with increasing birth weight. The odds ratio (OR) for a birth weight of 4000-4199 g was 22.40, while the OR for a birth weight of 4200 g or above was 76.10. Other independent risk factors for shoulder dystocia included instrumental delivery (OR 12.11), short stature (OR 2.16), maternal diabetes mellitus (OR 1.78), and obesity (OR 1.58).

CONCLUSION

Although the overall incidences of macrosomia and shoulder dystocia were low, the risk of shoulder dystocia was strongly linked to increasing birth weight. International guidelines for elective cesarean delivery in suspected cases of macrosomia may not, therefore, apply to Chinese women.

When is primary cesarean appropriate: fetal indications

The objective of this review was to assess the evidence that supports cesarean delivery for fetal indications. The main fetal reasons for abdominal delivery include abnormal fetal heart rate patterns in labor, malpresentation, fetal macrosomia, multiple gestation, and both functional and structural fetal abnormalities. Although the level of evidence is not as strong as anticipated, there is sufficient support for cesarean delivery when these fetal conditions complicate pregnancy. Efforts to decrease cesarean delivery for fetal indications in the current medicolegal environment will not be easy; however, the development of more sensitive tools to assess fetal well-being in labor and practices to deliver or reduce fetuses in breech presentation at term have the potential for greatest impact on the overall primary cesarean delivery rate.

[Prediction, prevention and management of shoulder dystocia]

Shoulder dystocia is one of the most tragic, fatal and unexpected obstetrical events, which is mostly unpredictable and unpreventable. This clinical picture is defined as a delivery that requires additional obstetric maneuvers to release the shoulders after gentle downward traction has failed. Shoulder dystocia occurs when the fetal shoulder impacts on the maternal symphysis or sacral promontory. The incidence of shoulder dystocia is 0.2-0.6%. High perinatal mortality and morbidity is associated with the condition, even when it is managed appropriately. Obstetricians should be aware of the existing risk factors, but should always be alert to the possibility of shoulder dystocia in all labors. Maternal morbidity is also increased, particularly postpartum hemorrhage, rupture of the uterus, injury of the bladder, urethra and the bowels and fourth-degree perineal tears. Complications of the newborn include asphyxia, perinatal mortality, fracture of the clavicula and the humerus. Brachial plexus injuries are one of the most important fetal complications of shoulder dystocia, complicating 4-16% of such deliveries. The purpose of this article is to review the current evidence regarding the possible prediction, prevention and management of shoulder dystocia.