High birthweight and shoulder dystocia: the strongest risk factors for obstetrical brachial plexus palsy in a Swedish population-based study

BACKGROUND

Obstetrical brachial plexus palsy (OBPP) is a serious form of neonatal morbidity.

OBJECTIVE

The aim of this work was to study the incidence of OBPP and to analyze its risk factors.

METHODS

This is a population-based retrospective case-control study. All deliveries recorded in the Swedish Medical Birth Registry between 1987 and 1997 (n = 1 213 987) were investigated. Cases (n = 2399) with OBPP were compared to all other cases.

RESULTS

The incidence of OBPP increased from 0.17 in 1987 to 0.27% in 1997 (p = 0.002). During the same time period, the mean birthweight increased from 3483 to 3525 g. Birthweight increasing from 4000 g was associated with a progressive rise in OBPP risk. Other significant risk factors associated with the injury were shoulder dystocia, breech presentation in vaginal delivery, operative vaginal delivery, diabetes mellitus, induction of labor, protracted active phase, secondary arrest of dilatation, and epidural anesthesia. Cesarean section was associated with a decreased risk of OBPP. If 5000 g is chosen as cut-off for cesarean section, 85% of the infants in this weight class are underestimated using ultrasonography. Approximately, 331 abdominal deliveries have to be performed to avoid one case of OBPP.

CONCLUSIONS

Shoulder dystocia and infant birthweight of 4500 g and more are the strongest risk factors for OBPP in a Swedish population.

Suspicion and treatment of the macrosomic fetus: a review

OBJECTIVE

To review the prevalence of and our ability to identify macrosomic (birthweight >4000 g) fetuses. Additionally, based on the current evidence, propose an algorithm for treatment of suspected macrosomia.

STUDY DESIGN

A review.

RESULTS

According to the National Vital Statistics, in the United States, the prevalence of newborns weighing at least 4000 g has decreased by 10% in seven years (10.2% in 1996 and 9.2% in 2002) and 19% for newborns with weights >5000 g (0.16% and 0.13%, respectively). Bayesian calculations indicates that the posttest probability of detecting a macrosomic fetus in an uncomplicated pregnancy is variable, ranging from 15% to 79% with sonographic estimates of birth weight, and 40 to 52% with clinical estimates. Among diabetic patients the post-test probability of identifying a newborn weighing >4000 g clinically and sonographically is over 60%. Among uncomplicated pregnancies, there is sufficient evidence that suspected macrosomia is not an indication for induction or for primary cesarean delivery. For pregnancies complicated by diabetes, with a prior cesarean delivery or shoulder dystocia, delivery of a macrosomic fetus increases the rate of complications, but there is insufficient evidence about the threshold of estimated fetal weight that should prompt cesarean delivery.

CONCLUSION

Due to the inaccuracies, among uncomplicated pregnancies suspicion of macrosomia is not an indication for induction or for primary cesarean delivery.

Évolution anthropologique du bassin osseux des femmes

The existence of dystocia in human presents a vexing problem for an evolutionary point of view. Dealing with the great apes and modern human's pelvis evolution, considering the bipedalism and the cerebral growth, the adaptative mechanisms and their obstetrical and social consequences are discussed.

Effect of treatment of gestational diabetes mellitus on pregnancy outcomes

BACKGROUND

We conducted a randomized clinical trial to determine whether treatment of women with gestational diabetes mellitus reduced the risk of perinatal complications.

METHODS

We randomly assigned women between 24 and 34 weeks' gestation who had gestational diabetes to receive dietary advice, blood glucose monitoring, and insulin therapy as needed (the intervention group) or routine care. Primary outcomes included serious perinatal complications (defined as death, shoulder dystocia, bone fracture, and nerve palsy), admission to the neonatal nursery, jaundice requiring phototherapy, induction of labor, cesarean birth, and maternal anxiety, depression, and health status.

RESULTS

The rate of serious perinatal complications was significantly lower among the infants of the 490 women in the intervention group than among the infants of the 510 women in the routine-care group (1 percent vs. 4 percent; relative risk adjusted for maternal age, race or ethnic group, and parity, 0.33; 95 percent confidence interval, 0.14 to 0.75; P=0.01). However, more infants of women in the intervention group were admitted to the neonatal nursery (71 percent vs. 61 percent; adjusted relative risk, 1.13; 95 percent confidence interval, 1.03 to 1.23; P=0.01). Women in the intervention group had a higher rate of induction of labor than the women in the routine-care group (39 percent vs. 29 percent; adjusted relative risk, 1.36; 95 percent confidence interval, 1.15 to 1.62; P<0.001), although the rates of cesarean delivery were similar (31 percent and 32 percent, respectively; adjusted relative risk, 0.97; 95 percent confidence interval, 0.81 to 1.16; P=0.73). At three months post partum, data on the women's mood and quality of life, available for 573 women, revealed lower rates of depression and higher scores, consistent with improved health status, in the intervention group.

CONCLUSIONS

Treatment of gestational diabetes reduces serious perinatal morbidity and may also improve the woman's health-related quality of life.

Brachial plexus injury: a 23-year experience from a tertiary center

OBJECTIVE

The purpose of this study was to analyze the data on brachial plexus injury and its relationship with shoulder dystocia from a tertiary center for a 23-year period.

STUDY DESIGN

A review of the logbooks on labor and delivery and the nursery and the International Classification of Diseases codes identified all newborn infants with brachial plexus injury who were delivered at our center.

RESULTS

During the 23 years (1980-2002), there were 89,978 deliveries, of which there were 85 cases of brachial plexus injury (1/1000 births) with vaginal delivery. The injury was permanent (> or =1 year) in 12% of the cases, and only 2 cases have been litigated. Newborn infants that weighed > or =4 kg were significantly more common among those infants who had shoulder dystocia and brachial plexus injury than those infants without injury (odds ratio, 6.55; 95% CI, 2.30, 18.63). The rate of permanent brachial plexus injury was similar between the 2 groups.

CONCLUSION

A case of brachial plexus injury occurs 1 time in every 1000 births, is permanent in 1 of every 10,000 deliveries, and is litigated 1 time for every 45,000 deliveries. The infrequent nature of injury may preclude prevention.

Accuracy of estimated fetal weight in shoulder dystocia and neonatal birth injury

OBJECTIVE

This study was undertaken to determine whether there is any difference in the rate of error of estimated fetal weight (EFW) in cases of shoulder dystocia compared with controls.

STUDY DESIGN

Women whose delivery was complicated by shoulder dystocia were studied and compared with a control group matched for parity, race, labor type (spontaneous or induced), and birth weight (BW). Accuracy (%) was defined as [(EFW-BW)/BW] x 100. The primary outcome of the study was rate of EFW underestimation error 20% or greater.

RESULTS

During the 5-year study period, there were 206 cases of shoulder dystocia that met all study criteria. There was no difference in the number of patients that had EFW underestimation error 20% or greater (shoulder dystocia 9.8% vs control 12.8%; P = .38). There was also no difference in the number of patients that had EFW underestimation error 20% or greater between shoulder dystocia with and without injury (injury 8.3% vs no injury 7.1%; P = .79).

CONCLUSION

EFW underestimation error in cases of shoulder dystocia is an infrequent event and does not occur more often than in deliveries without shoulder dystocia.

Shoulder dystocia: are historic risk factors reliable predictors?

OBJECTIVE

Our purpose was to determine the rate of associated risk factors for shoulder dystocia from a large cohort of patients delivered within our Southern California perinatal program.

STUDY DESIGN

A retrospective analysis was performed of patients delivered from January 1991 to June 2001. Patients with and without shoulder dystocia were identified from our computer-stored perinatal database and compared. Statistical methods used included: chi 2 test, t test, calculation of odds ratios, and Fisher exact test, as indicated.

RESULTS

Among the 267,228 vaginal births during the study period, there were 1,686 cases of shoulder dystocia (rate 0.6%). Rates for operative vaginal delivery, diabetes, epidural use, multiparity, and postdatism were similar among cases with and without shoulder dystocia. The clinical triad of oxytocin use, labor induction, and birth weight greater than 4,500 g yielded a cumulative odds ratio of 23.2 (95% CI 17.3-31.0) for shoulder dystocia, but its sensitivity and positive predictive value were only 12.4% and 3.4%, respectively.

CONCLUSION

Historic obstetric risk factors for shoulder dystocia are not useful predictors for the event. Furthermore, although shoulder dystocia was observed more frequently with increasing birth weight, current limitations in estimating birth weight antenatally with accuracy preclude its practical use as a reliable predictor.

Risk factors and obstetric complications associated with macrosomia

OBJECTIVE

Macrosomia is associated with adverse maternal outcomes. The objective of this study was to characterize the epidemiology of macrosomia and related maternal complications.

METHOD

Live births (146,526) were identified between 1995 and 1999 in the Kaiser Permanente Medical Care Program's Northern California Region (KPMCP NCR) database. Bivariate and multivariate analyses were performed for risk factors and complications associated with macrosomia (birth weight >4500 g).

RESULT

Male infant sex, multiparity, maternal age 30-40, white race, diabetes, and gestational age >41 weeks were associated with macrosomia (p<0.001). In bivariate and multivariate analyses, macrosomia was associated with higher rates of cesarean birth, chorioamnionitis, shoulder dystocia, fourth-degree perineal lacerations, postpartum hemorrhage, and prolonged hospital stay (p<0.01).

CONCLUSION

Macrosomia was associated with adverse maternal outcomes in this cohort. More research is needed to determine how to prevent complications related to excessive birth weight.

Labor Progression and Risk of Cesarean Delivery in Electively Induced Nulliparas

OBJECTIVE

To describe the pattern of labor progression and risk of cesarean delivery in women whose labor was electively induced.

METHODS

We analyzed data on all low-risk, nulliparous women with an elective induction or spontaneous onset of labor between 37 + 0 and 40 + 6 weeks from January 2002 to March 2004 at a single institution. The median duration of labor by each centimeter of cervical dilation and the risk of cesarean delivery were computed for 143 women with preinduction cervical ripening and oxytocin induction, 286 women with oxytocin induction, and 1,771 women with a spontaneous onset of labor. An intracervical Foley catheter was used to ripen the cervix.

RESULTS

Electively induced labor with cervical ripening had substantially slower latent and early active phases. After controlling for potential confounders, women who had an elective induction with cervical ripening had 3.5 times the risk of cesarean delivery during the first stage of labor (95% confidence interval 2.7-4.5), compared with those admitted in spontaneous labor. Elective induction without cervical ripening, on the other hand, was associated with a faster labor progression from 4 to 10 cm (266 compared with 358 minutes, P < .01) and did not increase the risk of cesarean delivery, compared with those in spontaneous labor.

CONCLUSION

The pattern of labor progression differs substantially for women with an electively induced labor compared with those with spontaneous onset of labor. Furthermore, elective induction in nulliparous women with an unfavorable cervix has a high rate of labor arrest and a substantially increased risk of cesarean delivery.

LEVEL OF EVIDENCE

II-2.

Is abnormal labor associated with shoulder dystocia in nulliparous women?

OBJECTIVE

This study was undertaken to examine the relationship between labor abnormalities and shoulder dystocia in nulliparous women.

STUDY DESIGN

Nulliparous women whose delivery was complicated by shoulder dystocia were studied and compared with a control group selected based on the best possible match for race, labor type (spontaneous or induced), and birth weight. The duration of first and second stage of labor, as well as the rates of labor progress, were calculated and compared between groups.

RESULTS

During this 4-year study period, there were 8010 nulliparous singleton deliveries of which 65 (0.8%) were complicated by shoulder dystocia. Compared with controls, there was no difference in the rate of cervical dilation in the active phase of the first stage of labor. In the shoulder dystocia group, more patients had a second stage of labor greater than 2 hours (22% vs 3%; P <.05) and had operative vaginal deliveries (26% vs 1.5%; P <.001). In shoulder dystocia cases with birth weight greater than 4000 g, 33% had a second stage of labor greater than 2 hours.

CONCLUSION

In our population, the combination of fetal macrosomia, second stage of labor longer than 2 hours and the use of operative vaginal delivery were associated with shoulder dystocia in nulliparous women.

Shoulder dystocia

Shoulder dystocia can be one of the most frightening emergencies in the delivery room. Although many factors have been associated with shoulder dystocia, most cases occur with no warning. Calm and effective management of this emergency is possible with recognition of the impaction and institution of specified maneuvers, such as the McRoberts maneuver, suprapubic pressure, internal rotation, or removal of the posterior arm, to relieve the impacted shoulder and allow for spontaneous delivery of the infant. The "HELPERR" mnemonic from the Advanced Life Support in Obstetrics course can be a useful tool for addressing this emergency. Although no ideal manipulation or treatment exists, all maneuvers in the HELPERR mnemonic aid physicians in completing one of three actions: enlarging the maternal pelvis through cephalad rotation of the symphysis and flattening of the sacrum; collapsing the fetal shoulder width; or altering the orientation of the longitudinal axis of the fetus to the plane of the obstruction. In rare cases in which these interventions are unsuccessful, additional management options, such as intentional clavicle fracture, symphysiotomy, and the Zavanelli maneuver, are described.

[Maternal risks for newborn macrosomia, incidence of a shoulder dystocia and of damages of the plexus brachialis]

PATIENTS RESPECTIVELY AND METHODS: In the HEPE 619 242 births have been analysed (1990 - 2000) to calculate the incidence of a birthweight between 4000 and 4499 g and of a weight > or = 4500 g in relationship to maternal obesity, high maternal weight gain and of a duration of pregnancy more than 298 days.

RESULTS

The risk of a macrosomia > or = 4500 g is in cases of obesity 3.4 times higher, in cases of obesity and prolongation of pregnancy 6.6 times higher and in the presence of all 3 risk factors 10 times higher. Data of the Frauenklinik Wiesbaden (HSK) (n = 6075 births) complete the results, because a correlation between macrosomia, shoulder dystocia and a damage to the plexus brachialis has been found. The incidence of a damage to the plexus brachialis is in case of a shoulder dystocia and a birth weight of < or = 4000 g 6.3%, at a birth weight between 4000-4499 g 25% and in newborns with a weight > or = 4500 g 40%.

CONCLUSIONS

Because of the low sensitivity (60%) of the ultrasonic weight measurement the 3 maternal risk factors--if they exist--of a shoulder dystocia and of a damage of the plexus brachialis should be discussed with the pregnant woman to help her about the decision of an alternative cesarean section. Still one third of the newborns weigh more than 4000 g if all 3 maternal risk factors exist.

Recurrent persistent occipito-posterior position in subsequent deliveries

A nine year follow up study of the delivery pattern of 119 women after delivery in the persistent occiput posterior position and their occipito-anterior controls. The studied parameters were: number of deliveries, number of repeated cases of persistent occiput posterior position and operative deliveries. Deliveries in the occipito-posterior position were more common in the study group than in the controls (P= 0.031). Except for this, no statistically significant differences were found between the groups. According to the results, recurrence of the persistent occiput posterior position is common. A history of delivery in the persistent occiput posterior position does not seem to have any major impact on future childbearing.

Postpartum fetal head circumference and its influence on labour duration in nullipara

A retrospective analysis of postpartum fetal head circumference (FHC) and birth weight and its effect on the duration of labour was undertaken. The aim was to assess the predictive value of postpartum FHC versus birth weight in predicting dystocia. A FHC > 37 cm was associated significantly with a prolonged first and second stage of labour. A receiver operator curve (ROC) shows that the sensitivity and specificity of a FHC > 37 cm is as good as a fetal weight > 4.5 kg in predicting dystocia.

Fetal shoulder dystocia

Shoulder dystocia is an unpredictable obstetric complication with the incidence of 0.15% to 2%. An increase in the incidence of shoulder dystocia has been recorded over the last 20 years, probably just because it has now been regularly registered at maternity wards as an obstetric complication. The risk factors for shoulder dystocia include fetal macrosomia, fetal malformations and tumors, maternal adiposity, excessive weight gain during pregnancy, diabetes mellitus, pathologic pelvis, multiparity, short maternal stature, advanced maternal age, postterm pregnancy, so-called midforceps delivery or vacuum extraction, prolonged delivery stage II, oxytocin labor induction, premature fetal expression according to Kristeller, and previous shoulder dystocia in macrosomatic children. The sequels of shoulder dystocia and obstetric maneuvers for incarcerated shoulder release include clavicular fracture, brachial plexus lesions, sternocleidomastoid muscle distension with or without hematoma, diaphragmatic paralysis, Horner's syndrome, peripartal asphyxia and consequential cerebral lesions (cerebral palsy), and peripartal death. Maternal complications due to shoulder dystocia are postpartal hemorrhage, cervical and vaginal lacerations, frequent infections during the puerperium, symphysiolysis and rupture of the uterus, and secondary cesarean section with related complications due to unsuccessful obstetric procedures or as continuation of Zavanelli's maneuver. McRoberts' maneuver (or Gaskin maneuver) is recommended as the initial procedure for shoulder release in case of shoulder dystocia. If it fails, other obstetric procedures such as Resnik's suprapubic pressure and Woods' grip with posteriorly placed arm release should be used, always with gross lateral episiotomy. The performance of all these obstetric procedures requires skilfull and highly experienced obstetrician and obstetric team as a whole.

Shoulder dystocia and brachial plexus injury: a case-control study

OBJECTIVE AND BACKGROUND

To evaluate risk factors for shoulder dystocia and brachial plexus injury using a case-control study at the departments of obstetrics and gynecology at the four largest hospitals in southern Sweden. All cases of shoulder dystocia between 1987 and 1993 inclusive were identified. For each case, two control infants with similar birthweight (+/- 100 g) and identical year of birth were randomly selected.

METHODS

Original maternal records were reviewed and information regarding 10 potential risk factors was extracted. Odds ratios (ORs) were calculated using the Mantel-Haenszel method. Stratification was made for year of delivery, parity (0, I, II, III+), and maternal age (5-year class).

RESULTS

In all, 107 infants with shoulder dystocia and 198 controls were included. The OR was greater than unity for all risk factors except gestational age. Three of the risk factors, induction of labor, epidural analgesia, and instrumental delivery, reached statistical significance. Thirty-four infants also suffered brachial plexus injury, giving a brachial plexus injury rate of 32% among the shoulder dystocia cases. We also made a separate analysis of the nine risk factors for brachial plexus injury following a shoulder dystocia, however none reached statistical significance.

CONCLUSION

In this case-control study based on more than 100,000 deliveries at four large hospitals during a 7-year period, induction of labor, epidural analgesia, and instrumental delivery turned out to be significant risk factors for shoulder dystocia. For brachial plexus injury following shoulder dystocia, no significant risk factor was identified.

A Darwinian view of obstructed labor

This essay discusses the evolutionary biology of dystocia. From a Darwinian standpoint, the high frequency of dystocia observed today seems evolutionarily untenable. Hunter-gatherers, most notably the Inuit, appear not to suffer from dystocia. It may be that people from an agriculture-based background are, obstetrically speaking, less well adapted to the good nutrition of a modern affluent diet.

Is maternal obesity a predictor of shoulder dystocia?

OBJECTIVE

To explore the relationship between maternal obesity and shoulder dystocia while controlling for the potential confounding effects of other variables associated with obesity.

METHODS

We performed a case-control study of provincial delivery records audited by the Northern and Central Alberta Perinatal Outreach Program. Risk factors evaluated were selected based on previously published studies. Cases and controls were drawn from 45,877 live singleton cephalic vaginal deliveries weighing more than 2500 g between January 1995 and December 1997. There were 413 cases of shoulder dystocia (0.9% incidence). Controls (n = 845) were randomly chosen from the remainder of the target population to create a 1:2 case/control ratio. Univariate analysis with calculation of odds ratios (ORs) was used to determine which of the chosen risk factors were significantly related to the incidence of shoulder dystocia. Multivariable regression analyses were then used to determine the independently associated variables, and the adjusted ORs were obtained for each relevant risk factor.

RESULTS

Maternal obesity was not significant as an independent risk factor for shoulder dystocia after adjusting for confounding variables (adjusted OR 0.9; 95% confidence interval [CI] 0.5, 1.6). Fetal macrosomia was the single most powerful predictor. The adjusted ORs were 39.5 (95% CI 19.1, 81.4) for birth weight greater than 4500 g and 9.0 (95% CI 6.5, 12.6) for birth weight between 4000 and 4499 g.

CONCLUSION

The strongest predictors of shoulder dystocia are related to fetal macrosomia. For obese nondiabetic women carrying fetuses whose weights are estimated to be within normal limits, there is no increased risk of shoulder dystocia.

Diabetes, hypertension and birth injuries: a complex interrelationship

Seemingly coincidental occurrence of various pathological conditions may derive from common etiologic denominators. While reviewing 240 malpractice claims involving shoulder dystocia related fetal injuries, we found two antenatal complications in the background conspicuously often. Chronic or pregnancy induced hypertension was identifiable in 80 instances (33%). Pregnancy induced or preexisting diabetes was diagnosed 48 times (20%). Many of these patients were poorly controlled. The blood pressure was usually checked during the antenatal visits. However, about one-half of all patients received no diabetic screening. Therefore, this study may underestimate the actual incidence of diabetes. It has been calculated that the frequency of diabetes in pregnancy and that of hypertension, is about 5% in the United States. Thus, the rates of these complications in this selected group of gravidas was severalfold higher than in the general population. Since hypertension causes retarded fetal growth, it cannot be a direct cause of arrest of the shoulders at delivery. The likely common denominator is maternal diabetes a known predisposing factor both for preeclampsia and shoulder dystocia at birth. In the course of litigations for fetal injuries, demonstration of the predisposing role of seemingly unrelated shortcomings of the medical management may profoundly influence the outcome. This principle is demonstrated by the presentation of an actual malpractice action which resulted in a substantial settlement.

Maternal obesity and pregnancy outcomes

PURPOSE OF REVIEW

The rates of obesity are increasing rapidly in the United States and other countries. Because obesity is a major factor in the development of many chronic diseases, it is an important individual and public health issue. This review focuses on the pregnancy complications associated with maternal obesity.

RECENT FINDINGS

Maternal obesity adversely impacts pregnancy outcome primarily through increased rates of hypertensive disease (chronic hypertension and pre-eclampsia), diabetes (pregestational and gestational), cesarean section and infections. It is associated with a higher rate of venous thromboembolic disease and respiratory complications, and may be an independent risk factor for neural tube defects, fetal mortality and preterm delivery. Maternal obesity also increases the risk of delivering a large for gestational age or macrosomic neonate, who is in turn at an increased risk of subsequent childhood obesity and its associated morbidity.

SUMMARY

Recommendations regarding the counselling of obese pregnant women and specific guidelines for the obstetrician, family physician, or midwife managing the pregnancy are presented. Cultural and political changes with the potential to decrease the epidemic of obesity in our society are discussed.