Sonography, suspected macrosomia, and prophylactic cesarean: a limited partnership

Recurrent Shoulder Dystocia: Risk Factors and Counseling

A prior history of delivery complicated by shoulder dystocia confers a 6-fold to nearly 30-fold increased risk of shoulder dystocia recurrence in a subsequent vaginal delivery, with most reported rates between 12% and 17%. Whereas prevention of shoulder dystocia in the general population is neither feasible nor cost-effective, directing intervention efforts at the particular subgroup of women with a prior history of shoulder dystocia has merit. Potentially modifiable risk factors and individualized management strategies that may reduce shoulder dystocia recurrence and its associated significant morbidities are reviewed.

Labor and Delivery Experiences of Mothers with Suspected Large Babies

OBJECTIVE

To characterize the prevalence of and factors associated with clinicians' prenatal suspicion of a large baby; and to determine whether communicating fetal size concerns to patients was associated with labor and delivery interventions and outcomes.

METHODS

We examined data from women without a prior cesarean who responded to Listening to Mothers III, a nationally representative survey of women who had given birth between July 2011 and June 2012 (n = 1960). We estimated the effect of having a suspected large baby (SLB) on the odds of six labor and delivery outcomes.

RESULTS

Nearly one-third (31.2%) of women were told by their maternity care providers that their babies might be getting "quite large"; however, only 9.9% delivered a baby weighing ≥4000 g (19.7% among mothers with SLBs, 5.5% without). Women with SLBs had increased adjusted odds of medically-induced labor (AOR 1.9; 95% CI 1.4-2.6), attempted self-induced labor (AOR 1.9; 95% CI 1.4-2.7), and use of epidural analgesics (AOR 2.0; 95% CI 1.4-2.9). No differences were noted for overall cesarean rates, although women with SLBs were more likely to ask for (AOR 4.6; 95% CI 2.8-7.6) and have planned (AOR 1.8; 95% CI 1.0-4.5) cesarean deliveries. These associations were not affected by adjustment for gestational age and birthweight.

CONCLUSIONS FOR PRACTICE

Only one in five US women who were told that their babies might be getting quite large actually delivered infants weighing ≥4000 g. However, the suspicion of a large baby was associated with an increase in perinatal interventions, regardless of actual fetal size.

Fetal macrosomia and pregnancy outcomes

BACKGROUND

Pregnancies with a macrosomic fetus comprise a subgroup of high-risk pregnancies. There is uncertainty in the clinical management and outcomes of such pregnancies.

AIM

We sought to examine clinical management and maternal and fetal outcomes in pregnancies with macrosomic infants at Royal Brisbane and Women's Hospital (RBWH).

METHODS

Data from 276 macrosomic births (weighing > or = 4500 g) and 294 controls (weighing 3250-3750 g) delivered during 2002-2004 at RBWH were collected from the hospital database. Univariate and logistic regression analyses were performed for maternal risk factors and maternal and neonatal outcomes that were associated with fetal macrosomia.

RESULTS

Macrosomia was more than two times likely in women with body mass index (BMI) of > 30 kg/m(2) (odds ratio (OR) 2.41, 95% confidence interval (CI) 1.26-4.61) and in male infant sex (OR 2.05, 95% CI 1.35-3.12), and four times more likely in gestation of > 40 weeks (OR 3.93, 95% CI 1.99-7.74). Maternal smoking reduced the risk of fetal macrosomia (OR 0.27, 95% CI 0.14-0.51). Macrosomia was associated with nearly two times higher risk of emergency caesarean section (OR 1.75, 95% CI 1.02-2.97) and maternal hospital stay of > 3 days (OR 1.66, 95% CI 1.11-2.50), and four times higher risk of shoulder dystocia (OR 4.08, 95% CI 1.62-10.29). Macrosomic infants were twice as likely to have resuscitation (OR 2.21, 95% CI 1.46-3.34) and intensive care nursery admission (OR 1.89, 95% CI 1.03-3.46).

CONCLUSION

Macrosomia was associated with an increased risk of adverse maternal and neonatal health outcomes. Optimal management strategies of macrosomic pregnancies need evaluation.

Sonographic prediction of macrosomia cannot be improved by combination with pregnancy-specific characteristics

OBJECTIVE

To evaluate the predictive value of a combination of sonographic, clinical and demographic data for detecting fetal macrosomia compared to ultrasound fetal weight estimation alone.

METHODS

Retrospective cohort data were obtained from 1062 pregnancies in an unselected population. Estimated fetal sonographic weight was obtained within the last week prior to delivery. Two different combination models-published by Mazouni et al. and Nahum and Stanislaw-were employed to predict the presence of macrosomia at birth in these infants. Receiver-operating characteristics (ROC) curves were generated to compare the prediction of macrosomia when using different observation methods and sensitivity, specificity, positive predictive value, negative predictive value (NPV) and accuracy were calculated.

RESULTS

Macrosomia (birth weight >or= 4000 g) was present in 135/1062 (12.7%) newborns. ROC curve analysis revealed the prediction of macrosomia using ultrasound alone to be significantly superior to the combined method of Mazouni et al. (area under the curve (AUC) 0.922, 95% CI 0.902-0.943 vs. 0.747, 95% CI 0.700-0.794, respectively; P < 0.0005), whereas the performance of the Nahum and Stanislaw equation was similar but not superior to ultrasound alone (AUC 0.895, 95% CI 0.839-0.950 vs. 0.912, 95% CI 0.867-0.958, respectively; P > 0.05). The accuracy of macrosomia prediction was similar for ultrasound alone and the Nahum and Stanislaw equation (approximately 90%), whereas the nomogram of Mazouni et al. reached only 51.7% accuracy (using a probability cut-off level of 50%). The NPV was found to be over 90% for all methods.

CONCLUSIONS

Combination of sonographic estimates with clinical and demographic variables does not improve the prediction of macrosomia at delivery in comparison with a routine ultrasound scan within a week before delivery, at least in unselected populations.

After shoulder dystocia: managing the subsequent pregnancy and delivery

Among risk factors for shoulder dystocia, a prior history of delivery complicated by shoulder dystocia is the single greatest risk factor for shoulder dystocia occurrence, with odds ratios 7 to 10 times that of the general population. Recurrence rates have been reported to be as high as 16%. Whereas prevention of shoulder dystocia in the general population is neither feasible nor cost-effective, intervention efforts directed at the particular subgroup of women with a prior history of shoulder dystocia can concentrate on potentially modifiable risk factors and individualized management strategies that can minimize recurrence and the associated significant morbidities and mortality.

Mode of delivery and the survival of macrosomic infants in the United States, 1995-1999

BACKGROUND

Although increases in perinatal mortality risk associated with fetal macrosomia are well documented, the optimal route of delivery for fetuses with suspected macrosomia remains controversial. The objective of this investigation was to assess the risk of neonatal death among macrosomic infants delivered vaginally compared with those delivered by cesarean section.

METHODS

Data were derived from the U.S. 1995-1999 Linked Live Birth-Infant Death Cohort files and term (37-44 wk), single live births to United States resident mothers selected. A proportional hazards model was used to analyze the risk of neonatal death associated with cesarean delivery among 3 categories of macrosomic infants (infants weighing 4,000-4,499 g; 4,500-4,999 g; and 5,000+ g).

RESULTS

After controlling for maternal characteristics and complications, the adjusted hazard ratio for neonatal death associated with cesarean delivery among the 3 categories of macrosomic infants was 1.40, 1.30, and 0.85.

CONCLUSIONS

Although cesarean delivery may reduce the risk of death for the heaviest infants (5,000+ g), the relative benefit of this intervention for macrosomic infants weighing 4,000-4,999 g remains debatable. Thus, policies in support of prophylactic cesarean delivery for suspected fetal macrosomia may need to be reevaluated.

Secular trends in cesarean delivery rates among macrosomic deliveries in the United States, 1989 to 2002

OBJECTIVES

We describe national trends in cesarean delivery rates among macrosomic infants during 1989 to 2000 and evaluate the maternal characteristics and risk factors for macrosomic infants delivered by cesarean section as compared to macrosomic infants delivered vaginally.

STUDY DESIGN

We analyzed US 1989 to 2000 Natality files, selecting term (37 to 44 week) single live births to U.S. resident mothers. We compare macrosomic infants (4000 to 4499, 4500 to 4999 and 5000+ g infants) to a normosomic (3000 to 3999 g) control group.

RESULTS

The proportion of cesarean deliveries among 5000+ g infants increased significantly over the time period. The adjusted odds ratio of cesarean delivery increased for all macrosomic categories over the 12-year period, as compared to normal birth weight infants.

CONCLUSIONS

Rates of cesarean delivery among macrosomic infants continue to increase despite a lack of evidence of the benefits of cesarean delivery within this population. Further exploration of the rationale for this trend is warranted and should include the development of an optimal delivery strategy for such patients.

Fetal growth and well-being

Accurate monitoring of fetal growth is one of the most critically important components of prenatal care. Whether too large or too small for gestational age, the ramifications of abnormal fetal growth have both short-term and long-term sequelae for early neonatal life and beyond. Although not perfectly accurate, ultrasound and other monitoring technologies have markedly improved the ability to follow abnormalities of fetal growth and to decide if early intervention or early delivery is necessary. Clearly, perinatal morbidity and mortality are decreased with close surveillance of these at-risk fetuses.

Perinatal outcome of fetuses with a birth weight greater than 4500 g: an analysis of 3356 cases

OBJECTIVE

To assess the perinatal outcome in a series of macrosomic fetuses according to the intended mode of delivery, and to estimate the individual risk of shoulder dystocia and brachial plexus injury upon information available either prior the onset of labor or at delivery.

STUDY DESIGN

Perinatal and postnatal information of 3356 women who delivered during a 10-year period a macrosomic fetus (>4500 g) in vertex presentation were analyzed. After the exclusion of cases with extraneous factors that may have affected the health of the neonate, patient and neonatal characteristics were compared according to the intended mode of delivery. The contribution of factors known prior labor and at the time of deliver on the occurrence of shoulder dystocia and brachial plexus injury was analyzed using multiple logistic regression analysis.

RESULTS

During the study period, 2371 women were admitted to spontaneous labor, 778 underwent an induction of labor, and 207 had an elective cesarean section. All cases of shoulder dystocia (n=310), and brachial plexus injury (n=94) occurred among women who delivered vaginally. The rate of brachial plexus injury was higher in cases who had shoulder dystocia than in those who did not (58/310 versus 36/2329, P<0.001). The incidence of brachial plexus injury increases steadily from 0.8 in fetuses weighing 4500-4599 g to 2.86% in those weighing more than 5000 g (P<0.01) and from 2.1 in women taller than 180 cm to 12.5% in those shorter than 155 cm (P<0.05). After adjustment for confounding variables shoulder dystocia (OR 9.2, 95% C.I. 5.38; 15.59), operative vaginal delivery (OR 1.96, 95% C.I. 1.10; 3.49) and clavicular fracture (OR 2.9, 95% C.I. 1.31; 6.44) remained predictors of brachial plexus injury.

CONCLUSION

Since some of these risk factors are known prior to delivery, each woman whose fetus is suspected to weight more than 4500 g should be counseled on her individual risk of severe perinatal morbidity before a decision on the mode of delivery is taken.

Macrosomic births in the united states: determinants, outcomes, and proposed grades of risk

OBJECTIVE

We describe maternal risk factors for macrosomia and assess birth weight categories to determine predictive thresholds of adverse outcomes.

STUDY DESIGN

We analyzed linked live birth and infant death cohort files from 1995 to 1997 for the United States with the use of selected term (37-44 weeks of gestation) single live births to mothers who were US residents. We compared macrosomic infants (4000-4499 g, 4500-4999 g, and >5000 g infants) with a normosomic control group of infants who weighed 3000 to 3999 g.

RESULTS

Maternal risk factors for macrosomia included nonsmoking, advanced age, married, diabetes mellitus, hypertension, and previous macrosomic infant or pregnancy loss. The risks of labor complications, birth injuries, and newborn morbidity rose with each gradation of macrosomic birth weight. Infant mortality rates increased significantly among infants weighing >5000 g.

CONCLUSION

Although a definition of macrosomia as >4000 g (grade 1) may be useful for the identification of increased risks of labor and newborn complications, >4500 g (grade 2) may be more predictive of neonatal morbidity, and >5000 g (grade 3) may be a better indicator of infant mortality risk.

Shoulder dystocia

Shoulder dystocia is an uncommon but not rare obstetric emergency. Death of the infant is unusual but perinatal morbidity is frequent and can result in permanent injury. These cases carry significant medico-legal implications. This chapter covers the mechanisms, predisposing factors and management of shoulder dystocia. A well-rehearsed sequence of manoeuvres to manage shoulder dystocia will minimize fetal trauma.