Fetal macrosomia: does antenatal prediction affect delivery route and birth outcome?

Vaginal delivery rate by near delivery sonographic weight estimation and maternal stature among nulliparous women

BACKGROUND

We evaluated the risk for cesarean delivery among term nulliparous women, categorized by maternal stature and recent sonographic estimated fetal weight (EFW).

METHODS

A retrospective study including singleton deliveries of nulliparous women between 2011 and 2020, with sonographic EFW within 1 week of delivery. We categorized maternal height into five groups: ≤150, 151-155, 156-160, 161-165, and ≥166 cm. Fetal weight estimation was categorized into five groups as well: ≤2500 g, 2501-2999, 3000-3499, 3500-3999, and ≥4000 g.

RESULTS

Overall, 13 107 deliveries were included. The cesarean delivery rate was inversely correlated with maternal height, ranging from 41.0% in group 1 to 13.1% in group 5. The vaginal delivery rate ranged from 33.3% in maternal height group 1 with EFW of ≥4000 g to 85% in maternal height group 5 with EFW of ≤2500 g. In weight categories above 2500 g, maternal height correlated significantly with vaginal delivery rate, except in weight category ≥4000 g in which vaginal delivery rate ranged around 30% in maternal height categories 1-3 and increased significantly in groups 4-5 to 50-60%. In multivariable logistic regression analysis, EFW was independently associated with CD for EFW categories 3500-3999 and ≥4000 g [aOR 95% CI 1.49 (1.08-2.06) and 4.39 (2.97-6.50), respectively]. Maternal height was negatively associated with CD [aOR 95% CI 0.67 (0.64-0.70)] for each increase in maternal height group.

CONCLUSIONS

Cesarean delivery rate was inversely correlated with maternal height, ranging from 41.0% among women ≤150 cm to 13.1% among women ≥166 cm. Maternal height and EFW of ≥3500 g are independently associated with CD rates among term nulliparous women.

Caesarean Section Delivery Is Associated with Childhood Overweight and Obesity, Low Childbirth Weight and Postnatal Complications: A Cross-Sectional Study

Background and Objectives: In the last decades, simultaneously increasing trends have been recorded for both caesarean section delivery and childhood overweight/obesity around the world, which are considered serious public health concerns, negatively affecting child health. Aim: The present study aims to investigate whether caesarean section is associated with the increased rates of childhood overweight/obesity, low childbirth anthropometric indices and postnatal complications in pre-school age. Materials and Methods: This is a cross-sectional study in which 5215 pre-school children aged 2–5 years old were enrolled from nine different Greek regions after applying specific inclusion and exclusion criteria. Non-adjusted and adjusted statistical analysis was performed to assess the impact of caesarean section in comparison to vaginal delivery. Results: Children delivered by caesarean section were significantly more frequently overweight or obese at the age of 2–5 years, also presenting a higher prevalence of low birth weight, length and head circumference. Caesarean section was also associated with higher incidence of asthma and diabetes type I at the age of 2–5 years. In a multivariate analysis, caesarean section increased the risk of childhood overweight/obesity and low childbirth anthropometric indices even if adjusting for several childhood and maternal confounding factors. Conclusions: Increasing trends were recorded for both caesarean section delivery and childhood overweight/obesity, which are considered serious public health concerns. Caesarean section independently increased childhood overweight/obesity in pre-school age, highlighting the emergent need to promote health policies and strategies to inform future mothers about its short and long-term risks and that this mode of delivery should preferably be performed only when there are strong medical recommendations in emergency obstetric conditions.

Induction of labour at or near term for suspected fetal macrosomia

BACKGROUND

Women with a suspected large-for-dates fetus or a fetus with suspected macrosomia (birthweight greater than 4000 g) are at risk of operative birth or caesarean section. The baby is also at increased risk of shoulder dystocia and trauma, in particular fractures and brachial plexus injury. Induction of labour may reduce these risks by decreasing the birthweight, but may also lead to longer labours and an increased risk of caesarean section.

OBJECTIVES

To assess the effects of a policy of labour induction at or shortly before term (37 to 40 weeks) for suspected fetal macrosomia on the way of giving birth and maternal or perinatal morbidity.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2016), contacted trial authors and searched reference lists of retrieved studies.

SELECTION CRITERIA

Randomised trials of induction of labour for suspected fetal macrosomia.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We contacted study authors for additional information. For key outcomes the quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We included four trials, involving 1190 women. It was not possible to blind women and staff to the intervention, but for other 'Risk of bias' domains these studies were assessed as being at low or unclear risk of bias. Compared to expectant management, there was no clear effect of induction of labour for suspected macrosomia on the risk of caesarean section (risk ratio (RR) 0.91, 95% confidence interval (CI) 0.76 to 1.09; 1190 women; four trials, moderate-quality evidence) or instrumental delivery (RR 0.86, 95% CI 0.65 to 1.13; 1190 women; four trials, low-quality evidence). Shoulder dystocia (RR 0.60, 95% CI 0.37 to 0.98; 1190 women; four trials, moderate-quality evidence), and fracture (any) (RR 0.20, 95% CI 0.05 to 0.79; 1190 women; four studies, high-quality evidence) were reduced in the induction of labour group. There were no clear differences between groups for brachial plexus injury (two events were reported in the control group in one trial, low-quality evidence). There was no strong evidence of any difference between groups for measures of neonatal asphyxia; low five-minute infant Apgar scores (less than seven) or low arterial cord blood pH (RR 1.51, 95% CI 0.25 to 9.02; 858 infants; two trials, low-quality evidence; and, RR 1.01, 95% CI 0.46 to 2.22; 818 infants; one trial, moderate-quality evidence, respectively). Mean birthweight was lower in the induction group, but there was considerable heterogeneity between studies for this outcome (mean difference (MD) -178.03 g, 95% CI -315.26 to -40.81; 1190 infants; four studies; I2 = 89%).  For outcomes assessed using GRADE, we based our downgrading decisions on high risk of bias from lack of blinding and imprecision of effect estimates.

AUTHORS' CONCLUSIONS

Induction of labour for suspected fetal macrosomia has not been shown to alter the risk of brachial plexus injury, but the power of the included studies to show a difference for such a rare event is limited. Also antenatal estimates of fetal weight are often inaccurate so many women may be worried unnecessarily, and many inductions may not be needed. Nevertheless, induction of labour for suspected fetal macrosomia results in a lower mean birthweight, and fewer birth fractures and shoulder dystocia. The observation of increased use of phototherapy in the largest trial, should also be kept in mind. Findings from trials included in the review suggest that to prevent one fracture it would be necessary to induce labour in 60 women. Since induction of labour does not appear to alter the rate of caesarean delivery or instrumental delivery, it is likely to be popular with many women. In settings where obstetricians can be reasonably confident about their scan assessment of fetal weight, the advantages and disadvantages of induction at or near term for fetuses suspected of being macrosomic should be discussed with parents. Although some parents and doctors may feel the evidence already justifies induction, others may justifiably disagree. Further trials of induction shortly before term for suspected fetal macrosomia are needed. Such trials should concentrate on refining the optimum gestation of induction, and improving the accuracy of the diagnosis of macrosomia.

Additional single third trimester ultrasound scan in detection of large for gestational age fetuses

PURPOSE OF REVIEW

To evaluate the accuracy of growth scans in the third trimester. To evaluate the accuracy of universal third trimester ultrasound scans in the detection of large for gestational age (LGA) fetuses. To investigate how universal ultrasound scans affect the delivery and outcomes.

RECENT FINDINGS

Universal third trimester screening for LGA recorded a 22% positive predictive value (PPV), and 96% negative predicted value (NPV). The sensitivity in most studies reaches around 70% or more, of all the LGA fetuses delivered, there are different studies for and against universal ultrasonic screening of LGA. Estimated fetal weight (>4 kg/90th centile) and abdominal circumference are the best predictors of LGA with nearly 70% sensitivity. One study reported that an antenatal ultrasonic diagnosis of LGA in a low risk population has a weak association with the incidence of shoulder dystocia or poor neonatal outcomes. Universal screening in the third trimester for LGAs is not cost effective.

SUMMARY

Low risk pregnancies constitute the majority of the pregnancy population. All low risk pregnancy women will only receive two routine scans throughout the whole pregnancy. There is no evidence at present that conclusively demonstrates that an additional scan at 36 weeks improves maternal and neonatal outcomes and is cost effective.

Risk Factors for Intrapartum Cesarean Section Delivery in Low-risk Multiparous Women Following at Least a Prior Vaginal Birth (Robson Classification 3 and 4)

OBJECTIVE

 The aim of the present study was to evaluate the risk factors for cesarean section (C-section) in low-risk multiparous women with a history of vaginal birth.

METHODS

 The present retrospective study included low-risk multiparous women with a history of vaginal birth who gave birth at between 37 and 42 gestational weeks. The subjects were divided into 2 groups according to the mode of delivery, as C-section Group and vaginal delivery Group. Risk factors for C-section such as demographic characteristics, ultrasonographic measurements, smoking, weight gain during pregnancy (WGDP), interval time between prior birth, history of macrosomic birth, and cervical dilatation at the admission to the hospital were obtained from the charts of the patients. Obstetric and neonatal outcomes were compared between groups.

RESULTS

 The most common C-section indications were fetal distress and macrosomia (33.9% [n = 77 and 20.7% [n = 47] respectively). A bivariate correlation analysis demonstrated that mothers aged > 30 years old (odds ratio [OR]: 2.09; 95% confidence interval [CI]: 1.30-3.34; p = 0.002), parity >1 (OR: 1.81; 95%CI: 1.18-2.71; p = 0.006), fetal abdominal circumference (FAC) measurement > 360 mm (OR: 34.20; 95%CI: 8.04-145.56; p < 0.001)) and < 345 mm (OR: 3.06; 95%CI: 1.88-5; p < 0.001), presence of large for gestational age (LGA) fetus (OR: 5.09; 95%CI: 1.35-19.21; p = 0.016), premature rupture of membranes (PROM) (OR: 1.52; 95%CI: 1-2.33; p = 0.041), and cervical dilatation < 5cm at admission (OR: 2.12; 95%CI: 1.34-3.34; p = 0.001) were associated with the group requiring a C-section.

CONCLUSION

 This is the first study evaluating the risk factors for C-section in low-risk multiparous women with a history of vaginal birth according to the Robson classification 3 and 4. Fetal distress and suspected fetal macrosomia constituted most of the C-section indications.

Fetal nondiabetic-macrosomia: risk factors for pregnancy adverse outcome and comparison of two growth curves in the prediction of cesarean section

BACKGROUND

Randomized trials reported no difference whether induction or expectant management is performed in non-diabetic women with large for gestational age babies but no tool has been validated for the prediction of high risk cases.

AIM

Assessing the performance of different growth curves in the prediction of complications.

METHODS

Data from 1066 consecutive non-diabetic women who delivered babies ≥4000 g were collected. Logistic regression analysis was used to analyze the impact of the maternal variables on: instrumental delivery, shoulder dystocia (SD), perineal tears, cesarean section (CS), and postpartum hemorrhage. Intergrowth21 curves and customized Gardosi's curves were compared in terms of prediction of adverse outcomes.

FINDINGS

Induction of labor was performed in 23.1% cases. The rate of CS was 17%. Hemorrhage, fetal distress, and SD occurred in 2%, 1.3%, and 2.7% of cases, respectively. Induction was significantly associated with instrumental delivery (p < .001), CS (p = .001), third and fourth degree perineal tears (p = .031), and post-partum hemorrhage (p = .02). The cutoff of 90th percentile according to Intergrowth21 did not show significant performance in predicting CS, while the same cutoff according to the Gardosi curves showed an OR 1.92 (CI 1.30-2.84) (p = .0009).

DISCUSSION

Gardosi curves showed a better performance in predicting the risk of CS versus Intergrowth curves. Induction is significantly associated with adverse outcome in non-diabetic women with LGA babies.

Are there specific factors associated with prenatally undiagnosed foetal macrosomia?

OBJECTIVE

Fetal macrosomia is known to increase maternal and neonatal complications, but 20%-50% of the macrosomic fetuses are prenatally undiagnosed. Our objective was to identify specific factors associated with undiagnosed fetal macrosomia in women without diabetes.

METHODS

Retrospective case-control study in a tertiary maternity unit between January 1st and December 31st, 2016. Inclusion of all women delivering after 37 weeks of a single live-born macrosomic infant, i.e., with a birth weight ≥ 90th percentile for gestational age (GA). Women with pre-existing or gestational diabetes were excluded. To identify specific factors associated with undiagnosed foetal macrosomia, we compared risk factors for macrosomia, maternal characteristics, father's body mass index (BMI) and prenatal follow up between two groups depending on whether macrosomia was prenatally diagnosed or not.

RESULTS

Among 428 macrosomic newborns, 224 (52.3 %) were prenatally undiagnosed. Known risk factors for macrosomia, maternal characteristics (such as low socio-economic level, low education level) and father's BMI were similar between the two groups. The prenatal follow up was comparable between the two groups. Ultrasound estimated foetal weight during the 3rd trimester was lower in the undiagnosed macrosomic foetuses compared to diagnosed macrosomic foetuses (2130±279 vs 2445±333, p<0.001).

CONCLUSIONS

No specific factor of undiagnosed macrosomia was identified, and women with prenatally undiagnosed fetal macrosomia had the same risk factors than women with diagnosed macrosomia. Our study suggests that our groups have different growth curves. This hypothesis has yet to be studied.

Does the Porter formula hold its promise? A weight estimation formula for macrosomic fetuses put to the test

Purpose

Estimating fetal weight using ultrasound measurements is an essential task in obstetrics departments. Most of the commonly used weight estimation formulas underestimate fetal weight when the actual birthweight exceeds 4000 g. Porter et al. published a specially designed formula in an attempt to improve detection rates for such macrosomic infants. In this study, we question the usefulness of the Porter formula in clinical practice and draw attention to some critical issues concerning the derivation of specialized formulas of this type.

Methods

A retrospective cohort study was carried out, including 4654 singleton pregnancies with a birthweight ≥ 3500 g, with ultrasound examinations performed within 14 days before delivery. Fetal weight estimations derived using the Porter and Hadlock formulas were compared.

Results

Of the macrosomic infants, 27.08% were identified by the Hadlock formula, with a false-positive rate of 4.60%. All macrosomic fetuses were detected using the Porter formula, with a false-positive rate of 100%; 99.96% of all weight estimations using the Porter formula fell within a range of 4300 g ± 10%. The Porter formula only provides macrosomic estimates.

Conclusions

The Porter formula does not succeed in distinguishing macrosomic from normal-weight fetuses. High-risk fetuses with a birthweight ≥ 4500 g in particular are not detected more precisely than with the Hadlock formula. For these reasons, we believe that the Porter formula should not be used in clinical practice. Newly derived weight estimation formulas for macrosomic fetuses must not be based solely on a macrosomic data set.

Electronic supplementary material

The online version of this article (10.1007/s00404-019-05410-7) contains supplementary material, which is available to authorized users.

Birth weight prediction models for the different gestational age stages in a Chinese population

The study aims to develop new birth weight prediction models for different gestational age stages using 2-dimensional (2D) ultrasound measurements in a Chinese population. 2D ultrasound was examined in pregnant women with normal singleton within 3 days prior to delivery (28–42 weeks’ gestation). A total of 19,310 fetuses were included in the study and randomly split into the training group and the validation group. Gestational age was divided into five stages: 28–30, 31–33, 34–36, 37–39 and 40–42 weeks. Multiple linear regression (MLR), fractional polynomial regression (FPR) and volume-based model (VM) were used to develop birth weight prediction model. New staged prediction models (VM for 28–36 weeks, MLR for 37–39 weeks, and FPR for 40–42 weeks) provided lower systematic errors and random errors than previously published models for each gestational age stage in the training group. The similar results were observed in the validation group. Compared to the previously published models, new staged models had the lowest aggregate systematic error (0.31%) and at least a 19.35% decrease; at least a 4.67% decrease for the root-mean-square error (RMSE). The prediction rates within 5% and 10% of birth weight for new staged models were higher than those for previously published models, which were 54.47% and 85.10%, respectively. New staged birth weight prediction models could improve the accuracy of birth weight estimation for different gestational age stages in a Chinese population.

Does prenatal identification of fetal macrosomia change management and outcome?

PURPOSE

To assess whether there is an association between predicted fetal macrosomia and adverse outcomes in macrosomic newborns (> 4000 g), based on a sonographic evaluation up to 2 weeks prior to delivery.

METHODS

A retrospective cohort study of 3098 mothers of macrosomic babies who were delivered at our institution (2000-2015). We compared the management and outcomes of women with predicted fetal macrosomia with that of women with unknown fetal macrosomia. The primary outcomes were cesarean section (CS) rate and postpartum hemorrhage. Secondary outcomes were composite maternal and neonatal outcomes and birth injuries.

RESULTS

In 601 (19.4%) women fetal macrosomia was predicted, and in 2497 (80.6%) women, fetal macrosomia was unknown. CS rate was more than 3.5 times higher in the group of predicted macrosomia (47.2% vs. 12.7%, P < 0.001) than those with unpredicted macrosomia; not only due to non-progressive labor, but for non-reassuring heart rate as well. However, predicted fetal macrosomia reduced the risk of postpartum hemorrhage (aOR 0.5, 95% CI 0.2-1.0), maternal (aOR 0.3, 95% CI 0.2-0.5) and neonatal composite adverse outcomes (aOR 0.7 95% CI 0.6-0.9). It was also associated with increased risk for induction of labor, episiotomy, 3rd- or 4th-degree tears and a longer maternal hospitalization. Birth injuries and shoulder dystocia were not different between the groups.

CONCLUSIONS

Antepartum CS was found to be associated with predicted fetal macrosomia. Moreover, a planned CS due to macrosomia was associated with reduced risk for postpartum hemorrhage, maternal and neonatal outcome, even for babies with a mean birth weight < 4500 g.

Disadvantages of a weight estimation formula for macrosomic fetuses: the Hart formula from a clinical perspective

Purpose

Sonographic fetal weight (FW) estimation to detect macrosomic fetuses is an essential part of everyday routine work in obstetrics departments. Most of the commonly used weight estimation formulas underestimate FW when the actual birth weight (BW) exceeds 4000 g. One of the best-established weight estimation formulas is the Hadlock formula. In an effort to improve the detection rates of macrosomic infants, Hart et al. published a specially designed formula including maternal weight at booking. The usefulness of the Hart formula was tested.

Methods

Retrospective study of 3304 singleton pregnancies, birth weight ≥ 3500 g. The accuracy of the Hadlock and Hart formula were tested. A subgroup analysis examined the influence of the maternal weight. The Chi-squared test and one-way analysis of variation were carried out. For all analyses, p < 0.05 was considered statistically significant.

Results

The overall percentages of births falling within ± 5% and ± 10% of the BW using the Hadlock formula were 27% and 53%, respectively. Using the Hart formula, 24% and 54% were identified within these levels. With the Hart formula, 94% of all weight estimations fall within 4200 g ± 5% and nearly 100% fall within 4200 g ± 10%.

Conclusions

Applying the Hart formula results in an overestimation of fetal weight in neonates with a birth weight < 4000 g and fails to identify high-risk fetuses. We, therefore, do not consider Hart’s formula to be of clinical relevance.

Neonatal Morbidity of Small- and Large-for-Gestational-Age Neonates Born at Term in Uncomplicated Pregnancies

OBJECTIVE

To compare morbidity among small-for-gestational-age (SGA; birth weight less than the 10th percentile for gestational age), appropriate-for-gestational-age (AGA; birth weight 10th to 90th percentile; reference group), and large-for-gestational-age (LGA; birth weight greater than the 90th percentile) neonates in apparently uncomplicated pregnancies at term (37 weeks of gestation or greater).

METHODS

This secondary analysis, derived from an observational obstetric cohort of 115,502 deliveries, included women with apparently uncomplicated pregnancies of nonanomalous singletons who had confirmatory ultrasound dating no later than the second trimester and who delivered between 37 0/7 and 42 6/7 weeks of gestation. We used two different composite neonatal morbidity outcomes: hypoxic composite neonatal morbidity for SGA and traumatic composite neonatal morbidity for LGA neonates. Log Poisson relative risks (RRs) with 95% CIs adjusted for potential confounding factors (nulliparity, body mass index, insurance status, and neonatal sex) were calculated.

RESULTS

Among the 63,436 women who met our inclusion criteria, SGA occurred in 7.9% (n=4,983) and LGA in 8.3% (n=5,253). Hypoxic composite neonatal morbidity was significantly higher in SGA (1.1%) compared with AGA (0.7%; adjusted RR 1.44, 95% CI 1.07-1.93) but similar between LGA (0.6%) and AGA (adjusted RR 0.84, 95% CI 0.58-1.22). Traumatic composite neonatal morbidity was significantly higher in LGA (1.9%) than AGA (1.0%; adjusted RR 1.88, 95% CI 1.51-2.34) but similar in SGA (1.3%) compared with AGA (adjusted RR 1.28, 95% CI 0.98-1.67).

CONCLUSION

Among women with uncomplicated pregnancies, hypoxic composite neonatal morbidity is more common with SGA neonates and traumatic-composite neonatal morbidity is more common with LGA neonates.

Association of Recorded Estimated Fetal Weight and Cesarean Delivery in Attempted Vaginal Delivery at Term

OBJECTIVE

To evaluate the association between documentation of estimated fetal weight, and its value, with cesarean delivery.

METHODS

This was a secondary analysis of a multicenter observational cohort of 115,502 deliveries from 2008 to 2011. Data were abstracted by trained and certified study personnel. We included women at 37 weeks of gestation or greater attempting vaginal delivery with live, nonanomalous, singleton, vertex fetuses and no history of cesarean delivery. Rates and odds ratios (ORs) were calculated for women with ultrasonography or clinical estimated fetal weight compared with women without documentation of estimated fetal weight. Further subgroup analyses were performed for estimated fetal weight categories (less than 3,500, 3,500-3,999, and 4,000 g or greater) stratified by diabetic status. Multivariable analyses were performed to adjust for important potential confounding variables.

RESULTS

We included 64,030 women. Cesarean delivery rates were 18.5% in the ultrasound estimated fetal weight group, 13.4% in the clinical estimated fetal weight group, and 11.7% in the no documented estimated fetal weight group (P<.001). After adjustment (including for birth weight), the adjusted OR of cesarean delivery was 1.44 (95% confidence interval [CI] 1.31-1.58, P<.001) for women with ultrasound estimated fetal weight and 1.08 for clinical estimated fetal weight (95% CI 1.01-1.15, P=.017) compared with women with no documented estimated fetal weight (referent). The highest estimates of fetal weight conveyed the greatest odds of cesarean delivery. When ultrasound estimated fetal weight was 4,000 g or greater, the adjusted OR was 2.15 (95% CI 1.55-2.98, P<.001) in women without diabetes and 9.00 (95% CI 3.65-22.17, P<.001) in women with diabetes compared to those with estimated fetal weight less than 3,500 g.

CONCLUSION

In this contemporary cohort of women attempting vaginal delivery at term, documentation of estimated fetal weight (obtained clinically or, particularly, by ultrasonography) was associated with increased odds of cesarean delivery. This relationship was strongest at higher fetal weight estimates, even after controlling for the effects of birth weight and other factors associated with increased cesarean delivery risk.

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.

Induction of labour at or near term for suspected fetal macrosomia

EDITORIAL NOTE

It has been brought to the authors' attention that there may be an error in the data (Analysis 1.9). This is currently under investigation, and a correction will be made if the data are found to be incorrect. Details can be found in the comments.

BACKGROUND

Women with a suspected large-for-dates fetus or a fetus with suspected macrosomia (birthweight greater than 4000 g) are at risk of operative birth or caesarean section. The baby is also at increased risk of shoulder dystocia and trauma, in particular fractures and brachial plexus injury. Induction of labour may reduce these risks by decreasing the birthweight, but may also lead to longer labours and an increased risk of caesarean section.

OBJECTIVES

To assess the effects of a policy of labour induction at or shortly before term (37 to 40 weeks) for suspected fetal macrosomia on the way of giving birth and maternal or perinatal morbidity.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2016), contacted trial authors and searched reference lists of retrieved studies.

SELECTION CRITERIA

Randomised trials of induction of labour for suspected fetal macrosomia.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We contacted study authors for additional information. For key outcomes the quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We included four trials, involving 1190 women. It was not possible to blind women and staff to the intervention, but for other 'Risk of bias' domains these studies were assessed as being at low or unclear risk of bias.Compared to expectant management, there was no clear effect of induction of labour for suspected macrosomia on the risk of caesarean section (risk ratio (RR) 0.91, 95% confidence interval (CI) 0.76 to 1.09; 1190 women; four trials, moderate-quality evidence) or instrumental delivery (RR 0.86, 95% CI 0.65 to 1.13; 1190 women; four trials, low-quality evidence). Shoulder dystocia (RR 0.60, 95% CI 0.37 to 0.98; 1190 women; four trials, moderate-quality evidence), and fracture (any) (RR 0.20, 95% CI 0.05 to 0.79; 1190 women; four studies, high-quality evidence) were reduced in the induction of labour group. There were no clear differences between groups for brachial plexus injury (two events were reported in the control group in one trial, low-quality evidence). There was no strong evidence of any difference between groups for measures of neonatal asphyxia; low five-minute infant Apgar scores (less than seven) or low arterial cord blood pH (RR 1.51, 95% CI 0.25 to 9.02; 858 infants; two trials, low-quality evidence; and, RR 1.01, 95% CI 0.46 to 2.22; 818 infants; one trial, moderate-quality evidence, respectively). Mean birthweight was lower in the induction group, but there was considerable heterogeneity between studies for this outcome (mean difference (MD) -178.03 g, 95% CI -315.26 to -40.81; 1190 infants; four studies; I(2) = 89%). In one study with data for 818 women, third- and fourth-degree perineal tears were increased in the induction group (RR 3.70, 95% CI 1.04 to 13.17).For outcomes assessed using GRADE, we based our downgrading decisions on high risk of bias from lack of blinding and imprecision of effect estimates.

AUTHORS' CONCLUSIONS

Induction of labour for suspected fetal macrosomia has not been shown to alter the risk of brachial plexus injury, but the power of the included studies to show a difference for such a rare event is limited. Also antenatal estimates of fetal weight are often inaccurate so many women may be worried unnecessarily, and many inductions may not be needed. Nevertheless, induction of labour for suspected fetal macrosomia results in a lower mean birthweight, and fewer birth fractures and shoulder dystocia. The unexpected observation in the induction group of increased perineal damage, and the plausible, but of uncertain significance, observation of increased use of phototherapy, both in the largest trial, should also be kept in mind.Findings from trials included in the review suggest that to prevent one fracture it would be necessary to induce labour in 60 women. Since induction of labour does not appear to alter the rate of caesarean delivery or instrumental delivery, it is likely to be popular with many women. In settings where obstetricians can be reasonably confident about their scan assessment of fetal weight, the advantages and disadvantages of induction at or near term for fetuses suspected of being macrosomic should be discussed with parents.Although some parents and doctors may feel the evidence already justifies induction, others may justifiably disagree. Further trials of induction shortly before term for suspected fetal macrosomia are needed. Such trials should concentrate on refining the optimum gestation of induction, and improving the accuracy of the diagnosis of macrosomia.

Routine ultrasound in late pregnancy (after 24 weeks' gestation)

BACKGROUND

Diagnostic ultrasound is used selectively in late pregnancy where there are specific clinical indications. However, the value of routine late pregnancy ultrasound screening in unselected populations is controversial. The rationale for such screening would be the detection of clinical conditions which place the fetus or mother at high risk, which would not necessarily have been detected by other means such as clinical examination, and for which subsequent management would improve perinatal outcome.

OBJECTIVES

To assess the effects on obstetric practice and pregnancy outcome of routine late pregnancy ultrasound, defined as greater than 24 weeks' gestation, in women with either unselected or low-risk pregnancies.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2015) and reference lists of retrieved studies.

SELECTION CRITERIA

All acceptably controlled trials of routine ultrasound in late pregnancy (defined as after 24 weeks).

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy.

MAIN RESULTS

Thirteen trials recruiting 34,980 women were included in the systematic review. Risk of bias was low for allocation concealment and selective reporting, unclear for random sequence generation and incomplete outcome data and high for blinding of both outcome assessment and participants and personnel. There was no difference in antenatal, obstetric and neonatal outcome or morbidity in screened versus control groups. Routine late pregnancy ultrasound was not associated with improvements in overall perinatal mortality. There is little information on long-term substantive outcomes such as neurodevelopment. There is a lack of data on maternal psychological effects.Overall, the evidence for the primary outcomes of perinatal mortality, preterm birth less than 37 weeks, induction of labour and caesarean section were assessed to be of moderate or high quality with GRADE software. There was no association between ultrasound in late pregnancy and perinatal mortality (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.67 to 1.54; participants = 30,675; studies = eight; I² = 29%), preterm birth less than 37 weeks (RR 0.96, 95% CI 0.85 to 1.08; participants = 17,151; studies = two; I² = 0%), induction of labour (RR 0.93, 95% CI 0.81 to 1.07; participants = 22,663; studies = six; I² = 78%), or caesarean section (RR 1.03, 95% CI 0.92 to 1.15; participants = 27,461; studies = six; I² = 54%). Three additional primary outcomes chosen for the 'Summary of findings' table were preterm birth less than 34 weeks, maternal psychological effects and neurodevelopment at age two. Because none of the included studies reported these outcomes, they were not assessed for quality with GRADE software.

AUTHORS' CONCLUSIONS

Based on existing evidence, routine late pregnancy ultrasound in low-risk or unselected populations does not confer benefit on mother or baby. There was no difference in the primary outcomes of perinatal mortality, preterm birth less than 37 weeks, caesarean section rates, and induction of labour rates if ultrasound in late pregnancy was performed routinely versus not performed routinely. Meanwhile, data were lacking for the other primary outcomes: preterm birth less than 34 weeks, maternal psychological effects, and neurodevelopment at age two, reflecting a paucity of research covering these outcomes. These outcomes may warrant future research.

Are there modifiable risk factors that may predict the occurrence of brachial plexus injury?

OBJECTIVE

To identify risk factors, particularly modifiable, associated with brachial plexus injury.

STUDY DESIGN

A retrospective case-control study conducted at a single hospital between the years 1993 and 2012. All neonates who were diagnosed of brachial plexus injury were included. A control group matched at a ratio of 1:2 was randomly selected. Demographic and obstetric data were obtained from the hospital discharge register with ICD-9 codes and crosschecked with the labor medical records. All medical files were manually checked and validated. A stepwise logistic regression model was performed to identify independent predictors for brachial plexus injury before delivery among those found significant in the univariate analysis.

RESULTS

Of all 83 806 deliveries that took place during this period, 144 cases of brachial plexus injury were identified (1.7/1000 deliveries). Overall, 142 cases and 286 controls had available data. Among the study group, 41 (28.9%) had documented shoulder dystocia compared with 1 (0.4%) among the controls (P<0.0001). Logistic regression analysis revealed that maternal age above 35 years (P=0.01; odds ratio (OR) 2.7; 95% confidence interval (CI) 1.3 to 5.7), estimated fetal weight before delivery (P<0.0001; OR 2.5; 95% CI 1.7 to 3.8, for each 500 g increase), vaginal birth after cesarean (P=0.02; OR 3.3; 95% CI 1.2 to 8.8) and vacuum extraction (P=0.02; OR 3.6; 95% CI 1.2 to 10.3) were all found to be independent predictors for developing brachial plexus injury. When stratifying the analysis according to parity, vacuum delivery was found to be an independent risk factor only among primiparous women (OR 6.0; 95% CI 1.7 to 21.6).

CONCLUSIONS

The findings suggest that very few factors contributing to brachial plexus injury are modifiable. For that reason, it remains an unpredictable and probably an unavoidable event.

Does induction of labor for constitutionally large-for-gestational-age fetuses identified in utero reduce maternal morbidity?

BACKGROUND

The number of infants with a birth weight > 97th percentile for gestational age has increased over the years. Although some studies have examined the interest of inducing labor for fetuses with macrosomia suspected in utero, only a few have analyzed this suspected macrosomia according to estimated weight at each gestational age. Most studies have focused principally on neonatal rather than on maternal (and still less on perineal) outcomes. The principal aim of this study was to assess whether a policy of induction of labor for women with a constitutionally large-for-gestational-age fetus might reduce the occurrence of severe perineal tears; the secondary aims of this work were to assess whether this policy would reduce either recourse to cesarean delivery during labor or neonatal complications.

METHODS

This historical cohort study (n = 3077) analyzed records from a French perinatal database. Women without diabetes and with a cephalic singleton term pregnancy were eligible for the study. We excluded medically indicated terminations of pregnancy and in utero fetal deaths. Among the pregnancies with fetuses suspected, before birth, of being large-for-gestational-age, we compared those for whom labor was induced from ≥ 37 weeks to ≤ 38 weeks+ 6 days (n = 199) to those with expectant obstetrical management (n = 2878). In this intention-to-treat analysis, results were expressed as crude and adjusted relative risks.

RESULTS

The mean birth weight was 4012 g ± 421 g. The rate of perineal lesions did not differ between the two groups in either primiparas (aRR: 1.06; 95% CI: 0.86-1.31) or multiparas (aRR: 0.94; 95% CI: 0.84-1.05). Similarly, neither the cesarean rate (aRR: 1.11; 95% CI: 0.82-1.50) nor the risks of resuscitation in the delivery room or of death in the delivery room or in the immediate postpartum or of neonatal transfer to the NICU (aRR = 0.94; 95% CI: 0.59-1.50) differed between the two groups.

CONCLUSIONS

A policy of induction of labor for women with a constitutionally large-for-gestational-age fetus among women without diabetes does not reduce maternal morbidity.

Precipitous and difficult deliveries

Any delivery in the emergency department is considered a precipitous birth and is an anxiety-producing event. Many deliveries proceed without incident. However, the emergency physician must be prepared for several dreaded scenarios, such as nuchal cord, shoulder dystocia, and breech birth. This article reviews the basics, complications, and management of such deliveries.

Estimated fetal weight by ultrasound: a modifiable risk factor for cesarean delivery?

OBJECTIVE

The purpose of this study was to investigate whether knowledge of ultrasound-obtained estimated fetal weight (US-EFW) is a risk factor for cesarean delivery (CD).

STUDY DESIGN

Retrospective cohort from a single center in 2009-2010 of singleton, term live births. CD rates were compared for women with and without US-EFW within 1 month of delivery and adjusted for potential confounders.

RESULTS

Of the 2329 women in our cohort, 50.2% had US-EFW within 1 month of delivery. CD was significantly more common for women with US-EFW (15.7% vs 10.2%; P < .001); after we controlled for confounders, US-EFW remained an independent risk factor for CD (odds ratio, 1.44; 95% confidence interval, 1.1-1.9). The risk increased when US-EFW was >3500 g (odds ratio, 1.8; 95% confidence interval, 1.3-2.7).

CONCLUSION

Knowledge of US-EFW, above and beyond the impact of fetal size itself, increases the risk of CD. Acquisition of US-EFW near term appears to be an independent and potentially modifiable risk factor for CD.

Failed induction of labor: strategies to improve the success rates

The rates of induction of labor (IOL) are rising all over the world. In developed countries, one of every 4 babies is born after IOL at term. The recent World Health Organization guidelines on IOL recommend that failure of induction does not necessitate cesarean delivery [WHO recommendations for induction of labor. World Health Organization, 2011]. These guidelines come when there are concerns that failed primary inductions in nulliparous women, which have led to escalation of the cesarean delivery rates. Obstetricians must recognize the risks associated with IOL (including failure and need for cesarean delivery) and avoid inductions for borderline indications, which are not evidence based. The issue of "failed induction of labor" is topical, and there is a need to define this entity and offer alternatives to cesarean delivery in the management of this group of women. Research is required to develop a test to accurately identify those fetuses most at risk of morbidity or stillbirth who would truly benefit from an early IOL and assess the cost-effectiveness of policies of routine IOL. In this review, we summarized the current recommendations for best practice in the area of IOL, defined "failed induction," and described options to improve the success rate after "failed primary induction of labor."

TARGET AUDIENCE

Obstetricians & Gynecologists and Family Physicians.

LEARNING OBJECTIVES

After the completing the CME activity, physicians should be better able to classify the factors determining success or failure of induction of labor, counsel women about risks and benefits of various methods of induction of labor, and compare the options of management available after failed primary induction of labor.

A scoring system for detection of macrosomia and prediction of shoulder dystocia: A disappointment

OBJECTIVE

To develop a scoring system for the detection of a macrosomic fetus (birth weight (BW) >or= 4000 g) and predict shoulder dystocia among large for gestational age fetuses.

STUDY DESIGN

We retrospectively identified all singletons with accurate gestational age (GA) that were large for GA (abdominal circumference (AC) or estimated fetal weight (EFW) >or= 90% for GA) at >or=37 weeks with delivery within three weeks. The scoring system was: 2 points for biparietal diameter, head circumference, AC, or femur length >or=90% for GA, or if the amniotic fluid index (AFI) was >or=24 cm; for biometric parameters <90% or with AFI <24 cm, 0 points. The predictive values for detection of shoulder dystocia were calculated.

RESULTS

Of the 225 cohorts that met the inclusion criteria the rate of macrosomia was 39% and among vaginal deliveries (n = 120) shoulder dystocia occurred in 12% (15/120; 95% confidence interval (CI) 7-20%). The sensitivity of EFW >or=4500 g to identify a newborn with shoulder dystocia was 0% (95% CI 0-21%), positive predictive values 0% (95% CI 0-46%), and likelihood ratio of 0. For a macrosomia score >6, the corresponding values were 20% (4-48%), 25% (5-57%) and 2.3.

CONCLUSION

Though the scoring system can identify macrosomia, it offers no advantage over EFW. The scoring system and EFW are poor predictors of shoulder dystocia.

Fetal macrosomia in non-diabetic mothers: antenatal diagnosis and delivery outcome

This is a retrospective study of 74 non-diabetic women that delivered babies in excess of 4,500 g. The women were divided into two groups, depending on whether there had been suspected macrosomia antenatally or not. Mode of delivery and rates of induction of labour were examined. Women diagnosed with a macrosomic fetus were more likely to have elective caesarean sections or premature induction of labour. Those women in whom macrosomia was not suspected had higher rates of vaginal deliveries without any increase in neonatal morbidity.

Routine ultrasound in late pregnancy (after 24 weeks' gestation)

BACKGROUND

Diagnostic ultrasound is used selectively in late pregnancy where there are specific clinical indications. However, the value of routine late pregnancy ultrasound screening in unselected populations is controversial. The rationale for such screening would be the detection of clinical conditions which place the fetus or mother at high risk, which would not necessarily have been detected by other means such as clinical examination, and for which subsequent management would improve perinatal outcome.

OBJECTIVES

To assess the effects on obstetric practice and pregnancy outcome of routine late pregnancy ultrasound, defined as greater than 24 weeks' gestation, in women with either unselected or low-risk pregnancies.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (February 2008).

SELECTION CRITERIA

All acceptably controlled trials of routine ultrasound in late pregnancy (defined as after 24 weeks).

DATA COLLECTION AND ANALYSIS

All three review authors were involved in assessing trial quality and data extraction.

MAIN RESULTS

Eight trials recruiting 27,024 women were included. The quality of trials overall was satisfactory. There was no difference in antenatal, obstetric and neonatal intervention or morbidity in screened versus control groups. There was a slightly higher caesarean section rate in the screened group, but this difference did not reach statistical significance. Routine late pregnancy ultrasound was not associated with improvements in overall perinatal mortality. Placental grading as an adjunct to third trimester examination scan was associated with a significant reduction in the stillbirth rate in the one trial that assessed it. There is little information on long-term substantive outcomes such as neurodevelopment. There is a lack of data on maternal psychological effects.

AUTHORS' CONCLUSIONS

Based on existing evidence, routine late pregnancy ultrasound in low-risk or unselected populations does not confer benefit on mother or baby. It may be associated with a small increase in caesarean section rates. There is a lack of data about the potential psychological effects of routine ultrasound in late pregnancy, and limited data about its effects on both short- and long-term neonatal and childhood outcome. Placental grading in the third trimester may be valuable, but whether reported results are reproducible remains to be seen, and future research of late pregnancy ultrasound should include evaluation of placental textural assessment.

WITHDRAWN: Routine ultrasound in late pregnancy (after 24 weeks' gestation)

BACKGROUND

Diagnostic ultrasound is used selectively in late pregnancy where there are specific clinical indications. However, the value of routine late pregnancy ultrasound screening in unselected populations is controversial. The rationale for such screening would be the detection of clinical conditions which place the fetus or mother at high risk, which would not necessarily have been detected by other means such as clinical examination, and for which subsequent management would improve perinatal outcome.

OBJECTIVES

To assess the effects on obstetric practice and pregnancy outcome of routine late pregnancy ultrasound, defined as greater than 24 weeks gestation, in women with either unselected or low risk pregnancies.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group Specialised Register of Controlled Trials and the Cochrane Controlled Trials Register were searched.

SELECTION CRITERIA

All acceptably controlled trials of routine ultrasound in late pregnancy (defined as after 24 weeks).

DATA COLLECTION AND ANALYSIS

The principal reviewer assessed trial quality and extracted data, under supervision of the co-reviewer.

MAIN RESULTS

Seven trials recruiting 25,036 women were included. The quality of trials overall was satisfactory. There was no difference in antenatal, obstetric and neonatal intervention or morbidity in screened versus control groups. Routine late pregnancy ultrasound was not associated with improvements in overall perinatal mortality. Placental grading as an adjunct to third trimester examination scan was associated with a significant reduction in the stillbirth rate in the one trial that assessed it. There is a lack of data with regard to long term substantive outcomes such as neurodevelopment. There is a lack of data on maternal psychological effects.

AUTHORS' CONCLUSIONS

Based on existing evidence, routine late pregnancy ultrasound in low risk or unselected populations does not confer benefit on mother or baby. There is a lack of data about the potential psychological effects of routine ultrasound in late pregnancy, and the effects on both short and long term neonatal and childhood outcome. Placental grading in the third trimester may be valuable, but whether reported results are reproducible remains to be seen, and future research of late pregnancy ultrasound should include evaluation of placental textural assessment.

Prévention de la dystocie des épaules par la sélection échographique en début de travail des fœtus à fort périmètre abdominal

OBJECTIVE

Prevent shoulder dystocia occuring with macrosomic foetuses, by an ultrasound screening, at the beginning of labour, made by a member of obstetrics staff.

MATERIAL AND METHOD

A prospective study in the maternity hospital, la Mère et l'Enfant of University Teaching Hospital, Besançon, about 170 patients. We have measured only one parameter: the foetal abdominal circumference (AC).

RESULTS

An AC>or=350 mm had a sensitivity of 100% to detect newborns of birth weight>or=4250 g.

CONCLUSION

An AC>or=350 mm measured during labour by a member of obstetrics staff allow to alert and to make the staff sensitive to a risk of macrosomia and shoulder dystocia.

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.

Shoulder dystocia: the unpreventable obstetric emergency with empiric management guidelines

OBJECTIVE

Much of our understanding and knowledge of shoulder dystocia has been blurred by inconsistent and scientific studies that are of limited scientific quality. In an evidence-based format, we sought to answer the following questions: (1) Is shoulder dystocia predictable? (2) Can shoulder dystocia be prevented? (3) When shoulder dystocia does occur, what maneuvers should be performed? and (4) What are the sequelae of shoulder dystocia?

STUDY DESIGN

Electronic databases, including PUBMED and the Cochrane Database, were searched using the key word "shoulder dystocia." We also performed a manual review of articles included in the bibliographies of these selected articles to further define articles for review. Only those articles published in the English language were eligible for inclusion.

RESULTS

There is a significantly increased risk of shoulder dystocia as birth weight linearly increases. From a prospective point of view, however, prepregnancy and antepartum risk factors have exceedingly poor predictive value for the prediction of shoulder dystocia. Late pregnancy ultrasound likewise displays low sensitivity, decreasing accuracy with increasing birth weight, and an overall tendency to overestimate the birth weight. Induction of labor for suspected fetal macrosomia has not been shown to alter the incidence of shoulder dystocia among nondiabetic patients. The concept of prophylactic cesarean delivery as a means to prevent shoulder dystocia and therefore avoid brachial plexus injury has not been supported by either clinical or theoretic data. Although many maneuvers have been described for the successful alleviation of shoulder dystocia, there have been no randomized controlled trials or laboratory experiments that have directly compared these techniques. Despite the introduction of ancillary obstetric maneuvers, such as McRoberts maneuver and a generalized trend towards the avoidance of fundal pressure, it has been shown that the rate of shoulder-dystocia associated brachial plexus palsy has not decreased. The simple occurrence of a shoulder dystocia event before any iatrogenic intervention may be associated with brachial plexus injury.

CONCLUSION

For many years, long-standing opinions based solely on empiric reasoning have dictated our understanding of the detailed aspects of shoulder dystocia prevention and management. Despite its infrequent occurrence, all healthcare providers attending pregnancies must be prepared to handle vaginal deliveries complicated by shoulder dystocia.

Determining factors associated with shoulder dystocia: a population-based study

OBJECTIVE

The study was aimed to define obstetric factors associated with shoulder dystocia.

METHODS

A population-based study comparing all singleton, vertex, term deliveries with shoulder dystocia with deliveries without shoulder dystocia was performed. Statistical analysis was done using multiple logistic regression analysis.

RESULTS

Shoulder dystocia complicated 0.2% (n = 245) of all deliveries included in the study (n = 107965). Independent risk factors for shoulder dystocia in a multivariable analysis were birth-weight > or =4000 g (OR = 24.3; 95% CI 18.5-31.8), vacuum delivery (OR = 5.7, 95% CI 3.4-9.5), diabetes mellitus (OR = 1.7, 95% CI 1.2-2.5) and lack of prenatal care (OR = 1.5, 95% CI 1.1-2.3). A significant linear association was found between birth-weight and shoulder dystocia, using the Mantel-Haenszel procedure. Pregnancies complicated with shoulder dystocia had higher rates of third-degree perineal tears as compared to the comparison group (0.8% versus 0.1%; P < 0.001). Similarly, perinatal mortality was higher among newborns delivered after shoulder dystocia as compared to the comparison group (3.7% versus 0.5%; OR = 7.4, 95% CI 3.5-14.9, P < 0.001). In addition, these newborns had higher rates of Apgar scores lower than 7 at 1 and 5 min as compared to newborns delivered without shoulder dystocia (29.7% versus 3.0%; OR = 13.8, 95% CI 10.3-18.4, P < 0.001 and 2.1% versus 0.3%; OR = 7.2, 95% CI 2.8-18.1, P < 0.001, respectively). Combining risk factors such as large for gestational age, diabetes mellitus and vacuum delivery increased the risk for shoulder dystocia to 6.8% (OR = 32.6, 95% CI 10.1-105.8, P < 0.001).

CONCLUSIONS

Independent factors associated with shoulder dystocia were birth-weight > or =4000 g, vacuum delivery, diabetes mellitus and lack of prenatal care.

Predicting operative delivery

OBJECTIVE

Unplanned operative delivery (vaginal or abdominal) is associated with maternal anxiety, maternal and neonatal morbidity and increased resource use. We aimed to identify potential predictors for emergency operative delivery.

METHODS

This was a prospective observational study of 202 nulliparous women in a tertiary antenatal unit between 36 and 40 weeks' gestation. The assessment included an interview, a vaginal examination for Bishop score (optional), and a translabial ultrasound examination performed with the woman in a supine position and after voiding to determine cervical length, bladder position on Valsalva, and fetal head engagement. Clinical data were obtained from the institutional obstetric database and patient records.

RESULTS

In the late third trimester, body mass index (P = 0.016), maternal age at due date (P < 0.0001), history of Cesarean section in first-degree relatives (P = 0.009), Bishop score (P = 0.0004), cervical length (P = 0.001), bladder position on Valsalva (P = 0.003) and head engagement (P < 0.0001) were significantly associated with delivery mode. On multivariate logistic regression analysis, the best model for predicting normal vaginal delivery contained maternal age, history of Cesarean section, Bishop score and bladder position on Valsalva and had excellent ability to discriminate between normal vaginal delivery and operative delivery (c = 0.85). The model with the best ability to discriminate between vaginal delivery and Cesarean section contained the same parameters plus body mass index; this model performed even better (c = 0.87).

CONCLUSIONS

Identification of women at increased risk of operative delivery appears feasible. A combination of clinical and ultrasound variables yielded a model that is likely to predict delivery mode accurately in up to 87% of cases. Such a model may become useful as an entry criterion for intervention trials in women at low or very high risk of operative delivery.

Outcome of Second Delivery After Prior Macrosomic Infant in Women With Normal Glucose Tolerance

OBJECTIVE

Our aim was to estimate the obstetric outcome of second delivery in women with normal glucose tolerance whose first fetus was macrosomic (fetal weight >/= 4,500 g).

METHODS

Primiparas delivering a macrosomic infant during the years 1997-2000 were identified from a hospital computer database, and the obstetric outcome of a second delivery was analyzed up until June 2003. A control group (birth weight 3,000-3,500 g) served for comparison.

RESULTS

Among 13,020 first pregnancies, 301 (2.3%) were macrosomic. A similar proportion in the macrosomic group, 156 of 301 (52%), and control group, 171 of 300 (57%), returned for second delivery (P = .252). Compared with controls, first macrosomic deliveries were characterized by higher rates of operative delivery, anal sphincter injury, and shoulder dystocia. At second delivery, 32% of neonates in the macrosomic group and 0.3% in the control group weighed 4,500 g or more (P < .001). More prelabor cesareans were performed in the macrosomic group compared with controls (27 of 156, 17.3%, compared with 8 of 171, 4.7%; P < .001). Among 104 women in the macrosomic group who labored after first vaginal delivery, 99% (103 of 104) delivered vaginally again compared with 44% (11 of 25) who labored after primiparous cesarean delivery (P < .001), which compares with 97% (146 of 150) and 77% (10 of 13), respectively, in the control group.

CONCLUSION

Despite a one-third recurrence of macrosomia, first vaginal delivery of a macrosomic infant was associated with a high incidence of second vaginal delivery. Conversely, primiparous macrosomic cesarean delivery conveyed a high risk (56%) for repeat intrapartum cesarean whether macrosomia recurred or not.

LEVEL OF EVIDENCE

II-2.

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.

Relationship between cerebroplacental Doppler ratio and birth weight in postdates pregnancies

OBJECTIVES

To explore the relationship between cerebroplacental Doppler impedance index and birth weight in postdates pregnancies, and to evaluate the use of a combination of Doppler parameters and ultrasound biometry in the prediction of large-for-gestational age (LGA) fetuses at 41 weeks of gestation.

METHODS

The pulsatility indices of the umbilical (UA-PI) and middle cerebral (MCA-PI) arteries, the cerebroplacental pulsatility index ratio (CPR) and the estimated fetal weight (EFW) were obtained in a cohort of 181 ultrasound-dated pregnancies at 41 weeks' gestation, 2 days before induction of delivery. A regression equation was established and the correlation between umbilical artery impedance and different birth-weight centile groups was determined. A receiver-operating characteristics (ROC) curve was used to compare prediction of LGA fetuses using biometry alone with that using biometry and UA-PI.

RESULTS

UA-PI was inversely related to EFW (Spearson's correlation coefficient rho = -0.28, P < 0.001). Logistic regression showed an independent contribution of UA-PI to the birth-weight estimation (birth weight = 1356.8 - 232.0 x UA-PI + 0.65 x EFW). On ROC curve analysis, the prediction of LGA with the regression equation was comparable to that using ultrasound biometry alone.

CONCLUSION

UA-PI was inversely correlated to EFW, but the combination of ultrasound biometry and UA-PI compared with biometry alone showed similar prediction of LGA fetuses in postdates pregnancies. Further prospective trials on larger populations or groups with a higher prevalence of LGA fetuses would be needed to validate the use of the new formula.

Will there ever be an end to the Caesarean section rate debate?

Caesarean section rates continue to rise. To date, no serious attempt has been made to address this issue. There are no scientific grounds for identifying an 'appropriate' level for Caesarean section rates. A 'Term Cephalic Trial' may provide such information, but poses major logistic and ethical challenges. The authors propose that a combination of known and newly developed predictors of emergency operative delivery may allow an antenatal risk assessment that could make intervention trials both ethically sound and logistically feasible.

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.

Clinical and ultrasonographic weight estimation in large for gestational age fetus

OBJECTIVE

To examine prospectively the effect on pregnancy outcome of a management protocol, that adds ultrasonographic weight estimation in fetuses suspected clinically as large.

STUDY DESIGN

Prospective follow up study of all singleton deliveries during a 1 year period. All patients underwent routine clinical estimation of fetal weight. When clinical estimation of fetal weight was > or = 3700 g, patients were referred for ultrasonographic estimation of fetal weight. When the latter was > or = 4000 g the patient was informed about the risks of birth trauma. Cesarean section was recommended only when > or = 4500 g. Ultrasonography was repeated every 4 days when possible. Predictive values of clinical and ultrasonographic estimations of fetal weight for diagnosing macrosomia, defined for the purpose of this study as 4000 g or more, and their effect on the rate of cesarean sections.

RESULTS

Five hundred fifty-five (14.4%) out of 3844 singletons were estimated as 3700 g or more. Only 315 fetuses had ultrasonographic estimation of weight within 3 days of delivery. The sensitivity of clinical and ultrasonographic prediction of macrosomia was 68 and 58%, respectively. Cesarean section rate in newborns weighing 4000 g or more was 22% when macrosomia was clinically suspected compared to 11% when it was not (P<0.05). In fetuses estimated ultrasonographically as 4000 g or larger the cesarean section rate was doubled (50.7% versus 24.9%, P<0.05) compared to those estimated as smaller than 4000 g, although actual weight of 4500 g or more was recorded in 10.6 and 8.5% of these groups, respectively. There were no cases of shoulder dystocia in macrosomic babies when macrosomia was not detected by ultrasound compared to two cases of shoulder dystocia (2.7%) when macrosomia was detected by ultrasound.

CONCLUSION

Antenatal suspicion of macrosomia increased the cesarean section rate while the associated improvement in pregnancy outcome remains questionable. The contribution of ultrasound, added to routine clinical estimation of fetal weight, was clinically insignificant apart from a further increase in cesarean section rate.

[Fetal macrosomia: management, obstetrical and neonatal results. Multicenter case-control study in 15 maternity hospitals in Paris and the Ile de France area]

OBJECTIVE

To study the perinatal management of fetal macrosomia (FM) and the obstetrical and neonatal results related to FM in the Ile de France area.

MATERIALS AND METHODS

Case-control study from the fifteenth of July to the fifteenth of September 1999 in fifteen maternity in Paris and the Ile de France area. All singletons, without malformation, weighing more than 4,000 grams, born after 37 weeks of pregnancy during the study were included. The control group had the same inclusion and exclusion criteria (except the birth-weight) and was defined by the next delivery of same parity.

RESULTS

384 FM and 384 controls have been included. Usual risk factors of macrosomia have been found. The screening of gestational diabetes was realised in 56.8% and FM was suspected before delivery in 59.3% in the FM group. In cases of FM, the midwife was alone at the time of delivery in 53.4% of spontaneous vaginal delivery. FM was associated with a longer labour and a more frequent use of oxytocin. There was six times more severe perineal tears (1.7 vs 0.3%; p = 0.05) for women with FM whereas the rate of haemorrhage at delivery was the same in both groups. Cesarean section' rate before and during labor was higher in the FM group whereas instrumental extraction was not different. In this study, FM was not associated with an excess of fetal morbidity (injury, Apgar score, pH cord) even if we found ten times more shoulder dystocia.

CONCLUSION

Complications related to FM were mainly maternal in this study. Some recommendations accounting fetal macrosomia were not widely adopted as screening of gestational diabetes or necessity to have a whole obstetric team at the time of delivery.

Suspected big baby: a difficult clinical problem in obstetrics

BACKGROUND

Large for gestational age fetuses, also called macrosomic fetuses, represent a continuing challenge in obstetrics.

METHODS

We review various problems with large for gestational age fetuses. We have performed a literature search, mainly through the database PubMed (includes the Medline database). The clinical problem is discussed from the primary care provider's, the patient's and the obstetrician's point of view.

RESULTS

Macrosomia is arbitrarily defined as having a fetal weight of above the 90th percentile, a birth weight of above 4000 g or 4500 g, or a birth weight of over +2 standard deviation of the mean birth weight by gestational age. The diagnosis of macrosomia is difficult, both by palpation and symphysis fundus measurement; even with sophisticated sonographic measures. The combination of biparietal diameter, femur length and abdominal circumference appears to be no better than abdominal circumference alone.

INTERPRETATION

Based on the literature, labor should not be induced in nondiabetic pregnancies. The best policy is to await spontaneous birth or to induce labor after 42 weeks completion. A great number of cesarean sections have to be performed to avoid a single case of plexus brachialis paresis resulting from a difficult shoulder delivery. Cesarean section should not be considered in nondiabetic pregnancies unless the estimated fetal weight is above 5000 g. In pregnancies complicated by diabetes mellitus there are reasons for selective induction of labor if macrosomia is suspected and for cesarean section if the calculated birth weight is above 4000 g. Each department should have a strategy to handle such a situation because the problem with the difficult shoulder delivery cannot be completely avoided. Different procedures of managing difficult shoulder delivery are described.

Prepregnancy body mass index in non-diabetic women with and without shoulder dystocia

OBJECTIVE

To investigate the distribution of prepregnancy body mass index (BMI) in non-diabetic women with and without shoulder dystocia.

STUDY DESIGN

Cases were 142 non-diabetic women experiencing shoulder dystocia during the period from 1 January 1993 to 31 December 1999. Shoulder dystocia was defined as the impossibility of delivering the fetal shoulders by standard procedures. Controls were 142 women vaginally delivering during the same period without experiencing shoulder dystocia. Cases and controls were matched for parity (primi-/multipara) and birthweight (+/-250 g). Women with diabetes mellitus, gestational diabetes or a history of shoulder dystocia in a previous birth were excluded. The BMI and selected obstetric data were extracted from an internal database in the department.

RESULTS

Delivery was performed using McRoberts maneuvre (42%), Woods screw (50%) or by primary delivery of the posterior arm (8%). Women experiencing shoulder dystocia had significantly more labor augmentation and more instrumental deliveries. No differences were shown in the prevalence of low Apgarscores. The proportion of children with Erbs palsy and clavicular fracture was very close to be significantly different in cases or controls. However, these data does not allow any conclusion. The distribution of BMI was equal in cases and controls.

CONCLUSION

Non-diabetic women experiencing shoulder dystocia do not have a higher BMI than non-diabetic women delivering without this experience, given a fixed fetal weight.

Indications for caesarean section

Caesarean section rates are rising. Caesarean section confers an increase in maternal mortality and morbidity as well as having considerable financial implications. Caesarean section is usually justified by the assumed benefit for the fetus. These benefits are often unquantified and based on scanty evidence. The changing trends in the rates of caesarean section for various indications may be explained partly by improved anaesthetic and neonatal techniques. Cultural changes and expectations in the general population and obstetricians' fear of litigation may have made the changing rate and indications for caesarean section seem more acceptable. There is little research evidence in this area. The evidence that caesarean section is the optimal mode of delivery for various major indications is critically examined. The obstetrician is under an obligation to share the evidence that caesarean section is the optimum mode of delivery with the pregnant woman and her birth attendants to allow the woman to make wise decisions about her management.

Obstetric and neonatal outcome of babies weighing more than 4.5 kg: an analysis by parity

OBJECTIVES

To analyse by parity the obstetric and neonatal outcome of babies delivered weighing more than 4.5 kg.

METHODS

All deliveries resulting in a baby weighing more than 4.5 kg, in the 5 years from 1991 to 1995, were identified using a computerised database. The following variables confined to singleton, cephalic pregnancies were recorded: mode of delivery, duration of labour, incidence of shoulder dystocia and admission to the neonatal centre. Outcome measures in primigravidae and multigravidae were compared using the Epi Info package (WHO, Version 6.0b January 1997).

RESULTS

There were 32,834 deliveries over the study period and 828 (2.5%) weighed more than 4.5 kg. Birthweight more than 4.5 kg occurred in 1.6% (n=198) of primigravidae and 3.1% (n=630) of multigravidae (P<0.05). Primigravidae had a higher risk of prolonged labour (27.7% vs. 4.9%), operative vaginal delivery (32% vs.9%) and emergency caesarean section (24.2% vs. 5.7%) compared to multigravidae. When delivering a macrosomic baby, primigravidae had a higher incidence of prolonged labour (27% vs. 7.9%), operative vaginal delivery (32% vs.25%) and emergency caesarean section (24.2% vs. 5.7%) compared to normal weight babies. The incidence of shoulder dystocia and elective caesarean section were similar in both primigravidae and multigravidae.

CONCLUSIONS

Macrosomic infants have an increased incidence of prolonged labour, operative vaginal delivery and emergency caesarean section compared with normal weight babies and these complications are more pronounced in primigravidae compared to multigravidae. Shoulder dystocia occurs with equal frequency in primigravidae and multigravidae. The poor antenatal predictability of macrosomia, the high rate of vaginal delivery and the low incidence of shoulder dystocia would not support the use of elective caesarean section for delivery of the macrosomic infant either in primigravidae or multigravidae.