Estimators of birth weight in pregnant women requiring insulin: a comparison of seven sonographic models

Accuracy of ultrasound estimation of fetal weight at term: A comparison of shepard and hadlock methods

Background

Ultrasound measurement provides a noninvasive means of obtaining information about fetal weight and may help in necessary preparations at and after delivery. Although some ultrasound methods include only one or two fetal indices, others, to improve accuracy, incorporate either three or all the four fetal indices. The aim of this report is to assess the accuracy of two different methods for fetal weight estimation.

Materials and Methods

This was a prospective study of 170 consecutive pregnant women at term. Ultrasound was used to estimate fetal weight by the Shepard and Hadlock methods, and the actual birth weight (ABW) was determined at birth. The ultrasound-estimated fetal weights (EFWs) and ABW were analyzed.

Results

The women were aged 21-42 years (mean 31.3 ± 7 years). The EFW using the Shepard method was 1.9 kg-5.0 kg (mean 3.6 ± 0.5 kg) and 1.8 kg-4.4 kg (mean 3.3 ± 0.4 kg) for Hadlock method, and ABW was 2.0 kg-4.5 kg (mean 3.4 ± 0.5 kg). The mean EFW using the Shepard method was significantly higher than that of ABW (P < 0.001). The Shepard method significantly overestimated macrosomia compared to that by the ABW. There was no significant difference in microsomia rate between the two methods and ABW.

Conclusion

The Hadlock method was more accurate at estimating fetal weight compared to the Shepard method and is recommended for the ultrasound estimation of fetal weight in our setting and similar settings.

Antenatal prediction of fetal macrosomia in pregnancies affected by maternal pre-gestational diabetes

AIMS

Higher rates of fetal macrosomia may occur in infants of women with pre-gestational diabetes compared with non-diabetic controls. Antenatal predication of fetal macrosomia remains challenging. Ultrasound over-estimated fetal weight could result in over-classification of fetuses as macrosomic with corresponding inappropriate clinical interventions. Previously we had studied a measurement - the anterior abdominal wall measurement (AAW) - to predict fetal macrosomia in fetal estimation of weight. The purpose of the study was to study whether specific third trimester ultrasound measurements with measures of glycaemic control (HbA1c) predicted macrosomia in babies born to women with pre-gestational diabetes. In particular, a new variant of this measurement (fetal anterior abdominal wall thickness (AAW), abdominal circumference (AC) ratio: AAW:AC) was investigated.

METHODS

This was a prospective cohort study in a tertiary referral maternity hospital. Serial growth scans including measurement of AAW and AC: AAW ratio was performed at 30, 33- and 36-weeks' gestation. Birth-weight data was collected, and macrosomia was defined as >90th centile based on gestational age and gender of the baby. Serial HbA1c as measured at the first antenatal visit, 14, 20- and 36-weeks' gestation were reported for this study.

RESULTS

Of the 416 pregnancies analyzed, mean maternal age was 33.3 years. One in five women were primigravida's. The mean birthweight was 3548 g (+/- 581 g), of which 142 (34%) babies were classified as macrosomic. The median gestational age at delivery was 38³ weeks (31⁴ - 40² weeks). There were 37 (9%) babies born preterm at <37 weeks' gestation. Mean AC measurements in fetuses that would be born with macrosomia compared with those with a non-macrosomic birth weight were 282 mm vs. 266 mm at 30 weeks, 318.3 mm vs. 297 mm at 33 weeks and 350 mm vs. 325 mm at 36 weeks' gestation (all p < .001). Mean AAW measurements in macrosomic fetuses compared with normal size fetuses were 3.7 mm vs. 3.3 mm at 30 weeks, 4.9 mm vs 4.3 mm at 33 weeks and 5.9 mm vs. 5.3 mm at 36 weeks' gestation (all p < .001). The mean AC: AAW was 0.01 for both normal and macrosomic fetuses at 30 weeks. There was no clinical or statistical difference in AC:AAW ratios between non-macrosomic and macrosomic infants. Binary logistic regression showed that AC at 36 weeks was most predictive of macrosomia (76.5%), followed by AAW at 30 weeks (68.5%). Using a combination of HbA1c booking, 14, 20, 36 weeks and AAW 30, 33, 36 weeks and AC 30, 33, 36 weeks predicted macrosomia in 80.9%. The ratio of AC: AAW did not act as a useful antenatal clinical predictor of macrosomia at birth.

CONCLUSIONS

Abdominal circumference at 36 weeks was the single best predictor of fetal macrosomia. A combined model of HbA1c, AC and AAW was the best antenatal predictor of macrosomia, with intriguing clinical possibilities in the possible prevention of maternal and fetal complications of macrosomia.

Maternal diabetes and fetal cardiac output

BACKGROUND

The intrauterine environment is a key determinant for long-term health outcomes. Adverse fetal environments, such as maternal diabetes, obesity and placental insufficiency are strongly associated with long-term health risks in children. Little is known about differences in fetal cardiac output hemodynamics of diabetic mothers (DM) vs. non-diabetic mothers (NDM). Our study aims to investigate the left-sided, right-sided, and combined cardiac output (CCO) in fetuses of DM vs. NDM.

METHODS

Retrospective data were collected in fetuses of DM (N = 532) and NDM (103) at mean gestational age 24 weeks. Examination included 2D echo and pulse wave Doppler. Wilcoxon rank sum tests and Chi-square tests were used to test for distribution difference of maternal and fetal continuous and categorical measures respectively between DM and NDM. Intraclass correlation coefficients were calculated to assess intra-observer reliability of fetal cardiac measurements.

RESULTS

DM mothers had higher mean weight (89.7±22.2 kg) than NDM (76.8±19.8 kg), p <  0.0001 and higher mean BMI (33.4±7.5) than NDM (28.3±5.8), p <  0.0001. C-section delivery occurred in 66% of DM vs. 35% of NDM fetuses. Fetuses of DM mothers had significantly larger semilunar valve diameter, higher left ventricular (LV) output, higher combined cardiac output and lower right ventricle /left ventricle ratio compared to NDM.

CONCLUSION

The greater CCO (adjusted for fetal weight), left sided cardiac output in the fetuses of DM, compared to NDM, represent differences in cardiac adaptation to the diabetic environment.

The effect of fetal weight on the accuracy of sonographic weight estimation among women with diabetes

Objective: The assessment of sonographic estimated fetal weight (EFW) enables identification of fetuses in the extremes of weight, thus aiding in the planning and management of peripartum care. There are conflicting reports regarding the accuracy of EFW in diabetic mothers. We aimed to study the factors associated with the accuracy of EFW at term, specifically the role of gestational and pre-gestational diabetes in this setting.Methods: A retrospective study including all women carrying singleton term gestations who delivered within a week following a sonographic fetal weight estimation between 2011 and 2019. Accurate EFW was defined as within 10% of the actual birthweight. We allocated the study cohort into two groups: (1) Accurate EFW (2) inaccurate EFW. Both groups were compared in order to identify factors associated with the inaccuracy of EFW.Results: Overall, 41,263 deliveries were available for evaluation, including 412 (1.0%) deliveries among women with pre-gestational diabetes and 4,735 (11.5%) among women with gestational diabetes. Of them, 7,280 (17.6%) had inaccurate EFW. Inaccurate EFW was associated with nulliparity, OR 0.82 [95% CI] (0.78-0.87), oligohydramnios, OR 0.81 [95% CI] (0.71-0.93), pregestational diabetes, OR [95% CI] 0.61 (0.50-0.79), and extremity of fetal weight; <2,500 grams-OR [95% CI] 0.37 (0.33-0.41) and >4,000 grams OR [95% CI] 0.52 (0.48-0.57). On multiple regression analysis, the following factors were independently associated with inaccurate EFW: pregestational diabetes, OR [95% CI] 0.58 (0.46-0.73), p < .001, nulliparity, OR [95% CI] 0.86 (0.82-0.91), p < .001 and higher fetal weight (for each 500 grams), OR [95% CI [1.25 (1.21-1.30), p < .001. On analysis of different weight categories, pregestational diabetes was associated with inaccurate EFW only in those with birthweight >3,500 grams, OR [95% CI] 0.37 (0.24-0.56) (p < .001).Conclusion: Among pregestational diabetic women, the accuracy of sonographic EFW when assessed to be >3,500 grams is questionable. This should be taken into consideration when consulting women and planning delivery management.Synopsis: Among pregestational diabetic women, the accuracy of estimated sonographic fetal weight higher than 3,500 grams is of limited accuracy.

Sonographic Estimated Fetal Weight among Diabetics at ≥ 34 Weeks and Composite Neonatal Morbidity

Objectives  The objective was to assess the composite neonatal morbidity (CNM) among diabetic women with sonographic estimated fetal weight (SEFW) at 10 to 90th versus >90th percentile for gestational age (GA). Study Design  The inclusion criteria for this retrospective study were singleton pregnancies at 34 to 41 weeks, complicated by diabetes, and that had SEFW within 4 weeks of delivery. Odds ratios (ORs) with 95% confidence intervals (CI) were calculated. Results  Among the 140 cohorts that met the inclusion criteria, 72% had SEFW at 10th to 90th percentile for GA, and 28% at >90th percentile. Compared with women with diabetes with last SEFW at 10th to 90th percentile, those with estimate > 90th percentile for GA had a significantly higher rate of CNM (13 vs. 28%; OR, 2.65; 95% CI, 1.07-6.59). Among 109 diabetic women who labored, the rate of shoulder dystocia was significantly higher with SEFW at >90th percentile for GA than those at 10th to 90th percentile (25 vs. 2%; p  = 0.002); the corresponding rate of CNM was 29 versus 10% ( p  = 0.02). Conclusion  Among diabetic women with SEFW > 90th percentile for GA, CNM was significantly higher than in women with estimate at 10 to 90th percentile. Despite the increased risk of CNM, these newborns did not have long-term morbid sequela.

Practice Bulletin No. 173: Fetal Macrosomia

Suspected fetal macrosomia is encountered commonly in obstetric practice. As birth weight increases, the likelihood of labor abnormalities, shoulder dystocia, birth trauma, and permanent injury to the neonate increases. The purpose of this document is to quantify those risks, address the accuracy and limitations of methods for estimating fetal weight, and suggest clinical management for a pregnancy with suspected fetal macrosomia.

Large-for-Gestational-Age Ultrasound Diagnosis and Risk for Cesarean Delivery in Women With Gestational Diabetes Mellitus

OBJECTIVE

To assess the accuracy of a large-for-gestational-age (LGA) ultrasound diagnosis and the subsequent risk for cesarean delivery associated with ultrasound diagnosis of LGA among women with gestational diabetes mellitus.

METHODS

This was a retrospective cohort study of 903 women with GDM who delivered after 36 weeks of gestation with an ultrasound-estimated fetal weight within 31 days of delivery. Delivery outcomes were compared between women with an ultrasound diagnosis of LGA and a non-LGA ultrasound diagnosis.

RESULTS

Based on ultrasound assessments, we identified 248 women with an LGA fetus and 655 women with a non-LGA fetus. Among women with an LGA ultrasound diagnosis, 56 of 248 (22.6%) delivered an LGA neonate, whereas, of women with a non-LGA ultrasound diagnosis, 18 of 655 (2.8%) delivered an LGA neonate. Ultrasound diagnosis of LGA was associated with increased risk for cesarean delivery (adjusted odds ratio [OR] 3.13, 95% confidence interval [CI] 2.10-4.67, P<.001) after adjusting for relevant covariates. Stratified analyses demonstrated that ultrasound diagnosis of LGA was associated with an increased risk for cesarean delivery whether the birth weight was between 2,500 and 3,499 g (OR 2.82, 95% CI 1.62-4.84, P<.001) or between 3,500 and 4,500 g (OR 3.47, 95% CI 2.06-5.88, P<.001).

CONCLUSION

Ultrasonography significantly overestimates the prevalence of LGA in women with gestational diabetes mellitus, and an ultrasound diagnosis of LGA is associated with an increased risk for cesarean delivery independent of birth weight.

LEVEL OF EVIDENCE

II.

Accuracy of Fetal Weight Estimation in Women with Diet Controlled Gestational Diabetes

Purpose: To evaluate whether ultrasound accuracy of estimated fetal weight (EFW) differs in women with diet controlled gestational diabetes mellitus (GDM) compared to nondiabetic pregnant women. Material and Methods: We included 363 patients, 121 patients with diet controlled GDM and 242 patients with a normal oral glucose tolerance test (oGTT). Each case of diet controlled GDM was matched with 2 unaffected controls. All patients were screened/diagnosed for GDM by means of an oGTT. Both groups received ultrasound examination including fetal biometry, using Hadlock's Formula, within 7 days to delivery. After birth, gestational age, birthweight and Apgar scores were collected from each newborn. Results: There was a good correlation between EFW and birth weight (coefficient = 0.747, p < 0.001 by Pearson correlation, even after adjustment for glucose status). Regression analyses, including noGDM/GDM, maternal age, maternal body mass index, birth weight and time interval between ultrasound and delivery revealed that only fetal birth weight significantly influences weight difference between ultrasound EFW and actual birth weight at term. Conclusion: Our data suggests that ultrasound accuracy of EFW using Hadlock's Formula at term does not differ in women with diet controlled GDM compared to women with normal glucose tolerance.

Comparison of abdominal palpation, Johnson's technique and ultrasound in the estimation of fetal weight in Northern Iran

OBJECTIVES

to assess the accuracy of abdominal palpation, Johnson's technique and ultrasound in the estimation of fetal weight (EFW).

DESIGN, SETTING AND PARTICIPANTS

174 pregnant women were recruited at random in a large teaching hospital in Iran. Fetal weight was estimated by palpation and Johnson's technique at the time of admission by one qualified midwife, and then estimated by ultrasound by one radiologist. After birth, all newborns were weighed using the same scale.

FINDINGS

a significant correlation was found between EFW by ultrasound, palpation and Johnson's technique and actual birth weight. The differences between EFW by palpation, ultrasound and Johnson's technique and actual birth weight were significant for small-for-gestational-age fetuses (p<0.05, p<0.01 and p<0.001, respectively), but not for appropriate-for-gestational-age fetuses. These differences were significant for ultrasound (p<0.001) and palpation (p<0.05) in large-for-gestational-age fetuses. The sensitivity of ultrasound for EFW of low-birthweight fetuses (72.2%) and the sensitivity of Johnson's technique for EFW of normal-weight and macrosomic fetuses (97.3% and 75%, respectively) appeared to be higher than the sensitivities of the other methods.

CONCLUSION

palpation and Johnson's technique can be used as alternatives to ultrasound for EFW, particularly if the measurements are taken by experienced, skilled personnel.

A review of sonographic estimate of fetal weight: Vagaries of accuracy

PURPOSE

To determine the factors that might influence the accuracy of sonographic estimated fetal weight.

STUDY DESIGN

A PubMed search (Jan 1975 to Jan 2003) of articles published in the English language was carried out and the inclusion criterion was that estimates were within 10% of birth weight. A Chi-square test for trend was used and odds ratio (OR) with 95% confidence intervals (CI) was calculated.

RESULTS

Over 28 years, 175 articles were identified but only 54 (31%) met the inclusion criterion. Overall 62% (8895/14 384) of the predictions were within 10% of the actual weight. The accuracy was significantly different in articles where <7 vs. >7 days were allowed to lapse between examination and delivery (OR 2.17, 95% CI 1.93, 2.45); where examinations were done by registered diagnostic medical sonographers (RDMS; 65%) versus physicians (59%) or residents (57%; p < 0.0001); in term vs. preterm patients (OR 1.97, 95% CI 1.67, 2.13); and in studies with >1000 vs. <1000 cohorts (OR 1.62; 95% CI 1.51, 1.74).

CONCLUSIONS

If feasible the sonographic examination should be done by RDMS and within a week of delivery.

Sonographic fetal weight estimation: which model should be used?

OBJECTIVE

The purpose of this study was to compare the accuracy of different sonographic models for fetal weight estimation.

METHODS

We evaluated 26 different models using 3705 sonographic weight estimations performed less than 3 days before delivery. Models were ranked on the basis of systematic and random errors and were grouped according to the combination of biometric indices in each model. Cluster analysis was used to compare the accuracy of the different model groups.

RESULTS

A considerable variation in the accuracy of the different models was found. For birth weights (BWs) in the range of 1000 to 4500 g, models based on 3 or 4 fetal biometric indices were significantly more accurate than models that incorporated only 1 or 2 indices. The accuracy of weight estimation decreased at the extremes of BWs, leading to overestimation in low-BW categories as opposed to underestimation when the BW exceeded 4000 g. The precision of most models was lowest in the low-BW groups.

CONCLUSIONS

To improve the accuracy of fetal weight estimation, sonographic models that are based on 3 or 4 fetal biometric indices should be preferred. Recognizing the accuracy and the tendency for underestimation or overestimation of each of the available models is important for the judicious interpretation of fetal weight estimations, especially at the extremes of fetal weight.

Severe chronic morbidity following childbirth

Three special, chronic morbidities of childbirth are reviewed with the most up-to-date knowledge in this article. Firstly, obstetric fistulas secondary to prolonged obstructed labour are still prevalent tragedies in underdeveloped countries. The damage is not only physical but psychosexual and social. The surgical skill and technology required to prevent and to treat obstetric fistulas are simple, but culture-social antagonism, geographic distance, political instability and financial constraint have to be overcome before effective management can take place. Congenital brachial plexus palsy is associated with shoulder dystocia and macrosomia, and both excessive exogenous traction and strong endogenous pushing forces contribute to its occurrence. As shoulder dystocia and macrosomia are not easily predictable, regular training and drill is essential to ensure proper management of shoulder dystocia. Most of the babies with brachial palsy will recover in 3 months but a minority of patients will suffer a more severe degree of damage, requiring early micro-neurosurgical intervention. Finally, although birth asphyxia is not the major cause of cerebral palsy, brain injury resulting from acute intrapartum hypoxic-ischemic insult is potentially alleviated by early neonatal hypothermic therapy. Both clinical and radiological assessments are essential in selecting suitable candidates for this innovative neuroprotective strategy.

New regression formulas for sonographic weight estimation within 10, 7, and 3 days of delivery

OBJECTIVES

The purpose of this study was to develop new regression formulas based on large numbers of sonographic examinations performed within 10, 7, and 3 days of delivery.

METHODS

Sonographic fetal biometric measurements and delivery ward data for an unselected population were analyzed. Multivariate linear regression models were fitted to the sonographic data to predict the actual birth weight (BW) within 10, 7, and 3 days.

RESULTS

The analyses included 6289, 5449, and 4007 patients who underwent sonographic examinations within 10, 7, and 3 days of delivery, respectively. All models yielded very high correlation coefficients (r = 0.927-0.958; R(2) = 0.859-0.918), low mean deviations between the calculated and actual BWs (6.4%-6.6% +/- 1 SD of 5.5%-5.9%), and high percentages of the calculated BW within 10% of the actual BW (78.5%-80.4%). Estimated fetal weight analyses made within 3 days of delivery yielded slightly better results than within 7 and 10 days.

CONCLUSIONS

The new regression formulas yielded overall similar results, with a small advantage for estimates calculated within 3 days of delivery. Further prospective studies are needed to compare the accuracy of these formulas with those used to date.

Accuracy of a single fetal weight estimation at 29-34 weeks in diabetic pregnancies: can it predict large-for-gestational-age infants at term?

OBJECTIVES

This study was undertaken to evaluate the accuracy of a single sonographic estimated fetal weight at 29-34 weeks' gestation with respect to birthweight determination in diabetic pregnancies.

STUDY DESIGN

A retrospective cohort study of 423 diabetic pregnancies with detailed fetal measurements at 29-34 weeks' gestation. Multivariate regression analysis was used to predict the birthweight. The percentiles of the estimated fetal weight and the calculated birthweight were compared with the actual birthweight percentile.

RESULTS

The mean birthweight percentile at term was significantly higher than the estimated fetal weight percentile at 29-34 weeks' gestation in the women with poor glycemic control, but not the women with good control. On multivariate analysis, the estimated fetal weight, interval from ultrasound to delivery, hemoglobin A1C level, gestational age at ultrasound, and classification of glycemic control were independently associated with the birthweight. Both the estimated fetal weight and the calculated birthweight had a low sensitivity and a low positive predictive value for predicting large-for-gestational-age infants.

CONCLUSION

Accelerated fetal growth is evident primarily in diabetic women with poor glycemic control. These fetuses cannot be identified by a single ultrasound examination at 29-34 weeks' gestation.

Suspicion and treatment of the macrosomic fetus: a review

OBJECTIVE

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

STUDY DESIGN

A review.

RESULTS

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

CONCLUSION

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

Elective cesarean section to prevent anal incontinence and brachial plexus injuries associated with macrosomia?a decision analysis

Our aim was to determine the cost-effectiveness of a policy of elective C-section for macrosomic infants to prevent maternal anal incontinence, urinary incontinence, and newborn brachial plexus injuries. We used a decision analytic model to compare the standard of care with a policy whereby all primigravid patients in the United States would undergo an ultrasound at 39 weeks gestation, followed by an elective C-section for any fetus estimated at > or =4500 g. The following clinical consequences were considered crucial to the analysis: brachial plexus injury to the newborn; maternal anal and urinary incontinence; emergency hysterectomy; hemorrhage requiring blood transfusion; and maternal mortality. Our outcome measures included (1) number of brachial plexus injuries or cases of incontinence averted, (2) incremental monetary cost per 100,000 deliveries, (3) expected quality of life of the mother and her child, and (4) "quality-adjusted life years" (QALY) associated with the two policies. For every 100,000 deliveries, the policy of elective C-section resulted in 16.6 fewer permanent brachial plexus injuries, 185.7 fewer cases of anal incontinence, and cost savings of $3,211,000. Therefore, this policy would prevent one case of anal incontinence for every 539 elective C-sections performed. The expected quality of life associated with the elective C-section policy was also greater (quality of life score 0.923 vs 0.917 on a scale from 0.0 to 1.0 and 53.6 QALY vs 53.2). A policy whereby primigravid patients in the United States have a 39 week ultrasound-estimated fetal weight followed by C-section for any fetuses > or =4500 g appears cost effective. However, the monetary costs in our analysis were sensitive to the probability estimates of urinary incontinence following C-section and vaginal delivery and the cost estimates for urinary incontinence, vaginal delivery, and C-section.

Delivery assistance in fetal macrosomia

OBJECTIVES: to evaluate delivery assistance in fetal macrosomia. METHODS: this was a hospital-based cohort study of consecutive births at a tertiary perinatal center from January 1, 1996 to October 31, 1999. A total of 5261 pregnancies met the inclusion criteria which were singleton pregnancies with minimal birth weight of 1000 g. Fetal macrosomia was defined as birth weight of 4000 g or more. We studied the mode of delivery, the newborn condition at birth, considered low when the Apgar scored below seven in the first or fifth minute, and the presence of abnormalities that could indicate a Caesarian section (disproportion, uterine dysfunction, prolonged second period of birth and fetal distress). RESULTS: 296 (5,6%) of the babies were macrosomic. Macrosomia was a risk factor for Caesarian section (RR = 1,59, p <0,001) and for operative vaginal delivery RR = 1,12 (p <0,001). Newborn conditions was not worse in macrosomic babies. There was a positive correlation between fetal macrosomia and disproportion but not with uterine dysfunction, prolonged second period of birth or fetal distress. CONCLUSIONS: caesarian section was indicated more often for macrosomic babies, but our data did not suggest that a more extensive use of C-Sections was justified.

Arrest of descent in second stage of labour secondary to macrosomia: a case report

BACKGROUND

Fetal macrosomia, defined as birth weight greater than 4000 g, complicates 10% of pregnancies and is a well-documented cause of prolonged second stage of labour, as well as of arrest of descent of the fetal presenting part.

CASE

A multigravida woman with gestational diabetes mellitus was admitted in labour at term, and progressed to full dilatation. The fetal vertex failed to descend beyond -3 station. An emergency Caesarean section was performed and a 6452 g male infant was delivered.

CONCLUSION

Physicians should be aware of the possibility of macrosomia as the cause of failure of descent in the second stage. A heightened state of suspicion should be maintained, particularly in a multigravida woman with a prior macrosomic baby and the presence of other predisposing factors such as gestational diabetes mellitus.

Altered fetal circulation in type-1 diabetic pregnancies

OBJECTIVE

Type-I diabetic pregnancies are associated with congenital cardiac malformations, fetal cardiomyopathy, venous thrombosis and altered placental vascularization, even with tight maternal glucose control. The aim of this study was to investigate if, with good glucose control achieved with continuous subcutaneous insulin infusion, normal blood flow within the fetal heart can be achieved.

METHODS

Seventeen fetuses of women with well-controlled type-I diabetes were studied longitudinally to evaluate effects on the fetal circulation. Doppler frequency shift tracings, valve diameters and intercept angles were measured at right and left atrioventricular valve orifices at 4-week intervals starting at 15 weeks' gestation. Atrioventricular valve flow was calculated and compared to normal fetal data obtained in previous studies.

RESULTS

Maximum and mean temporal velocities across the atrioventricular valves increased in both groups during gestation but significantly more in fetuses of type-I diabetic pregnancies. Combined ventricular output, both absolute and per kg estimated fetal weight, were also greater in these fetuses. In the normal group the ratio of the right/left ventricular output decreased significantly during gestation (from 1.34 +/- 0.28 to 1.08 +/- 0.28 standard deviations), but in type-I diabetic pregnancies this decrease did not occur (1.2 +/- 0.26 to 1.25 +/- 0.29 standard deviations)[corrected].

CONCLUSIONS

These data indicate that there are significant differences in the fetal circulation between normal pregnancy and well-controlled type-I diabetic pregnancy, suggesting the existence of a compensatory mechanism which increases fetal cardiac output and causes cardiac hypertrophy.

Delivery of the macrosomic infant: cesarean section versus vaginal delivery

The macrosomic fetus of a diabetic woman faces increased risk for injury at the time of birth. Cesarean section offers the potential for avoiding trauma to the fetus, but can result in increased morbidity in the mother as compared to vaginal delivery. In this article, the advantages and disadvantages of the 2 routes of delivery for the overgrown fetus of a diabetic mother are discussed. In addition, methods for diagnosing macrosomia by ultrasound are examined, along with the benefits and pitfalls of ultrasonic fetal weight estimation in the setting of diabetes. Finally, management approaches for selecting route of delivery for the macrosomic fetus are described and analyzed.

Sonographic estimation of fetal weight in macrosomic fetuses: diabetic versus non-diabetic pregnancies

The objective of this study is to compare the accuracy of sonographic estimation of fetal weight of macrosomic babies in diabetic vs non-diabetic pregnancies. All babies weighing 4,000 g or more at birth, and who had ultrasound scans performed within one week of delivery were included in this retrospective study Pregnancies with diabetes mellitus were compared to those without diabetes mellitus. The mean simple error (actual birthweight--estimated fetal weight); mean standardised absolute error (absolute value of simple error (g)/actual birthweight (kg)); and the percentage of estimated birthweight falling within 15% of the actual birthweight between the two groups were compared. There were 9,516 deliveries during the study period. Of this total 1,211 (12.7%) babies weighed 4,000 g or more. A total of 56 non-diabetic pregnancies and 19 diabetic pregnancies were compared. The average sonographic estimation of fetal weight in diabetic pregnancies was 8% less than the actual birthweight, compared to 0.2% in the non-diabetic group (p < 0.01). The estimated fetal weight was within 15% of the birthweight in 74% of the diabetic pregnancies, compared to 93% of the non-diabetic pregnancies (p < 0.05). In the diabetic group, 26.3 % of the birthweights were underestimated by more than 15 %, compared to 5.4% in the non-diabetic group (p < 0.05). In conclusion, the prediction accuracy of fetal weight estimation using standard formulae in macrosomic fetuses is significantly worse in diabetic pregnancies compared to non-diabetic pregnancies. When sonographic fetal weight estimation is used to influence the mode of delivery for diabetic women, a more conservative cut-off needs to be considered.

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.

Sonographic and clinical methods in the diagnosis of macrosomia

Receiver operator characteristic curves for both clinical and sonographic predictions of macrosomia subsume areas between 0.81 and 0.95, significantly larger than the area of 0.5 that indicates a useless test. Thus, these tests are defined as useful from a statistical point of view. Prediction of macrosomia by clinical or imaging techniques, however, is limited by the substantial false-positive and false-negative rates inherent in these tests. We recommend that physicians continue to use clinical methods to estimate fetal weight, including asking women with parity to provide their own estimates. We recognize that the relative error associated with clinical or sonographic estimates of fetal weight limits their use in clinical practice. Sonographic laboratories may improve their results by performing ROC curve analysis on their own data and by selecting cutoff values that best predict macrosomia in their setting. Serial sonographic measurements that are above the limits chosen to define macrosomia increase the likelihood that a birth weight will be macrosomic. Separate ROC curves must be generated for twins and breech presentations and for patients with diabetes to answer weight-related clinical questions such as mode and timing of delivery. Three-dimensional ultrasound and magnetic resonance imaging are expected to generate ROC curves for estimates of fetal weight that are better than those for two-dimensional ultrasound or clinical estimates. Such analyses have yet to be published.

Prenatal diagnosis of macrosomia in pregnancy complicated by diabetes mellitus

OBJECTIVE

To provide a concise review of current practices regarding prenatal diagnosis of excess fetal growth in pregnancies complicated by diabetes mellitus.

METHODS

A literature review of relevant publications.

RESULTS

Sonographic estimation of fetal size at term is frequently undertaken in the management of diabetic pregnancy. Considerable error in fetal weight estimations, particularly in asymmetrically enlarged fetuses, may limit the accuracy and clinical utility of these measurements.

CONCLUSIONS

The limitations and potential inaccuracy of current sonographic methods to detect the large-for-gestational age fetus of a diabetic mother are acknowledged. Customized formulae are of limited benefit so that further study of techniques aimed at assessing fetal fat content and distribution should be undertaken. These methods may improve detection of the large fetus and aid in clinical decision making.

Sonographic EFW and macrosomia: is there an optimum formula to predict diabetic fetal macrosomia?

OBJECTIVE

To compare the accuracy of 31 published formulas for estimated fetal weight (EFW) in predicting macrosomia (birthweight 4,000 gm or more) in infants of diabetic mothers.

METHODS

The study population comprised 165 women with gestational or pregestational diabetes who had sonograms to estimate fetal weight after 36 weeks of gestation and within 2 weeks of delivery. Three measures of accuracy were compared: 1) area under the receiver operating characteristic (ROC) curve relating EFW to macrosomia, 2) systematic error, and 3) absolute error. For each measure, the 31 formulas were rank-ordered from 1 (best) to 31 (worst). For each formula, the three rank scores were summed to give a total score. The formula with the lowest total score was considered the "best" formula.

RESULTS

Macrosomia occurred in 49 cases (30%). Areas under the ROC curves ranged from 0.8361-0.8978. Differences in areas were not significantly different between the 31 formulas. The 1986 formula of Ott et al. had the lowest total score. Using this "best" formula, an EFW of 4,000 gm or more had a sensitivity of 45% to predict macrosomia and a positive predictive value of 81%. To achieve 90% sensitivity with this formula would have required diagnosis of macrosomia with an EFW of 3,535 gm or more, but this would have comprised 46% of the population with a 42% false-positive rate. All 31 formulas were better at predicting macrosomia than predictions based on gestational age alone, and 28 were better than predictions based on abdominal circumference alone.

CONCLUSIONS

All 31 formulas for EFW had comparably poor accuracy for prediction of macrosomia. Delivery decisions based on EFW will often be in error. Future studies should determine whether specific sonographic measurements, ratios, or differences are better than EFW or birthweight as predictors of birth trauma.

A simple estimated fetal weight equation for fetuses between 24 and 34 weeks of gestation

OBJECTIVE

To develop a mathematical equation that is simple, accurate and easy to use when applied to low-birth weight or preterm fetuses (< 35 weeks) and to assess previous normal ultrasonic fetal weight curves and make a comparison with normal fetal delivery weight curves.

METHOD

In a large teaching hospital, 269 pregnant mothers were identified by the criteria of normalities, such as: well known LMP, regular menstrual cycles, no use of OCP for the last 3 months, no smoking and no history of diabetes. Birth-weight measurements (adjusted for maternal age, baby's sex, parity and week of gestation) were taken immediately after birth.

RESULTS

Mean gestational age and mean birth' weight + S.D. were 29.5 + 3.02 weeks and 1530.238 237.856 g, respectively. With the aid of a scientific calculator the data were analyzed and a simple regression equation has been derived: EFW (kg) = 0.17 (G.A. - 20), S.D. - 235 g (Honarvar's Formula 1).

CONCLUSION

For estimating weights of preterm or low-birth weight fetuses of less than 2500 g, this simple equation appears to be clinically reliable and easy to use and suggests that previous normal ultrasonic fetal weight curves may underestimate or overestimate normal fetal delivery weight between the 24th and 34th week of gestation. Our formula approximates actual birth weight better and recommends Ott's ultrasonic weight curve for Iranian population.

Prophylactic cesarean delivery for fetal macrosomia diagnosed by means of ultrasonography--A Faustian bargain?

Both our previously performed decision analysis and more recent clinical data considered in the context of our decision analytic framework support the claim that in the pregnancies of women without diabetes the level of intervention and the economic costs of prophylactic cesarean delivery for fetal macrosomia diagnosed by means of ultrasonography are predicted to be excessive. Under the most plausible assumptions, a prophylactic cesarean policy with either a 4000- or 4500-g macrosomia threshold would require more than 1000 cesarean deliveries and millions of dollars to avert a single permanent brachial plexus injury. In the pregnancies of diabetic women, although such policies would be expected to perform appreciably better, their use would nevertheless entail considerable intervention for any benefit achieved. Under most assumptions, hundreds of cesarean deliveries and hundreds of thousands of dollars would be required to avert a single permanent brachial plexus injury. In light of the available data, optimizing the management of shoulder dystocia seems at present to be the most immediate and tenable approach to the prevention of birth-related brachial plexus injury.

Fetal growth in diabetic pregnancy

In summary, fetal macrosomia occurs in almost one third of diabetic pregnancies regardless of class. Abnormal fetal fat stores lead to difficult labor, dystocia, and birth injury as well as postnatal metabolic transition. The abnormal body fat distribution at birth may destine some of these infants to lifelong obesity. Abnormal fetal growth in diabetic pregnancy appears to occur with any elevations in maternal glucose levels, however modest. Detection of macrosomia is therefore a major goal of diabetic pregnancy management.

The accuracy of intrapartum ultrasonographic fetal weight estimation in diabetic pregnancies

OBJECTIVE

Our purpose was to compare the accuracy of ultrasonographic fetal weight estimation in pregnant diabetic women with that of matched nondiabetic controls.

STUDY DESIGN

We performed a case-control study of pregnant patients who underwent ultrasonographic fetal weight estimation within 3 days of delivery. The study group consisted of pregnant diabetic women and nondiabetic controls matched for maternal body mass index and neonatal birth weight. Fetal weight estimates were calculated with use of Hadlock's and Shepard's formulas. The difference between ultrasonographic fetal weight estimation and actual birth weight (absolute percent error) was analyzed with respect to maternal diabetic status and actual birth weight.

RESULTS

A total of 450 patients were studied (225 patients in each group). The mean (+/- SD) gestational age at delivery was 39.0 +/- 1.5 weeks versus 39.9 +/- 1.7 weeks for the diabetic and nondiabetic patients, respectively. There was no statistically significant difference between the two groups with respect to the mean (+/- SD) time interval between the ultrasonographic examination and delivery (0.9 +/- 1.8 days vs 0.8 +/- 2.1 days) or the mean (+/- SD) absolute percent error (9.0% +/- 7.1% vs 8.4% +/- 6.3%). The mean (+/- SD) absolute percent error of fetal weight estimates among subjects with macrosomic fetuses (birth weight > or = 4500 gm) was significantly greater than that observed in fetuses with birth weights < 4500 gm (12.6% +/- 8.4% vs 8.4% +/- 6.5, p = 0.001). This difference was observed irrespective of maternal diabetic status.

CONCLUSION

When matched for maternal body mass index and birth weight, the accuracy of ultrasonographic fetal weight estimation was similar among diabetic and nondiabetic women. Birth weights > or = 4500 gm rather than maternal diabetes seem to be associated with less accurate ultrasonographic fetal weight estimates.