Real-time ultrasound estimations of weight in fetuses of diabetic gravid women

Detection of small for gestational age in preterm prelabor rupture of membranes by Hadlock versus the Fetal Medicine Foundation growth charts

Objective

The primary outcome was to compare the diagnostic accuracy of neonatal small for gestational age (SGA) by the Hadlock and Fetal Medicine Foundation (FMF) charts in our cohort, followed by the ability to predict composite severe neonatal outcomes (SNO) in pregnancies with preterm prelabor rupture of membranes (PPROM).

Methods

This study was a secondary analysis of a prospective cohort of pregnancies with PPROM from 2015 to 2018, from 23 to 36 completed weeks of gestation. Sensitivity, specificity, and positive and negative predictive values for the primary and secondary outcomes of the Hadlock and FMF fetal charts were calculated. The discriminatory ability of each chart was compared using the area under the receiver’s operating curves of clinical characteristics.

Results

Of the 106 women who met the inclusion criteria, 48 (45%) were screened positive using the FMF fetal growth chart and 22 (21%) were screened positive using the Hadlock chart. SGA was diagnosed in 12 infants (11%). Both fetal growth charts had comparable diagnostic accuracies and were statistically significant predictors of SGA (Hadlock: area under the receiver operating characteristic curves [AUC], 0.76, risk ratio [RR], 7.6, 95% confidence interval [CI], 2.5–23; and FMF: AUC, 0.76 RR, 13.3 95%CI 1.8–99.3). Both growth standards were poor predictors of SNO.

Conclusion

The Hadlock and FMF fetal growth charts have a similar accuracy to predict SGA in pregnancies complicated by PPROM. The FMF fetal growth chart may result in a 2-fold increase in positive screens, potentially increasing fetal surveillance.

Ultrasonographic estimation of fetal weight: development of new model and assessment of performance of previous models

OBJECTIVES

To develop a new formula for ultrasonographic estimation of fetal weight and evaluate the accuracy of this and all previous formulae in the prediction of birth weight.

METHODS

The study population consisted of 5163 singleton pregnancies with fetal biometry at 22-43 weeks' gestation and live birth of a phenotypically normal neonate within 2 days of the ultrasound examination. Multivariable fractional polynomial analysis was used to determine the combination of variables that provided the best-fitting models for estimated fetal weight (EFW). A systematic review was also carried out of articles reporting formulae for EFW and comparing EFW to actual birth weight. The accuracy of each model for EFW was assessed by comparing mean percentage error, absolute mean error (AE), proportion of pregnancies with AE ≤ 10% and Euclidean distance.

RESULTS

The most accurate models, with the lowest Euclidean distance and highest proportion of AE ≤ 10%, were provided by the formulae incorporating ≥ 3 rather than < 3 biometrical measurements. The systematic review identified 45 studies describing a total of 70 models for EFW by various combinations of measurements of fetal head circumference (HC), biparietal diameter, femur length (FL) and abdominal circumference (AC). The most accurate model with the lowest Euclidean distance and highest proportion of AE ≤ 10% was provided by the formula of Hadlock et al., published in 1985, which incorporated measurements of HC, AC and FL; there was a highly significant linear association between EFW and birth weight (r = 0.959; P < 0.0001), and EFW was within 10% of birth weight in 80% of cases. The performance of the best model developed in this study, utilizing HC, AC and FL, was very similar to that of Hadlock et al. CONCLUSION: Despite many efforts to develop new models for EFW, the one reported in 1985 by Hadlock et al., from measurements of HC, AC and FL, provides the most accurate prediction of birth weight and can be used for assessment of all babies, including those suspected to be either small or large. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Fetal Hemodynamics and Fetal Growth Indices by Ultrasound in Late Pregnancy and Birth Weight in Gestational Diabetes Mellitus

Background:

The offspring of women with gestational diabetes mellitus (GDM) are prone to macrosomia. However, birth weight is difficult to be correctly estimated by ultrasound because of fetal asymmetric growth characteristics. This study aimed to investigate the correlations between fetal hemodynamics, fetal growth indices in late pregnancy, and birth weight in GDM.

Methods:

A total of 147 women with GDM and 124 normal controls (NC) were enrolled in this study. Fetal hemodynamic indices, including the systolic/diastolic ratio (S/D), resistance index (RI), pulsatility index (PI) of umbilical artery (UA), middle cerebral artery (MCA), and renal artery (RA), were collected. Fetal growth indices, including biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length, were also measured by ultrasound. Birth weight, newborn gender, and maternal clinical data were collected.

Results:

The independent samples t-test showed that BPD, HC, and AC were larger in GDM than in NC (P < 0.05). Fetal hemodynamic indices of the UA and MCA were lower (P < 0.05), but those of the RA were higher (P < 0.001) in GDM than in NC. Birth weight was higher in GDM than in NC (P < 0.001). Pearson's correlation analysis showed that hemodynamic indices of the UA were negatively correlated with birth weight, BPD, HC, and AC in both groups (P < 0.05). MCA (S/D, PI, and RI) was negatively correlated with birth weight, HC, and AC in GDM (r = −0.164, −0.206, −0.200, −0.226, −0.189, −0.179, −0.196, −0.177, and − 0.172, respectively, P < 0.05), but there were no correlations in NC (P > 0.05). RA (S/D, PI, and RI) was positively correlated with birth weight in GDM (r = 0.168, 0.207, and 0.184, respectively, P < 0.05), but there were no correlations in NC (P > 0.05).

Conclusion:

Fetal hemodynamic indices in late pregnancy might be helpful for estimating newborn birth weight in women with GDM.

Normal Fetal Growth Assessment: A Review of Literature and Current Practice

A review of literature and current practice of normal fetal growth assessment is presented. Ultrasonographic dating of pregnancy in the first, second, and third trimester is reviewed. Individual biometric parameters are examined, and the proper use of the fetal growth profile is explained. Use of this information is discussed as it pertains to the single pregnancy.

Ultrasound Prediction of Fetal Macrosomia in Diabetic Women and its Effect on the Route of Delivery and the Outcome of Pregnancy

Objective: The purpose of this study is to review the maternal and neonatal outcome in pregnant diabetic women given a trial of labor and delivered macrosomic infants (>4000 grams) and to assess the accuracy of birth weight prediction by ultrasound examination at term.

Methods: One hundred and twenty-nine charts of pregnant diabetic women were reviewed, sixty eight women were given a trial of labor and delivered macrosomic fetuses (>4000 grams), fifty of them had vaginal delivery and the other eighteen had caesarean delivery. In the other group, 61 patients delivered by elective caesarean section, for 41 of them the indication was fetal macrosomia (>4000 grams) as estimated by ultrasound examination and in the other 20, it was due to clinical estimation of big baby. Maternal and neonatal complications were reviewed in each group. Maternal complications included lacerations, hemorrhage and infection and the neonatal complications evaluated were shoulder dystocia and associated birth trauma, asphyxia, and mortality. The accuracy of ultrasound in estimating fetal weight was also evaluated.

Results: Sixty eight (52.7%) women attempted a trial of labor; 73.5% delivered vaginally and 26.5% had a caesarean delivery. All, except two, had macrosomic fetuses (>4000 grams). Only one woman, of those who delivered vaginally, had postpartum hemorrhage due to atonic uterus. The incidence of shoulder dystocia for infants weighing 4000-4499 grams was 6.3% and those infants had the same incidence (6.3%) of brachial plexus injury. There was no perinatal asphyxia or perinatal mortality among those infants who were delivered vaginally. There were no maternal complications for women who had caesarean delivery after labor (18 patients) but there was perinatal asphyxia in two infants who were treated properly without any neurological sequele. Elective caesarean delivery was performed in 47.3% of the study population. There were no neonatal complications or perinatal mortality in this group of patients and only one woman had wound infection. The sonographic prediction of fetal weight was accurate in 52.4% of the cases. The over estimation was in 50.8% of the estimated fetal weights and 49.2% of them were underestimated when compared to actual birth weights.

Conclusions: Caution should be taken in the use of sonographic estimations of fetal weight to guide obstetric decisions concerning labor and delivery. Special consideration should be given to diabetic patients having fetuses with estimatedfetal weights between 4000 and 4500 grams. Flexibility in the management of these patients is best, taking in consideration their previous obstetric performance and if the estimated fetal weight is closer to 4500grams than to 4000 grams, it is perhaps, better to proceed to a primary caesarean delivery.

Accuracy of ultrasound biometry in the prediction of macrosomia: a systematic quantitative review

OBJECTIVE

To determine the accuracy of ultrasonographically estimated fetal weight (EFW) and abdominal circumference (AC) in the prediction of macrosomia.

DESIGN

Systematic quantitative review.

METHODS

Studies were identified without language restrictions from MEDLINE (1966-2003), EMBASE (1980-2003), Cochrane Library (2003:4), SCISEARCH (1974-2003) and manual searching of bibliographies of known primary and review articles. Studies were selected if accuracy of ultrasonographically EFW or AC was evaluated for predicting macrosomia using birthweight as the reference standard. Data were extracted on study characteristics, quality and accuracy. Data were pooled to produce summary receiver operating characteristic curves (sROC) for studies with various test thresholds. Summary likelihood ratios for positive (LR+) and negative (LR-) test results were generated for an EFW of 4000 g and an AC of 36 cm for predicting birthweight of over 4000 g.

MAIN OUTCOME MEASURES

Birthweight over various thresholds.

RESULTS

There were 36 primary articles consisting of 63 accuracy studies (51 evaluating the accuracy of EFW, and 12 accuracy of fetal AC), including a total of 19,117 women. The sROC area for EFW was not different from the area for fetal AC (0.87 vs 0.85, P= 0.91). For predicting a birthweight of over 4000 g, the summary LRs were 5.7 (95% CI: 4.3 to 7.6) for a positive test and 0.48 (95% CI: 0.38 to 0.60) for a negative test, using Hadlock's method of ultrasonographically estimating fetal weight. For ultrasound fetal AC of 36 cm, the respective LRs for predicting a birthweight over 4000 g were 6.9 (95% CI: 5.2 to 9.0) and 0.37 (0.30-0.45).

CONCLUSION

There is no difference in accuracy between ultrasonographically EFW and AC in the prediction of a macrosomic baby at birth. A positive test result is more accurate for ruling in macrosomia than a negative test result for ruling it out.

Fetal cheek-to-cheek diameter in the prediction of mode of delivery

OBJECTIVE

The purpose of this study was to assess sonographic fetal cheek-to-cheek diameter (CCD) in predicting mode of delivery.

STUDY DESIGN

Two hundred sixty-four patients were considered in 2 parts. First, a retrospective analysis of 214 patients entered into a birth weight (BW) study. Measurements of the CCD, biparietal diameter (BPD), and BW, as well as labor data, were collected. Then a prospective study of patients at > or =38 weeks gestational age was conducted. Fetal weight (EFW) was estimated by routine measurements. Information regarding CCD was withheld from the delivering caregiver. Labor records were reviewed for BW and complications, defined as: instrumental delivery, cesarean section (C/S) for nonprogress of labor or "CPD," and "difficult" vaginal delivery. The CCD, BW (both parts), or EFW (prospective part) and mode of delivery were compared.

RESULTS

Abnormal CCD (>2SD above previously published norms for each GA) was closely associated with cesarean delivery, regardless of EFW. At term, risk of C/S with a CCD >7.9 cm was 94%.

CONCLUSION

Within limits, EFW alone has weak correlation with cesarean delivery. CCD, as a reflector of fetal adipose tissue, performs as well as actual BW and demonstrates good prediction for delivery by C/S.

Choosing route of delivery for the macrosomic infant of a diabetic mother: Cesarean section versus vaginal delivery

The macrosomic fetus of a diabetic woman faces increased risk for injury at the time of vaginal birth. Cesarean section offers the promise of 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 two routes of delivery for the overgrown fetus of a diabetic mother are discussed. Specifically, data regarding risk of permanent neurological damage to the infant from vaginal delivery, and maternal morbidity from elective, pre-labor Cesarean delivery are critically examined. In addition, methods for diagnosing macrosomia by ultrasound are discussed, 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.

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.

Correctly identifying the macrosomic fetus: improving ultrasonography-based prediction

OBJECTIVE

Our goal was to improve the accuracy of estimating fetal weights among macrosomic fetuses with the traditional measurements of abdominal circumference, femur length, and head circumference.

STUDY DESIGN

We used 4831 cases without anomalies from an ultrasonography laboratory database with an estimated fetal weight obtained a maximum of 14 days before delivery. Abdominal circumference, femur length, and head circumference were each regressed on birth weight to obtain estimated fetal weight by abdominal circumference, femur length, and head circumference, respectively. We compared the individual variation for estimated fetal weight by abdominal circumference, femur length, and head circumference by calculating a within-subject standard deviation to quantify the level of disparity. We adjusted the estimated fetal weight to the date of delivery and for dependencies on maternal diabetes mellitus, weight, and height. We then weighted cases with birth weight >4500 g and diabetic cases with birth weight >4000 g 20-fold (weighted estimated fetal weight) for the purpose of creating a favorable bias for classifying these cases. The equation of Hadlock et al, with abdominal circumference, femur length, and head circumference, was applied as a benchmark estimated fetal weight.

RESULTS

Of the 4831 newborns, 308 (6.4%) had a birth weight >4000 g, and 56 (1.2%) had a birth weight >4500 g. There were 154 pregnancies complicated by diabetes mellitus; 26 (16.9%) of the resulting infants weighed >4000 g, and 5 (3.2%) weighed >4500 g. At 95% specificity, the weighted estimated fetal weight had a sensitivity of 85.7% at a cut point of 3912 g, compared with a sensitivity of 71.4% at 3604 g by use of the estimated fetal weight of Hadlock et al.

CONCLUSIONS

We were able to improve the accuracy of identifying the macrosomic fetus compared to reliance on the equation by Hadlock et al. A fetus was found to be at significantly increased risk for birth weight >4000 g when the estimated fetal weight based on abdominal circumference is larger than that based on either head circumference or femur length or when there is a large within-subject variance in estimated fetal weight based on abdominal circumference, femur length, and head circumference. We also found that there were significantly different groups of patients whose estimated fetal weights require different equations for better estimates. Even given ultrasonographic measurements, taking into account maternal height, weight, and presence of diabetes mellitus can improve macrosomia detection. Although these findings remain to be optimized and validated, the approach used here appears to yield better predictions than the current "one function fits all" approach.

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.

Fetal ultrasound biometry: 2. Abdomen and femur length reference values

OBJECTIVE

To create reliable reference ranges and calculate Z scores for fetal abdomen and femur ultrasound biometry using a large sample size which is evenly distributed from 12 to 42 weeks of pregnancy.

DESIGN

A prospective, cross-sectional study.

SETTING

Obstetric clinics (outpatient and delivery units) at the University Hospital of Zurich.

SAMPLE

The study data were obtained from 6557 pregnant women.

METHODS

Only the first ultrasound examination between 12 and 42 weeks of each fetus with certainly established gestational age was used for analysis. No exclusions were made on the grounds of small-for-date birthweight, prematurity or other events several weeks after the examination. Separate regression models were fitted to estimate the mean and standard deviation at each gestational age for each parameter.

RESULTS

A total of 5807 mean abdominal diameters and abdominal circumferences were derived from fetal transverse and anterio-posterior fetal abdominal diameter measurements. Fetal femur length was measured in 5860 instances. The charts, tables and regression formulae of the biometrical measurements are presented. A comparison of our charts with others showed no significant difference. Only Merz's centiles for abdominal biometry were lower and for femur length higher than ours. An application to calculate Z scores was developed using Excel (Microsoft Corporation, USA); the macros are presented in detail in the Figure 6 footnote.

CONCLUSIONS

We have presented centile charts, tables and formulae for fetal abdominal diameter and circumference and femur length derived from a large and minimally selected sample size in a carefully designed cross-sectional study. Complete tables and regression formulae to calculate reference ranges and Z scores are presented to use in computer-aided evaluation of fetal ultrasound biometry.

Utilizing sonography to follow fetal growth

In utero diagnosis of fetal growth abnormalities continues to pose a clinical dilemma. Although significant advances have been made in the understanding of growth disturbances and their clinical importance, false-positive and false-negative diagnoses of IUGR and excessive fetal growth continue to affect the accuracy of antenatal diagnosis. Until more accurate methods are developed to aid in diagnosis, multiple biometric parameters should be assessed in patients either at risk for or with a suspected growth disturbance. Serial measurements obtained every 2 to 3 weeks may enhance diagnostic capabilities. Although antenatal diagnosis of IUGR has been shown to be of benefit in improving outcome, more study is needed to determine whether there is a benefit in antenatal diagnosis of macrosomia or LGA.

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 relationship of ponderal index and other measurements to birthweight in preterm neonates

The objective was to determine the relationship between birthweight and anthropometric indices (PI and MAC/ OFC) in preterm infants. A group of 163 singleton preterm neonates born at 24-36 weeks were examined. Measurements were made of crown-heel length, midarm circumference, and occipito-frontal circumference. Birthweights were calculated as multiples of the mean (MoMs) for a given stage of gestation. There was a highly significant correlation between gestational age and MAC/OFC (p < 0.0001) but none with ponderal index. There was a significant correlation between weight expressed as multiples of the mean and both ponderal index (p < 0.008) and MAC/OFC (p < 0.0001). This relationship between birthweight and anthropometric indices suggests that measurement of the ponderal index does not provide a useful index of intrauterine nutrition.

Clinical and ultrasound prediction of macrosomia in diabetic pregnancy

OBJECTIVE

To study prospectively the prediction power, at different gestations, of clinical and ultrasound measurements for fetal size in diabetic pregnancy.

SETTING

A large combined obstetric diabetic clinic in a teaching hospital.

PARTICIPANTS

One hundred and eighty-one pregnancies in which women had scans at least two of three specific time points and who were delivered of singletons after 34 weeks: 73% were pre-gestational insulin-dependent diabetics, the others were pre-gestational White class A or gestational diabetics.

INTERVENTIONS

Clinical estimates of fundal height and fetal size and ultrasound estimates of abdominal circumference and head circumference were routinely carried out at gestational ages of 28, 34 and 38 weeks or before delivery.

MAIN OUTCOME MEASURES

Standardised birthweight, corrected for gestation and parity. The relation with clinical and ultrasound measurements was investigated using multiple linear regression and the capability of the measurements to predict macrosomic births (> 95th centile of normals) using receiver-operator characteristic curves.

RESULTS

All measurements are poor predictors of eventual standardised birthweight. Prediction improves with closeness to delivery. Prediction is significantly improved by adding ultrasound to clinical information, but at 34 weeks or later this only contributes 8% of the variance. There is no difference in the prediction power for macrosomia between clinical and ultrasound measurements.

CONCLUSIONS

Even regular serial scanning and clinical examination will not always diagnose the macrosomic fetus in diabetic pregnancy. In our hands, clinical examination is as predictive as ultrasound measurements. Ultrasound does add to clinical prediction power but only to a small extent. Ultrasound should be used in a selected way, as defined by clinical findings, and with recognition and understanding of the errors and biases involved.

Common clinical manifestations of maternal diabetes in newborn infants: implications for the practicing pediatrician

Even though perinatal mortality of infants of diabetic mothers has decreased remarkably in recent years and now approaches that of the general population, these infants still face a multitude of potential complications and the propensity for increased morbidity, both in utero and postnatally. Many of these complications are clearly related to the metabolic status of the diabetic mother. Increasing awareness among insulin-dependent diabetic patients and health providers of the need for glycemic control and the ever-growing understanding of the peculiarities of diabetic pregnancies eventually should combine to provide the best possible outcome for these infants.

The use of a neural network for the ultrasonographic estimation of fetal weight in the macrosomic fetus

The error associated with regression analysis methods for the ultrasonographic estimation of fetal weight in the suspected macrosomic fetus, approximately 10%, is clinically unacceptable. This study was undertaken to evaluate the applicability of an emerging technique, biologically simulated intelligence, to this problem. One hundred patients with suspected macrosomic fetuses underwent ultrasonographic measurements of biparietal diameter, head and abdominal circumference, femur length, abdominal subcutaneous tissue, and amniotic fluid index. The biologically simulated intelligence model included gestational age, fundal height, age, gravidity, and height. The model was then compared with results obtained from previously published formulas relying on the abdominal circumference and femur length. The biologically simulated intelligence yielded an average error of 4.7% from actual birth weight, statistically better (p = 0.001) than the results obtained from regression models.

Ultrasonographic fetal weight estimation by an integrated computer-assisted system: can each laboratory improve its accuracy?

Estimated fetal weights from 1684 cases with singleton, live infants born within 7 days of an ultrasonographic examinations were compared with their birth weights, which ranged from 520 to 5920 gm. Estimated weight calculated from Shepard's equation produced a linear relationship of birth weight against estimated weight with an intercept and slope of 209.5 gm and 0.929. Overall, 75% of the estimated weights were within 15% of the actual weight. A separate regression model that used the same variables from Shepard's equation failed to improve the comparison between estimated and actual weights. All cases were reevaluated with multiple regression modeling. Various examination-to-birth intervals were analyzed; intervals less than or equal to 3 days appeared optimal. The best equation increased the percent of cases that were within 15% of the actual birth weight to 80%. The plot of birth weight against estimated weight had an intercept and slope of 33.1 gm and 0.994. Unlike Shepard's equation, the best equation was not statistically different from the ideal one-to-one relationship between estimated and actual weight. When the new equation was applied to an additional 339 new cases, equally accurate results were obtained. Customizing a laboratory's ultrasonographic weight estimation equations may be necessary to obtain the best estimate of fetal weight.

Ultrasonographic estimation of fetal weight in the clinically macrosomic fetus

The purpose of this study is to evaluate models for the prediction of birth weight in fetuses suspected of being macrosomic. A total of 141 patients with standard measurements of the head, abdomen, and femur were studied. Linear regressions were performed with single parameters, squares, and all possible cross products in the generation of models with log (birth weight) and birth weight as dependent variables. These models were then compared with a group of previously published equations. Clinically, all models performed poorly. However, two models were significantly less accurate in the prediction of birth weight (p less than or equal to 0.05). The best results were obtained by equations that used abdominal circumference and femur length measurements. There was no improvement in models that contained log (birth weight) or birth weight as dependent variables or models with complex variables such as squares or cross products of measured parameters. In conclusion, when evaluating patients at risk of macrosomia, the best estimates of fetal weight can be obtained by models that contain abdominal circumference and femur length.

Ultrasonographic identification of the macrosomic fetus

Ultrasonographically determined biparietal diameter, femur length, abdominal circumference, and estimated fetal weight were analyzed with regard to their ability to predict the macrosomic newborn. Receiver operating characteristic curves were plotted for each of these variables. Estimated fetal weight was superior to biparietal diameter or femur length measurements in the identification of the overgrown fetus. Because of limitations of positive predictive values and sensitivities, application of these observations varies with the clinical setting in which they are used.

Early third-trimester ultrasound screening in gestational diabetes to determine the risk of macrosomia and labor dystocia at term

The purpose of this study was to determine whether an early third-trimester fetal abdominal circumference measurement can be used in patients with gestational diabetes to predict the presence or absence of macrosomia and labor dystocia at term. The predictive accuracy of a 30- to 33-week abdominal circumference measurement was tested, using the ninetieth percentile as the discriminant point. The study consisted of 201 patients with gestational diabetes who maintained weekly fasting glucose levels less than 100 mg/dl and 2-hour postprandial glucose levels less than 120 mg/dl with dietary management alone. The predictive accuracy of a 30- to 33-week fetal abdominal circumference measurement was 96.4% for ruling out macrosomia and 56.3% for predicting macrosomia. Patients with fetal abdominal circumference measurements greater than the ninetieth percentile at 30 to 33 weeks had a significantly increased incidence of cesarean section for failure to progress, shoulder dystocia, and birth trauma, whereas patients with abdominal circumference measurements less than or equal to the ninetieth percentile were at no greater risk than the general population. These results suggest that patients with non-insulin-dependent gestational diabetes with fetal abdominal circumference measurements less than or equal to the ninetieth percentile at 30 to 33 weeks are not at increased risk for macrosomia, cesarean section, or birth trauma at term, as long as their weekly glucose testing remains within normal limits. Efforts to decrease the incidence of macrosomia and its attendant risks should focus on those gestational diabetic patients whose fetal abdominal circumference greater than the ninetieth percentile at 30 to 33 weeks.

Sonographic determination of fetal weights in diabetic pregnancies

Accurate antenatal diagnosis of the macrosomic infant of a diabetic mother should lead to a decrease in perinatal morbidity. Several formulas for weight estimation based on sonographic measurements are in common use, but none of them has been devised specifically for the infant of a diabetic mother. We assessed the accuracy of conventional formulas at estimating fetal weight in 160 of these infants and found their relative errors (error as a percentage of birth weight) had standard deviations of 12.2% to 13.1% (greater than has been reported in the general population) with no statistically significant difference among formulas. We also devised customized formulas generated from a "training set" of 80 patients and tested on a second set of 80 patients. The best formula yielded a standard deviation of 11.0%. The difference between customized and conventional formulas was not statistically significant. With use of one conventional formula, the likelihood of macrosomia was found to be 77% when the estimated weight was greater than 4000 gm and 86% when the estimated weight was greater than 4500 gm. We conclude that fetal weight prediction is even less accurate in the infant of a diabetic mother than in the general population and that "customized" formulas fare no better than conventional formulas in diabetics. Despite this, estimated weights can offer guidance in predicting fetal macrosomia and therefore aid in obstetric management.