A comparison of fetal abdominal circumference measurements and Doppler ultrasound in the prediction of small-for-dates babies and fetal compromise

Summary. A total of 145 pregnancies clinically suspected of being small-for-dates was studied at presentation with a single measurement of the fetal abdominal circumference and Doppler studies of the umbilical and arcuate arteries. The abdominal circumference measurement gave the best prediction of the small-for-gestational-age (SGA) baby (sensitivity 73%, umbilical artery sensitivity 47%, arcuate artery sensitivity 29%). The umbilical artery measurement gave the best prediction of antenatal fetal compromise; the performance of the tests was compared for a fixed sensitivity of 100% (i. e. all cases of antenatal compromise would be detected), the specificity of the umbilical artery measurement was 77%, abdominal circumference measurement 12% and arcuate artery measurement 2%. In our data, umbilical artery studies were not a sensitive predictor of the SGA baby but they did give an accurate prediction of the potentially compromised SGA fetus.     

Intrauterine volume, fetal abdominal area and biparietal diameter measurements with ultrasound in the prediction of small-for-dates babies in a high-risk obstetric population

The value of fetal biparietal diameter and abdominal area, total intrauterine, intra-amniotic and placental volume measurements for predicting small-for-dates babies in a high-risk obstetric population was investigated in 130 women. A parallel planimetric area method was used to measure volume. The commonest risk factors were suspected intrauterine growth-retardation, hypertensive complications and previous poor obstetric history. The prevalence of birthweight at and below the 10th or 3rd centiles was 30 and 16% respectively. Fetal abdominal area and total intrauterine volume measurements had the highest and comparable sensitivity, specificity and positive predictive value in the detection of infants with birthweights of less than or equal to 10th and less than or equal to 3rd centiles. While these measurements are of use in consolidating the clinical diagnosis of small-for-dates fetuses (growth retardation), high false positive rates (10% and 16-17% for birthweights less than or equal to 10th centile, and less than or equal to 3rd centile respectively) make further discriminatory tests necessary for part of the population.     

Intrauterine volume, fetal abdominal area and biparietal diameter measurements with ultrasound in the prediction of small-for-dates babies in a high-risk obstetric population.

Summary. . The value of fetal biparietal diameter and abdominal area, total intrauterine, intra-amniotic and placental volume measurements for predicting small-for-dates babies in a high-risk obstetric population was investigated in 130 women. A parallel planimetric area method was used to measure volume. The commonest risk factors were suspected intrauterine growth-retardation, hypertensive complications and previous poor obstetric history. The prevalence of birthweight at and below the 10th or 3rd centiles was 30 and 16% respectively. Fetal abdominal area and total intrauterine volume measurements had the highest and comparable sensitivity, specificity and positive predictive value in the detection of infants with birthweights of 10th and 3rd centiles. While these measurements are of use in consolidating the clinical diagnosis of small-for-dates fetuses (growth retardation), high false positive rates (10% and 16–17% for birthweights 10th centile, and 3rd centile respectively) make further discriminatory tests necessary for part of the population.     

Efficacy of intrauterine volume, fetal abdominal area and biparietal diameter measurements with ultrasound in screening for small-for-dates babies

Summary. The efficacy of total intrauterine, intra-amniotic and placental volume measurements with ultrasound in screening for low birthweight (10th and 3rd centile) was compared prospectively with fetal biparietal diameter and abdominal area measurements at 32 and 36 weeks gestation in an unselected population of 362 women. In all of them the gestation was dated by ultrasound in the first half of pregnancy. Reference values were from a separate normal population studied previously. Total intrauterine volume showed the highest sensitivity in predicting babies weighing 10th centile (58% at 32 weeks and 62% at 36 weeks) and those weighing 3rd centile (78% at 32 weeks and 83% at 36 weeks). A higher number of false-positive tests resulted in a lower predictive value of a positive test (mean 34% for babies weighing 10th centile) than that found for abdominal area (mean 54%). Abdominal measurements selected a smaller'at risk'group. Biparietal diameter, intra-amniotic and placental volume measurements had inferior predictive capability than total intrauterine volume and abdominal area. For screening purposes abdominal area measurements are presently more suitable than intrauterine volume. The higher sensitivity of intrauterine volume, particularly in early third trimester, is an advantage that requires further investigation with reference to intrauterine growth retardation.     

An improved method of fetal weight estimation using ultrasound measurements of fetal abdominal circumference

A simple and accurate method is described for estimating fetal weight from a single fetal abdomen circumference measurement at the level of the umbilical vein. The abdominal circumference was converted into a weight centile for the maturity at the time of measurement so that the weight at delivery could be predicted. This method was tested on a population of fetuses presenting by the breech near term. Although the error between actual and predicted weights was 194 g (1 SD) for all the patients, for a large well-defined subgroup the error was much smaller, being only 104 g (1 SD).     

Macrosomia prediction using ultrasound fetal abdominal circumference of 35 centimeters or more

OBJECTIVE: To determine if birth weights greater than 4000 g can be predicted by ultrasound measurements of abdominal circumferences. METHODS: In 1996, 254 newborns delivered at Tampa General Hospital weighed at least 4000 g, 84 of whom had ultrasound examinations within 2 weeks of delivery. Those were compared with 84 neonates with recent ultrasounds who weighed less than 4000 g. Data were abstracted retrospectively from maternal medical records. RESULTS: The best linear predictor of birth weight was ultrasound measurement of abdominal circumference (AC), which had a correlation coefficient of 0.95. An AC measurement of 35 cm or more predicted 93% of macrosomic infants. Among 177 macrosomic infants born vaginally, 23 (13%) had shoulder dystocia. In that group, induction of labor was associated with a greater than three-fold increase in risk of shoulder dystocia (odds ratio [OR] 3.4, 95% confidence interval [CI] 1.4, 8.2; P < .01). Labor augmentation was not associated with increased risk of shoulder dystocia. CONCLUSION: Abdominal circumference measurements were useful in screening for suspected macrosomia. An AC measurement of 35 cm or more identified more than 90% of macrosomic infants who were at risk for shoulder dystocia. Induction of labor in macrosomic patients increased the risk of shoulder dystocia.     

Sonographic evaluation of fetal abdominal circumference and cerebroplacental Doppler indices for the prediction of fetal macrosomia in full term pregnant women. Cohort study

ObjectivesThe aim of the study was to explore the relationship between cerebroplacental Doppler ratio and birth weight in cases of suspected fetal macrosomia.MethodsThe 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 150 ultrasound-dated pregnancies at ⩾ 37 weeks’ gestation divided into two groups as follows; large for gestational age (LGA, n = 50) and average for gestational age (AGA, n = 100).ResultsThere is a significant difference between groups in abdominal circumference (AC), head circumference (HC), biparital diameter (BPD), estimated fetal weight (EFW) and actual fetal weight with a mean difference of 92.7 g in the LGA group and 84 g in the AGA group. MCA-RI and PI were significantly lower in the LGA group with no difference in UA-RI, PI and CPR-PI between both groups.ConclusionsCPR-PI could not differentiate between LGA and AGA.     

Doppler ultrasound prediction of fetal outcome in twin pregnancies

The usefulness of pulsed Doppler ultrasound in predicting twin pregnancies destined for unsatisfactory outcomes was examined in 30 twin pregnancies. Fetal flow velocity waveform analysis (systolic/diastolic ratio and pulsatility index) and quantitative analysis in the descending aorta and umbilical artery demonstrated good sensitivity and specificity when compared with biparietal diameter and abdominal circumference measurements. This technique shows some promise as a useful adjunct in the management of twin pregnancies.     

Accuracy of an average ultrasonic laboratory in measurements of fetal biparietal diameter, head circumference and abdominal circumference

Twenty patients between 14 and 28 gestational weeks were scanned on three occasions during a single day by six operators with different ultrasonic experience (three use a compound scanner and three a real-time equipment). On each occasion every operator had to measure in a "blind" manner the fetal biparietal diameter (BPD), head circumference and abdominal circumference (HC and AC); a coded copy of head and abdominal circumference was subsequently measured by one of the members of the staff. Statistical analysis was carried out on the 1800 measurements, and it was concluded that the accuracy was not dissimilar from that reported by pilot studies. The reproducibility of the parameters studied did not change throughout pregnancy and real-time and compound scanner yielded homogeneous results.     

Ultrasonic fetal abdominal circumference: comparison of direct versus calculated measurement

The ultrasonically derived fetal abdominal circumference is one of the essential parameters used to predict birth weight, assess fetal growth, and follow the evolution of fetal ascites. Growth curves relating abdominal circumference to gestational age have been reported for directly measured abdominal circumferences. However, none have been reported for abdominal circumferences calculated from measurements of fetal abdominal diameters. In this report, 197 normal fetuses ranging from 18 to 41 weeks' gestation are studied. The validity of 468 abdominal circumferences calculated from fetal abdominal diameters is tested by comparing the data with a similar number of direct abdominal circumference measurements obtained by a digitizer. From 18 to 41 weeks' gestation, directly measured fetal abdominal circumferences are significantly larger than fetal abdominal circumferences calculated from abdominal diameters (P less than .0001). The authors conclude that clinical management decisions based on abdominal circumference data are predicated on the use of appropriate abdominal circumference and/or abdominal diameter growth curves.     

Effectiveness of ultrasound determination of fetal abdominal circumference and fetal ponderal index in the diagnosis of asymmetrical growth retardation

A total of 310 unselected women attending an antenatal clinic was screened for growth retardation by ultrasound between 34 and 36 weeks gestation, by measuring the fetal abdominal circumference (AC) and femoral length (FL), from which the 'fetal ponderal index' (AC/FL) was calculated. Asymmetrical growth retardation in the newborn was assessed by Rohrer's ponderal index and the mid-arm/occipito-frontal circumference (MAC/OFC) ratio within 72 h of birth, a neonatal ponderal index or MAC/OFC ratio below the 10th centile being considered abnormal. The sensitivities of an AC below the 25th centile in identifying a birthweight, neonatal ponderal index or MAC/OFC ratio below the 10th centile were 86, 62 and 67% respectively, the specificities being 80, 78 and 76%. The sensitivities of a fetal ponderal index below the 25th centile in identifying a neonatal ponderal index or MAC/OFC ratio below the 10th centile were 52 and 47% respectively, the specificities being 77 and 77%. A possible reason for the poor performance of the fetal ponderal index is discussed.     

Effectiveness of ultrasound determination of fetal abdominal circumference and fetal ponderal index in the diagnosis of asymmetrical growth retardation

Summary. A total of 310 unselected women attending an antenatal clinic was screened for growth retardation by ultrasound between 34 and 36 weeks gestation, by measuring the fetal abdominal circumference (AC) and femoral length (FL), from which the 'fetal ponderal index' (AC/FL) was calculated. Asymmetrical growth retardation in the newborn was assessed by Rohrer's ponderal index and the mid-arm/ occipito-frontal circumference (MAC/OFC) ratio within 72 h of birth, a neonatal ponderal index or MAC/OFC ratio below the 10th centile being considered abnormal. The sensitivities of an AC below the 25th centile in identifying a birthweight, neonatal ponderal index or MAC/ OFC ratio below the 10th centile were 86, 62 and 67% respectively, the specificities being 80, 78 and 76%. The sensitivities of a fetal ponderal index below the 25th centile in identifying a neonatal ponderal index or MAC/OFC ratio below the 10th centile were 52 and 47% respectively, the specificities being 77 and 77%. A possible reason for the poor performance of the fetal ponderal index is discussed.     

Ultrasound determination of fetal abdominal circumference: a comparison of measurement methods

The measurement of fetal abdominal circumference by the direct perimeter method using a digitizer was compared with calculation of this measurement using the fetal mean abdominal diameter in 235 cases. The directly measured abdominal circumference was found to be greater than the calculated value (p = 0.00014). The magnitude of the difference, however was only 1.3 +/- 2.2%, which is smaller than the average interobserver measurement error. Although statistically significant, the difference between these two measurement methods is not clinically significant, and these data and discussion show that either method is acceptable to determine fetal abdominal circumference.     

Serial fetal abdominal circumference measurements in predicting normal birth weight in gestational diabetes mellitus

ObjectivesTo construct a clinical management matrix using serial fetal abdominal circumference measurements (ACMs) that will predict normal birth weight in pregnancies complicated by gestational diabetes (GDM) and reduce unnecessary ultrasound examination in women with GDM.Study designRetrospective cohort study of 144 women with GDM in a specialist obstetric-diabetes clinic. Women with GDM who delivered singleton infants were identified from a clinical register. Regression analysis was used to identify associations between serial ACMs, maternal parameters and normal birth weight (birth weight between the 10th and 90th percentiles). Predictive clinical models were designed with the aim of identifying normal birth weight infants with the lowest number of fetal ultrasound scans.ResultsCompared to mothers of large-for-gestational-age (LGA) infants, mothers of normal weight infants had lower fasting glucose measurements at diagnosis (5.9 mmol/l ± 1.0 vs. 6.6 mmol/l ± 0.7, p < 0.05), lower maternal weight at delivery (90 kg ± 17 vs. 96 kg ± 17, p < 0.05), and a lower rate of prior LGA infants (31% vs. 60%, p < 0.05). Maternal weight and a history of prior LGA delivery were identified as useful predictors of fetal birth weight in predictive models. Serial ACMs below the 50th, 75th and 90th percentiles could predict normal birth weight with 100%, 97% and 96% positive predictive value respectively when used in these risk factor based models. Two measurements sufficed in low-risk pregnancies.ConclusionSerial ACMs can predict normal birth weight in GDM.     

A comparison of fetal organ measurements by echo-planar magnetic resonance imaging and ultrasound

OBJECTIVES: To compare fetal organ size measured using echo-planar magnetic resonance imaging and 2D ultrasound. To determine the relative accuracy with which each technique can predict fetal growth restriction. DESIGN: A cross sectional, observational study comparing two different measurement techniques against a gold standard, in a normal clinical population and an abnormal population. SETTING AND POPULATION: Seventy-four pregnant women (33 who were ultimately found to be normal and 37 with fetal growth restricted fetuses) were recruited from the City Hospital Nottingham UK to be scanned once (at various gestations). METHODS: Each fetus had a standard ultrasound biometry assessment followed by magnetic resonance imaging measurement of organ volumes. MAIN OUTCOME MEASURES: For each measurement for both techniques, the normal population was plotted with 90% confidence intervals. Fetal growth restricted subjects were compared with the normal population using this plot; 2 x 2 tables were created for each measurement. This was used to calculate the relative sensitivities and positive predictive value of the different measurements. A Bland-Altman plot was used to compare the ultrasound and magnetic resonance imaging measurements of fetal weight. RESULTS: Brain sparing was seen in ultrasonic head circumference measurements, but an overall reduction in fetal growth restriction brain volume was apparent using magnetic resonance imaging at late gestations. Across the whole range of gestational ages, ultrasound assessment of fetal weight was the best predictor of fetal growth restriction. CONCLUSION: Ultrasound fetal weight assessment appears to identify more fetuses with fetal growth restriction than abdominal circumference. The brain sparing apparent in ultrasonic head circumference measurements of fetuses with fetal growth restriction masks a reduction in brain volume observed with magnetic resonance imaging.     

Fetal abdominal circumference rather than fetal femur length/abdominal circumference ratio predicts fetal malnutrition in high risk pregnancies

The aim of this study was to compare the ability of abdominal circumference (AC) and fetal femur length/abdominal circumference ratio (FFL/AC) measured by ultrasound within a period of 2 weeks before birth to predict low birth weight percentile and neonatal signs related to fetal malnutrition. From longitudinal ultrasound measurements in 35 normal pregnancies reference data of AC and FFL was obtained. FFL/AC ratio was constant from 21 weeks until term (mean 20.9, SD 1.2) (figure 1). In 350 risk pregnancies AC standard deviation score (AC-SDS) correlated far better than FFL/AC ratio with the deviation of birth weight from normal (figure 3). Furthermore AC-SDS correlated better with ponderal index (PI) and skinfold thickness (ST) than did FFL/AC ratio. Using cut-off levels on AC-SDS and FFL/AC ratio, which selected about 30% of the population, the sensitivity of AC-SDS in predicting the infant being LGA was 81.8% versus 42.9% using FFL/AC ratio (table II). The prediction of the infant being SGA was not improved when the change in AC-SDS or FFL/AC over the last 6-8 weeks of pregnancy was considered. We conclude that AC-SDS correlates well with birth weight deviation and predicts the infant being SGA with a precision equal to the best results reported in the literature, and that FFL/AC ratio is unreliable even when GA is not known because of a high false positive rate.     

Direct measurements of fetal cerebral blood-flow velocity with duplex Doppler ultrasound

A new Doppler technique for assessing the fetal cerebral circulation is described. Cerebral blood-flow velocity was measured in 15 fetuses and 18 neonates of similar gestational age. The median fetal and neonatal velocities were 4.5 cm/s and 8 cm/s, respectively, with a larger range in the neonatal values. This technique is a noninvasive method of studying fetal cerebral physiology and may be of value in detecting intra-uterine asphyxia.