Could birthweight prediction models be improved by adding fetal subcutaneous tissue thickness?

AIM: The aims of the study were to: (i) compare the accuracy of standard ultrasonic algorithms in the estimation of fetal weight and; (ii) test two new algorithms in order to improve the global performance of birthweight prediction by adding fetal subcutaneous tissue thickness. METHODS: We enrolled 398 patients who were between 34 and 42 weeks' gestation. Routine ultrasonographic biometric parameters as well as subcutaneous tissue thickness ultrasound parameters were measured. Correlation matrices between ultrasound parameters, in order to evaluate the degree of multicollinearity between these parameters, were assessed to develop a stepwise multiple regression birthweight predictive model. RESULTS: Contributions of single ultrasound measurements in predicting birthweight were examined, by fitting Log-transformed birthweight versus single ultrasound measurements. We found that the mid-thigh tissue area was able to significantly improve the performance of the birthweight prediction process when added to the other standard ultrasound measurements. We derived two new algorithms which appeared to be better at predicting birthweight. Furthermore there was a lower minimum absolute estimation error noted when compared to other reported formulae. CONCLUSIONS: Our algorithms showed that the addition of the mid-thigh tissue evaluation in birthweight prediction was valuable in comparison to birthweight prediction models which are based on routine ultrasound parameters.     

Differences in fat and lean mass proportions in normal and growth-restricted fetuses

OBJECTIVE: The purpose of this study was to assess fetal subcutaneous fat and lean mass areas as predictors of fetal growth restriction. STUDY DESIGN: Seventeen severe fetal growth-restricted (abdominal circumference, < 2 SD) fetuses and 20 control fetuses underwent ultrasound measurements of subcutaneous fat, lean mass, and standard biometry. Thigh subcutaneous fat and lean mass were measured on enlarged ultrasound axial images (subcutaneous fat area = total cross sectional area - lean mass area [bone + muscle areas]). Subcutaneous fat and lean mass areas were expressed as a percentage of the total cross-sectional area and were normalized to femur length and head circumference. Measurements were modeled as a function of fetal growth-restriction status and week of gestation with multiple linear regression. RESULTS: Fetal growth-restriction fetuses showed reductions in fat and lean mass (in standard biometry) and showed a disproportionate reduction in fat mass compared with lean mass. These were all associated significantly with fetal growth restriction. CONCLUSION: Fetal growth-restricted fetuses have reduced subcutaneous fat and lean mass compared with control fetuses; a further reduction occurs in subcutaneous fat concentration compared with the reduction in lean mass when fat is normalized for body size, with either head circumference or femur length. Fat-to-bone proportions may be useful in distinguishing the small for gestational age fetus who is truly fetal growth restriction from the constitutionally small fetus.     

Factors associated with fetal growth and body composition as measured by ultrasound

OBJECTIVE: This study seeks to determine which parental demographic and metabolic factors best correlate with fetal growth and body composition as estimated by ultrasound. STUDY DESIGN: Thirty-one gravid patients had ultrasound estimates of fetal anthropometry in mid-third trimester. These measurements included estimated fetal weight, abdominal subcutaneous fat, and/or thigh subcutaneous fat thickness. Independent variables included diagnosis of gestational diabetes, parental demographic factors, neonatal sex, and late gestation estimates of carbohydrate metabolism. RESULTS: In the multivariate stepwise model the strongest predictor of ultrasound estimated fetal weight was basal hepatic glucose production, followed by late gestation insulin sensitivity (total R (2) = 0.27). The strongest predictors of abdominal subcutaneous fat thickness were weight gain and presence of gestational diabetes (total R (2) = 0.25). CONCLUSION: Measures of maternal carbohydrate metabolism, rather than fat mass, explain sonographic measurements of fetal weight. We speculate that factors other than maternal carbohydrate metabolism further explain the variances of fetal adiposity.     

Sonographic estimation of fetal weight in diabetic pregnancy.

OBJECTIVE: To investigate whether fetal weight estimation by ultrasound in diabetic pregnancy might be based upon fetal abdominal circumference (AC) alone. DESIGN: A retrospective study. SETTING: Diabetes Center, Rigshospitalet and Ultrasound Laboratory, Glostrup Hospital, Copenhagen. SUBJECTS: Eighty-six diabetic pregnant women who had an ultrasound study within 2 days before delivery. RESULTS: We assessed in 73 fetuses various formulas based upon biparietal diameter and AC against formulas based upon AC alone, and these were only marginally less effective than the more complex ones. In 86 fetuses an AC was available. These fetuses were divided into a study population and a test population. The linear model was customized for the study population. Evaluation on the test population showed that the relative error (error as a percentage of birthweight) in predicting birthweight had a standard deviation of 7.8%. The efficacy of AC in detecting fetuses greater than 4000 g was examined in the test population: If AC greater than 36.0 cm was chosen as criterion for macrosomia the positive and negative predictive values were 80% (8/10) and 91% (30/33), respectively. CONCLUSION: Formulas for estimating fetal weight in diabetic pregnancy based on AC alone are almost as effective as more complex ones. We recommend a simple linear formula of fetal weight as a function of AC.     

Estimation of fetal weight by ultrasound prior to 33 weeks gestation

The aim of this study was to develop an accurate formula for the ultrasonic prediction of fetal weight for infants < 33 weeks gestational age and < or = 1500 g birthweight. The subjects comprised live births free of lethal malformations or chromosomal anomalies, < 33 weeks gestational age and with birthweights +/- 1500 g born in the Royal Women's Hospital between January 1990 and March 1996. All subjects had accurate gestational age confirmed by ultrasound prior to 20 weeks gestation and ultrasound measurements within 72 hours of birth of biparietal diameter (BPD), femur length (FL) and abdominal circumference (AC). A formula with the highest explained variance was computed by linear regression analysis using the three fetal variables in various combinations from 54 infants born between January 1990 and December 1993. The optimal formula was: Log(10)birthweight = 0.714627 + 0.077362.AC + 0.058758.BPD + 0.287037.FL - 0.011274.AC.FL. The new formula was more accurate compared with existing formulae when tested in a separate cohort of 39 infants born between January 1994 and March 1996.     

单项超声测量指标预测胎儿体重的临床应用

目的：探讨应用胎儿腹围单项超声测量指标预测胎儿出生体重的临床价值。方法：（１）应用Ｂ型超声对３００例胎儿的腹围、小脑横径、双顶径、股骨长进行测量，并与新生儿出生体重的关系进行分析。经单元线性回归得出腹围预测胎儿体重的单元方程式。（２）应用此方程对３３０例胎儿进行前瞻性验证。结果：腹围与新生儿体重的相关性最好，（ｒ＝０．８６６７９）。依据腹围可以初步预测胎儿出生的体重范围。其符合率达８０．０％。结论：应用超声测量胎儿腹围预测出生体重，方法简单，且较准确，有较好的临床实用价值。     

Subcutaneous fat in the fetal abdomen as a predictor of growth restriction.

OBJECTIVE: To determine if measuring fetal abdominal fat antenatally using ultrasound can predict fetal growth restriction (FGR). METHODS: One hundred thirty-seven unselected women with singleton pregnancies had serial ultrasound scans at 20, 26, 31, and 38 weeks' gestation. Subcutaneous fat in the fetal abdomen was measured using the same section as the abdominal circumference (AC). Outcome measures were birth weight, neonatal morbidity, and ponderal index. RESULTS: Infants with subcutaneous fat less than 5 mm at 38 weeks (n = 51) were almost five times more likely to have a birth weight below the 10th centile than those with subcutaneous fat of 5 mm or more (n = 75). The incidence of neonatal morbidity was significantly higher in infants with subcutaneous fat less than 5 mm, compared with those with subcutaneous fat of 5 mm or more (20% versus 8%, P < .05). Decreased subcutaneous fat was also associated with a high prevalence of low ponderal index, regardless of birth weight category. CONCLUSION: Measurement of fat in the abdominal wall is a simple technique with a sensitivity for predicting low birth weight similar to that of conventional sonography and might potentially predict FGR irrespective of fetal weight.     

超声测量胎儿腹围预测巨大胎儿

目的　探讨产前预测新生儿出生体重的相关因素及超声测量胎儿腹围能否预测巨大胎儿。　方法　前瞻性选择 148例宫高 腹围≥ 135 cm的足月单胎已临产的孕妇 ,超声测量其胎儿双顶径、腹围、股骨长度 ,皮尺测量孕妇宫高、腹围 ,核对孕龄 ,分析这些因素与新生儿出生体重的相关性 ;按新生儿体重将这些孕妇分为巨大儿组和非巨大儿组 ,比较两组的资料 ;分析胎儿腹围与巨大儿的特定关系。　结果　多因素逐步回归分析显示单一胎儿腹围是预测胎儿体重的最好参数 ,优于胎儿腹围与股骨长的联合应用。其与胎儿体重呈直线正相关 ,r=0 .85。胎儿腹围≥ 36 cm可以预测 82 %的巨大儿 ,巨大儿组剖宫产率 70 .2 %。　结论　胎儿腹围与胎儿体重呈高度直线正相关 ,是预测胎儿体重的较好参数。在产前怀疑有巨大儿的可能时 ,超声测量胎儿腹围有助于其诊断。     

Reduction of subcutaneous mass, but not lean mass, in normal fetuses in Denver, Colorado

OBJECTIVE: To test the hypothesis that reduced birth weight in normal fetuses born at moderately high altitude (Denver), compared with the birth weight in normal fetuses born at sea level (Milan), is caused by a reduction in both lean mass and subcutaneous fat mass. STUDY DESIGN: Ninety-four normal singleton pregnancies (46 in Denver, 48 in Milan) had serial ultrasonographic axial images obtained to assess subcutaneous tissues of fetuses as a measure of body fat. The abdominal wall thickness and mid upper arm and mid thigh were examined. The equation was: Subcutaneous tissue equals total cross-sectional area minus bone and muscle area. Lean mass included the area of muscle and bone, head circumference, and femur length. RESULTS: Gestational age at delivery was similar between groups. Birth weight was less at Denver's altitude (2991 +/- 79 g versus 3247 +/- 96 g; P =.04). Abdominal wall thickness, mid upper arm, and mid thigh subcutaneous tissues measurements were significantly reduced at Denver's altitude and increased further in significance with advancing gestational age. Lean mass measurements were similar between groups. CONCLUSIONS: The reduced birth weight of the newborns in Denver was the result of a reduction in fetal subcutaneous fat tissue and not lean mass. Ultrasonography can be used to follow subcutaneous measurements longitudinally and to detect differences, and potentially disease processes, in study populations.     

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.     

Visceral fat is more important than peripheral fat for endometrial thickness and bone mass in healthy postmenopausal women

OBJECTIVE: The purpose of this study was to investigate the influence of body mass index and body composition on endometrial thickness and bone mass. STUDY DESIGN: This was a cross-sectional study that included 531 healthy postmenopausal women aged 48 to 65 years. Endometrial thickness was measured as double-layer thickness. Body composition was measured by dual energy x-ray absorptiometry, which divides the body into fat mass, lean mass, and bone mass, both for the total body and regional body compartments. An abdominal region was inserted manually. Statistics were Pearson correlations and analysis of variance. RESULTS: Endometrial thickness and total body bone mass were correlated, respectively, to body mass index (r = 0.14, P <.01; r = 0.35, P <.001), total body fat mass (r = 0.14, P <.01; r = 0.38, P <.001), abdominal fat mass (r = 0.16, P <.001; r = 0.33, P <.001), peripheral fat mass (r = 0.10, P <.05; r = 0.41, P <.001), and abdominal/peripheral fat mass (r = 0.12, P <.01; r = 0.11, P <.01). CONCLUSION: High body mass index and abdominal fat distribution correlate with increased endometrial thickness and bone mass.     

Impact of maternal cigarette smoking on fetal growth and body composition

OBJECTIVE: The aim of this study was to determine the impact of maternal cigarette smoking on the fetal accretion of fat and lean body mass. We hypothesized that maternal smoking would result in a reduction in the deposition of lean body mass. STUDY DESIGN: Longitudinal ultrasonographic examinations on 65 singleton fetuses without anomalies of smoking mothers were compared with 36 singleton fetuses without anomalies of nonsmoking mothers. A total of 214 ultrasonographic examinations were performed between 27 and 37 weeks' gestation. All subjects underwent at least 2 ultrasonographic examinations separated by 4 weeks. We compared the slopes of the growth curves for individual morphometric parameters including head circumference, femur length, abdominal circumference, thigh muscle area, thigh fat area, estimated fetal weight and percentage of thigh fat between groups. Analysis was performed with a repeated measures analysis of covariance. Potential covariates included prepregnancy body mass index (in kilograms per square meter), weight gain during pregnancy, maternal age, parity, and fetal sex recorded at birth. Demographic variables are expressed as mean +/- SD; fetal measurements are expressed as mean +/- SE. Both t tests and chi(2) analyses were used to compare groups with respect to demographic variables. P <.05 was accepted for significance. RESULTS: There were no significant differences between groups in maternal prepregnancy weight, maternal height, maternal prepregnancy body mass index, weight gain in pregnancy, parity, or fetal sex. Smokers were younger than nonsmokers (smokers, 23.7 +/- 6.0 years; nonsmokers, 31.8 +/- 6. 0 years; P <.0001), and neonatal weight was reduced among smokers (smokers, 3269 +/- 507 g; nonsmokers, 3519 +/- 411 g; P <.01). There were no differences in the growth rates of head circumference (P =. 79) and femur length (P =.67). Growth rates of abdominal circumference (smokers, 9.0 +/- 0.3 mm/wk; nonsmokers, 10.3 +/- 0.5 mm/wk; P =.01), estimated fetal weight (smokers, 171 +/- 5.4 g/wk; nonsmokers, 193 +/- 8.0 g/wk; P =.008), and muscle area (smokers, 64. 1 +/- 3.8 mm(2)/wk; nonsmokers, 76.4 +/- 5.6 mm(2)/wk; P =.03) were significantly reduced among smokers. There was a reduction in the rate of fat deposition in the thighs of fetuses of smoking mothers (smokers, 38.7 +/- 3.7 mm(2)/wk; nonsmokers, 54.6 +/- 5.4 mm(2)/wk; P =.004); however there was no absolute difference in the amount of fat measured in the thigh between 33 and 37 weeks' gestation. CONCLUSION: We detected reduced fetal growth that selectively affected abdominal circumference and peripheral muscle mass while not affecting head circumference and femur length in fetuses of smoking mothers. The effect of cigarette smoking on fetal fat deposition was less clear. Cigarette smoking appears to have a selective effect within lean body mass compartments, with affected compartments including peripheral fetal muscle. The findings of a reduction in abdominal circumference growth compared with control subjects in combination with no difference in subcutaneous fat content beyond 33 weeks' gestation are potentially explained by a reduction in fetal liver size that may result from maternal smoking.     

Fetal anterior abdominal wall thickness in diabetic pregnancy

OBJECTIVE: The purpose of this study was to investigate whether third trimester fetal anterior abdominal wall (AAW) thickness in diabetic pregnancy reflects glycaemic control and predicts macrosomia. STUDY DESIGN: Prospective cohort study in a tertiary level maternity unit. One hundred and twenty-five diabetic mothers (71 pre-gestational and 54 gestational diabetics on insulin) underwent routine serial third trimester ultrasound examination with the additional measurement of AAW thickness. Pregnancy outcome was obtained. RESULTS: 335 fetal AAW measurements were recorded in diabetic pregnancy from 30 to 38 weeks gestation. Third trimester AAW was significantly higher in macrosomic babies (5.4+/-1.4mm vs. 4.7+/-1.4mm, p<0.05). ROC derived cut off for AAW in the prediction of macrosomia was 3.5mm at 30 weeks, 4.5mm at 33 weeks and 5.5mm at 36 weeks gestation. Using either a raised AAW measurement or an AC>90th centile, the prediction of birth weight greater than the 90th centile was better (88%) than with AC alone (70%). This improvement in sensitivity held even at earlier gestations in the third trimester. CONCLUSION: Measurement of AAW in diabetic pregnancy may have a role in the prediction of macrosomia.     

产前超声估测胎重多参数新回归方程及准确性比较

目的:创建新的适合于中国人的多参数回归公式用于胎重估测。方法:750例孕妇,在分娩前3d以内超声检查,记录胎儿双顶径(BPD)、头围(HC)、腹围(HC)和股骨长(FL),出生后记录新生儿体重。其中600例用于公式创建,采用非线性回归设计公式,另150例用于公式的验证。结果:Log10EFW=1.0163+0.0023(HC)+0.0603(AC)+0.2571(FL)+0.0011(BPD)(AC)-0.0074(AC)(FL)(R=0.846)。在验证组,新公式与其他常用公式相比,平均绝对误差及平均绝对百分误差均为最低,准确性较高。结论:新公式更适宜于评估中国胎儿体重。     

Accuracy of ultrasonic fetal weight estimation and detection of small for gestational age fetuses

One hundred and eight-six pregnant women were studied with ultrasound for clinical suspicion of poor fetal growth. Fetal weight was estimated using biparietal diameter and mean abdominal diameter with a special nomogram. The fetal femur length (FL) to abdominal circumference (AC) ratio was also calculated. The mean interval between the last ultrasound examination and delivery was 9 days (range, 0 to 14 days). Eighty-three women had their last ultrasonic examination 0 to 4 days (mean, 2 days) before delivery. In this group the arithmetic mean of weight estimation errors was -1 gm (SD, 159 gm). The signed mean percent error was +0.6% (SD, 6.6%). Neither systematic nor random errors were found between different growth percentile groups. When small for gestational age (SGA) was defined as birthweight below 2.5 percentile, the sensitivity, specificity, and positive predictive value of the weight estimations were 82%, 92%, and 84%, respectively, in 186 cases. Significant differences were found in FL to AC ratios between growth pattern groups but fetal weight estimation was found to be superior in the detection of SGA fetuses.     

Sonographic diagnosis of intrauterine growth retardation using the postnatal ponderal index and the crown-heel length as standards of diagnosis

One hundred twenty-one patients underwent an ultrasound examination within 48 hours of delivery to assess prospectively the reliability of the diagnosis of intrauterine growth retardation. Sonographic parameters examined included the abdominal circumference, sonographic estimate of fetal weight, the head to abdominal circumference ratio, and the femur length to abdominal circumference ratio. The best obstetric estimate of gestational age was used. The diagnosis of growth retardation was based on the postnatal ponderal index, and or the birthweight and crown-heel length percentiles. Seventeen infants were growth retarded. Fifteen infants had a birthweight less than the 10th percentile, but only nine (60%) were either asymmetrically growth retarded (by their ponderal index) or symmetrically growth retarded (by virtue of a birthweight and length less than the 10th percentile). All sonographic parameters were better able to predict a birthweight below the 10th percentile for gestational age than growth retardation. An abdominal circumference less than the 2.5 percentile for gestational age had the highest sensitivity for growth retardation (88.0%) of the parameters studied. Only the abdominal circumference centile identified all infants with either symmetric growth retardation or asymmetric growth retardation associated with a birthweight below the 10th percentile. A sonographic estimate of fetal weight below the 10th percentile had the highest positive predictive value for growth retardation--38%. In contrast to the overall poor positive predictive values, the negative predictive values for all parameters studied exceeded 90%. Combining the abdominal circumference percentile with one of the three remaining techniques did not significantly improve diagnostic accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sonographic assessment of fetal subcutaneous fat tissue thickness as an indicator of gestational diabetes

Objective

We used ultrasound to measure fetal subcutaneous fat in pregnancies with normal and abnormal glucose tolerance tests (GTT).

Study design

Thirty-five women with singleton pregnancies between 24 and 26 weeks’ gestation participated in our study. We measured fetal subcutaneous fat tissue thickness in 20 women with abnormal GTT (Group A, study group) and 15 women with normal GTT (Group B, control group). Maximum subcutaneous fat tissue thickness of the fetuses was measured at three different levels of the fetal body, from the inner to the outer aspect of the echogenic subcutaneous fat. One measurement was taken at the level of the biparietal diameter (BPD), a second at the level of the abdominal circumference (AC) and the third was performed sagittally at the level of the thoracic spine (TS).

Results

Each variable was tested separately for statistically significant differences between the two groups using two statistical tests, the parametric Student's t-test and the non-parametric Mann-Whitney (M-W) test. Both tests verified a statistically significant difference for the three variables of interest (HC, AC and TS) between the two groups. Receiver Operating Characteristic (ROC) curves were used to determine the diagnostic value of each of the three variables regarding the detection of gestational diabetes. Finally, all three variables were used to construct a linear discriminant analysis model in order to evaluate their combined discrimination ability.

Conclusion

Assessing these parameters using a noninvasive tool such as ultrasound could enhance the detection of gestational diabetes and limit the potential morbidity resulting from undiagnosed gestational diabetes. It could be useful in women who are unable to tolerate GTT or have poor follow-up during pregnancy.     

超声测量胎儿股骨皮下组织厚度与预测出生体重的相关性探讨

目的为预测新生儿出生体重.方法应用超声对100例正常孕妇在分娩前1周内测量股骨皮下组织厚度(TSTT)、双顶径(BPD)、腹围(AC)、股骨长度(FL),并与新生儿出生体重的关系进行分析.结果股骨皮下组织厚度与体重的相关性最好(R=0.9027),逐步回归分析中FTSTT的F值最大(F=198.67).结论超声测量胎儿股骨皮下组织厚度预测出生体重的方法简单、准确,有较好的临床应用价值.     

Fetal biacromial diameter as a new ultrasound measure for prediction of macrosomia in term pregnancy: a prospective observational study

Objective: The current study aims to evaluate a simple method for sonographic measurement of the fetal biacromial diameter for prediction of fetal macrosomia in term pregnancy.

Materials and methods: The current study was a single center prospective observational study conducted in a tertiary University Hospital from January 2015 to May 2017. We included all consecutive term (37–42 weeks) pregnant women presented to the labor ward for delivery. Ultrasound parameters were measured as biparietal diameter, head circumference, transverse thoracic diameter, mid arm diameter, abdominal circumference, femur length, estimated fetal weight, and amniotic fluid index. The proposed ultrasound formula “Youssef’s formula” to measure the fetal biacromial diameter is: [Transverse thoracic diameter +2?×?midarm diameter]. The accuracy of proposed formula was compared to the actual biacromial diameter of the newborn after delivery. The primary outcome of the study was accuracy of sonographic measurement of fetal biacromial diameter in prediction of fetal macrosomia in terms of sensitivity and specificity

Results: The study included 600 participants; 49 (8.2%) of them delivered a macrosomic neonates and 551 (91.8%) delivered average weight neonates. There was no statistical significant difference between the proposed fetal biacromial diameter measured by ultrasound and the actual neonatal biacromial diameter measured after birth (p?=?.192). The area under the curve (AUC) for prediction of macrosomia at birth based on the fetal biacromial diameter and the abdominal circumference was 0.987 and 0.989, respectively, on receiver operating characteristic (ROC) curve analysis. Using the biacromial diameter cutoff of 15.4?cm has a PPV for prediction of macrosomia (88.4%) and 96.4% sensitivity with overall accuracy of 97%. Similarly, with the abdominal circumference (AC) cutoff of 35.5?cm, the PPV for prediction of macrosomia (87.7%) and 96.4% sensitivity with overall accuracy of 96.83%. No statistical significant difference between both of them was observed for prediction of fetal macrosomia (p?=?.841)

Conclusions: The sonographic measurement of fetal biacromial diameter seems to be a new simple and accurate method for prediction of fetal macrosomia and shoulder dystocia at birth.     

Defining fetal growth restriction: abdominal circumference as an alternative criterion

Purpose: The purpose of this study is to determine if using abdominal circumference percentile (AC) to define fetal growth restriction (FGR) improves ultrasound at ≥36 weeks as a screening test for small for gestational age (SGA).

Materials and methods: All non-anomalous singletons undergoing ultrasound at a single center at ≥36 weeks during 12/2008–5/2014 were included. FGR was defined as (estimated fetal weight) estimated fetal weight (EFW) and/or abdominal circumference (AC)?Results: There were 1594 ultrasounds. Median (IQR) ultrasound GA was 37.3 (36.6–38.0), days to delivery 10.6 (5.0–18.4), and delivery GA 39.29 (38.6–39.9). EFW <10 had the following characteristics: sensitivity 50.6%, FPR 2.0%, PPV 83.8%, and AUC 0.743. Using AC <10, these were 64.0, 2.9, 81.3, and 0.806, respectively. Using AC or EFW <10, these were 67.5, 3.3, 80.3, and 0.821, respectively; this criterion has the largest AUC (p?Conclusions: AC <10 is more sensitive and has a similar PPV compared with EFW <10 for SGA. Using AC <10 or EFW <10 has the best balance of sensitivity and specificity as a screening test and has a low FPR. AC may be a reasonable alternative criterion to EFW for FGR diagnosis.