Chinese fetal biometry: reference equations and comparison with charts from other populations

Objective: This study aimed to construct new reference charts and equations for fetal biometry from Chinese fetuses at 15–40 weeks and to compare them with previous references.

Method: This was a prospective, cross-sectional study of singleton pregnancies in patients with a confirmed gestational age who underwent ultrasound examinations between the 15th and 40th weeks of gestation. Each woman was selected only once for this study. Biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were recorded. For each measurement, separate regression models were fitted to estimate the mean and standard deviation at each menstrual age. Z-scores were calculated with our reference equations for comparison with other references.

Results: New charts and reference equations involving 7553 Chinese women were created for BPD, HC, AC, and FL. Reference equations were cubic models. Prediction intervals for the new reference charts were similar to those of previous references, but with some slight differences. The main difference in our fetal biometric measurements compared with those of Korea and Hong Kong was the FL.

Conclusions: We report new Chinese reference charts and equations for fetal biometry. These reference charts and equations are available for clinical use in obstetric ultrasound studies for the Chinese population.     

Ultrasound biometry of Arabian fetuses.

OBJECTIVE: To establish fetal ultrasound biometry charts for Arabian fetuses between 14 and 40 weeks of gestation. METHOD: Cross-sectional fetal ultrasound data of normal singleton pregnancies, which had been performed over a period of 7 years, were retrieved. Only pregnant Arab women with certain last menstrual period dates and/or early ultrasound examinations were included. Each fetus contributed to only one set of data. Normal ranges for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were established. The mean and 5th and 95th percentiles at 18th, 28th, and 36 weeks of gestation were compared with similar ranges of published data from pregnancies of American and Anglo-Saxon population. RESULTS: Fetal ultrasound biometry has been established for our local population. Comparing our data with Western population emphasizes the presence of significant variation in fetal morphometric measurements, particularly in the later weeks of gestation and at the extremes of the range of fetal size. CONCLUSION: The clinical significance of this variation differs according to the primary objective of ultrasound fetal measurements. For estimation of fetal age, usually by head and femur measurements in early gestation, ethnic variation seems to have limited significance. Whereas for estimation of fetal growth and/or weight in the third trimester, based on abdominal circumference, the use of given points, e.g., 10th or 5th percentile derived from other population charts, has the potential of either over- or underdiagnosis of IUGR fetuses. The adoption of locally developed charts is recommended.     

Longitudinal reference charts for growth of the fetal head, abdomen and femur

OBJECTIVES: The aims of the present study were to establish improved reference charts for growth of the fetal head, abdomen and femur, and to determine the effect of fetal and maternal factors. STUDY DESIGN: This prospective longitudinal study included 650 low-risk pregnancies. Outer-outer biparietal diameter (BPD), head circumference (HC), mean abdominal diameter (MAD), abdominal circumference (AC) and femur length (FL) were measured by ultrasound, and the statistical analysis was based on regression analysis and multilevel modeling. RESULTS: Reference percentiles for the growth of MAD, AC and FL showed continuous growth in gestational week 10-40, while BPD and HC showed a slightly blunted growth toward the end of pregnancy. FL was the only variable that was not influenced by gender. There was a significant negative association between breech presentation and all five biometrical variables, while maternal weight was positively associated with all five variables. Cephalic index significantly influenced BPD and HC. Maternal height had a positive effect on BPD, HC, AC and FL, and parity had a positive effect on MAD and AC, while smoking influenced negatively HC, MAD, and FL. Terms for calculating conditional reference values and customisation for individualised growth assessment are presented. CONCLUSIONS: New reference charts for the growth of fetal head, abdomen and femur are suggested for assessing fetal size and growth, and can be adjusted for maternal and fetal factors to suite individual pregnancies.     

First-trimester screening for fetal triploidy at 11 to 14 weeks: a role for fetal biometry

OBJECTIVE: Intrauterine growth restriction in triploidy has been reported as early as in the first trimester. This study was undertaken to evaluate the ability of first-trimester crown rump length (CRL)-based charts to detect triploid fetuses. MATERIAL AND METHODS: Analysis of fetal biometry in cases of triploidy diagnosed in the first trimester over the last three years. Biometry for abdominal circumference (AC), head circumference (HC) and biparietal diameter (BPD) was analyzed in relation to both gestational age (GA)-based charts and to CRL-based charts. RESULTS: Five cases of fetal triploidy were diagnosed at 11 to 14 weeks. Screening based on nuchal translucency (NT) and maternal age showed a risk > 1/300 in only one of the 5 cases of triploid fetus. In all of these five cases, CRL-based biometry was grossly abnormal, although it was abnormal in only two of these five cases in relation to GA-based charts. CONCLUSION: First-trimester CRL-based biometry charts seem to reflect early asymmetrical growth delay in triploidy more accurately than GA-based charts. CRL-based biometry is likely to improve the early detection of triploid pregnancies without leading to dating error.     

Neck Circumference Measurements in Second Trimester Fetuses with Down's Syndrome

Ultrasound examinations were performed on 132 normal fetuses between 12 and 25 weeks of gestation to measure the fetal neck circumference (NC), biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). The relationships between the fetal neck circumference and gestational age, as well as between the fetal neck circumference and fetal biometric parameters (BPD, HC, AC, FL) were linear. Nomograms between the fetal neck circumference and all other parameters were established including the 5th, 50th, and 95th percentile lines. Only one of nine fetuses with Down's syndrome was found to have abnormally increased fetal neck circumference (above the 95th percentile), whereas the remaining eight cases were equally distributed above and below the 50th percentile of these nomograms. The positive predictive value of an abnormally increased fetal neck circumference was 1.6% in our tested population, where the prevalence of Down's syndrome was 1 in 132. Our observations suggest that the use of fetal neck circumference in second trimester fetuses does not add in the prenatal diagnosis of Down's syndrome.     

Fetal size charts for the Italian population. Normative curves of head, abdomen and long bones

OBJECTIVE: To describe size charts developed from fetuses of Italian couples. METHOD: Prospective cross-sectional investigation conducted in three referral centers for prenatal diagnosis. The population of the study included fetuses between the 16th and the 40th week of gestation recruited prospectively and examined only once for the purpose of this study. Exclusion criteria comprised all maternal and/or fetal conditions possibly affecting fetal biometry. The following biometric variables were measured: biparietal diameter, head circumference, abdominal circumference, femur, tibia, humerus, ulna and radio length. The statistical procedure recommended for analyzing this type of data set was employed to derive normal ranges and percentiles. Birthweight was also recorded. Our centiles were then compared with results from other studies. RESULTS: The best-fitted regression model to describe the relationships between head circumference and abdominal circumference and gestational age was a cubic one, whereas a simple quadratic model fitted BPD, and length of long bones. Models fitting the SD were straight lines or quadratic curves. Neither the use of fractional polynomials (the greatest power of the polynomials being 3) nor the logarithmic transformation improved the fitting of the curves. CONCLUSION: We have established size charts for fetuses from Italian couples using the recommended statistical approach. Since the mean birthweight in this study is not statistically different from the official birthweight reported for the Italian population, these reference intervals, developed according to the currently approved statistical methodology, can be employed during second- and third-trimester obstetric ultrasound of fetuses from Italian couples.     

Improving customized fetal biometry by longitudinal modelling

Objective: To develop customized biometric charts to better define abnormal fetal growth.

Methods: A total of 1056 singleton fetuses from the Raine Study underwent serial ultrasound biometry (abdominal circumference [AC], head circumference, and femur length) at 18, 24, 28, 34, and 38 weeks’ gestation. Customized biometry trajectories were developed adjusting for epidemiological influences upon fetal biometry using covariates available at 18 weeks gestation. Prediction accuracy (areas under the receiver operating characteristic curve [AUC] and 95% confidence interval [95%CI]) was evaluated by repeated random sub-sampling cross-validation methodology.

Results: The model for derived estimated fetal weight (EFW) performed well for EFW less than 10th predicted percentile (AUC?=?0.695, 95%CI, 0.692–0.699) and EFW greater than 90th predicted percentile (AUC?=?0.705, 95%CI, 0.702–0.708). Fetal AC was also well predicted for growth restriction (AUC?=?0.789, 95%CI, 0.784–0.794) and macrosomia (AUC?=?0.796, 95%CI, 0.793–0.799). Population-derived, sex-specific charts misclassified 7.9% of small fetuses and 10.7% of large fetuses as normal. Conversely, 9.2% of those classified as abnormally grown by population-derived charts were considered normal by customized charts, potentially leading to complications of unnecessary intervention.

Conclusions: Customized fetal biometric charts may offer improved ability for clinicians to detect deviations from optimal fetal growth and influence pregnancy management.     

First-trimester fetal limb biometry in Chinese population

OBJECTIVES: To establish reference ranges for fetal limb biometry obtained by transabdominal ultrasound examination at 12-14 weeks of gestation in Chinese women. METHODS: A total of 1489 normal singleton fetuses between 12(+0) and 14(+6) weeks of gestation were examined transabdominally by two experienced observers. The gestation was ascertained by measurement of fetal crown-rump length (CRL) or biparietal diameter (BPD) and head circumference (HC). The lengths of the humerus and femur were prospectively worked out. RESULTS: Gestation-specific reference ranges for limb measurements were calculated. The femur length (FL) (mean +/- SD) was 9.15 +/- 1.44 mm at 12-12(+6) weeks, 11.45 +/- 1.35 mm at 13-13(+6) weeks, and 13.64 +/- 1.60 mm at 14-14(+6) weeks; the corresponding humerus length (HL) (mean +/- SD) was 9.63 +/- 1.44 mm, 12.01 +/- 1.41 mm, 14.29 +/- 1.48 mm, respectively. CONCLUSIONS: There was a general increase in fetal limb biometry with gestation. Fetal limb length can be an early marker of early growth restriction as well as fetal skeletal dysplasia among women in the local population.     

Fetal age assessment based on ultrasound head biometry and the effect of maternal and fetal factors

BACKGROUND: Maternal height and weight have increased during the past 20 years, as has birthweight. The aim of the present study was to establish new reference charts for gestational age (GA) assessment using fetal biparietal diameter (BPD) and head circumference (HC), and to determine the effect of maternal and fetal factors on age assessment. METHODS: This was a prospective, cross-sectional study of 650 healthy women with regular menstrual periods and singleton uncomplicated pregnancies, recruited after written consent. BPD (outer-outer) and HC were measured at 10-24 weeks of gestation. We used regression analysis to construct mean curves and assess the effect of maternal and fetal factors on age assessment. RESULTS: BPD and HC were successfully measured in 642 participants. Using BPD and HC before 20 weeks, the new charts gave 3-8 days higher GA assessment than the charts presently in use, and <1 day difference compared to other recently established charts. Maternal age, multiparity, fetal gender, breech position and shape of fetal head affect GA estimation by 1-2 days when using BPD (p = 0.0001-0.02). Only maternal age and fetal gender affected GA estimation when using HC (相似文献   

Second trimester growth velocities: assessment of fetal growth potential in SGA singletons

Objective: To evaluate the validity of second trimester growth velocities as measures of fetal growth potential in Small-for-Gestational-Age (SGA) singletons.

Methods: Second trimester growth velocities for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur diaphysis length (FDL) were determined by linear regression analysis or direct measurement in 53 SGA singletons with normal growth outcomes (SGA N Group) and 73 with growth restriction (SGA GR) based on a composite fetal growth pathology score (FGPS1). The latter were subdivided into six groups based on their growth restriction pattern (Patterns group). Similar data were available for 118 singletons with normal neonatal growth outcomes (NNGO group). Coefficients of determination (R²) and growth velocities for each anatomical parameter were compared between Patterns subgroups and the SGA N, SGA GR and NNGO groups.

Results: Median R² values in the six Patterns subgroups ranged from 98.2% (Pattern 2, FDL) to 99.9% (Pattern 5, AC). Within each anatomical parameter set, no significant differences were found (Kruskal–Wallis). Patterns subgroup data were pooled to form the SGA GR group for each anatomical parameter. Mean values for the three main groups ranged from 98.4% (SGA N, FDL) to 99.6% (SGA N, HC). No significant differences between groups (ANOVA) were found for any anatomical parameter (ANOVA). Only 1.7–3.8% had R² values <95th%. No significant differences in median second trimester growth velocities among different Patterns subgroups were found for any anatomical parameter. In the SGA N and SGA GR groups, mean BPD and HC values did not differ but were significantly smaller than the NNGO group values. No differences in mean FDL values were seen. With AC, all three means were significantly different, having the following order: NNGO?>?SGA N?>?SGA GR. Of all 504?second trimester growth rates, 92.5% were within their respective 95% reference ranges.

Conclusion: Growth in the second trimester is linear in fetuses at risk for growth restriction. Except for FDL, growth velocities were lower than those for fetuses with NNGO. Only AC had mean velocities that differed between the SGA N and the SGA GR groups. Since most velocities (92.5%) were within normal reference ranges, they are reasonable measures of growth potential in fetuses at risk for growth restriction.     

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。     

Fetal ultrasound biometry: 1. Head reference values.

OBJECTIVE: To create reliable reference ranges and calculate Z scores for fetal head 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 exactly 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 6217 fetal head biparietal diameters and 5510 occipito-frontal diameters were measured. Both head circumference and cephalic index were derived in 5462 cases where both biparietal diameter and occipito-frontal diameter could be measured on the same fetus. The centile charts, tables and regression formulae for biparietal and occipito-frontal diameters, head circumference and cephalic index are presented. An application to calculate Z scores was developed using Excel (Microsoft Corporation, USA) and macros are presented in detail in the Figure 8 footnote. The comparison of our charts with those of the two most recent studies revealed almost no differences in biparietal diameter centiles. In one publication, occipito-frontal diameter charts, and in another, head circumference charts were different from the current study. CONCLUSIONS: We have presented centile charts, tables and regression formulae for fetal head ultrasound biometry 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 for use in computer-aided evaluation of fetal ultrasound biometry.     

The effect of fetal sex on customized fetal growth charts

Objective: To evaluate the effect of fetal sex on singleton pregnancy growth charts customized for parental characteristics, race, and parity

Methods: In a multicentric cross-sectional study, 8070 ultrasonographic examinations from low-risk singleton pregnancies between 16 and 40 weeks of gestation were considered. The fetal measurements obtained were biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). Quantile regression was used to examine the impact of fetal sex across the biometric percentiles of the fetal measurements considered together with parents’ height, weight, parity, and race.

Results: Fetal gender resulted to be a significant covariate for BDP, HC, and AC with higher values for male fetuses (p?≤?0.0009). Minimal differences were found among sexes for FL. Parity, maternal race, paternal height and maternal height, and weight resulted significantly related to the fetal biometric parameters considered independently from fetal gender.

Conclusion: In this study, we constructed customized biometric growth charts for fetal sex, parental, and obstetrical characteristics using quantile regression. The use of gender-specific charts offers the advantage to define individualized normal ranges of fetal biometric parameters at each specific centile. This approach may improve the antenatal identification of abnormal fetal growth.     

Fetal biometry: does patient ethnicity matter?

Abstract

Objective: To determine if fetal biometry varies according to race.

Methods: We performed a retrospective chart review of prenatal ultrasounds completed in our Perinatal Center from January 2009 to December 2010. Singleton pregnancies 17 to 22.9 weeks were included. Pregnancies complicated by IUGR, fetal anomalies, chronic maternal diseases, or dated by an ultrasound after the first trimester were excluded. Biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and humerus length (HL) were compared between African Americans (AA), Caucasians, and Hispanics using ANOVA and Student t-test.

Results: Included were 1327 AA, 147 Caucasian, and 86 Hispanic subjects. The AC was significantly smaller in AA than Caucasians (p?=?0.008). There was no difference between AA and Caucasians in BPD, HC, FL, or HL. There were no differences between Hispanics and either Caucasians or AA in any of the biometries evaluated.

Conclusions: A single fetal growth curve is not applicable across all ethnicities. AA fetuses have smaller AC then Caucasian fetuses from 17 to 22.9 weeks, which is typically the period when anatomic surveys are performed. Because AC contributes heavily to estimated fetal weight calculations, physicians may be over estimating growth restriction in AA patients. Ethnicity-specific fetal growth curves are indicated to limit unnecessary follow up.     

Ultrasonic fetal measurements: new Australian standards for the new millennium

In over 30 years of ultrasound assessment of the fetus, Australian researchers have only produced growth curves for the biparietal diameter (BPD) and occipito-frontal diameter (OFD) for general use. The overseas curves used for other fetal parameters are up to 25 years old and based on predominantly white middle class sample populations. In the last decade the ethnicity in Australia has changed significantly, putting into question the accuracy of the existing charts. This 3-year study of 3,800 pregnancies has resulted in the production of fetal measurement charts for the BPD, OFD, head circumference (HC), abdominal circumference (AC), crown rump length (CRL), femur and humerus lengths. Using over 11,600 measurements collected from diverse ethnic, social and economic groups within the Australian population, rigorous statistical analysis was performed. The results showed that statistically significant differences occur between the curves currently in regular use and those for the OFD, HC, AC, CRL and humerus length obtained from our data.     

A novel reference chart and growth standard of fetal biometry in the Taiwanese population

ObjectiveThe purpose of this study was to establish a new reference chart and growth standards for fetal biometry in Taiwan.Materials and methods2047 singleton pregnancies were enrolled in this study with 15,813 fetal scans between 18 and 40 gestational weeks. A reference chart and normal range for fetal biparietal diameter (BPD), abdominal circumference (AC) and femur length (FL) was established by longitudinal quantile regression model. 330 women with comorbidities including gestational hypertension, preeclampsia and gestational diabetes were excluded and 1717 pregnant women were enrolled for the growth standard.ResultsThe new reference values were significantly larger across all gestational ages compared with the prior National Taiwan University reference chart in 1983. Compared with Intergrowth-21st, the BPD was larger at 18–23 weeks, the AC was larger at 18–24 weeks and the FL was larger at 18–36 weeks whereas they were all smaller at 29–40 weeks for the BPD, at 32–40 weeks for the AC and at 38–40 weeks for the FL. A quantile regression equation of biometry was established. BPD, AC, and FL had weekly growth of 2.5, 9.87 and 2.15 mm. Prepregnancy body weight, height, age, and gestational diabetes increased fetal size. Both gestational and chronic hypertension decreased fetal size.ConclusionTo promote maternal-fetal safety, a new reference chart and growth standard for fetal biometry is necessary to measure fetal growth.     

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.     

孕晚期营养素摄入与B超下胎儿各生长指标的关系

目的:探讨妊娠晚期孕妇不同营养素摄入量与B超下胎儿各部位测量值的关系。方法:对799例无妊娠合并症及并发症的健康孕妇进行前瞻性营养调查,在妊娠32、34、36周调查3天。用食物日志形式记录3天摄入食物的种类及重量。将食物摄入量转换成营养素摄入量。于妊娠28周及38周左右行两次B超检查,测量胎儿双顶径、头围、腹围、股骨及肱骨长度,并用两次测量之差值反映胎儿孕晚期的生长情况。采用多元线性回归分析孕晚期营养与胎儿生长的关系。结果:孕晚期脂肪供能比与胎儿腹围、头围和股骨增长有关,脂肪供能比每增加1%,胎儿腹围增加2.27mm(P=0.023),胎儿头围增加3.86mm(P=0.01),胎儿股骨长度增加1.35mm(P=0.04)。钙的摄入量与胎儿股骨增长有关;锌、维生素B1、、B2及维生素E与胎儿双顶径关系密切。结论:脂肪供能比与胎儿多个生长指标密切相关,是影响胎儿出生体重的重要因素。不同的营养素对B超测量的胎儿生长指标的影响不完全相同的。     

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

To test the applicability of equations for fetal weight estimations in a group of fetuses suspected of being large for gestational age, real-time ultrasound measurements of fetal biparietal diameters and abdominal circumferences were obtained for 34 fetuses of diabetic mothers. In the first phase of the study the accuracy in the prediction of weight was assessed with use of two known equations. In the second phase, biparietal diameter, abdominal circumference, and actual birth weight data of the 34 study fetuses were used as independent variables to determine the best-fitting equation for relating estimated fetal weight (EFW) to biparietal diameter (BPD) and abdominal circumference (AC); this equation is log (EFW) = 0.02597 AC + 0.2161 BPD - 0.1999 (AC X BPD2)/1000 + 1.2659. The standard deviation of differences is 322.26 gm and multiple R = 0.781. In the final phase the reliability of this equation was compared to those of Thurnau and Shepard in 34 additional fetuses of diabetic gravid women. The data suggest that in these fetuses suspected of being large for gestational age the weight estimates calculated at or near term may be enhanced if predictive equations are formulated specifically from the data for such fetuses.