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.     

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.     

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。     

Reference charts and equations of Korean fetal biometry

OBJECTIVE: To construct new reference charts and equations for fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur diaphysis length (FDL) from Korean fetuses at 12-40 weeks. METHOD: Prospective cross-sectional data obtained in one center for 5 years from a population of pregnant women undergoing ultrasound examination between the 12th and 40th week of gestation. Exclusion criteria comprised all maternal and fetal conditions possibly affecting fetal biometry. No fetuses were excluded on the basis of abnormal biometry. For each measurement, regression models were fitted to estimate both the mean and the standard deviation at each menstrual age. RESULTS: Biometric measurements were obtained for 10 455 fetuses. New charts and reference equations are reported for BPD, HC, AC and FDL. Reference equations are cubic models. CONCLUSION: We present new Korean reference charts and equations for fetal biometry. They can be easily used in obstetric ultrasound studies for the Korean population.     

Fetal age assessment based on femur length at 10-25 weeks of gestation, and reference ranges for femur length to head circumference ratios

BACKGROUND: The aim of the present study is to establish new reference charts for gestational age assessment based on fetal femur length (FL), and new reference ranges for FL to head ratios at gestational weeks 10-25, and to determine the effect of maternal and fetal factors on these charts. METHODS: Six hundred fifty low-risk women with regular menstrual periods and singleton pregnancies were recruited to a prospective cross-sectional study after obtaining written consent. FL, outer-outer biparietal diameter (BPD), and head circumference (HC) were measured at 10-25 weeks of gestation. We used regression analysis in order to construct mean curves and to assess the effect of maternal and fetal factors on age assessment. RESULTS: The new chart for age assessment by means of FL was based on 636 measurements. The 95% CI of the mean corresponded to <1 day. The variation between the mean and the 90th percentile was 5, 6, and 7 days at 13, 18, and 23 weeks, respectively, similar to the results when using BPD or HC. Maternal age modestly influenced gestational age assessment (1.3 days/10 years, P = 0.005), whereas smoking, height, body mass index, multiparity, fetal sex, cephalic index, and breech presentation had no impact. Reference charts for FL to head ratios have been presented. Maternal age, fetal sex, and cephalic index influenced the FL/BPD ratio, whereas only fetal sex influenced FL/HC. CONCLUSIONS: Fetal age assessment based on FL is an equally robust method as using HC. FL/HC is a more robust ratio to characterize fetal proportions than is FL/BPD.     

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.     

Evaluation of fetal sonographic measurements in the first trimester by transvaginal sonography.

To assess the reliability of early biometric measurements in pregnancy, transvaginal sonography was performed in 92 pregnancies in the first trimester in a cross-sectional fashion. Measurements included crown-to-rump length (CRL), biparietal diameter (BPD), head and abdominal circumference (HC and AC), and femur length (FL). Stepwise regression analysis of the gestational age was performed. CRL maintained the highest correlation with gestational age (r = 0.99, p less than 0.001). BPD, HC, AC also correlated well. FL showed a less strong correlation with gestational age (r = 0.76, p less than 0.001). CRL remains the standard for early sonography measurements.     

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.     

Evidence That Normal Fetal Growth Can Be Noncontinuous

Fetal growth is presumed by current models to be continuous. We hypothesized that normal fetal growth is not continuous and that it demonstrates a pulsatile pattern. Fetal morphometric parameters were examined in 9 healthy women at an average interval of 2.7 days between 25 and 36 weeks gestation using an Acuson XP3 unit (Mountain View, CA) employing a 3.5 MHz curvilinear transducer. Parameters examined included biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), and humeral length (HL). Mothers had normal prepregnancy weight, were nonsmokers, had normal glucose tolerance screening, and were without medical complications. Mean maternal age was 28.7 ± 5.8 years (S.D.) and mean maternal weight gain was 16.8 ± 3.3 kg. All neonates were born at term (range 39–42 weeks), without anomalies and a mean percentile birth weight at the 53rd centile (range 20–95th). Wald-Wolfowitz runs test was used to test for nonrandom patterns in the residuals from the fitted regression curve. When modeled by second order regression equations, 4/9 AGs and 3/9 BPDs demonstrated significant nonrandom patterns in the residuals (P < 0.05 Wald-Wolfowitz runs test) from the fitted curve consistent with pulsatile growth. In addition, prolonged periods without detectable growth (<2.0 mm) were observed for both AC (up to 28 days) and BPD (up to 25 days). All parameters demonstrated no measurable growth in a majority of fetuses (BPD 5/9, AC 7/9, FL 5/9, HL 7/9) for at least a single 2 week interval. In conclusion, in this data set BPD and AC demonstrated significant noncontinuous growth in several fetuses suggestive of pulsatility. Prolonged periods (≥2 weeks) without measurable growth were detected for all parameters in most fetuses. These findings support the hypothesis that fetal growth can be noncontinuous under normal conditions.     

Below median birth weight in appropriate-for-gestational-age preterm infants as a risk factor for bronchopulmonary dysplasia

AIMS: To assess the presence of chorioamnionitis and intrauterine growth as prenatal risk factors for broncho pulmonary dysplasia (BPD) in appropriate-for-gestational-age (AGA) infants of <28 weeks' gestation. METHODS: Gender, race, birth weight, gestational age, histology of the placenta, diagnosis of BPD at 36 weeks' gestation, postnatal dexamethasone treatment, and death were recorded in 150 preterm infants born at <28 weeks' gestation, and admitted between 1996 and 2001. RESULTS: In 122 AGA infants (mean gestational age: 26.18 weeks, mean birth weight: 837 g), BPD was associated with gestational age-related birth weights below the 50(th) centile. Intrauterine growth deceleration started between 25 and 26 weeks' gestation. Chorioamnionitis was not related to BPD. CONCLUSIONS: AGA infants of 26-28 weeks' gestation with birth weights below the median showed an increased risk of developing BPD.     

Doppler evaluation as a predictor of asphyxia in fetuses with intrauterine growth retardation (IUGR)

Many papers showed that the pulsatility index of the fetal middle cerebral artery decreases during gestation. We observed equalization of the PI in MCA and PI in UMB in the perinatal period (after 38 weeks of gestation). We observed the increase the diastolic cerebral flow through the brain in cases of hypoxia. We interpreted that situation as a vasomotor response to fetal hypoxia (for example in IUGR). This phenomenon, is called in the literature as brain sparing effect. The aim of our study was estimation of application Doppler technique in diagnosis of changes in circulatory system in pregnancies complicated by intrauterine growth restriction (IUGR). We included 66 fetuses with IUGR and sonographic signs of the brain sparing effects, without any congenital malformation, oedema and genetic abnormalities to the study group. We included 1730 foetuses from normal, physiological pregnancies to the control group. In all cases time of gestation were calculated from Naegele's rule and were confirmed in sonographic examination before 16 weeks of gestation. SGA fetuses were defined on the basis of ultrasonographic measurements of BPD, HC, AC, FL and weight below 10th percentile of our reference curve. Sonographic examination were performed on Acuson 128 XP/10 with transducers (2.5 MHz-5 MHz). We performed Doppler examinations in MCA and UMB. Redistribution (brain sparing effect) was diagnosed when CPR (cerebroplacental ratio) was less than 1. We analysed the way and time of delivery and neoanatal follow up. Obtained in advance of researches results made possible expression of following conclusions: 1. Use of Doppler techniques in pregnancies complicated by IUGR makes possible diagnosis of hypoxia that helps in settlement of continuing or ending of pregnancy. 2. Changes in Doppler flows in foetus resoluteness outdistance irregular other values of biophysical methods of foetus monitoring.     

Evaluation of intrauterine growth pattern of twins by linear discriminant analysis of the values of biparietal diameter, femur length and abdominal circumference1.

In a cross-sectional study, the intrauterine growth pattern of 32 twins was compared to that of 205 singletons by analysis of the coefficients of the equations of biparietal diameter (BPD), femur length (FL) and abdominal circumference (AC). Lower values were observed in twins from the 20th week. BPD and AC curves showed a progressively diverging pattern, and yielded different coefficients of equations. AC showed the highest discriminant capacity followed by BPD and FL. Combined values of the two series solved by discriminant function output produced an overlapping of 58%. Based on our data, nomograms of growth of singletons should not be used for twins.     

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.     

早中孕期联合筛查对胎儿生长受限的风险评估与预测

目的：通过早中孕期联合筛查建立数学模型,探讨不同模型对胎儿生长受限（FGR）的风险评估与预测价值。方法：选取2010年1月-2015年12月于暨南大学第一附属医院行孕早期联合筛查及孕中期四维彩超并纳入标准的2 621例孕妇,最终确诊为FGR者49例（1.87%）。收集孕妇年龄、孕前体质量指数（BMI）,孕早期联合筛查的游离人绒毛膜促性腺激素β亚单位（β-hCG）和妊娠相关蛋白A（PAPP-A）,子宫动脉搏动指数（UtA PI）和大脑中动脉压（MAP）,颈项透明层（NT）,孕中期胎儿双顶径（BPD）、头围（HC）、腹围（AC）和股骨长（FL）,并同时将NT、UtA PI、MAP、BPD、HC、AC及FL采用中位数倍数（MoM）表示。以原始所有参数组合为A组,β-hCG、PAPP-A、UtA PI、MAP转化为MoM后与剩余参数组合为B组,β-hCG、PAPP-A、UtA PI、MAP、NT、BPD、HC、AC及FL均转化为MoM后与剩余参数组合为C组,分别将3组数据采用Logistic逐步回归分析方法建立FGR预测模型,并进一步采用受试者工作特征曲线（ROC曲线）分析,比较各模型的敏感度和特异度。结果：ROC曲线结果显示,3组回归模型ROC曲线下的面积（AUC）分别为0.69（95%CI：0.61～0.76）、0.69（95%CI：0.61～0.77）和0.71（95%CI：0.64～0.78）,在假阳性率为5%条件下,各组的检出率分别为12.26%、14.29%和16.32%;敏感度分别为10.2%、10.2%和16.3%;特异度分别为97.3%、97.2%和96.8%。结论：在早、中孕期联合筛查时,胎儿生长发育的指标应用MoM值进行评估可提高FGR联合预测检出率。     

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。     

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.     

Ultrasonic estimation of fetal weight at term: an evaluation of eight formulae

AIM: To compare the accuracy of eight sonographic formulae for predicting fetal birth weight at term in a multiethnic population. METHODS: Pregnant women at term who were booked for induction of labor or elective cesarean section were included in the study. Eight ultrasonic fetal biometric formulae were used to predict fetal birth weight. RESULTS: A total of 173 patients were included in the study; 53 (30.6%) patients were from the Indian subcontinent, 44 (25.4%) patients were from Africa, 33 (19.1%) patients were from the Arabian Peninsula and 43 (24.9%) were from other ethnic groups. The mean absolute error ranged from a minimum of 0.3% (+/-11.3) for Hadlock (biparietal diameter [BPD], head circumference [HC], abdominal circumference [AC], femur length [FL]) to a maximum of 37.5% (+/-10.0) for Warsof (FL). The correlation of estimated fetal weight with actual birth weight ranged from a minimum of 0.09 with Warsof (FL) to a maximum of 0.77 with Shepard and Warsof (BPD, AC) and Hadlock (BPD, HC, AC, FL). The combination of AC with BPD measurements rather than FL achieves a high level of accuracy. CONCLUSIONS: Shepard (BPD, AC) provides a simple and accurate logarithm for the prediction of fetal weight at term in the studied multiethnic population.     

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 assessment of fetal biparietal diameter and femur length during normal pregnancy in Iranian women.

OBJECTIVES: To determine the pattern of intrauterine growth and predicted biparietal diameter (BPD) and femur length (FL) at point in gestation of Iranian fetuses. METHODS: In an extensive and long-standing prospective study in Tehran, Iran 15693 BPD and 15594 FL measurements were obtained from the fetuses of 1324 normal pregnant women. Weekly mean values and the standard deviations (S.D. ) were calculated for both BPD and FL from 12 to 40 weeks of pregnancy. Comparison was also made between our results and previous Western studies using t-test analysis. RESULTS: Iranian fetuses had smaller BPD and shorter FL measurements in comparison with Western studies (P<0.05). There is a lag in BPD growth of our fetuses. The lag in FL growth is even more than BPD. Growth of the BPD and FL showed an asymptotic curve like that of Western studies but both of our values were lower. CONCLUSION: Ethnicity may influence ultrasonic fetal biometric measurements.