Estimating fetal age: computer-assisted analysis of multiple fetal growth parameters

Regression models for predicting menstrual age based on real-time sonographic measurements of four fetal parameters (biparietal diameter, head circumference, abdominal circumference, and femur length), used alone and in combination, were developed in a cross-sectional study of 361 fetuses between 14 and 42 menstrual weeks. The head circumference and femur length were the strongest individual predictors of age. A number of combinations of fetal parameters, including the combination of head circumference and femur length, provided age estimates that were significantly better (p = 0.05) than those using any single parameter alone. It was also demonstrated that simply averaging individual age estimates in a given case could provide results that were not significantly different from those obtained by using the same parameters in a complex regression equation. The advantages and potential pitfalls of this system of fetal dating are discussed.     

B型超声对妊娠胎儿体重预测的研究

目的为了提高B型超声预测胎儿体重的准确性。材料与方法对262例在分娩前5天内,用B型超声测定胎儿双顶径、腹围、肝脏长度、股骨长度,分别用各种方程式得出胎儿体重,并与新生儿实际出生体重进行比较。结果单项腹围预测胎儿体重与新生儿实际体重的相关性最好。结论应用B型超声测量胎儿腹围预测胎儿体重的方法简便、准确,有较好的临床应用价值。     

Sonographic estimation of fetal age and weight

Real-time ultrasound is a very effective tool in the estimation of fetal age and weight. The most accurate fetal age estimates are from crown-rump length measurements in early pregnancy. Late pregnancy age estimates are less accurate, but the use of multiple body measurements provides a composite age estimate generally accurate to within 7 per cent of actual age. Estimates of fetal weight are improved with the use of head, body, and femur measurements, and generally are accurate to within 15 per cent of actual birth weight.     

巨大儿发生的危险因素及产前预测

目的研究巨大儿发生的高危因素及产前预测,以便更好地指导孕妇孕期保健,减少新生儿及孕产妇的早期及远期并发症。方法对比巨大儿组及正常体重儿组两组孕妇的孕周、宫高、腹围,B超观察胎儿双顶径、胎儿腹围。回顾性分析孕妇孕前BMI、孕期体重增加情况、是否合并GDM等。结果①孕妇孕前BMI〉24、孕期体重增）加〉18kg、合并妊娠期糖尿病、孕周大于40周巨大儿组与正常体重儿组比较差异有统计学意义,为分娩巨大儿的高危因素。②胎儿腹同大于35cm,双顶径大于9．6cm,股骨长大于7．5cm,宫高＋腹围≥140cm,这4个指标巨大儿组与正常体重组比较差异有统计学意义,可作为巨大儿预测的方法。结论应该加强孕前及孕期指导,控制体重及血糖以降低巨大儿的发生率。对孕前胎儿体重采取多方面综合评估,以期能预测巨大儿的发生,以便做好相应的应对措施。     

Fetal growth curves for an ethnically diverse military population: the American Institute of Ultrasound in Medicine-accredited platform experience

OBJECTIVE: To determine which fetal growth curve provided the best estimates of fetal weight for a cohort of ethnically diverse patients at sea level. METHODS: The study consisted of a population of 1,729 fetuses examined at sea level between January 1, 1997, and June 30, 2000, at 18 weeks, 28 weeks, and term. Gestational age (GA) based on menstrual dates was confirmed or adjusted by crown-rump length or early second-trimester biometry. Fetal weight was estimated by using biparietal diameter, head circumference, abdominal circumference, and femur length. Our fetal growth curves were analyzed with fourth-order polynomial regression analysis, applying four previously defined formulae for fetal growth. RESULTS: Fetal growth curves for estimated fetal weight demonstrated the expected parabolic shape, which varied according to the formulae used. Our curve best fit the following equation: estimated fetal weight = 4.522 - 0.22 x GA age + 0.25 x GA(2) - 0.001 x GA(3) + 5.248 x 10(-6) x GA(4) (R2 = 0.976). SD increased in concordance with GA. CONCLUSION: Madigan Army Medical Center serves a racially mixed, culturally diverse, military community with unrestricted access to prenatal care. Determination of the optimal population-appropriate growth curve at the correct GA assists clinicians in identifying fetuses at risk for growth restriction or macrosomia and therefore at risk for increased perinatal morbidity and death.     

Reconstruction of femur length from its proximal fragments in a Bulgarian modern population

Estimation of stature from bones has anthropological and forensic importance. It is well known that the intact femur has the highest correlation with stature. However, the intact femur is not always recovered in forensic cases. The current study introduces a method of estimating the length of femur from partial proximal elements specific to the Bulgarian population. One-hundred and forty adult femora belonging to known age and sex were studied. The method is based on several landmarks and distance between them, such as vertical head diameter, transverse diameter of the head, maximum head diameter, head circumference, sagittal subtrochanteric diameter, transverse subtrochanteric diameter and supero-inferior neck diameter. Simple and multiple linear regressions were obtained to define these estimates. For males, regression formula, which included head circumference measurement, provided the best fit of the data, resulting in the highest correlation and lowest standard error of estimate compared with all other variables. For females, the vertical diameter of the head showed the best correlation with maximum length. A combination of all variables into a single equation only improved the standard error of the estimate. The regression formula suggested that the proximal end is the best estimator of femur length. The derived formulae are population and sex specific.     

Sonographic prediction of gestational age: accuracy of second- and third-trimester fetal measurements

We measured the accuracy of second- and third-trimester sonographic predictors of gestational age against highly reliable gold standard (crown-rump length) in a group of fetuses. Using a prospectively collected computerized data base, we selected 460 fetal sonograms obtained at 14-42 weeks of gestation in which age could be reliably established on the basis of crown-rump length in the first trimester. We used data obtained from these sonograms to compare several predictors of fetal age. The accuracy of all predictors worsened progressively as pregnancy proceeded. In the second trimester, corrected biparietal diameter and head circumference were more accurate predictors of gestational age than were biparietal diameter, femoral length, and abdominal circumference (p less than .05, F test). In the third trimester, the corrected biparietal diameter, head circumference, and femoral length were the best predictors, significantly better than biparietal diameter and abdominal circumference (p less than .05, F test). Prediction of gestational age that relies on a single sonographic measurement should be based on the head circumference or corrected biparietal diameter in the second trimester and on one of these two predictors or the femoral length in the third trimester.     

Fetal intracranial anatomy in the first trimester of pregnancy: transvaginal ultrasonographic evaluation

Summary The normal values and ranges of fetal intracranial structures were studied by high resolution transvaginal ultrasonic scan at 12, 13 and at 14 weeks' gestation. The data including measurements of crown rump length (CRL), bi-parietal diameter (BPD), head circumference (HC), hemispheric width (HW), lateral ventricle width (LVW), LVW/HW ratio, thalamus and cerebellum may be useful in determining deviations from the normal and also in expanding the range of prenatal diagnoses of fetal structural abnormalities in early pregnancy.     

Use of ultrasonography to estimate fetal weight in premature infants. Development of a new mathematical formula

In 73 pregnant patients at a gestational age under 36 weeks, who gave birth within 72 hours from the last US examination, mathematical equations were elaborated. The equations were aimed at predicting fetal weight by measuring the main US biometric parameters; the results were compared to the actual birth weight. A statistical analysis was performed using the "backward elimination" method. The linear equation that has provided with the best estimation of fetal weight is the following: fetal weight = 12.9875 BPD +29.5642 AD +28.8023 FL -3496.1265. According to this equation, about 95.22% of the variability of the unknown quantity (i.e. birth weight) can be ascribed to its correlation to the variables: biparietal diameter (BPD), abdominal diameter (AD) and femur length (FL). Estimated fetal weight by US, as calculated on the basis of biparietal diameter, abdominal diameter and femur length measurements, showed, in our study, a standard error of 143 g (9.02%) (R = 0.95).     

Ultrasonographic prenatal diagnosis of isolated acephaly

First trimester obstetric ultrasonography of a 32-year old female patient revealed a 13-week-old (according to the length of the femur and abdominal circumference) intrauterine live pregnancy with the absence of the fetal head. Medical abortus was performed with the diagnosis of acephaly and final diagnosis was confirmed by pathological and radiological examinations. We present and discuss the possible etiopathologic mechanisms of an acephaly case, which is described as acardia-acephaly complex in the literature, and usually appears in cases of twin reversed arterial perfusion sequence, but has not been previously reported as an isolated finding.     

A date-independent predictor of intrauterine growth retardation: femur length/abdominal circumference ratio

The relation between sonographically measured fetal femur length and abdominal circumference (expressed as femur length/abdominal circumference X 100) was studied in 361 normal pregnancies between 15 and 42 weeks. This ratio was found to be independent of menstrual age, with a normal range after 21 weeks (mean +/- 2 SD) of 22 +/- 2. This ratio also was evaluated as a predictor of intrauterine growth retardation in 30 cases using the 90th percentile (23.5) as the upper limit of normal, which resulted in identification of 63% of the growth-retarded fetuses. Because it is independent of menstrual age, this ratio should prove most useful in evaluating high-risk patients who present in the third trimester of pregnancy with no dates. It is also of value in detecting growth retardation in patients with good menstrual history, since it was shown to become abnormal in asymmetrically growth-retarded fetuses before the estimated weight fell below the 10th percentile.     

14～17+6孕周超声筛查胎儿畸形的临床价值

 目的 探讨14～17⁺⁶孕周超声筛查胎儿畸形的临床价值。方法 回顾性分析2012-2014年在我院进行超声检查的14～17⁺⁶孕周胎儿1200例,对其进行标准切面检查,包括测量胎儿双顶径、腹围、股骨长、羊水及胎儿心率,观察头颅、心脏、腹部及脊柱、四肢。结果 受检的1200例胎儿中,37例胎儿发现结构异常。其中胎儿水肿6例(包括颈部水囊瘤4例),脉络丛囊肿10例,露脑畸形3例,全前脑3例,脐膨出2例,心脏异常5例,肢体异常2例,脊柱异常2例,巨膀胱3例,连体双胎1例。结论 14～17⁺⁶孕周的超声检查可以有效地检出胎儿畸形,是产前超声筛查胎儿畸形的重要阶段。     

Fetal central nervous system biometry on MR imaging

OBJECTIVE: We sought to compare the biometry of the fetal head on MR imaging with sonographic measurements in fetuses with and without suspected central nervous system abnormalities. MATERIALS AND METHODS: Blinded retrospective measurements of biparietal diameter, head circumference, and cerebellar width obtained on MR imaging were assigned a gestational age on the basis of median sonographic measurements and compared with sonographic and clinical assignment of gestational age in fetuses with no central nervous system abnormalities. In fetuses with central nervous system abnormalities, the same MR measurements were compared with sonographic measurements obtained within 1 week. Single-shot fast spin-echo sequences were obtained. Pearson's product moment correlation coefficients and paired sample t tests were performed. RESULTS: In 22 fetuses with no suspected central nervous system abnormalities, significant correlation was seen in the assignment of gestational age by MR measurements and sonographic gestational age. In 25 fetuses with central nervous system abnormalities, significant correlation was also seen between biparietal diameter and head circumference measurements. The mean biparietal diameter on MR imaging was greater than on sonography in those fetuses with central nervous system abnormalities (p = 0.038). CONCLUSION: MR imaging measurements of biparietal diameter, head circumference, and cerebellar width are strongly correlated to gestational age in fetuses without central nervous system abnormalities. Significant correlation is found between MR imaging and sonographic measurements of biparietal diameter and head circumference in fetuses with central nervous system abnormalities. Larger biparietal diameter measurements were seen with MR imaging than with sonography in the abnormal group. Fetal central nervous system biometry can be performed as part of the MR imaging evaluation of the fetal central nervous system.     

Use of femur length/abdominal circumference ratio in detecting the macrosomic fetus

The femur length/abdominal circumference ratio, expressed as FL/AC X 100, was determined in 156 fetuses and evaluated as a predictor of fetal macrosomia within one week prior to delivery. The normal range (mean +/- 2 SD) in the 105 normal-weight fetuses was 22.0 +/- 2, while the normal range in the 51 macrosomic fetuses was 20.5 +/- 2; these differences were highly significant (P = less than .0001). The predictive power of a positive ratio was 68%, with a sensitivity of 63%. This ratio was particularly useful in the subset (n = 9) of macrosomic fetuses whose mothers were diabetic, correctly identifying 89% of this group. Because it is age independent, this ratio should prove most helpful in identifying fetuses at risk for macrosomia in patients whose dates are not known, since it may become abnormal before the fetal weight falls above the 90th percentile at term (3,900 g). In patients whose dates are known, early fetal macrosomia is best predicted by evaluating the abdominal circumference against normal standards for age.     

Ultrasonic fetal size measurements in Brisbane, Australia

The purpose of this paper was to construct population-specific charts of fetal biometry for 11-41 weeks gestation in relation to known gestational age from a large population of normal Australian pregnancies when examination is performed to a standard protocol by experienced operators. All consenting eligible women attending a large Brisbane clinic between January 1993 and April 2003 were recruited. Menstrual history was taken prior to examination. Measurements were performed to a standard protocol. Prospective assessment was made about the association between gestational age from the last menstrual period and biometry. Exclusion principles were applied. Statistical analyses were performed using polynomial regression models and thorough diagnostic checks were undertaken. Included within the study were separate scans for 20 555 pregnancies from 17 660 women. Equations, means and 95th reference intervals were derived and reported for the following sonographic measurements: biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). Population-specific regression equations for BPD, HC, AC and FL have been proposed for Australian pregnancies. Once validated by others, we believe they will warrant consideration for adoption by the Australasian Society for Ultrasound in Medicine.     

Three-dimensional US assessment of hepatic volume,head circumference,and abdominal circumference in healthy and growth-restricted fetuses

PURPOSE: To establish reproducibility and normal values for fetal hepatic volume and its significance in identification of fetal growth restriction relative to head and upper abdominal circumferences according to a cross-sectional study design. MATERIALS AND METHODS: Pregnant women (n = 135) underwent ultrasonography. The coefficient of variation (CV) for hepatic volume scans obtained at 0 and 20 minutes and hepatic area tracings, performed twice for each scan, was determined (n = 20; range, 23-36 weeks). Normal data for hepatic volume and head and upper abdominal circumferences were obtained (n = 85; range, 20-36 weeks) and related to data from growth-restricted fetuses (birth weight < P5 centile; n = 24; range, 22-36 weeks). RESULTS: CV was 2.9% for volume scans and 1.6% for area tracings. In 85 uncomplicated cases, mean fetal hepatic volume (P50 centile) was 9.7 mL +/- 4.4 (SD) at 20 weeks and 96.4 mL +/- 8.2 at 36 weeks of gestation. In 24 growth-restricted fetuses, hepatic volume, head circumference, and upper abdominal circumference expressed as percentages of the normal P50 centile were 45%, 90%, and 82%, respectively. Mean difference in hepatic volume between fetal growth restriction and normal fetal development, as expressed with the z score, -4.32 +/- 1.4, was significantly different (P <.05) from that for head circumference, -3.04 +/- 1.3, but not from that for upper abdominal circumference, -4.7 +/- 1.2. Fetal hepatic measurement was obtained in 109 pregnancies. CONCLUSION: Acceptable reproducibility exists for hepatic volume determinations. In fetal growth restriction, reduction is more pronounced for hepatic volume than for head or upper abdominal circumference; hepatic volume is a better discriminator than head circumference but not upper abdominal circumference.     

Sonographic standards for normal infant kidney length

Standards for kidney length in relation to size were derived from measures of 34 normal, full-term, healthy infants aged 2-56 weeks. Of six general size variables (age, weight, length, head circumference, abdominal circumference, and C7 to coccyx length), net kidney length correlated best with a combination of infant length and weight. A nomogram has been generated from these data for use by the radiologist.     

Ultrasonographic measurement of subarachnoid space in normal term newborns

This study was conducted in order to assess the normal range of subarachnoid space width in healthy term newborns. A total of 230 healthy newborns were evaluated within the first 28 days of life. Measurements were correlated with body weight, height and head circumference. Mean measurements for falx-cortex and craniocortical widths and the correlations are given in tables. Subarachnoid space widths increased as weight, height and head circumference increased and the correlation was statistically significant.     

Prediction of the length of the femur from its fragments in a Sri Lankan population

ABSTRACT

In many forensic circumstances, the femur is fragmented due to decomposition and mutilation, thus necessitating development and application of regression equations to estimate the length of the femur from its fragments. In this study, regression equations were derived for the prediction of the femoral length, utilizing 11 standard femoral measurements (maximum length of femur, epicondylar breadth, vertical head diameter, transverse head diameter, vertical neck diameter, transverse neck diameter, neck length, subtrochanteric anterior–posterior diameter, subtrochanteric transverse diameter, mid-shaft anterior–posterior diameter and mid-shaft transverse diameter) obtained from 86 femora belonging to a contemporary Sri Lankan population. Univariate regression equations with moderate to high correlations (0.226 to 0.714) were formulated for the estimation of the maximum femoral length from the measurements of fragments of the femur. Of the single variables, the transverse neck diameter emerged as the best predictor (r = 0.714, SEE = 18.6596) of the maximum length of the femur. The multiple regression equations using a combination of variables yielded higher correlations (0.774–0.857) with lower error estimates (14.18–16.96). The regression equations presented in this study can be used to estimate the length of the femur of unknown, mutilated and dismembered human skeletal remains with considerable accuracy.