Determination of gestational age after the 24th week of gestation from fetal kidney length measurements.

OBJECTIVE: To evaluate the application of kidney length measurement to the determination of gestational age between the 24th and 38th weeks and to compare its accuracy with that of other fetal biometric indices. STUDY DESIGN: Seventy-three women with singleton uncomplicated pregnancies underwent standard ultrasound fetal biometry and kidney length measurement every 2 weeks between 24 and 38 weeks' gestation. These measurements were used to date the pregnancies relative to crown-rump length dating between 8 and 10 weeks' gestation. Linear regression models for estimation of gestational age were derived from the biometric indices and kidney length. In addition, stepwise regression models were constructed to determine the best model for determining gestational age between 24 and 38 weeks. Comparisons were then made between the accuracy of these models in the determination of gestational age. RESULTS: The best model for estimating gestational age in late pregnancy included the variables kidney length, biparietal diameter, head circumference, femur length and abdominal circumference. This model accurately predicted gestational age with a standard error of +/- 8.48 days. A model including kidney length, biparietal diameter, head circumference and femur length accurately predicted gestational age with a standard error of +/- 8.57 days. These models were slightly more accurate than models derived from the biometric indices of biparietal diameter, head circumference and femur length (+/- 9.87 days), biparietal diameter, head circumference, femur length and abdominal circumference (+/- 9.45 days) and biparietal diameter and femur length (+/- 9.9 days). Kidney length and femur length were the most accurate single parameters for predicting gestational age using simple linear regression models (+/- 10.29 and 10.96 days, respectively); the abdominal circumference was the least accurate (+/- 14.54 days). CONCLUSION: Kidney length is a more accurate method of determining gestational age than the fetal biometric indices of biparietal diameter, head circumference, femur length and abdominal circumference between 24 and 38 weeks' gestation. When combined with biparietal diameter, head circumference and femur length, the precision of dating is improved by 2 days. This measurement is easy to make and could therefore be easily incorporated into the model for dating pregnancies after 24 weeks of gestation, in particular when measurements of the biparietal diameter and head circumference are difficult.     

Comparison of biparietal diameter and femur length in the third trimester: effects of gestational age and variation in fetal growth

A multiple regression-based statistical model capable of quantitatively comparing two or more sonographic parameters for the effects of gestational age, variation in fetal growth and error in sonographic measurement is presented and then used to compare the biparietal diameter and femur length as estimators of gestational age in late pregnancy. A total of 311 patients were studied between 24 and 42 weeks' gestation. Variation in fetal growth was expressed as the birth weight percentile for gestational age. Biparietal diameter and femur length correlated equally well with gestational age. However, the biparietal diameter was more than twice as sensitive as the femur length to variation in fetal growth. Femur length had a larger error associated with its measurement. These results suggest that the biparietal diameter and femur length in late pregnancy are equal estimators of gestational age; that the femur length is a more stable estimator of gestational age when fetal growth deviates from normal; and that the femur length is technically more difficult to obtain.     

A direct method for ultrasound prediction of day of delivery: a new, population-based approach.

OBJECTIVES: To introduce a direct population-based method for prediction of term based on ultrasound measurements of the biparietal diameter and femur length in the second trimester of pregnancy. METHODS: Our data consisted of 41 343 ultrasound scans from a non-selected population, prospectively collected during the years 1987-2004. Using measurements of biparietal diameter and femur length, we constructed prediction curves for term by computing median remaining time of pregnancy from the ultrasound measurement to birth. A local linear quantile regression method was used to smooth the median and quantile curves. RESULTS: The quality of term prediction was stable over the prediction range for both biparietal diameter (25-60 mm) and femur length (11-42 mm). The femur-based predictions were nearly as good as those of the biparietal diameter. For the biparietal diameter, the median of the prediction residual was -0.09 days; 87.2% of the births fell within +/- 14 days of the predicted day of delivery, 3.5% births were classified as preterm and 4.3% as post-term. The corresponding figures for femur length were - 0.04 days, 86.7%, 3.6% and 4.5%. The covariates maternal age, parity, mother's smoking habits, sex of the fetus and examination year generally affected the predicted term by less than 1 day. CONCLUSIONS: This direct ultrasound-based prediction of term using population-based data avoids selection biases possibly present in smaller prospective samples. The model obviates the dependence on last menstrual period found in standard methods for term prediction, and allows an immediate assessment of prediction quality in a population setting. The femur-based predictions had a quality similar to those based on the biparietal diameter. The model can be updated continuously as new data are collected.     

Evaluation of fetal femur length for prediction of gestational age in a racially mixed obstetric population

In a retrospective study, a group of 314 patients between 19 and 32 completed weeks' gestation were evaluated for differences in sonographic measurement of femur length vs. gestational age between the following racial categories: Hispanic, black, Oriental, and Caucasian. Selection criteria included known last menstrual period, singleton gestation, and a historic absence of maternal diabetes, hypertension, or renal disease or fetal anomalies. The gestational age against which the femur length was judged was determined from the last normal menstrual period, provided that this date differed by less than 2 weeks from age determined by fetal biparietal diameter and evaluation of the newborn. No statistically significant difference in femur length vs. gestational age was noted between the various racial categories.     

A new mathematical formula for predicting long bone length in early pregnancy.

OBJECTIVE: To propose new mathematical formulae to estimate fetal long bone biometry in early pregnancy and to establish their efficacy in comparison to previously constructed mathematical formulae. METHODS: A study population of 1960 singleton euploid fetuses was referred for transvaginal ultrasound examinations between 71 and 112 days of gestation prior to genetic amniocentesis. To determine the relationship between the biparietal diameter and long bone length, a sample group of 400 randomly chosen normal fetuses was evaluated. Regression equations were derived, then tested in the remaining 1560 control fetuses and compared with previously reported mathematical formulae by other authors. Mean absolute error, mean absolute percentage error and mean systematic error with their standard deviations were calculated. RESULTS: The relationships between femur or humerus length vs. biparietal diameter (BPD) and gestational age (GA) were, respectively: expected femur length = -16.92108 + 0.4569402 x BPD + 0.171617 x GA (P < 0.001) and expected humerus length = -16.28531 + 0.4283019 x BPD + 0.1696017 x GA (P < 0.001). The confidence intervals of the predicted values for different values of biparietal diameter and gestational age and confidence intervals for the regression coefficients, such as the distribution of the residuals, are given. All previous formulae obtained by transabdominal ultrasound demonstrated an overestimation of expected long bones measurements; this was reduced using different formulae obtained in early pregnancy. Using our mathematical formulae, the mean absolute percentage error and the mean systematic error in estimating femur and humerus length were very low (11.15% and -2.02%; 10.59% and -1.74%, respectively). CONCLUSIONS: The new ultrasonographic morphometric models derived from transvaginal measurements in early pregnancy show a good reliability in estimating fetal long bone length.     

Nomograms of sonographic measurements throughout gestation of the fetal hard palate width, length and area.

OBJECTIVE: To assess the feasibility of sonographic depiction of the fetal hard palate and secondarily to create nomograms throughout gestation of its sonographic width, length and area. METHODS: This was a cross-sectional study of pregnant patients between 15 and 41 weeks' gestation. Inclusion criteria consisted of well-established dates (confirmed by early ultrasound), and singleton, non-anomalous fetuses. Sonographic measurements obtained included biparietal diameter, head circumference, abdominal circumference and femur length. Fetal hard palate measurements included maximum width, maximum length and the calculated area. Tables were prepared depicting the estimated mean +/- SD and 5(th), 50(th) and 95(th) centiles at each gestational week between 15 and 41 weeks. Pearson's correlation coefficient and associated P-values for the relationships between fetal hard palate measurements and other sonographic measurements and coefficients of variation for each of the fetal hard palate measurements were calculated. RESULTS: The study included 602 consecutive patients. The mean maternal age was 28.7 +/- 6.3 years, with median gravidity of 2 (range, 1-12) and parity 1 (range, 0-8). All attempts at obtaining fetal hard palate ultrasound measurements were successful. Mean fetal hard palate width (cm) = -0.73579345 + 0.11370432 x GA - 0.00083919 x GA(2) and SD = -0.017842055 + 0.005142475 x GA, where GA is gestational age in weeks. Mean fetal hard palate length (cm) = -0.82020463 + 0.11767777 x GA - 0.00092801 x GA(2) and SD = -0.043064317 + 0.006378869 x GA. Mean fetal hard palate area (cm(2)) = -2.40090641 + 0.17136556 x GA + 0.00097308 x GA(2) and SD = -0.603647741 + 0.040740282 x GA. Sonographic measurements of the fetal hard palate width, length and area correlated significantly and strongly with gestational age (all P < 0.001) and significantly but less strongly with femur length (P = 0.004). CONCLUSION: The fetal hard palate may be depicted sonographically with relative ease between 15 and 41 weeks' gestation and measurements of the fetal hard palate width, length and area correlate well with gestational age, biparietal diameter, abdominal circumference, sonographic estimated fetal weight, and femur length.     

Computer assisted analysis of fetal age in the third trimester using multiple fetal growth parameters

A new technique is described for predicting menstrual age in the third trimester of pregnancy (28-42 weeks) using multiple fetal growth parameters (biparietal diameter, head circumference, abdominal circumference, femur length). Evaluation of this technique in 177 normal third trimester pregnancies demonstrated that significant improvement in the variability in predicting menstrual age can be achieved when two or more parameters are used collectively instead of a single parameter used individually. The optimal combination prior to 36 weeks was biparietal diameter, abdominal circumference, and femur length, while after 36 weeks the optimal combination was head circumference, abdominal circumference, and femur length. The use of these combinations resulted in smaller mean errors, standard deviations, and maximum errors. Regression equations and tables of normal values are provided to facilitate the use of this dating method.     

Biparietal diameter and femur length discrepancies: are maternal characteristics important?

We examined whether gestational age, maternal race or height can be used to explain discrepancies between biparietal diameter- and femur length-derived gestational ages by analyzing ultrasound scans from 8041 consecutively scanned, singleton pregnancies, using multiple regression analysis. While a consistent association was noted between differences of more than 3 weeks and less than 3 weeks and advancing gestational age, neither maternal height nor race were significantly related. We conclude that, first, discrepancies between gestational age by biparietal diameter and femur length are rare (5%) and, second, the presence of discrepancies should not be dismissed on the basis of maternal stature or race and should alert the clinician to possible abnormal fetal growth or development.     

Is fetal femur length a better indicator of gestational age in the growth-retarded fetus as compared with biparietal diameter?

The accuracy of gestational age prediction in 30 growth-retarded fetuses as derived from the fetal femur length (FL) was compared with that derived from the biparietal diameter (BPD). The mean difference between the actual and predicted gestational age was smaller when FL was used, but the difference did not reach statistical significance when compared with that associated with the use of the BPD. No consistent pattern of head/limb growth retardation was obvious. The femur length and BPD were both reduced in varying proportions in the growth-retarded fetuses. The significance of such findings in the assessment of intrauterine growth retardation is discussed.     

胎儿小脑横径与孕龄的相关性探讨

本文应用实时线阵超声对７５０例妊娠１６～４０周的正常孕妇的胎儿小脑横径（ＣＴＩ））、双顶径（ＢＰＤ）、头围（ＨＣ）、腹围（ＡＣ）及股骨长度（ＦＬ）进行测量，线性相关分析结果显示ＣＴＩ）、ＢＰＤ、ＨＣ、ＡＣ及ＦＬ均与孕龄（ＭＡ）呈高度的正相关，以ＣＴＤ的相关性最好，小脑位于后颅窝内，因后颅窝特定的解剖特点，使小脑形状不受外界因素的影响，故用ＣＴＤ推算孕龄更为准确，并能在胎儿期及早发现中枢神经系统异常，对围产监测具有重要的意义，提出超声测量胎儿小脑横径可作为估计孕龄的可靠指标之一。     

超声检测与经验性预测胎儿出生体重的价值比较

目的：应用超声检测胎儿多项生物学指标预测胎儿出生体重,并与临床医生经验性预测比较。方法超声检测208例晚孕胎儿双顶径、腹围、股骨径,分析其与胎儿出生时体重的关系,同时与临床多因素经验性体重预测进行比较。结果超声多参数预测及经验预测208例胎儿出生体重与胎儿出生时实测体重差异均无统计学意义（ P＞0.05）。胎儿的双顶径、腹围、股骨长与新生儿体重之间均存在线性相关关系。结论训练有素的临床医生综合各种因素预测的胎儿体重值和超声多参数预测的胎儿体重值没有差异。     

Prediction of discordant twins by real-time ultrasonography combined with umbilical artery velocimetry.

OBJECTIVE: To evaluate the role of umbilical Doppler velocimetry combined with ultrasonographic intertwin differences derived from estimated fetal weight, biparietal diameter, abdominal circumference and femur length as a comprehensive test for the prediction of discordancy. METHODS: The sets of twins were studied with real-time ultrasonography for morphometric measurements and with duplex Doppler velocimetry for the S/D ratio of the umbilical artery in third trimester. The following cutoff values were used to indicate abnormal test results: delta biparietal diameter > 6 mm, delta abdominal circumference > 20 mm, delta femur length > 5 mm, delta estimated fetal weight > 15% and delta systolic/diastolic ratio > 15%. Discordancy was identified when the birth weight difference exceeded 15%. RESULTS: Among the 52 sets of twin pregnancies studied, 40 sets of twins fulfilled the study criteria. Thirteen sets of twins were discordant (32.5%) The mean gestational age at delivery was 37.15 +/- 2.24 weeks (range 28-41 weeks). The diagnostic accuracy provided by ultrasonographic morphometries was not significantly different from that provided by umbilical Doppler velocimetry. Overall the best predictors appeared to be the presence of either delta systolic/diastolic ratio > 15% or delta estimated fetal weights > 15% with sensitivity and specificity values of 92% and 70%, respectively. CONCLUSION: Real-time ultrasonography combined with umbilical artery velocimetry is useful in predicting discordant twins.     

The fetal mandible measurement: an objective determination of fetal jaw size.

The sonographic diagnosis of micrognathia has been limited by the lack of an objective measurement of the fetal mandible. A cross-sectional study of 134 normal patients of known gestational age between 14 and 39 weeks' gestation was performed. Models to predict mandible length based on gestational age, biparietal diameter, head circumference or femur length were derived by least squares regression analysis. The 95% prediction limits were also derived. Utilization of these curves generated from a normal population should allow for a more sensitive and reproducible method to diagnose micrognathia in the fetus.     

超声测量晚孕期正常双胎生长参数的初步分析

目的拟初步建立孕28-34周的双胎胎儿生长参数超声测量值的正常范围,比较晚孕期单、双胎妊娠胎儿的宫内生长发育模式。方法对2009年5月一2010年4月超声诊断为正常宫内双活胎、单活胎孕妇,采用超声测量胎儿相关生长发育指标,包括双顶径、头围、腹围、股骨长等,测量其中部分双胎的小脑横径并应用虚拟器官计算机辅助分析技术测量其小脑容积,比较晚孕期单、双胎胎儿生长发育的差异。结果①自妊娠30周以后,双胎胎儿的双顶径发育速度比单胎胎儿延缓,单、双胎胎儿平均每周增长分别约2．3、1．7mini②自妊娠32周以后,双胎胎儿的头围的发育速度比单胎胎儿延缓,单、双胎胎儿平均每周增长分别约6．7、5．8Inrn;③自妊娠30周以后,双胎胎儿的腹围的发育速度比单胎胎儿延缓,单、双胎胎儿平均每周增长分别约6．9、5．3mm;④双胎胎儿股骨长从孕28～34周发育速度均较单胎胎儿缓慢,单、双胎胎儿平均每周增长分别约2．0、1．7mml⑤多元分析孕28－34周的双胎胎儿双顶径、头围、腹围和股骨长,相对于单胎胎儿而言,自28周起,双胎妊娠胎儿的生长发育较延缓;⑥自孕28～34周,双胎胎儿小脑横径、小脑容积与单胎胎儿无明显差异。结论双胎妊娠胎儿与单胎妊娠胎儿在晚孕期有着不同的生长发育规律。     

Sonographic dating of pregnancies conceived after contraceptive pill therapy.

A total of 358 women succeeded in conceiving in the first cycle after stopping oral contraception. The estimated day of delivery was calculated from both an ultrasonographically measured fetal biparietal diameter, in the second trimester, and from the date of the withdrawal bleed. According to the biparietal diameter measurement, the estimated day of delivery was postponed more than 1 week in 138 cases (38.5%). For 304 women who delivered after the spontaneous onset of labor, the biparietal diameter estimate gave the best prediction of the day of delivery in 175 cases (57.6%), the date of the withdrawal bleed gave the best estimate in 91 (29.9%) (p < 0.001) and they were equally good in 38 (12.5%). The estimated day of delivery using a biparietal diameter measurement was within +/- 14 days of the day of delivery for 267 of these 304 women (87.8%). The corresponding figure for the withdrawal bleed date was 218 (71.7%) (p 相似文献   

Can transvaginal fetal biometry be considered a useful tool for early detection of skeletal dysplasias in high-risk patients?

OBJECTIVE: To evaluate the possibility of an early diagnosis of skeletal dysplasias in high-risk patients. METHODS: A total of 149 consecutive, uncomplicated singleton pregnancies at 9-13 weeks' amenorrhea, with certain menstrual history and regular cycles, were investigated with transvaginal ultrasound to establish the relationship between femur length and menstrual age, biparietal diameter and crown-rump length, using a polynomial regression model. A further eight patients with previous skeletal dysplasias in a total of 13 pregnancies were evaluated with serial examinations every 2 weeks from 10-11 weeks. RESULTS: A significant correlation between femur length and crown-rump length and biparietal diameter was found, whereas none was observed between femur length and menstrual age. Of the five cases with skeletal dysplasias, only two (one with recurrent osteogenesis imperfecta and one with recurrent achondrogenesis) were diagnosed in the first trimester. CONCLUSIONS: An early evaluation of fetal morphology in conjunction with the use of biometric charts of femur length against crown-rump length and femur length against biparietal diameter may be crucial for early diagnosis of severe skeletal dysplasias. By contrast, in less severe cases, biometric evaluation appears to be of no value for diagnosis.     

Growth retardation in fetuses with gastroschisis

This study was designed to determine the prevalence of intrauterine growth restriction in neonates with gastroschisis and to evaluate the accuracy of the ultrasonographic diagnosis of intrauterine growth restriction. Birth weight and gestational age were determined for 46 infants diagnosed prenatally as having gastroschisis. Biometric data were analysed for the 30 pregnancies in which an examination was conducted within 1 week of delivery. Fetal growth parameters were compared with norms for gestational age. The prevalence of intrauterine growth restriction in the entire study group was 24% with a mean birth weight of 2401 +/- 508 g. Ultrasonographic estimated fetal weight was significantly less than birth weight (mean, 2079 +/- 508 g versus 2331 +/- 512 g, respectively; P < 0.0001). Intrauterine growth restriction was predicted in 43% of infants but was present in only 23%. The percentage difference between measured abdominal circumference and gestational age norm was significantly more than for biparietal diameter and for femur length (P < 0.001). Of the three biometric measures, only the difference between measured abdominal circumference and gestational age norms and the difference between estimated fetal weight and birth weight showed a significant correlation. Both abdominal circumference and femur length correlated with the difference between estimated fetal weight and birth weight. We conclude that the prevalence of intrauterine growth restriction is increased in infants with gastroschisis but is overestimated with prenatal ultrasonography, primarily because of smaller than average abdominal circumference measurements.     

Regression formula for estimation of fetal weight with use of abdominal circumference and femur length: a prospective study.

Ultrasonographic fetal measurements from 293 singleton pregnancies were obtained within 7 days of delivery. Biparietal diameter, abdominal circumference, femur length, and actual birth weight data of the first 93 fetuses in the study were used as variables to determine the best mathematical model for relating estimated fetal weight to biparietal diameter, abdominal circumference, and femur length. With the aid of a computer, three regression equations were derived. The best model was Log10 (weight) = 0.77125 + 0.13244 (AC) - 0.12996 (FL) - 1.73588 (AC x AC)/1000 + 3.09212 (FL x AC)/1000 + 2.18984 (FL/AC); (R2 = 0.987). The accuracy of this formula was then compared prospectively, first with the formulas published by Shepard and coworkers, Rose and McCallum, and Hadlock and colleagues in the entire sample of 200 patients, second in 46 large, 101 appropriate, and 53 small for gestational age fetuses, and then in 44 fetuses of pregnancy complicated by diabetes. The difference between actual and estimated birth weights generated by the study formula had no systematic error (Student's t-test, P > 0.05) in cumulative data, and in small or appropriate and large for gestational age fetuses. As this derived formula is very cumbersome to manipulate, tables have been prepared with computer assistance to read the estimated fetal weight directly.     

预测足月胎儿体重中逐步回归分析的应用研究

目的探讨逐步回归分析用于预测足月胎儿体重的可行性。方法监测了200例孕妇的年龄、孕期体重增加、孕次、产次、孕周、宫高、腹围、胎儿双顶径、股骨长度、羊水平段、胎儿体重、性别(出生后)共12项,胎儿体重为因变量,其余11项为自变量。结果在全部样本参与运算的前提下,起作用的是孕周、腹围、双顶径,精确度可达80％。结论逐步回归分析可以用于预测胎儿体重。     

Ultrasound measurement of the fetal head: computer versus operator.

In obstetrical ultrasound practice, biparietal diameter, occipito-frontal diameter and head circumference are among the most commonly used fetal measurements. To minimize the limitations associated with manual measurement, we have undertaken an investigation with a focus on (1) the design of a personal computer-based system for automated measurements of biparietal diameter, occipito-frontal diameter and head circumference, and (2) integration of such a system (including measurements of abdomen and femur) into the routine obstetrical ultrasound examination. This report presents preliminary results of a comparison of computer-determined fetal head measurements with those obtained by an operator. Data were obtained from 75 consecutive singleton fetal ultrasound examinations free of any obvious structural anomalies. The computer obtained acceptable measurements of biparietal diameter, occipito-frontal diameter and head circumference from 74 images and failed on one image. There was a highly significant correlation between computer-determined measurements of biparietal diameter (r = 0.986), occipito-frontal diameter (r = 0.958) and head circumference (r = 0.972) and those obtained by the operators. The mean measurement difference (computer minus operator) was 1.87 +/- 1.94 mm for biparietal diameter, 2.82 +/- 4.13 mm for occipito-frontal diameter and -0.36 +/- 9.87 mm for head circumference. These differences were independent of the operator's identity, the instrument used and gestational age. The key finding of this study is that, with the use of inexpensive personal computer technology, it is possible to design and implement a system that can give fetal head measurements which correlate highly with manual determination by a skilled operator and which take a fraction of the time.