Three-dimensional sonographic measurement of fetal renal volume

Objective The objective of this longitudinal study was to evaluate the growth of the fetal kidney in normal pregnancies using three-dimensional ultrasound. Methods Three-dimensional sonographic examinations were performed on 13 appropriate-for-gestational-age fetuses. Fetal renal volume was measured every 2 to 3 weeks after 20 weeks gestational age until delivery. Results There was a good linear correlation between left and right renal volumes (r = 0.9614, P < 0.0001). Curvilinear relationships were found between gestational age and left and right renal volume (left: R² = 79.1%, P < 0.0001; right: R² = 74.2%, P < 0.0001), and normal ranges of left and right renal volume measurements for estimating the growth of the fetal kidney during normal pregnancy were generated. There was a difference for each predicted value of the fetal renal volume in the third trimester of pregnancy in our study and in two other previous studies. The left and right fetal renal volume to estimated fetal weight ratios were constant during the pregnancies studied. Conclusion Our findings suggest that fetal renal volume measurement plays a role in assessment of the growth of fetal kidneys. However, we are doubtful about the reproducibility of fetal renal volume measurements made by using three-dimensional ultrasound in utero. Further studies involving larger sample sizes are needed to reevaluate the usefulness and reproducibility of fetal renal volume measurements.     

三维超声计算机辅助虚拟脏器分析技术评价胎儿胆囊发育

目的 探讨三维超声计算机辅助虚拟脏器分析(VOCAL)技术测量不同孕龄胎儿胆囊体积,建立胆囊体积的正常参考值范围,并评价其与孕周的相关性。方法 选择19~40孕周正常胎儿230胎作为研究对象,采用二维超声和三维超声测量胎儿胆囊体积,并观察其重复性和一致性,分析胆囊体积与孕周的相关性。结果 同一操作者和不同操作者应用三维超声的重复性和一致性均优于二维超声。胎儿胆囊体积随孕周增加而增大,回归方程为Y=-0.027+0.104X-0.005X²(r=0.774,P=0.0001)。结论 三维超声VOCAL技术在胎儿胆囊体积测量方面的重复性和一致性优于二维超声,有助于评价胎儿胆囊发育。     

Assessment of fetal cerebellar volume using three-dimensional ultrasound

The purposes of this study were to assess the fetal cerebellar volume during normal gestation using three-dimensional (3-D) ultrasound (US) and to establish a normal chart of fetal cerebellar volume using Altman's model of statistics. In total, 231 healthy fetuses were studied for assessment of cerebellar volume using a 3-D US volume scanner. The fetuses to be studied were selected to give a cross-sectional series (i.e., each fetus was examined only once). Polynomial regression analysis was calculated to find the best-fit model using gestational age as the independent variable and cerebellar volume as the dependent variable. Altman's model was used to calculate the age-related reference centiles for the variance of cerebellar volume. In addition, common fetal growth indices, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight, were also measured for the correlation between cerebellar volume and these indices. Our results indicated that the fetal cerebellar volume was highly correlated with gestational age in normal pregnancies with the best-fit polynomial regression equation of a second-order (r = 0.91, p < 0.0001). In addition, fetal cerebellar volume in normal gestation is also highly correlated with common fetal growth indices, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight (all p < 0.0001). Following the Altman's model, a normal growth chart of fetal cerebellar volume was established for clinical reference. In conclusion, with 3-D US, the assessment of fetal cerebellar volume becomes feasible. We believe that fetal cerebellar volume assessed by 3-D US may be useful in detecting cerebellar hypoplasia and relevant syndromes prenatally.     

Three-dimensional sonographic volume measurement of the fetal stomach

The objective of this study was to measure the fetal gastric volume using three-dimensional (3-D) ultrasound during pregnancy. Three-dimensional sonographic examinations were performed involving 35 pregnant women from 12 to 38 weeks of gestation. The fetal gastric volume was monitored every 5 min for a minimum of 40 min (40-60 min) in each woman. The rotational technique with Virtual Organ Computer-aided AnaLysis (VOCAL) was used to calculate the fetal gastric volume. Maximum and minimum gastric volumes were curvilinearly associated with the gestational age, respectively (R(2) = 0.611, p < 0.0001, and R(2) = 0.407, p < 0.0001, respectively). A curvilinear relationship was noted between the functional capacity (maximum volume - minimum volume) of the fetal stomach and gestational age (R(2) = 0.531, p < 0.0001). The maximum volume change [(maximum volume - minimum volume/maximum volume) × 100] did not change during pregnancy (mean and standard deviation, 64.1% ± 16.1%). However, gastric emptying cycles could not be determined in this study because of the short observation period and small number of subjects. Our findings suggest that the fetal gastric volume calculated by conventional two-dimensional ultrasound in previous investigations is approximately one-third of the maximum volume using 3-D ultrasound in the present study and that 3-D ultrasound is a superior means of evaluating the fetal gastric volume in utero. However, the data and their interpretation in the present study should be viewed with some degree of caution because of the small number of subjects. Further studies involving a larger sample size are needed to confirm these findings.     

Fetal Cerebellar Volume and Symmetry on 3-D Ultrasound: Volume Measurement with Multiplanar and Vocal Techniques

The purpose of this prospective longitudinal study was to evaluate the growth of the fetal cerebellar volume by means of 3-D ultrasound to evaluate whether there is a difference between the volumes of the left and right cerebellar hemispheres, and to evaluate the intra- and interobserver reliability of two different techniques of volume measurement. Three-dimensional ultrasound examinations were performed every two to three weeks on 27 fetuses between 20 and 40 weeks' gestation. Measurements of the total cerebellar volume and of the left and right cerebellar hemispheres were done using the multiplanar technique. Multilevel analysis was used to determine the growth of cerebellar volume based on individual developmental trajectories and compare the volume of the right and left hemispheres of the cerebellum. The intra- and interobserver reliability was calculated for the multiplanar and VOCAL™ techniques in a subgroup of 10 fetuses. A nonlinear growth curve of cerebellar volume in normal pregnancy was generated. The cerebellar growth per two-week decreased from a gain of 51% of the first measurement at 20 weeks to a gain of 16% of the first measurement at 38 weeks. The left cerebellar hemisphere was significantly larger (12.3%, p < 0.01) than the right. The intraclass correlation coefficient for the measurements by the two techniques was 0.99. Intraobserver reliability: the intraclass correlation coefficient for the measurements using the multiplanar technique was 0.96 and 0.97 and for VOCAL™ it was 0.98 and 0.97 for the two observers, respectively. Interobserver reliability: the intraclass correlation coefficient for the measurements using the multiplanar technique was 0.97 and for VOCAL™ 0.98. Longitudinal growth curves based on individual developmental trajectories were generated for the cerebellar volume. The left fetal cerebellar hemisphere was found to be significantly larger than the right. Both multiplanar and VOCAL™ techniques had a good intra- and interobserver reliability and yielded very similar results. (E-mail: l.pistorius@umcutrecht.nl)     

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。     

Fetal transverse cerebellar diameter measurements in normal and reduced fetal growth.

OBJECTIVES: To establish the increase in fetal transverse cerebellar diameter (TCD) relative to gestational age during normal and restricted fetal growth; to determine the significance of TCD and TCD/AC relationship in predicting fetal outcome as expressed by perinatal mortality. DESIGN: A retrospective cross-sectional study. SUBJECTS: Three hundred and sixty normally developing fetuses between 17 and 34 weeks of gestation and 73 growth-restricted fetuses between 24 and 34 weeks of gestation. METHODS: Ultrasonographic measurements included head circumference (mm), abdominal circumference (mm) and transverse cerebellar diameter (mm). A gestational age-related normal reference chart was produced for TCD. RESULTS: Statistically significant relationships between transverse cerebellar diameter and gestational age, abdominal circumference and head circumference were found. The normal fetal TCD exhibited a more than twofold increase in size during the second half of pregnancy. Twenty-six per cent of the small-for-gestational age (SGA) fetuses displayed a reduced TCD and 82% of the SGA fetuses demonstrated raised TCD/AC values. No statistically significant difference in perinatal mortality or birth weight was found between the subsets of growth-restricted fetuses with reduced or normal TCD; or between the subsets with normal or raised TCD/AC values. CONCLUSIONS: In the normally developing fetus the TCD increases with advancing gestational age. Increased TCD/AC values are suspicious of fetal growth restriction. The perinatal mortality in growth-restricted fetuses with a small cerebellum is increased twofold over that of other fetuses.     

Fetal trunk and head volume measured by three-dimensional ultrasound at 11 + 0 to 13 + 6 weeks of gestation in chromosomally normal pregnancies.

OBJECTIVE: To establish the relationship between fetal trunk and head volume measured by three-dimensional (3D) ultrasound and gestational age at 11 + 0 to 13 + 6 weeks of gestation. METHODS: The fetal trunk and head volume were measured using 3D ultrasound in 417 chromosomally normal fetuses from singleton pregnancies at 11 + 0 to 13 + 6 (median, 12 + 0) weeks of gestation. Regression analysis was used to determine the significance of the association between fetal volume and gestational age. The Bland-Altman analysis was used to compare the measurement agreement and bias for a single examiner and between different examiners. RESULTS: The fetal trunk and head volume increased linearly with gestation from a mean of 5.8 mL at 11 + 0 weeks to 33.3 mL at 13 + 6 weeks and 1 SD was 4.4 mL. There was also a significant linear association between fetal volume and crown-rump length (CRL), from a mean of 5.1 mL at a CRL of 45 mm to 37.5 mL at a CRL of 84 mm and 1 SD was 2.7 mL. However, within this gestational range, a doubling in CRL, from a mean of 48 mm at 11 + 0 weeks to 79 mm at 13 + 6 weeks, was associated with a 5-6-fold increase in fetal volume. The mean difference in fetal volume between paired measurements by the same sonographer was -0.87 mL (95% limits of agreement, -2.31 to 4.05 mL) and the mean difference between paired measurements by two sonographers was -1.09 mL (-5.49 to 3.32 mL). CONCLUSIONS: 3D ultrasound can provide a reproducible measurement of the fetal trunk and head volume in early pregnancy. At between 11 + 0 and 13 + 6 weeks there is a 5-6-fold increase in fetal volume but only a doubling in CRL.     

三维超声容积自动测量技术评价胎儿小脑蚓部发育

目的 应用三维超声容积自动测量技术检测胎儿小脑蚓部的发育,为产前筛查胎儿小脑发育异常提供理论依据.方法 选择20～36孕周正常胎儿387例,应用经腹三维容积自动测量技术(VOCAL)测量小脑蚓部体积,观察胎儿小脑蚓部发育规律.结果 应用VOCAL软件测量胎儿小脑蚓部体积成功率为98%.胎儿小脑蚓部体积与孕周及小脑横径呈正相关,r分别为0.98、0.98(P<0.0001).以孕周为自变量X,小脑蚓部体积测量值为因变量Y,直线回归分析认为X与Y之间有直线关系,方程为Y=-2.17 0.12X.以小脑横径为自变量,小脑蚓部体积测量值为因变量,直线回归分析认为X与Y之间有直线关系,方程为Y=-0.94 0.06X.结论 三维超声容积自动测量技术测量胎儿小脑蚓部体积有助于评价胎儿小脑蚓部的发育.     

Three-dimensional ultrasound in the assessment of fetal cerebellar transverse and antero-posterior diameters

Fetal cerebellum scanning by prenatal ultrasound (US) is very important for early detection of fetal central-nervous-system anomaly, as well as for the determination of gestational age (GA). Due to the small organ size and the unique shape of the fetal cerebellum (CL), accurate measurement of the dimensions of CL by two-dimensional (2-D) US is not easy if the appropriate plane cannot be reached. With the advent of three-dimensional (3-D) US, the disadvantages of 2-D US in assessing the fetal CL dimensions can be avoided. The purpose of this study was to assess the fetal cerebellar transverse diameter (CTD) and cerebellar antero-posterior diameter (CAD) using 3-D US. First, we compared the reproducibility of 2-D and 3-D US on the assessment of fetal cerebellar dimensions. Second, we prospectively measured CTD and CAD in 223 healthy fetuses using a cross-sectional design with an attempt to establish the normal growth charts of fetal CL. Our results showed 3-D US is superior to 2-D US in the reproducibility test of fetal cerebellar dimensions. In addition, with GA as the dependent variable, polynomial regression analysis showed that the best-fit equations for both CTD vs. GA and CAD vs. GA were the first-order. The best-fit predictive equation of GA by CTD was GA (week) = 9.0281 + 0. 58533 x CTD (mm) (r = 0.95, n = 223, SE = 1.82 weeks, p < 0.0001), and the best-fit predictive equation of GA by CAD was GA (week) = 10. 855 + 1.1672 x CAD (mm) (r = 0.82, n = 223, SE = 3.41 weeks, p < 0. 0001). Furthermore, all the correlation coefficients of CTD or CAD vs. the common fetal growth indexes were also highly significant (all p < 0.0001). In conclusion, our data of fetal CL dimensions assessed by 3-D US may serve as a useful reference in assessing fetal CL growth, dating GA or detecting fetal CL anomalies.     

A nomogram of fetal lung volumes estimated by 3-dimensional ultrasonography using the rotational technique (virtual organ computer-aided analysis).

OBJECTIVE: The purpose of this study was to build a nomogram of normal fetal lung volumes throughout gestational age estimated by 3-dimensional ultrasonography using the rotational technique (Virtual Organ Computer-Aided Analysis [VOCAL]; GE Healthcare, Kretztechnik, Zipf, Austria). METHODS: Fetal lung volume was assessed in 146 healthy fetuses by 3-dimensional ultrasonography using the technique of rotation of the multiplanar imaging (VOCAL). Inclusion criteria were healthy women with singleton normal pregnancies, normal fetal morphologic ultrasonographic findings, reliable dating established by dates and by ultrasonographic measurement of the crown-lump length in the first trimester, and gestational age from 20 to 37 weeks. Exclusion criteria were discordance between clinical and ultrasonographic dating, patients lost to follow-up, and birth weight disorders. Each patient was scanned once during pregnancy. RESULTS: The right, left, and total mean pulmonary volumes ranged, respectively, from 5.37, 4.66, and 9.95 cm3 at 20 weeks to 46.06, 37.34, and 84.35 cm3 at 37 weeks. The logistic transformation analysis yielded the following formulas: right lung volume = exp(4.07/[1 + exp(21.90 - gestational age/5.44)]); left lung volume = exp(3.82/(1 + exp[22.03 - gestational age/5.17)]); and, total lung volume = exp(4.72/[1 + exp(20.30 - gestational age/6.05)]). CONCLUSIONS: A new nomogram of fetal lung (right, left, and total) volumes throughout gestational age using the rotational technique (VOCAL) is described, and reference values have been generated.     

Assessment of placental fractional moving blood volume using quantitative three-dimensional power doppler ultrasound

To test the hypothesis that the placental fractional moving blood volume is different with advancing gestational age (GA), we assessed the vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) of the placenta in normal pregnancy by using three-dimensional (3-D) power Doppler ultrasound (US). We enrolled 100 healthy pregnant women with gestational age between 20 to 40 weeks for this study. Three-dimensional power Doppler ultrasonography was used to assess the VI, FI and VFI in each case. Our results showed that the linear regression equations for VI, FI and VFI, by using GA as the independent variable, were VI = 0.27107 x GA -4.02748 (r = 0.84, p < 0.0001), FI = 0.56115 x GA + 34.28945 (r = 0.49, p < 0.001), and VFI = 0.15663 x GA -2.53810 (r = 0.82, p < 0.0001), respectively. In addition, the VI, FI and VFI values of the placental flow were also positively correlated with the fetal growth indices, namely, biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference and estimated fetal weight (all p values < 0.001). In conclusion, our study illustrates that the fractional moving blood volume of the placenta is positively correlated with the increment of gestational age and the fetal growth indices. Our data may be used as a reference in the assessment of the placental fractional moving blood volume using the quantitative 3-D power Doppler US.     

Gestational sac volume measured by three-dimensional ultrasound at 11 to 13 + 6 weeks of gestation: relation to chromosomal defects.

OBJECTIVE: To determine the potential value of measuring the gestational sac volume (GSV) at 11 to 13 + 6 weeks of gestation in screening for chromosomal defects. METHODS: The GSV was measured using three-dimensional (3D) ultrasound in 500 consecutive singleton pregnancies immediately before chorionic villus sampling (CVS) for fetal karyotyping at 11 to 13 + 6 (median 12) weeks of gestation. RESULTS: The fetal karyotype was normal in 417 pregnancies and abnormal in 83. In the chromosomally normal group, the mean GSV increased significantly with gestational age from a mean of 69 mL at 11 weeks to 144 mL at 13 + 6 weeks (the standard deviation was 27 mL). In the chromosomally abnormal group, the mean GSV for gestational age was not significantly different from normal in fetuses with trisomy 21, trisomy 18 and Turner syndrome, but it was smaller in those with triploidy and trisomy 13. However, the mean GSV for crown-rump length (CRL) was significantly larger in trisomy 18, smaller in triploidy and trisomy 13, and not different from normal in trisomy 21 and Turner syndrome. The mean CRL for gestational age was significantly smaller than normal in trisomy 18, triploidy and trisomy 13. CONCLUSIONS: The measurement of the GSV at 11 to 13 + 6 weeks of gestation is unlikely to provide useful prediction of the major chromosomal defects. In trisomy 13 and triploidy, the small GSV may be due to early onset fetal growth restriction and reduced amniotic fluid volume. In trisomy 18, the increase in GSV is probably due to the presence of associated fetal abnormalities that interfere with fetal swallowing.     

三维超声扩展成像检测胎儿小脑蚓部发育的研究

目的 应用三维经腹超声检测胎儿小脑蚓部的发育,为产前筛查胎小儿脑蚓部发育异常提供依据.方法 选择于我院行产前超声检查的孕20～36周正常胎儿共387例.应用经腹三维超声扩展成像技术观察胎儿小脑蚓部发育规律,测量蚓部横径、前后径、上下径,上下蚓部面积之比,蚓部与脑干之间的夹角,并分析它们与孕周的关系.结果 应用经腹三维超声扩展成像多切面同屏显示模式和三维重建矢状切面可以评价蚓部形态的完整性和大小,识别蚓部特征性标志:第四脑室顶点和蚓部裂.正常蚓部与脑干之间几乎平行,夹角随着孕周无明显变化,均值为3.97°±1.65°.上下蚓部面积之比随着孕周无明显变化,均值为0.76±0.06.小脑蚓部横径、前后径、上下径均与孕周呈正相关.结论 应用三维扩展成像多切面同屏显示模式和三维重建矢状切面有助于观察小脑蚓部发育情况,显示小脑蚓部与脑干周围关系,为评价胎小儿脑蚓部的发育提供了新的思路.     

自动容积导航技术与二维超声获取胎儿颅脑正中矢状面的对比研究

目的评估三维超声自动容积导航技术（Smart Planes）与二维超声在获取胎儿颅脑正中矢状面（MSP）以及测量胎儿胼胝体及小脑蚓部参数的一致性和可重复性。 方法选取2017年10月至2017年12月在广东省妇幼保健院行产前超声检查的单胎妊娠孕妇168名作为研究对象。采用二维超声获取胎儿颅脑MSP并手动测量胼胝体前后径,测量小脑蚓部前后径、上下径及面积。随后应用三维容积探头获取胎儿颅脑容积数据,利用Smart Planes技术自动分析并测量胼胝体和小脑的相应数据。采用组内相关系数（ICC）及Bland-Altman法比较二维超声与Smart Planes技术对胎儿胼胝体以及小脑蚓部的测量的一致性和可重复性。对比不同操作者间测量的一致性及同一操作者采用两种方法测量的用时差异。 结果采用Smart Planes技术与二维超声获取胎儿颅脑MSP的成功率分别为97.0％（163/168）、79.8%（134/168）,差异有统计学意义（χ²=24.40,P<0.001）。其中76.8%（129/168）胎儿通过二维超声及Smart Planes技术均获得颅脑MSP并测量相关参数。比较二维超声与Smart Planes技术测量胼胝体前后径以及小脑蚓部前后径、上下径、面积的一致性,ICC分别为0.972、0.968、0.946、0.967。比较同一位操作者采用Smart Planes技术2次测量的一致性,ICC分别为0.995、0.987、0.962、0.993。比较不同操作者间采用Smart Planes技术测量的一致性,ICC分别为0.986、0.966、0.972、0.955。采用Smart Planes技术获取胎儿颅脑MSP所需时间[（13.49±5.38）s]明显短于采用二维超声所需时间[（89.99±113.42）s],差异有统计学意义（U=587.50,Z=-12.915,P<0.001）。 结论三维超声自动容积导航技术可快速获取胎儿颅脑MSP,测量所得胼胝体及小脑蚓部的参数与二维超声测量所得结果一致性较好,有助于超声医师对胎儿中线结构做出快速准确的识别和测量。     

The assessment of normal fetal liver volume by three-dimensional ultrasound

Liver volume (LIVV) is very important in determining the status of fetal growth. However, to measure human fetal LIVV in utero precisely and noninvasively is not an easy task. With the recent advancement of three-dimensional (3-D) ultrasound (US), the limitation in assessing fetal LIVV by 2-D US can be overcome. The purpose of this study was to establish a normal reference chart of fetal LIVV for clinical use. A prospective and cross-sectional study using 3-D US was undertaken to assess the fetal LIVV in normal pregnancy. In total, 226 singleton fetuses ranging between 20 and 40 weeks of gestation and fitting the criteria of normal pregnancies were enrolled in this study. Our results showed that fetal LIVV is highly correlated with the gestational age (GA). Furthermore, using GA as the independent variable and fetal LIVV as the dependent variable, the best-fit regression equation was LIVV (mL) = -398.26 + 46.199 xGA - 1.7567 x GA(2) + 0.0236 x GA(3) (r = 0.97, n = 226, p < 0.0001), with SD of LIVV (mL) = 1.2533 x (0.77956 + 0.17267 x GA). These common indexes of fetal biometry, such as biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference (HCi), abdominal circumference (ACi), femur length (FL), and estimated fetal weight (EFW), were all highly correlated with fetal LIVV (all p < 0.0001). In conclusion, our data of fetal LIVV assessed by 3-D US can serve as a useful reference in evaluating fetal growth status during normal gestation.     

Assessment of normal fetal upper arm volume by three-dimensional ultrasound

Fetal upper arm volume (UAV) is closely related to fetal growth and nutrition status. In the past, 2-D ultrasound (US) has shown limitations in assessing fetal UAV. With the recent advancement of 3-D US, the limitation in assessing fetal UAV by 2-D US can be overcome. To establish a reference chart of fetal UAV for clinical use, a prospective and cross-sectional study using 3-D US was undertaken to assess the fetal UAV in normal pregnancy. In total, 206 singleton fetuses ranging between 20 and 40 weeks of gestation that fit the criteria of normal pregnancies were enrolled in this study. Our results showed that fetal UAV is highly correlated with the gestational age. Furthermore, using gestational age (GA) as the independent variable and UAV as the dependent variable, the best-fit regression equation was UAV (mL) = 43.546 - 4.530 x GA + 0.133 x GA(2) (r = 0.913, n = 206, p < 0.0001). For further clinical use, a chart of normal growth centiles of fetal UAV in utero was then calculated based on this equation. In conclusion, we believe our data of fetal UAV assessed by 3-D US can serve as a useful reference in evaluating fetal growth and nutrition status during gestation.     

Comparison of methods for determining crown-rump measurement by real-time ultrasound

Determination of gestational age without an accurate last menstrual period is difficult. In the later stages of pregnancy, the correlation between fetal biparietal diameter (BPD), as determined by ultrasound, and gestational age is compromised by normal biologic variation in fetal growth rates. The fetal crown-rump measurement (CRM) by gray-scale sonography has been described but has not been evaluated using real-time ultrasound. Currently available tables for determining gestational age from the fetal CRM were evaluated using a linear array real-time ultrasound system. A normal obstetric population with known menstrual histories, delivery dates, and Dubowitz scores at delivery was used for evaluation. On the basis of this study, Robinson's data listed as “regression analysis values” are suggested for application to real-time ultrasound. Alternatively, the equation generated from data on the above 86 patients could be used and further evaluated. The fetal CRM appears to be a valid and accurate assessment of gestational age.     

Assessment of gestational age in the first trimester of pregnancy by maximum fetal diameter

A method using ultrasound to estimate fetal gestational age between the sixth and fourteenth week of pregnancy is described. The maximum fetal diameter is measured by a modification of the technique developed by Robinson (1973, 1975) to determine crown-rump length. Correlation of values for maximum fetal diameter with subsequent estimation of gestational age by ultrasound at adjudged 24 weeks, by X-ray at adjudged 37 weeks and also with the actual date of delivery, confirmed the accuracy for clinical purposes of this simplified method.