Nomograms of the fetal neck circumference and area throughout gestation.

OBJECTIVE: The purpose of this study was to create reference range nomograms of the axial fetal neck circumference (FNC) and fetal neck area (FNA) throughout gestation. METHODS: This prospective cross-sectional study involved pregnant patients between 14 and 40 weeks' gestation. Inclusion criteria consisted of well-established dates (confirmed by early sonography) and nonanomalous singleton fetuses with intact fetal membranes. Sonographic measurements included biparietal diameter, head circumference, abdominal circumference, femur length, humerus length, transcerebellar diameter, and sonographically estimated fetal weight. Axial FNC and FNA values were calculated as means of 3 separate measurements. The 5th, 50th, and 95th percentiles were estimated at each week of gestational age (GA) by least squares regression for the mean and SD of the FNC and FNA as functions of GA. R(2) and associated P values for the relationships between the FNC, FNA, and other sonographic biometric measurements were calculated. RESULTS: The study included 720 consecutive patients. The mean maternal age +/- SD was 27.3 +/- 6.6 years; median gravidity, 3 (range, 1-13); and median parity, 1 (range, 0-10). The following equations were devised: mean FNC (centimeters) = -11.85 + 1.687 x GA (weeks) -0.043 x GA(2) + 0.0004951 x GA(3); SD(FNC) = 3.15 - 0.3823 x GA + 0.01733 x GA(2) - 0.0002179 x GA(3); mean FNA (square centimeters) = 37.29 - 7.0 x GA + 0.4717 x GA(2) - 0.01245 x GA(3) + 0.0001222 x GA(4); and SD(FNA) = 7.08 - 0.9413 x GA + 0.04135 x GA(2) - 0.0004829 x GA(3). Both the FNC and FNA correlated significantly and strongly with biparietal diameter, head circumference, abdominal circumference, humerus length, femur length, transcerebellar diameter, and sonographically estimated fetal weight. CONCLUSIONS: Current nomograms of the axial FNC and FNA throughout gestation have been provided.     

Nomograms of the axial fetal cerebellar hemisphere circumference and area throughout gestation.

OBJECTIVE: The widely applied transcerebellar diameter (TCD) obtained at axial cranial imaging, measures the distance between the lateral aspects of the cerebellum and incorporates the width of the cerebellar vermis. Our objective was to create reference ranges of axial fetal cerebellar hemisphere circumference (CHC) and area (CHA), independent of the cerebellar vermis, throughout gestation. METHODS: This cross-sectional study involved pregnant patients between 14 and 41 weeks of gestation. Inclusion criteria consisted of well-established dates (confirmed by early ultrasound), non-anomalous singleton fetuses and intact amniotic membranes. Sonographic measurements included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), humerus length (HL), TCD, and estimated fetal weight (EFW). Values of axial fetal CHC and CHA were each calculated as the mean of three separate measurements. The 5th, 50th and 95th centiles were estimated at each week of gestational age (GA) by least-squares regression for the mean and standard deviation (SD) of the CHC and CHA as functions of GA. r2 and associated P-values for the relationships of CHC and CHA with other sonographic biometric measurements were calculated. RESULTS: The study included 651 consecutive patients. All attempts at obtaining axial fetal CHC and CHA were successful. Mean maternal age was 27.3+/-6.7 years, median gravidity was 1 (range 1-16), and median parity was 1 (range 0-6). Mean CHC (cm) throughout gestation was modeled as -2.091+0.2563xGA (weeks) (SD=-0.075+0.0164xGA), and mean CHA (cm2) was modeled as 0.245-0.0765xGA+0.00506xGA2 (SD=1.167-0.1565xGA+0.006785xGA(2)-0.00008028xGA3). Fetal axial CHC and CHA correlated significantly and strongly with BPD, HC, AC, HL, FL, TCD and EFW (all R2 values were >or=0.95, and all P-values were <0.001). CONCLUSION: Nomograms of axial fetal cerebellar hemisphere circumference and area throughout gestation, independent of the cerebellar vermis, have been provided.     

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.     

Nomogram of Wharton's jelly as depicted in the sonographic cross section of the umbilical cord.

OBJECTIVES: To generate a nomogram for the sonographic measurement of Wharton's jelly area (WJA) during gestation and to investigate whether WJA is related to fetal biometric parameters. METHOD: The sonographic cross-sectional area of the umbilical cord and of its vessels was measured in 659 fetuses between 15 and 42 weeks of gestation. The WJA was calculated by subtracting the vascular area from the umbilical cord area. The conventional biometric parameters were measured and correlated with the WJA. Polynomial regression analysis was utilized for statistical purposes. RESULTS: The WJA increased as a function of gestational age (r = 0.63, P < 0.001). The regression equation for the mean WJA (y) according to gestational age (x) was y = -114.7 + 4.142x - 0.01x2 and for the standard deviation (y') was y' = -7.567 + 1.319x. There was a strong correlation between the WJA and the umbilical cord area (r = 0.97, P < 0.001). A significant correlation was also found between the WJA and fetal biometric parameters before 32 weeks of gestation (WJA and biparietal diameter: r = 0.82, P < 0.001; WJA and abdominal circumference: r = 0.79, P < 0.001; WJA and femur length: r = 0.81, P < 0.001) while after 32 weeks of gestation no correlations were found between WJA and fetal anthropometric parameters. CONCLUSION: A nomogram for the WJA has been generated. The WJA increases as a function of gestational age and it is correlated with fetal size up to 32 weeks of gestation.     

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.     

Nomograms of the Axial Transverse Diameter of the Fetal Foramen Magnum Between 14 and 40 Weeks' Gestation

Objective. The purpose of this study was to create reference range nomograms of the axial transverse diameter of the fetal foramen magnum (TDFM) between 14 and 40 weeks' gestation. Methods. This cross‐sectional study included pregnant patients between 14 and 41 weeks' gestation. Inclusion criteria consisted of well‐established dates (confirmed by early sonography) and nonanomalous singleton fetuses with intact amniotic membranes. Sonographic measurements included biparietal diameter, head circumference, abdominal circumference, femur length, humerus length, transcerebellar diameter, and sonographically estimated fetal weight. Values of the TDFM were each calculated as the mean of 3 separate measurements. The 5th, 50th, and 95th percentiles were estimated at each week of gestational age (GA) by least squares regression for the mean and SD of the TDFM as functions of GA. R² and associated P values for the relationships between the TDFM and other biometric measurements were calculated. Results. The study included 602 consecutive patients meeting the inclusion criteria. The mean maternal age ± SD was 27.5 ± 6.4 years; median gravidity, 3 (range, 1–12); and median parity, 1 (range, 0–7). The mean TDFM was 13.5 ± 3.7 mm. The reference curve formulas for the mean and SD of the TDFM (mm) were TDFM = ?12.58 + GA/0.5616 – GA ² /24.9 + GA ³ /2430.7, and SD_TDFM = 1.05 – GA/19.4 + GA ² /588.8. The TDFM correlated significantly and strongly with biparietal diameter, head circumference, abdominal circumference, humerus length, femur length, transcerebellar diameter, and estimated fetal weight (all R² ≥ 0.90; all P < .0001). Conclusions. We present reference range nomograms of the TDFM between 14 and 40 weeks' gestation.     

Fetal clavicle length throughout gestation: a nomogram.

OBJECTIVE: To create a nomogram of fetal clavicle length (CL) throughout gestation. METHODS: Cross-sectional study of patients between 14 and 42 weeks' gestation. Inclusion criteria consisted of well-established dates (consistent with early ultrasound), singleton, non-anomalous fetuses, and intact amniotic membranes. Sonographic measurements included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), humerus length (HL) and sonographically estimated fetal weight (SEFW). For every case, the average of three separate measurements of the CL was used. The 5th, 50th and 95th centiles were obtained by least squares regression. Pearson's correlation coefficient and associated P-values for the relationships between CL and other biometric measurements were calculated. The data were compared to a nomogram of the CL generated in 1985 from the measurement of 85 fetuses. RESULTS: A total of 623 consecutive patients were studied. In all but three cases, CL was successfully measured. Mean maternal age was 27.7 +/- 6.2 years, median gravidity 3 (range, 1-14) and median parity 1 (range, 0-9). Mean CL (mm) = -75.30 + 32.70*ln(GA) and SD = -0.41 + 0.08328*GA, where ln represents the natural logarithm and GA the gestational age in weeks. Fetal CL correlated significantly and strongly with BPD, HC, AC, HL, FL and the logarithm of SEFW, with Pearson correlation values of 0.973, 0.977, 0.976, 0.979, 0.977 and 0.979, respectively (all P < 0.001). Measurements according to comparable 1985 data were consistently substantially below the present data (smaller CL for any given GA except below 17 weeks' gestation). CONCLUSIONS: We propose a new nomogram of CL, which differs significantly from the previously published nomogram. We suggest that the present data reflect the use of high-resolution ultrasound technology and propose that these data, based on a large number of fetuses, replace the previous nomogram. We also suggest that the '1 mm = 1 week' rule of thumb should no longer be used, since it can be erroneous by as much as 6 weeks.     

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 prospective evaluation of fetal femur length as a predictor of gestational age.

Variability (+/- 2 SD) in prediction of fetal gestational age from ultrasonographic measurements of fetal femur length was evaluated prospectively in 287 fetuses between 18 and 42 weeks' gestation. Variability increased throughout pregnancy, ranging from +/- 11.6 days between 18 and 24 weeks to +/- 22.7 days in the last six weeks of pregnancy. These findings are comparable with variability in prediction of gestational age from biparietal diameter measurement between 18 and 42 weeks, which indicates that the femur length may serve as an adequate alternative for prediction of gestational age in cases in which the biparietal diameter cannot, for technical reasons, be obtained.     

The assessment of normal fetal brain volume by 3-D ultrasound

The assessment of the fetal brain volume (BV) is very important in the evaluation of fetal growth. The purpose of this study is to use the three-dimensional (3-D) ultrasound (US) in constructing reference centiles of the fetal BV during normal gestation for clinical application. This study was undertaken by a prospective and cross-sectional design. In total, 203 singleton fetuses ranged between 20 and 40 weeks of gestation and fit the criteria of normal pregnancies were enrolled in this study. Our results showed that fetal BV is highly correlated with the gestational age (GA). Furthermore, using GA as the independent variable and the fetal BV as the dependent variable, the best-fit regression equation was BV (mL)=-171.48036+4.8079xGA+0.29521xGA2 (r=0.99, n=203, p<0.0001), with SD of BV (mL)=1.2533x(9.9474+0.07133xGA). In addition, the common growth parameters of the fetal biometry, such as biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference (HC), abdominal circumference (AC), femur length (FL) and estimated fetal weight (EFW), were all highly correlated with the fetal BV (all p<0.0001). In conclusion, our data on the fetal BV assessed by 3-D US may serve as a useful reference in evaluating fetal growth.     

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.     

Assessment of normal fetal liver blood flow using quantitative three-dimensional power Doppler ultrasound

Fetal liver blood flow is very important for fetal hemodynamics. To assess the development of fetal liver vascularization and blood flow in normal gestation, we measured the fetal liver vascularization and blood flow in normal fetuses using the three-dimensional (3-D) power Doppler ultrasound (US) and quantitative 3-D power Doppler histogram analysis. This study was undertaken with a prospective, cross-sectional design. In total, 196 normal singletons with gestational age between 20 and 40 weeks were included. The 3-D power Doppler US and the quantitative histogram analysis were used to assess the fetal liver vascularization index (VI), flow index (FI), vascularization-flow index (VFI) and mean greyness in each case. Our results showed that all the fetal liver VI, FI and VFI increased significantly with gestational age (GA), whereas, fetal liver mean greyness decreased with GA. Using GA as the independent variable, the linear regression equations for fetal liver VI, FI, VFI and mean greyness were VI = 0.5746 x GA - 5.8264 (r = 0.86, p < 0.0001), FI = 0.3291 x GA + 35.624 (r = 0.35, p < 0.001), VFI = 0.2905 x GA - 3.4871 (r = 0.82, p < 0.0001) and mean greyness = -0.2034 x GA + 42.315 (r = -0.20, p < 0.0001). In addition, fetal liver VI, FI, VFI and nean greyness were all significantly correlated with common fetal growth indexes, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight. Our study indicates that normal fetal liver vascularization and blood flow change significantly with the advancement of GA as well as fetal growth indexes. We believe our data may serve as a reference for further studies of fetal liver blood flow in abnormal conditions.     

Growth of the fetal gall bladder in normal pregnancies.

Our objective was to obtain dimensions of the fetal gall bladder as a basis, for further studies and to establish normative data to assess deviations in growth. The study group included 183 normal pregnant women from 13 to 40 weeks' gestation. Routine biometric measurements were obtained on all fetuses, including biparietal diameter, head and abdominal circumferences and measurements of the long bones and the two diameters of the fetal gull bladder. The gall bladder area and circumference were calculated for each gestational age.A linear growth function was observed across the gestational age and a first-degree correlation was found to exist between gestational age and both the longitudinal (r = 0.77067; p < 0.00001; y = -0.41060 + 0.0907 x gestational age) and transverse (r = 0.602; p < 0.00001; y = 0.58567 + 0.01925 x gestational age) diameters of the fetal gall bladder. A significant correlation was also found between gull bladder area and gestational age (r = 0.6878; p < 0.00001), biparietal diameter (r = 0.72768; p < 0.00001), abdominal circumference (r = 0.71363; p < 0.00001) and femoral length (r = 0.72190; p < 0.00001). In addition, a significant correlation was found between gall bladder circumference and gestational age (r = 0.76181; p < 0.00001), biparietal diameter (r = 0.80039; p < 0.00001), abdominal circumference (r = 0.78030; p < 0.00001) and femoral length (r = 0.79694; p < 0.00001).These results provide normative data of the fetal gall bladder in various dimensions and across gestational age. In addition, the data offer the potential for prenatal diagnosis of additional lesions in the extrahepatic biliary duct system.     

Nomogram of the fetal alveolar ridge: a possible screening tool for the detection of primary cleft palate.

OBJECTIVE: The objective of this study was to obtain a nomogram of the fetal alveolar ridge development, as a basis for the diagnosis of primary cleft palate. DESIGN: A cross-sectional study of 323 normal pregnant women of 14-32 weeks' gestation. Several biometric measurements were obtained throughout pregnancy, including the width of the fetal alveolar ridge. RESULTS: A nomogram of the width of the fetal alveolar ridge during 14-32 weeks' gestation is presented. A linear growth function was observed between alveolar ridge width and gestational age, biparietal diameter, head circumference, femoral length and humeral length. The alveolar ridge width in all eight cases of cleft palate was above two standard deviations and the 90th centile of our nomogram. CONCLUSION: We provide a nomogram of the growth of the fetal alveolar ridge between 14 and 32 weeks' gestation. This will aid the detection of primary cleft palate during routine prenatal sonography.     

Fetuses subsequently born premature are smaller than gestational age-matched fetuses not born premature.

OBJECTIVE: To determine whether singleton fetuses in pregnancies that subsequently deliver prematurely are smaller than singleton fetuses of the same gestational age who are not born premature. METHODS: Our study population consisted of singleton pregnancies meeting the following criteria: at least 1 first-trimester sonogram (to ensure accurate dating), at least 1 sonogram after 24 weeks' gestation, and a known delivery date. Controlling for gestational age at sonography using analysis of covariance, we compared very premature fetuses (delivery at 24-29.9 weeks; n = 26) and moderately premature fetuses (delivery at 30-36.9 weeks; n = 306) with nonpremature fetuses (n = 1,838) with respect to the following sonographic parameters: abdominal diameter, femur length, biparietal diameter, and estimated fetal weight. RESULTS: On 24- to 29.9-week sonograms, fetuses who were subsequently born very premature had significantly smaller fetal measurements than did fetuses who were not born premature (P < .05 for all parameters). Even after excluding 9 very premature fetuses with a risk factor for uteroplacental insufficiency (e.g., toxemia or hypertension), the remaining 17 fetuses had significantly smaller abdominal diameters, femur lengths, and estimated fetal weights than nonpremature fetuses (P < .05). Sonographic parameters in moderately premature fetuses were smaller than in nonpremature fetuses on 30- to 36.9-week sonograms (P < .05 for all parameters), but the only parameters that differed significantly between these 2 groups on 24- to 29.9-week sonograms were abdominal diameter and femur length. CONCLUSIONS. Singleton fetuses subsequently born premature are smaller than gestational age-matched fetuses not born premature, even in the absence of an identifiable cause of growth restriction. The lag in growth appears to occur in the last few weeks before delivery.     

Fractional spine length: a new parameter for assessing fetal growth

Sonographic measurement of a segment of the lower thoracic and lumbar fetal spine was performed on 218 normal fetuses of between 15 and 42 weeks' gestational age (GA) to establish a new parameter for assessing fetal growth. The increase of the fractional spine length (FSL) was represented by the equation: FSL = -37.62 + 4.36 (GA) - 0.04 (GA)2, with R2 = 0.92. The FSL also correlates strongly with fetal femur length (FL): FSL = 5.36 + 0.82 (FL), with R2 = 0.93. The ratio FSL/abdominal circumference (AC) X 100 was relatively constant at 20.4 +/- 3.1 (mean +/- 2 standard deviations) from 19 to 42 weeks in contrast to the ratio FL/AC X 100, which was constant at 22.3 +/- 2.4 (mean +/- 2 SD) only after 23 weeks. Nine of 10 small-for-gestational age fetuses examined during the study had a FSL within the normal range, as well as two fetuses who were thanatophoric dwarfs. The FSL provides a new ultrasonic longitudinal measurement of the fetus which may be used in addition to the femur length in fetal growth assessment.     

Biometric measurements in fetuses of different race and gender.

Sonographic fetal biometric measurements on 6082 low-risk patients were compared in the second and third trimesters of pregnancy with respect to fetal race and gender. Ultrasonic measurements were obtained from fetuses of women participating in the Routine Antenatal Diagnostic Imaging with Ultrasound Study (RADIUS), who underwent both an early sonographic evaluation between 15 and 22 weeks' gestation and a later scan between 31 and 35 weeks' gestation. In the 16-21-week scans, male fetuses had significantly larger biparietal diameter measurements compared to female fetuses (estimated difference 0.852 mm, 95% CI 0.737-0.967). There was only minimal difference in biparietal diameter between Black and White fetuses. Femur length was similar in both female and male fetuses, but longer in Black compared to White fetuses (estimated difference 0.808 mm, 95% CI 0.539-1.078).During the 31-35-week scans, male fetuses continued to have larger biparietal diameter measurements compared to female fetuses (estimated difference 1.22 mm, 95% CI 1.04-1.40), and femur lengths were persistently longer in Black compared to White fetuses (estimated difference 0.563 mm, 95% CI 0.234-0.893).Further investigation is necessary to evaluate the effect of these slight differences in morphometric fetal measurements between races and genders, so that we can determine how best to use them for optimizing prenatal care.     

Screening efficacy of the subcutaneous tissue width/femur length ratio for fetal macrosomia in the non-diabetic pregnancy.

BACKGROUND: Antenatal weight estimations have limited sensitivity and specificity for the detection of macrosomia. The objective of our study was to examine the screening efficacy of the subcutaneous tissue width/femur length ratio for the intrapartum detection of fetal macrosomia in a non-diabetic population at term. STUDY DESIGN: Intrapartum sonographic measurements were performed in 178 well-dated gravidas at 37-41 weeks' gestation with negative glucose tolerance screens. The biparietal diameter, femur length (FL), abdominal circumference and subcutaneous tissue width of the thigh (SCT) were determined. Subsequently, predictions for macrosomia (actual birth weights above the 90th centile) were made using varying cut-off points of the examined parameters or estimated fetal weights. RESULTS: Macrosomia occurred in 27 newborns (15.1%). The SCT/FL ratio was independent of gestational age (r = -0.017). Maternal age, gravidity, parity, gestational age and the ratio of male-to-female infants were similar in pregnancies resulting in appropriate-for-gestational-age and macrosomic infants (NS). There was no difference in the SCT/FL ratio between these groups (p = 0.067; 99% power to detect 2 standard deviation differences). Comparison of screening efficacy by the univariate z score for the area under receiver operating characteristic (ROC) curves (theta) revealed that the abdominal circumference had the best sensitivity-specificity trade-off (theta = 0.8843; p < 0.0001 for comparison with SCT/FL ROC curve), followed by weight estimations based on the Hadlock formula (theta = 0.8773; p < 0.0005), the Shepard formula (theta = 0.8606; p < 0.0001), subcutaneous tissue thickness alone (theta = 0.6872; p < 0.01) and the SCT/FL ratio (theta = 0.6303). CONCLUSIONS: We conclude that the SCT/FL ratio is a poor sonographic predictor of fetal macrosomia in the non-diabetic pregnancy and does not improve fetal weight estimations by conventional sonographic parameters.     

Nomograms of fetal thyroid measurements estimated by 2-dimensional sonography

PURPOSE: To build nomograms of fetal thyroid circumference (FTC), fetal thyroid area (FTA), and fetal thyroid transverse diameter (FTTD) throughout gestational age (GA). METHOD: Between January 2006 and July 2006, FTC, FTA, and FTTD were measured once in 196 normal fetuses examined at a GA of 22-35 weeks. Inclusion criteria were a healthy mother with normal maternal thyrotropin level during pregnancy, a singleton pregnancy with normal fetal morphology on sonography, and GA confirmed via first-trimester sonographic examination. RESULTS: Mean FTC, FTA, and FTTD ranged from 3.21 cm, 0.58 cm(2), and 1.19 cm at 22 weeks to 5.11 cm, 1.69 cm(2), and 1.89 cm at 35 weeks, respectively. Linear regression analysis yielded the following formulas for FTC, FTA, and FTTD according to GA: FTC (cm) = 0.146 x GA (weeks); FTA (cm(2)) = -1.289 + 0.085 x GA (weeks); FTTD (cm) = 0.054 x GA (weeks). The following logarithmic formulas were obtained for the expected fetal thyroid measurements according to estimated fetal weight (FW): FTC (cm) = -4.791 + 1.265 x logN FW; FTA (cm(2)) = -1.676 + 0.455 x logN FW; and FTTD (cm) = 0.399 + 0.001 x logN FW. CONCLUSION: We describe new nomograms of fetal thyroid measurements throughout gestation that may be useful in case of thyroid dysfunction.     

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.