Ultrasonographic assessment of fetal thyroid in Japan: thyroid circumference and distal femoral and proximal tibial ossification.

PURPOSE: The present study established a nomogram of fetal thyroid circumference (FTC) and the appearance timing of fetal distal femoral and proximal tibial ossification to assess fetal thyroid function in Japan. METHODS: Between April 2015 and July 2019, normal pregnant women at our hospital were recruited for the study. FTC was measured by the automatic ellipse outline and plotted against gestational age (GA). Fetal distal femoral and proximal tibial ossification measurements were obtained with standard electronic calipers from outer-to-outer margins (> 1 mm as the presence of ossification). RESULTS: A total of 199 pregnant women were examined. FTC increased logarithmically to GA. A nomogram of FTC was expressed by a logarithmic formula: [Formula: see text]. The respective 5-95th percentiles of FTC at each GA were 20.2-36.2 mm at 22 weeks, 25.0-44.8 mm at 26 weeks, 29.2-52.3 mm at 30 weeks, and 32.9-59.0 mm at 34 weeks. The fetal distal femoral epiphysis was not visualized before 30 weeks, but was visualized in 100% of fetuses after 35 weeks of gestation. The fetal proximal tibial epiphysis was not visualized before 33 weeks, but was visualized in 73.7% of fetuses at 37 weeks of gestation. CONCLUSION: We generated a GA-dependent FTC nomogram for Japanese fetuses. We also confirmed the appearance timing of fetal distal femoral and proximal tibial ossification to assess bone maturation. These assessments may be very useful for evaluating fetal thyroid function in Japan.

Impact of biometric measurement error on identification of small- and large-for-gestational-age fetuses.

OBJECTIVES: First, to obtain measurement-error models for biometric measurements of fetal abdominal circumference (AC), head circumference (HC) and femur length (FL), and, second, to examine the impact of biometric measurement error on sonographic estimated fetal weight (EFW) and its effect on the prediction of small- (SGA) and large- (LGA) for-gestational-age fetuses with EFW < 10th and > 90th percentile, respectively. METHODS: Measurement error standard deviations for fetal AC, HC and FL were obtained from a previous large study on fetal biometry utilizing a standardized measurement protocol and both qualitative and quantitative quality-control monitoring. Typical combinations of AC, HC and FL that gave EFW on the 10th and 90th percentiles were determined. A Monte-Carlo simulation study was carried out to examine the effect of measurement error on the classification of fetuses as having EFW above or below the 10th and 90th percentiles. RESULTS: Errors were assumed to follow a Gaussian distribution with a mean of 0 mm and SDs, obtained from a previous well-conducted study, of 6.93 mm for AC, 5.15 mm for HC and 1.38 mm for FL. Assuming errors according to such distributions, when the 10th and 90th percentiles are used to screen for SGA and LGA fetuses, respectively, the detection rates would be 78.0% at false-positive rates of 4.7%. If the cut-offs were relaxed to the 30th and 70th percentiles, the detection rates would increase to 98.2%, but at false-positive rates of 24.2%. Assuming half of the spread in the error distribution, using the 10th and 90th percentiles to screen for SGA and LGA fetuses, respectively, the detection rates would be 86.6% at false-positive rates of 2.3%. If the cut-offs were relaxed to the 15th and 85th percentiles, respectively, the detection rates would increase to 97.0% and the false-positive rates would increase to 6.3%. CONCLUSIONS: Measurement error in fetal biometry causes substantial error in EFW, resulting in misclassification of SGA and LGA fetuses. The extent to which improvement can be achieved through effective quality assurance remains to be seen but, as a first step, it is important for practitioners to understand how biometric measurement error impacts the prediction of SGA and LGA fetuses. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Ultrasonographic estimation of fetal weight: development of new model and assessment of performance of previous models.

OBJECTIVES: To develop a new formula for ultrasonographic estimation of fetal weight and evaluate the accuracy of this and all previous formulae in the prediction of birth weight. METHODS: The study population consisted of 5163 singleton pregnancies with fetal biometry at 22-43 weeks' gestation and live birth of a phenotypically normal neonate within 2 days of the ultrasound examination. Multivariable fractional polynomial analysis was used to determine the combination of variables that provided the best-fitting models for estimated fetal weight (EFW). A systematic review was also carried out of articles reporting formulae for EFW and comparing EFW to actual birth weight. The accuracy of each model for EFW was assessed by comparing mean percentage error, absolute mean error (AE), proportion of pregnancies with AE ≤ 10% and Euclidean distance. RESULTS: The most accurate models, with the lowest Euclidean distance and highest proportion of AE ≤ 10%, were provided by the formulae incorporating ≥ 3 rather than < 3 biometrical measurements. The systematic review identified 45 studies describing a total of 70 models for EFW by various combinations of measurements of fetal head circumference (HC), biparietal diameter, femur length (FL) and abdominal circumference (AC). The most accurate model with the lowest Euclidean distance and highest proportion of AE ≤ 10% was provided by the formula of Hadlock et al., published in 1985, which incorporated measurements of HC, AC and FL; there was a highly significant linear association between EFW and birth weight (r = 0.959; P < 0.0001), and EFW was within 10% of birth weight in 80% of cases. The performance of the best model developed in this study, utilizing HC, AC and FL, was very similar to that of Hadlock et al. CONCLUSION: Despite many efforts to develop new models for EFW, the one reported in 1985 by Hadlock et al., from measurements of HC, AC and FL, provides the most accurate prediction of birth weight and can be used for assessment of all babies, including those suspected to be either small or large. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Ultrasonographic assessment of fetal growth in miniature "Shiba" goats (Capra hircus).

The aim of the present study was to monitor fetal growth in relation to gestational stage to generate formulae which could be used to estimate fetal age in goats. Eight miniature Shiba goats (Capra hircus) were examined weekly by transrectal and transabdominal ultrasound scanning during the gestation period between Day 21 and 126 days of gestation. For accurate judgment, all fetometric parameters were measured at least three times per one examination for each animal. Quantification of the growth of the fetus allowed the development of a number of predictors of fetal age. Low correlations were associated with measurement of the chest diameter (R(2)=0.869), trunk diameter (R(2)=0.8969), tibia length (R(2)=0.8662) and placentome diameter (R(2)=0.8999). Moderate correlation was assessed by calculation of the length of six successive lumbar vertebrae (R(2)=0.9296), femur length (R(2)=0.9278), heart axis length (R(2)=0.9382 and 0.9589; for the longitudinal and transverse axis, respectively), occipitonasal length (R(2)=0.9527), umbilical cord diameter (R(2)=0.9119) and orbit diameter (R(2)=0.9239). A high correlation was estimated in investigating the length of six successive thoracic vertebrae (R(2)=0.9674), braincase diameter (R(2)=0.9831) and crown rump length (R(2)=0.9848). In conclusion, the intrauterine fetal biometry estimation through ultrasound might be useful to predict the accurate gestational age in miniature goats.

Use of fetal biometry in the assessment of gestational age in South East Nigeria: Femur length and biparietal diameter.

BACKGROUND: Fetal growth is influenced by many factors such as race, socioeconomic status, genetics, geographical location, maternal diseases, and number of babies. Consequent upon these, fetal growth charts may vary from one location to another even within the same geographical entity. OBJECTIVE: This study was designed to establish the fetal growth chart in antenatal women who had ultrasound scanning at the University of Nigeria Teaching Hospital, Enugu, South East Nigeria. PATIENTS AND METHODS: This is a descriptive analysis of fetal biometric measurement of antenatal women. Four hundred and seventy pregnant women were studied. RESULTS: The nomogram for the femur length (FL) and biparietal diameter (BPD) for the different weeks of gestation (from 13th to the 40th week) were established. Correlation coefficients between gestational age and the various fetal parameters were also reported. Growth charts using both FL and BPD were plotted. A regression model for prediction of fetal age using the fetal biometry was also deduced for the studied population. CONCLUSION: The fetal parameters used in this study were consistently smaller than reported values from European studies up to the 34th week of gestation after which a catch-up growth till the 40 weeks was observed. Fetal parameters observed in this study were larger than most of the reported Asian values.

Automatic fetal measurements for low-cost settings by using Local Phase Bone detection.

The estimation of gestational age is done mostly by measurements of fetal anatomical structures such as the head and femur. These measurement are also used in diagnosis and growth assessment. Manual measurements is operator dependent and hence subject to variability.

Charts for fetal age assessment based on fetal sonographic biometry in a population from Cali, Colombia.

OBJECTIVES: To create reference charts for fetal age assessment based on fetal sonographic biometry in a population of pregnant women living in the third largest city in Colombia and compare them with charts included in ultrasound machines. METHODS: The study data were obtained from women with a single pregnancy and confirmed gestational age between 12 and 40 completed weeks. All women were recruited specifically for the study, and every fetus was measured only once for biparietal diameter, head circumference, abdominal circumference, and femur length. Polynomial regression models for gestational age as a function of each fetal measurement were fitted to estimate the mean and standard deviation. Percentile curves of gestational age were constructed for each fetal measurement using these regression models. RESULTS: Biparietal diameter, head circumference, abdominal circumference, and femur length were measured in 792 fetuses. Tables and charts of gestational age were derived for each fetal parameter. A cubic polynomial model was the best-fitted regression model to describe the relationships between gestational age and each fetal measurement. The standard deviation was estimated by simple linear regression as a function of each fetal measurement. Comparison of our gestational age mean z scores with those calculated by reference equations showed statistically significant differences (P < .01). CONCLUSIONS: We present a set of reference charts, tables, and formulas for fetal age assessment based on fetal sonographic biometry. The results support the recommendation that these charts and tables could be more appropriate for assessing fetal age in Colombian populations than those currently included in the software of ultrasound machines.

Obstetric ultrasound scanning by local health workers in a refugee camp on the Thai-Burmese border.

OBJECTIVES: Ultrasound examination of the fetus is a powerful tool for assessing gestational age and detecting obstetric problems but is rarely available in developing countries. The aim of this study was to assess the intraobserver and interobserver agreement of fetal biometry by locally trained health workers in a refugee camp on the Thai-Burmese border. METHODS: One expatriate doctor and four local health workers participated in the study, which included examinations performed on every fifth pregnant woman with a singleton pregnancy between 16 and 40 weeks' gestation, and who had undergone an early dating ultrasound scan, attending the antenatal clinic in Maela refugee camp. At each examination, two examiners independently measured biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL), with one of the examiners obtaining duplicate measurements of each parameter. Intraobserver measurement error was assessed using the intraclass correlation coefficient (ICC) and interobserver error was assessed by the Bland and Altman 95% limits of agreement method. RESULTS: A total of 4188 ultrasound measurements (12 per woman) were obtained in 349 pregnancies at a median gestational age of 27 (range, 16-40) weeks in 2008. The ICC for BPD, HC, AC and FL was greater than 0.99 for all four trainees and the doctor (range, 0.996-0.998). For gestational ages between 18 and 24 weeks, interobserver 95% limits of agreement corresponding to differences in estimated gestational age of less than +/- 1 week were calculated for BPD, HC, AC and FL. Measurements by local health workers showed high levels of agreement with those of the expatriate doctor. CONCLUSIONS: Locally trained health workers working in a well organized unit with ongoing quality control can obtain accurate fetal biometry measurements for gestational age estimation. This experience suggests that training of local health workers in developing countries is possible and could allow effective use of obstetric ultrasound imaging.

Fetal age assessment based on 2nd trimester ultrasound in Africa and the effect of ethnicity.

BACKGROUND: The African population is composed of a variety of ethnic groups, which differ considerably from each other. Some studies suggest that ethnic variation may influence dating. The aim of the present study was to establish reference values for fetal age assessment in Cameroon using two different ethnic groups (Fulani and Kirdi). METHODS: This was a prospective cross sectional study of 200 healthy pregnant women from Cameroon. The participants had regular menstrual periods and singleton uncomplicated pregnancies, and were recruited after informed consent. The head circumference (HC), outer-outer biparietal diameter (BPDoo), outer-inner biparietal diameter and femur length (FL), also called femur diaphysis length, were measured using ultrasound at 12-22 weeks of gestation. Differences in demographic factors and fetal biometry between ethnic groups were assessed by t- and Chi-square tests. RESULTS: Compared with Fulani women (N = 96), the Kirdi (N = 104) were 2 years older (p = 0.005), 3 cm taller (p = 0.001), 6 kg heavier (p < 0.0001), had a higher body mass index (BMI) (p = 0.001), but were not different with regard to parity. Ethnicity had no effect on BPDoo (p = 0.82), HC (p = 0.89) or FL (p = 00.24). Weight, height, maternal age and BMI had no effect on HC, BPDoo and FL (p = 0.2-0.58, 0.1-0.83, and 0.17-0.6, respectively). When comparing with relevant European charts based on similar design and statistics, we found overlapping 95% CI for BPD (Norway & UK) and a 0-4 day difference for FL and HC. CONCLUSION: Significant ethnic differences between mothers were not reflected in fetal biometry at second trimester. The results support the recommendation that ultrasound in practical health care can be used to assess gestational age in various populations with little risk of error due to ethnic variation.

Individualized growth assessment of fetal thigh circumference using three-dimensional ultrasonography.

OBJECTIVES: To develop individualized growth assessment (IGA) standards for upper (ThC(u)) and middle (ThC(m)) fetal thigh circumferences using three-dimensional ultrasonography. METHODS: A prospective, longitudinal sonographic study of 30 fetuses was performed beginning at 18 weeks' menstrual age. Second-trimester sonographic parameters were measured from three-dimensional volume data to establish IGA standards. Normal infant growth outcomes were confirmed using modified Neonatal Growth Assessment Scores (m(3)NGAS(51)). ThC(u) and ThC(m) were studied in more detail. Rossavik growth model specification procedures, based on the slopes of the second-trimester growth curves, were developed for both ThC(u) and ThC(m). Third-trimester growth trajectories and birth measurements were subsequently predicted for these parameters. Percentage deviations during the third trimester and percentage differences at actual birth age were used to compare observed and predicted measurements. The 95% ranges for Growth Potential Realization Index (GPRI) values for both types of thigh circumference were determined. Values for m(3)NGAS(51) using GPRI(ThC(u)), GPRI(ThC(m)) and GPRI(ThC(o)) (original method) were compared. RESULTS: The 30 newborns had no postnatal evidence of abnormal growth. Two examiners demonstrated a satisfactory measurement bias of mean +/- SD 2.1 +/- 3.6 (95% limits of agreement,-4.9 to 9.1)% for ThC(m) and 3.3 +/- 4.1 (95% limits of agreement,-4.8 to 11.4)% for ThC(u). Rossavik functions fitted parameter trajectories well, with mean R(2) values of 99.5 +/- 0.4% for ThC(u) and 99.6 +/- 0.3% for ThC(m). By fixing coefficients k at their mean values, their respective fits did not change, and the variabilities of coefficients c and s were significantly reduced. For ThC(u), coefficient c was significantly related to the second-trimester slope (R(2)=98.6%), as was s to c(R(2)=91.0%). For ThC(m), coefficient c was significantly related to the second-trimester slope (R(2)=98.6%), as was s to c(R(2)=85.6%). Third-trimester growth trajectories, derived from second-trimester slopes for individual fetuses, had third-trimester deviations of 0.07 +/- 3.7% for ThC(u) and-0.04 +/- 3.7% for ThC(m). Percentage differences at birth age were 16.8 +/- 10.2% for ThC(u) and 8.9 +/- 9.5% for ThC(m). With correction for systematic overestimations, the mean GPRI values were 103.7 (95% range, 90-121)% for ThC(u) and 101.6 (95% range, 88-118)% for ThC(m). Corresponding mean +/- SD m(3)NGAS(51) values, using GPRI(ThC(u)), GPRI(ThC(m)) and GPRI(ThC(o)), were 203 +/- 11%, 201 +/- 10% and 200 +/- 9%, respectively. CONCLUSIONS: Fetal thigh circumference can be measured reliably and evaluated using standard IGA methods. Both ThC(u) and ThC(m) give similar results in the third trimester but neonatal thigh circumference predictions are improved by using ThC(m). Corresponding GPRI(ThC(m)) values are closer to the ideal value of 100% and can be used in m(3)NGAS(51) calculations for assessment of neonatal growth outcome.

A histological assessment on the distribution of the osteocytic lacunar canalicular system using silver staining.

Giving the complexity that characterizes the mechanisms of bone remodeling and the number of events that have to be in absolute harmony for it to occur flawlessly, the postulation that temporospatial distribution of osteocytes and their lacunar canalicular system might influence and be influenced by bone remodeling can be regarded, at least, as feasible. In this study, using Schoen's silver staining, we have examined the distribution of the osteocytic lacunar canalicular system (OLCS) in bones of developing mice. Trabecular bones of 3-day-old, 2-week-old, and 3-week-old mice displayed osteocytic cytoplasmic processes without any perceptible alignment. Also, many plump osteocytes were embedded in the mineralized bone matrix in a disorderly manner. At 4 weeks of age, however, mice bones showed some osteocytic processes that reached the bone surface on a right angle, while other osteocytes displayed the same features seen on 3-week specimens. Samples at 8 weeks of age featured osteocytes with their usual spindle shape, organized so as to parallel the longitudinal axis of trabecular bone. They also extended their cytoplasmic processes perpendicularly to the bone surface. However, several osteocytes immersed in older bone, i.e., a residual mix of cartilage and bone matrices, still showed a random pattern of distribution of their cytoplasmic processes. Up to 12 weeks of age, the majority of the osteocytes became flattened and were shown to be aligned with their long axis paralleling the bone surface. This tendency for such a gradual arrangement was also observed in cortical bones. We have further demonstrated that 8-week-old osteoprotegerin-deficient mice, which demonstrated histological evidence of higher than average bone turnover, revealed a disorganized OLCS. Given the data gathered in this work, the OLCS appears to assume an organized, probably function-related spatial distribution as normal bone remodeling goes on.

Prenatal detection of fetal growth restriction by fetal femur volume: efficacy assessment using three-dimensional ultrasound.

As fetal growth restriction (FGR) may have increased risks with perinatal morbidity and mortality, it is very important to detect FGR prenatally. Fetal femur dysplasia is associated with a variety of congenital syndromes and FGR as well. To date, no prenatal assessment of fetal FV in predicting FGR using three-dimensional (3D) ultrasound (US) has been reported. In this study, we used 3D US to test the efficacy of fetal femur volume (FV) measurement in predicting FGR. We calculated the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and efficacy of fetal FV assessed by 3D US in detecting FGR according to the Bayes' theorem. All the fetuses were singletons and were followed up to delivery to determine whether they were complicated with FGR or not. In total, 304 fetuses without FGR and 42 fetuses with FGR were included for FV assessment in utero by 3D US. Our results showed fetal FV assessed by 3D US can differentiate fetuses with FGR from fetuses without FGR well. The best predicting threshold for FGR is at the 10th percentile of FV. Using the 10th percentile as the cutoff, the sensitivity of fetal FV in predicting FGR was 71.4%, specificity 94.1%, positive predictive value 62.5%, negative predictive value 96.0% and accuracy 91.3%. In addition, fetal FV is superior to fetal biparietal diameter and fetal abdominal circumference in predicting FGR. In conclusion, fetal FV assessed by 3D US can be applied to detect FGR well prenatally. We believe fetal FV assessment by 3D US would be a useful test in detecting fetuses with FGR.

Cumulative sum (CUSUM) analysis in the assessment of trainee competence in fetal biometry measurement.

OBJECTIVE: To determine the value of cumulative sum (CUSUM) analysis in assessing trainee proficiency in fetal biometry measurement. METHODS: Three primary healthcare doctors with no prior ultrasound training were recruited. Each trainee measured the fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) on 100 consecutive pregnant women. The supervisor repeated the measurements. The CUSUM for each set of trainee measurements was calculated at a set failure rate of 10%. The point at which the graph fell below two consecutive boundary lines indicated the number of examinations required to achieve competence. RESULTS: The CUSUM graphs showed that the rate of learning measurement skills varied among the three trainees. The graph for the CUSUM series for BPD and HC measurement for all trainees fell below two consecutive boundary lines and remained there, indicating competence. The CUSUM series for AC measurement for two of the trainees indicated that competence was achieved; however, for the third trainee, while the graph fell below two consecutive boundary lines, indicating competence, it rose again, crossing two consecutive boundary lines. This indicated a loss of competence and the need for further training. FL measurements for the same trainee never fell below two consecutive boundary lines, indicating failure to achieve competence; the other two achieved competence, but failed to maintain it. CONCLUSIONS: CUSUM is a useful tool for identifying points of competence and for quantifying the duration of ultrasound training required for each trainee. It provides an early indication of performance, and highlights difficulties in individual performance.

Fetal growth in Peru: comparisons with international fetal size charts and implications for fetal growth assessment.

OBJECTIVES: To compare fetal biometry measurements obtained in a Peruvian population with reference fetal size charts obtained in Peruvian and non-Peruvian populations. METHODS: Fetal biometry measurements collected prospectively in 195 uncomplicated pregnancies were included in the presented analysis. At 20, 24, 28, 32, 36 and 38 weeks' gestation, fetal head circumference, abdominal circumference and femur diaphysis length were measured. Fetal biometry measurements were compared with fetal size charts obtained from another Peruvian and two non-Peruvian populations from North America and Europe. RESULTS: When compared with ultrasound-based reference fetal size charts obtained from North American and European populations, fetuses from the studied population appeared to grow more slowly with advancing gestational age. This trend was not observed when a Peruvian population, similar to the one studied here, was used as a reference. CONCLUSIONS: The results suggest that fetal growth in this Peruvian population may not be adequately assessed by using reference charts obtained from other populations and have implications for the use of growth standards in antenatal management.

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

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

Is manual foot lenght measurement of comparable value to ultrasound femur and humerus measurement in anatomical studies for the assessment of foetal age?

Contemporary anatomical studies require reliable methods for determining foetal age. Menstrual age is often found to be inadequate. A combination of several anatomical features showing age-dependency may result both in exact age approximation and pathology detection. The authors compared the manual foot length measurements with the ultrasound femur and humerus length measurements of aborted foetuses in the calculation of foetal age. The correlation between femur length and foot length as well as humerus length and foot length were statistically significant. The expected value formulae for foot length are presented. The authors conclude that foetal age assessment based on foot length metering is reliable before the 7th calendar month of pregnancy and correlates with ultrasound measurements of the humerus and femur.

Ovine fetal growth curves in twin pregnancy: ultrasonographic assessment.

PURPOSE OF INVESTIGATION: The fetal-lamb model is a fundamental tool for developing clinical applications for the treatment of human fetal pathology (e.g., open fetal surgery). Accurate estimation of gestational age is important to avoid size-related problems during surgery. METHODS: To evaluate the effect of twinning on ovine fetal growth, we followed seven twin pregnancies in Comiso ewes from mating through parturition. Fetal growth indexes (muzzle-occipital and mean abdominal diameters, abdominal circumference, femoral and humeral length) were measured weekly using perimammary ultrasonography and analyzed with a linear quadratic regression model based on natural logarithms of each parameter and fetal age. RESULTS: The model explained > 90% of the variability observed, with determination coefficients of 95% (femoral length, abdominal circumference), 94% (abdominal diameter, humeral length), and 89% (muzzle-occipital diameter). CONCLUSION: Mean birth weight was lower than that reported for singleton fetal lambs, as it is in bigeminal pregnancies in humans, despite the uterine and placental differences between these two species. With the exception of slightly earlier growth deceleration, curves for head and long-bone growth resembled those for singleton ovine fetuses. Ovine fetal growth patterns (like those of humans) in singleton and twin pregnancies are similar.

Postmortem assessment of fetal diaphyseal femoral length: validation of a radiographic methodology.

Depending on the general condition of fetal remains, forensic specialists might face difficulties concerning age estimation. Reference tables and regression equations are helpful devices in this task, although they are generally applied for complete fetuses or fetal remains including soft tissues. However, the problem of age estimation stays for osseous remains, both for entire bones and ossified parts, since most of the reference tables come from ultrasonographic measurements, which are not easily reproducible on fetal osseous remains. Furthermore, the ultrasonographic measurements contain slight errors in comparison to the real anatomical ones. This study describes a radiographic protocol and a measurement technique that facilitate and improve bone measurements, and therefore, facilitate age estimation, too. A qualitative criterion, namely a clear-cut bony endplate, was defined and tested. Its reliability (repeatability and reproducibility) turned out to be good, showing nonsignificative differences to the threshold of 0.05, with average errors of 0.26 and 0.44 mm respectively. Moreover, concerning the test of eventual size differences between the right and left femurs showed a P value < 0.0001. The test of the qualitative criterion was based on the comparison of the radiographic in situ femur measurements and the radiographic measurements of the same bones after dissection. The results were satisfactory, since an average error of 0.58 mm was obtained, which did not give any significant differences to the threshold of 0.05. It was concluded that this methodology provides an easy and precise new measurement tool for forensic practice, and can allow us to establish some nonultrasonographic tables, which fit our population.

Assessment of gestational age based on ultrasonic femur length after the first trimester: a simple mathematical correlation between gestational age (GA) and femur length (FL).

OBJECTIVE: The ultrasonic measurement of the fetal femur length is a sensitive and precise variable for estimation of fetal growth and development. The objective of this study was to predict gestational age in fetuses more than 13 weeks of gestation by ultrasound measurement of the femur length. METHOD: In this study, pregnant mothers were identified by the criteria of normalities such as: well-known LMP, regular menstrual cycles, no use of OCP for the last 3 months, no smoking, no history of diabetes, etc. RESULT: The relation between gestational age and fetal femur length has been determined by cross-sectional analysis of 900 normal fetuses (> or = 14 weeks of gestation) using real time ultrasonography. Mathematical modeling of the data has demonstrated that the femur growth curve is non-linear beyond 13 weeks of gestation. With the aid of a scientific calculator the data were analyzed and a simple second grade equation has been derived: GA (weeks) = 0.262(2) FL (cm) + 2 FL + 11.5, S.D. approximately +/- 5 days(Honarvar's Formula 3). With the use of this data, the error in the estimation of GA given as FL is +/-5 days. CONCLUSION: This simple, new and accurate equation appears to be clinically reliable and easy to use and suggests that previous normal ultrasonic fetal femur length curves for another population may under- or overestimate normal fetal age for the Iranian population. Thus, our formula is an excellent means of estimating true gestational age.

How accurate is fetal biometry in the assessment of fetal age?

OBJECTIVE: The purpose of the study was to assess the accuracy of fetal biometry in the midtrimester of pregnancy in the assignment of fetal age. STUDY DESIGN: A total of 152 singleton, 67 twin, and 19 triplet gestations resulting from in vitro fertilization with ultrasonographic fetal biometry from 14 to 22 weeks made up the study population. A gestational age prediction equation was derived from singletons with the use of stepwise linear regression. This equation was compared with 38 previously published equations and then applied to the twin and triplet populations. RESULTS: Head circumference was the best predictor of gestational age (random error [SD] 3.77 days). Addition of abdominal circumference and femur length to head circumference improved the accuracy of the dating equation (random error 3.35 days). Most dating formulas had systematic errors of <1 week. The systematic error was -0.32 day for averaging the singleton-based predictions for twins and -1.26 days for triplets. CONCLUSIONS: Gestational age assessment with the use of fetal biometry from 14 to 22 weeks is accurate for singleton, twin, and triplet gestations.