Femur Length Ratio Research Articles

Evaluation of fetal femur length to detect Down syndrome in a Thai population

Objective: To assess the value of femur length shortening for prenatal detection of Down syndrome in a Thai population. Method: A prospective study was performed by experienced perinatologists on 3137 women undergoing second-trimester amniocentesis, between 16 and 24 weeks of gestation, for the indications of advanced maternal age and past history of chromosomal abnormality. Biparietal diameter and femur length measurements were obtained before the procedures. Regression equations relating biparietal diameter to femur length were used to calculate observed femur length/expected femur length ratio in the chromosomally normal and Down syndrome fetuses. Sensitivity, specificity, false-positive rate and likelihood ratio of a positive test result at various observed femur length/expected femur length ratios for detection of Down syndrome were calculated. A receiver–operator characteristic curve was used to determine threshold screening ratio. Results: There were 3084 chromosomally normal pregnancies, 26 fetuses with Down syndrome (1:118), and 27 other chromosomal abnormalities. The relationship between femur length and biparietal diameter (BPD) was: expected femur length=−7.631+0.814 BPD, R 2=0.78, P<0.001). Femur length in Down syndrome fetuses was significantly shorter than in normal fetuses ( P<0.001). A ratio of 0.91 for observed femur length/expected femur length yielded a sensitivity of 42.3%, specificity of 86.2%, false positive rate of 13.8% and likelihood ratio of a positive test result of 3.07 (95% CI 1.94–4.84) for detection of Down syndrome. Conclusions: In this study, femur length shortening in the second trimester appears to be a useful screening parameter for fetal Down syndrome in a Thai population.

Femur length and trisomy 21: impact of gestational age on screening efficiency

This study assesses two methods used to define relatively short femur in screening for trisomy 21 and examines changes in performance of screening with gestational age. Retrospective analysis of data on menstrual age, femur length (FL) and biparietal diameter (BPD) in 49 trisomy 21 pregnancies and 6069 normal controls. Reference ranges were derived for BPD/FL versus menstrual age and for FL versus BPD. Two methods of defining short femur (BPD/FL and observed-to-expected FL ratio) were examined for false-positive rates and detection rates for trisomy 21 at different gestational ages. In the control group the BPD/FL ratio and its standard deviation decreased with menstrual age. Trisomy 21 was associated with a significantly higher BPD/FL ratio (P < 0.001) and the deviation increased significantly with menstrual age (P < 0.05). Eleven percent of 28 fetuses examined at 15-17 weeks had a BPD/FL above the 95th centile compared with 24% of 21 fetuses examined at 18-20 weeks (P = 0.40). The median observed-to-expected FL ratio in the control group was 1.0 throughout the gestational age range but the standard deviation decreased significantly with menstrual age (P < 0.01). Trisomy 21 was associated with a significantly reduced observed-to-expected FL ratio (P < 0.001) and the deviation increased significantly with menstrual age (P < 0.05). A fixed cut-off of 0.91 for observed-to-expected FL ratio provided a false-positive rate of 12% at 15-17 weeks compared with 6% at 18-20 weeks of gestation (P < 0.001) with detection rates of 29 and 38%, respectively (P = 0.73). Irrespective of the definition used to define the condition, relatively short femur is a poor marker for trisomy 21 particularly when the assessment takes place before 18 weeks of gestation.

Fetal biometry at 4300 m compared to sea level in Peru.

The aim of this study was to compare ultrasound fetal size at high altitude and sea level. Three hundred and thirty-four women in Cerro de Pasco at 4300 m (14,100 ft) altitude and 278 women in Lima (sea level) were recruited to the study. Ultrasound fetal biometry was carried out between 14 and 42 weeks of gestation. Biparietal diameter, occipitofrontal diameter, abdominal circumference and femur length were measured and head circumference and estimated fetal weight were derived from these data. Two hundred and seventy-seven women (82.9%) in Cerro de Pasco and 216 (77.7%) in Lima had normal singleton pregnancies and certain menstrual dates. These women were selected for statistical analysis. Fractional polynomial regression analysis on gestational age was performed, controlling for maternal height and parity. Fetal biometry measurements were significantly smaller in Cerro de Pasco compared with Lima. When gestation bands were compared this effect was present from 25 to 29 weeks onwards, and was greater in the abdominal circumference than in the head circumference and femur length (ratios Cerro de Pasco: Lima, 0.96, 0.97 and 0.98, respectively). Estimated fetal weight was also significantly lower in Cerro de Pasco (ratio 0.88), as were birthweights (ratio 0.88). If the centiles derived from the Lima population were applied for Cerro de Pasco, 11.2% of all estimated fetal weights would be below the fifth centile, and 1.08% above the ninety-fifth. These data suggest that at high altitude, all fetal biometry measurements follow a lower trajectory than at sea level. Specific biometry charts should therefore be used for obstetric ultrasound at high altitude.

Suspected skeletal dysplasias: Femur length to abdominal circumference ratio can be used in ultrasonographic prediction of fetal outcome

OBJECTIVES: Skeletal dysplasias are a group of bone growth disorders, some of which can be recognized prenatally. Certain types of skeletal dysplasias result in a lethal fetal outcome. The ability to predict this outcome prenatally would be important in counseling parents. This study evaluated the ratio of femur length to abdominal circumference as a predictor of fetal outcome in cases of suspected skeletal dysplasia. STUDY DESIGN: This 3-year retrospective study identified 18 cases of prenatally suspected skeletal dysplasia from a population of approximately 35,000 fetuses undergoing prenatal ultrasonography. The femur length/abdominal circumference ratio was calculated and compared with fetal-neonatal outcomes and diagnoses. RESULTS: Eighteen cases of suspected skeletal dysplasia were identified, and the femur length/abdominal circumference ratio was found to be a good predictor of fetal outcome independent of gestational age. A ratio <0.16 resulted in a lethal outcome in nine of nine cases. Conversely, a ratio ≥0.16 resulted in a diagnosis of a nonlethal form of skeletal dysplasia or a diagnosis that ruled out any form of skeletal dysplasia in nine of nine cases. CONCLUSIONS: The femur length/abdominal circumference ratio may be useful to predict a lethal fetal outcome when ultrasonography indicates a possible skeletal dysplasia. (Am J Obstet Gynecol 1997;177:864-9.)

The evaluation of accelerated fetal growth

The timely recognition of fetal macrosomia may reduce the complications associated with vaginal delivery of a macrosomic fetus. Today, the most frequently used tool for identification of fetal macrosomia is ultrasound. Although many different calculations have been applied, the most commonly used is the estimation of fetal weight. Generally, the detection rate of fetal macrosomia is 33-82%, with a specificity of 70-100%, a positive predictive value of 40-83%, and negative predictive value of 66-92%. Adding amniotic fluid volume, cheek-to-cheek diameter or fetal subcutaneous tissue: femur length ratio may improve the accuracy of the diagnosis. Other promising diagnostic tools include the echo-planar imaging and the neural network. Despite the progress that has been achieved since the use of Nagele's rule, our ability to fetal macrosomia remains limited.

The utility of fetal biometry as an adjunct to the multiple-marker screening test for Down syndrome

Objective: Our purpose was to investigate fetal biometry as an adjunct to the multiple-marker screen (maternal age, serum a-fetoprotein, estriol, and human chorionic gonadotropin) for Down syndrome.Study Design: Fifty-two cases of Down syndrome were compared with 7514 normal fetuses. The measured/predicted femur length ratio had the best discriminant value (1.0 ± 0.11 vs 0.93 ± 0.13, p < 0.0001). Multivariate gaussian algorithms were developed and each computed a likelihood ratio for Down syndrome. The trivariate algorithm incorporated the three maternal analytes, whereas the quadrivariate version also included the femur length ratio. The study population included 38 cases of Down syndrome and 1098 euploid controls. The midtrimester risk was the product of the age-related risk and the likelihood ratio.Results: The relative difference in the femur length ratio between normal and affected fetuses was small in comparison to that of the maternal serum analytes. At a risk cutoff of ≥ 1:190 the detection rates were similar and actually favored the trivariate algorithm but differed only by one case of Down syndrome.Conclusion: The addition of the measured/predicted. femur length ratio had a negligible effect on the performance of the multiple-marker screening test.

Humerus and femur length shortening in the detection of Down's syndrome

Our purpose was to determine the utility of screening for humerus and femur length shortening in prenatal detection of Down's syndrome (trisomy 21). On the basis of the biparietal diameter, predicted humerus and femur lengths were derived from a sample control group of 350 karyotypically normal fetuses. The regression formulas were prospectively applied to 45 consecutive fetuses with Down's syndrome and 942 fetuses with normal karyotypes. Ratios of measured humerus length/predicted humerus length and measured femur length/predicted femur length were calculated for each fetus. Eleven of 45 (24.4%) fetuses with Down's syndrome had short humerus (measured humerus length/predicted humerus length ratio of < or = 0.89), and 11 (24.4%) had short femur (measured femur length/predicted femur length ratio of < or = 0.91. In comparison, among 942 karyotypically normal fetuses only 43 (4.5%) showed short humerus and 44 (4.7%) showed short femur (p < 0.05). Fetuses with both short humerus and short femur carried an 11-fold greater risk of Down's syndrome (risk ratio = 11.1; 95% confidence interval = 5.0 to 25.0). Prenatal ultrasonographic detection of short humerus to short femur, or both significantly increase the risk of Down's syndrome; this information may be useful in screening programs.

184 Foot:Leg Length and Foot:Femur Length Ratio in Noninvasive Screening for Trisomy 21

184 Foot:Leg Length and Foot:Femur Length Ratio in Noninvasive Screening for Trisomy 21

Femur/stature ratio and estimates of stature in mid‐ and late‐pleistocene fossil hominids

In previous limited investigations of the human femur/stature ratio we (Feldesman and Lundy: Journal of Human Evolution 17:583-596, 1988; Feldesman et al.: American Journal of Physical Anthropology 79:219-220, 1989) have shown it to be remarkably stable across ethnic and gender boundaries. In this study we evaluate the femur/stature ratio in 51 different "populations" of contemporary humans (n = 13,149) sampled from all over the world. We find that the mean ratio of femur length to stature in these populations is 26.74%, with a very restricted range of variation. When we compare mean femur/stature ratios of males and females, there are no statistically significant differences. ANOVA performed on a naive grouping of samples into "whites," "blacks," and "Asians" indicates that there are significant racial differences (P less than 0.001). When we subject these groups to Tukey's HSD procedure (a post-hoc test), we find that "blacks" are responsible for the significant ANOVA, being significantly (P less than 0.005) different from the other ethnic groups. "Whites" and "Asians" are not significantly different (P = 0.067) under the conditions of this analysis, although all these racial comparisons may be suspect given the small sample sizes. We tested the efficacy of the ratio in three situations: predicting stature of repatriated white Vietnam veterans; predicting stature in a random sample of South African blacks (of known stature), and predicting the stature of a single Akka pygmy. In the first and third cases, the femur/stature ratio does better than the traditionally recommended regression equation, while in the second case the predictions from the femur/stature ratio are less accurate than from the appropriate regression equation. These results encouraged us to apply this ratio to mid- and late-Pleistocene fossil hominids, where the choice of reference population for stature estimates continues to trouble workers. We estimated stature for a sizeable number of Homo erectus (HE), early Neanderthal (EN), Near Eastern Neanderthal (NEN), and early anatomically modern Homo sapiens (EAMHS) by using the simple relationship: stature (cm) = femur length (cm) * 100/26.74. Our results show that HE fossils are slightly taller on average than either EN or NEN samples, which do not differ significantly in stature, while EAMHS fossils are significantly taller than all three earlier groups. While these results are not surprising, our stature estimates for these fossils differ from currently published estimates based on sample-specific regression-based formulae.(ABSTRACT TRUNCATED AT 400 WORDS)

Femur length shortening in the detection of Down syndrome:Is prenatal screening feasible?

The potential utility of screening for femur length shortening in prenatal detection of Down syndrome (trisomy 21) was evaluated by comparing 49 consecutive fetuses with Down syndrome with 572 chromosomally normal fetuses before genetic amniocentesis. Ratios of measured femur length/predicted femur length and biparietal diameter/femur length were calculated for each fetus. The predicted femur length was calculated from a regression equation relating the biparietal diameter and femur length derived from a sample control group. With this normal regression equation, 7 of 49 (14.3%) fetuses with Down syndrome had short femur lengths (measured femur length/predicted femur length ratio of less than or equal to 0.91) compared with 35 of 572 (6.1%) fetuses with a normal karyotype (p less than 0.05). However, the maximum positive predictive value for identification of Down syndrome based on short femur lengths was only 0.93% for a high-risk population (prevalence of Down syndrome, 1:250) and 0.33% for a low-risk population (prevalence of Down syndrome, 1:700). We conclude that ultrasonographic screening of short femur length is less effective for prenatal detection of Down syndrome than initially suggested.

The efficacy of fetal sonographic biometry in Down syndrome screening

Sonographic biometry has been proposed as a second-trimester Down syndrome screening modality. Approaches have relied on the apparent “shortened” femur length of fetuses with Down syndrome. Unfortunately, significant intercenter variation has been reported in the magnitude of this femur length reduction. In an effort to overcome many of these potential biases and better estimate the magnitude of femur length shortening in fetuses with Down syndrome, a retrospective review of femur length differences between 16 Down syndrome and 194 control fetuses was carried out. All scans were performed by one examiner who used the same equipment and measurement technique. A significant reduction in the observed to expected femur length ratio for a given biparietal diameter was identified in the Down versus control fetuses (0.9574 95% confidence interval 0.9197, 0.9952 versus 0.9999 95% confidence interval 0.9913, 1.0086) (p < 0.008). However, the magnitude of this reduction was not sufficient to permit the use of this sonographic approach as an isolated marker for fetal Down syndrome.

Ultrasound Detection of Down Syndrome: Is it Really Possible?

Several ultrasonographic signs have been described in second-trimester fetuses at high risk for Down syndrome. We examined these parameters in twin pregnancies in which one fetus was affected with Down syndrome and the other was normal. Biparietal diameter to femur length ratio was concordant (either normal or abnormal) in eight of nine sets of twins. Actual femur length to expected femur length ratio was concordant in seven of nine sets of twins. Nuchal fold thickening (6 mm or more) correctly identified five out of nine affected fetuses and was not present in any of the normal fetuses. In conclusion, neither ratio was helpful in differentiating the fetus with Down syndrome from its normal cotwin. A thickened nuchal fold was the most informative parameter examined.

Second-trimester sonographic diagnosis of Down syndrome: role of femur-length shortening and nuchal-fold thickening.

Relative shortening of femur length and nuchal-fold thickening were evaluated as sonographic signs for the prenatal detection of Down syndrome. The sonograms of 28 fetuses identified by amniocentesis as having trisomy 21 were reviewed. The sonograms of 128 fetuses with a normal karyotype were evaluated as a control group. The finding of either an actual-to-expected femur-length ratio of 0.91 or less or a nuchal-fold measurement of 6 mm or more detected Down syndrome with a sensitivity of 42% and a specificity of 88%. The positive predictive value for Down syndrome detection when using femur-length shortening alone was greater than that when using the combination of femur-length shortening and nuchal-fold thickness. We conclude that femur-length shortening may be potentially useful for the detection of Down syndrome, whereas nuchal-fold thickening has a limited role.

Use of ultrasound in antenatal diagnosis of large-for-gestational infants in diabetic gravid patients

Near-term ultrasonograms of 44 diabetic gravid patients and 47 nondiabetic gravid patients were retrospectively analyzed. The mean values of abdominal diameter to femur length ratios and abdominal diameter to biparietal diameter ratios in diabetic gravid patients with large-for-gestational age fetuses were significantly different from those values in diabetic patients with appropriate-for-gestational age fetuses and in nondiabetic patients. Glycosylated hemoglobin values were above 7.4% (mean +/- 2 SD) in 79% of diabetic patients with large-for-gestational age infants and abdominal diameter to femur length ratio exceeding 1.385. Glycosylated hemoglobin values were less than or equal to 7.4% in 69% of diabetic gravid patients with appropriate-for-gestational age fetuses and abdominal diameter to femur length ratio less than 1.385. These findings suggest that large-for-gestational age infants have a different growth characteristic with a disproportionate enlargement of the abdomen. This possibly results from a long period of elevated levels of maternal plasma glucose (as shown by elevated values of glycosylated hemoglobin).

The Migratory Locust, Tocusta migratoria L. (Orthoptera : Acrididae), in Japan I. Experiment on Crowding Effects

Experiments were caarried out to elucidate crowding effects on Locusta migratoria in Kyoto. Hatchlings were obtained from eggs that had been laid by females caught in the field. The hoppers were subjected to three different densities (1, 2 and 5 per cage). Clear crowding effects were found in some of the 24 characteristics examined, such as hopper coloration, sexual dimorphism, (elytron length)/(posterior femur length) ratio, (posterior femur length)/(maximum width of head) ratio, yellowing of male, adult longevity, number of egg pods per female, number of eggs per pod, viability of eggs, percentage of eggs entering diapause, hatchling weight of the progeny, etc. Although Locusta migratoria has not shown any outbreaks in Kyoto at least in the last hundred years, it has not lost its ability to respond to crowding. The effect of age of the female on her eggs was also examined.

Comparison of ultrasound femur length and biparietal diameter in late pregnancy

A linear relationship between growth of fetal femur length (FL) and biparietal diameter (BPD) after 22 weeks' gestation is described. The normal ratio of femur length to BPD(FL/BPD ratio) was found to be 79 ± 8%. Effective uses of the FL/BPD ratio include its use as a quality control check on femur length and BPD measurements and its use to diagnose short-limbed dwarfism, hydrocephalus, and microcephaly. Pregnancy dating by means of BPD can now be cross checked by use of femur measurements and new Observations on normal and abnormal fetal growth will now be possible.

Effect of dietary vitamin a, ascorbic acid and their interaction on turkey bone mineralisation1

At early ages, added dietary ascorbic acid did not affect growth or femur mineralisation of poults. In poults after 8 and 12 weeks, femur mass was reduced by 3000 mg ascorbic acid per kg diet. 2. Plasma calcium and magnesium were not influenced differently by 1000, 4000 and 16,000 IU vitamin A/kg diet, but plasma phosphorus was decreased by the 16,000 level. 3. Vitamin A at 1000 or 16,000 IU/kg diet reduced growth in both sexes to 12 weeks of age compared with the NRC recommended 4000 IU/kg diet. In males, the growth retardation continued to 18 weeks. 4. Vitamin A at 16,000 IU/kg reduced femur development as measured by femur weight to body weight or to femur length ratios.

Fetal Femur Length and Abdominal Circumference Ratio in Bangladesh

Objective: The ratio of fetal femur length and abdominal circumference is one of the important ratios. But we do not have any study on it in our country so far. Therefore a study was conducted to prepare a table based on Bangladeshi population. Method: Well dated pregnancies were included in a cross-sectional prospective study. By fitting Polynomial regression model a table and a graph were prepared. Nomograms of Caucasian population which were established before, were compared with this study. Results: A chart of the raw data of 1223 subjects with superimposed fitted percentiles was produced. The quadratic model showed a good fit to the data. 3rd, 10th, 50th, 90th and 97th percentiles, means and two standard deviations of the data were derived. Conclusion: These table and charts can be useful for accurate assessment of fetal femur length/abdominal circumference ratio to detect the type of fetal growth abnormality, symmetrical or asymmetrical. This study shows that there is similarity of this ratio with the western ratio unlike the individual fetal parameters. Key words: Femur length/abdominal circumference ratio; Bangladesh. Bangladesh J Obstet Gynaecol, 2009; Vol. 24(2) : 52-55 DOI: http://dx.doi.org/10.3329/bjog.v24i2.8528