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C B Benson

Publications and source records attributed to C B Benson.

82 records · Page 5Linked to original sources
PubMed1988

Improved prediction of intrauterine growth retardation with use of multiple parameters.

Several sonographic parameters have been proposed for predicting intrauterine growth retardation (IUGR), but each has been shown to have a low positive predictive value. To predict IUGR more reliably, the authors developed a multiparameter approach based on sonographic and clinical data from 62 fetuses with IUGR and 91 normal fetuses. Logistic regression analysis revealed that the combination of sonographically estimated fetal weight, amniotic fluid volume, and maternal blood pressure status best correlates with the presence or absence of IUGR and produced an IUGR scoring system based on these three parameters. The scoring system, which has a range of 0-100, was tested on a second set of fetuses (47 with IUGR, 81 normal) to determine its performance characteristics. An IUGR score below 50 virtually excludes the diagnosis of IUGR (0.9% likelihood of IUGR, or negative predictive value of 99.1%). A score above 75 allows confident diagnosis of IUGR (positive predictive value, 82%). A score of 50-75 is equivocal, in that it is associated with an intermediate (24%) likelihood of IUGR. The IUGR score is a practical tool that can be easily used in any ultrasound facility.

Amniotic Fluid↗
PubMed1988

Doppler criteria for intrauterine growth retardation: predictive values.

Published data concerning proposed antenatal Doppler criteria for intrauterine growth retardation (IUGR) were critically analyzed using the same technique that has been previously applied to conventional (non-Doppler) sonographic criteria for IUGR. Fifteen studies of Doppler criteria, each conducted in such a way that sensitivity and specificity could be determined, were identified through a literature review. These studies encompassed a variety of arterial waveform and volume blood flow criteria. Bayes' theorem was then used to determine the positive predictive value of each criterion if used as a screening test for IUGR. Criteria involving vessels that have been studied by at least two groups, including those involving umbilical artery waveform, uterine arcuate artery waveform, and umbilical vein volume blood flow, had positive predictive values that fell in a low range (17-57%) similar to that previously found for conventional criteria. Two criteria, using fetal internal carotid artery and thoracic aortic waveforms, had higher positive predictive values (66 and 100%, respectively) in initial studies, but the data have yet to be replicated by other groups. It is concluded that no Doppler criterion has yet been established as a clinically useful method to screen for IUGR antenatally.

Female↗
PubMed1987

Sonographic determination of fetal weights in diabetic pregnancies.

Accurate antenatal diagnosis of the macrosomic infant of a diabetic mother should lead to a decrease in perinatal morbidity. Several formulas for weight estimation based on sonographic measurements are in common use, but none of them has been devised specifically for the infant of a diabetic mother. We assessed the accuracy of conventional formulas at estimating fetal weight in 160 of these infants and found their relative errors (error as a percentage of birth weight) had standard deviations of 12.2% to 13.1% (greater than has been reported in the general population) with no statistically significant difference among formulas. We also devised customized formulas generated from a "training set" of 80 patients and tested on a second set of 80 patients. The best formula yielded a standard deviation of 11.0%. The difference between customized and conventional formulas was not statistically significant. With use of one conventional formula, the likelihood of macrosomia was found to be 77% when the estimated weight was greater than 4000 gm and 86% when the estimated weight was greater than 4500 gm. We conclude that fetal weight prediction is even less accurate in the infant of a diabetic mother than in the general population and that "customized" formulas fare no better than conventional formulas in diabetics. Despite this, estimated weights can offer guidance in predicting fetal macrosomia and therefore aid in obstetric management.

Embryonic and Fetal Development↗
PubMed1986

Intrauterine growth retardation: predictive value of US criteria for antenatal diagnosis.

We critically analyzed published data on proposed sonographic criteria for intrauterine growth retardation (IUGR) to determine the positive and negative predictive values of the criteria. The data were drawn from 21 studies and encompassed nine distinct criteria for which the sensitivity and specificity could be determined. Predictive values were computed using Bayes theorem, based on an IUGR prevalence rate of 10%. Seven of the nine criteria had positive predictive values of less than 50%, indicating that a fetus with an abnormal test result according to any of these criteria is more likely to be normal than growth retarded. The best criterion involves the ratio of head circumference to abdominal circumference, but even with this criterion, fully 38% of fetuses with abnormal test result will not be growth retarded. We conclude that none of the proposed criteria allows a confident antenatal diagnosis of IUGR to be made. Future prospective studies may reveal new criteria, or combinations of existing ones, that are highly predictive for this condition.

Female↗
PubMed1986

Femur length/abdominal circumference ratio. Poor predictor of macrosomic fetuses in diabetic mothers.

Antenatal diagnosis of fetal macrosomia can affect the management of diabetic mothers. Because the sonographically determined femur length/abdominal circumference (FL/AC) ratio has been shown to differ in macrosomic and non-macrosomic fetuses (in a population containing few diabetics), its value in establishing the diagnosis of macrosomia was examined. The results indicate that the FL/AC ratio differs in non-macrosomic (20.4 +/- 1.6) and macrosomic (19.5 +/- 1.4) fetuses of diabetic mothers, but there is considerable overlap. For no cutoff value is there a high sensitivity and high specificity. The positive predictive value is 36-43 per cent (depending on the cutoff), only slightly greater than the prevalence (26 per cent in the study population). The authors conclude that the FL/AC ratio is not useful in predicting macrosomia among diabetic mothers.

Abdomen↗
PubMed1985

FL/AC ratio: poor predictor of intrauterine growth retardation.

Early antenatal detection of intrauterine growth retardation (IUGR) may decrease the associated perinatal morbidity and mortality. A parameter based on sonographically measured femur length (FL) and abdominal circumference (AC), expressed as FL/AC X 100 and termed the FL/AC ratio, has recently been proposed by Hadlock et al as an age-independent predictor of IUGR. We studied 285 normal and 37 IUGR fetuses to verify that the FL/AC ratio is independent of gestational age (GA) and to assess its value as a predictor of IUGR. Our results confirm that the FL/AC ratio is age-independent above 20 weeks and that its mean value differs in normal (22.4 +/- 1.7) and IUGR (23.7 +/- 1.4) fetuses (P less than .01, t-test). Because of considerable overlap between these two groups, however, there is no cutoff value for the FL/AC ratio that yields both a high sensitivity and a high specificity, or that leads to a high positive predictive value. With a cutoff of 23.5, for example, the sensitivity is 56% and the specificity 74%, and, even assuming an IUGR prevalence rate of 10%, the likelihood of IUGR in a fetus with an FL/AC ratio above the cutoff is only 19%. We conclude that the FL/AC ratio, though an age-independent measure whose mean value differs in normal and IUGR fetuses, is not clinically useful as a predictor of IUGR.

Abdomen↗