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Biomedical subjects
R L Deter
Publications and source records attributed to R L Deter.
The use of ultrasound in the assessment of normal fetal growth: a review.
This review presents the basic principles underlying the quantitative assessment of normal fetal growth using ultrasound. Data on fetal growth derived from measurements of body, head, chest, and abdominal dimensions, are summarized, compared, and evaluated. Fetal volume and weight determination are also discussed. Most of the data evaluated were obtained in cross-sectional studies, but we present the preliminary results of our longitudinal study of fetal growth for comparison.
Abdomen↗
Longitudinal studies of fetal growth using volume parameters determined with ultrasound.
To explore the use of three-dimensional parameters in characterizing fetal growth with ultrasound, the accuracy of volume measurements and the ability to make such measurements during pregnancy have been investigated. Total fetal volumes (TOTV) determined with ultrasound in utero were compared to volume measurements obtained by hydrostatic weighing following induced abortion at 19.4 (+/- 1.8 SD) weeks, menstrual age (MA), and to those calculated from birth weights and density values for term fetuses [39.3 (+/- 0.8 SD) weeks, MA]. This study indicated that ultrasound measurements underestimate the fetal volume [-9.8 (+/- 9.5 SD)% at 19 weeks and -19.0 (+/- 9.3 SD)% at 39 weeks]. To assess the possibility of obtaining growth curves for volume parameters, 20 normal fetuses [based on crown-rump length (CRL), biparietal diameter (BPD), head circumference (HC) and abdominal circumference (AC) growth curves, birth weight (WT), crown-heel length (CHL) and postnatal examination] with known dates of conception were studied. Head volume (HV), thoracic volume (TV), abdominal volume (AV), limb volume (LV) and TOTV were measured at 2- to 3-week intervals during the third trimester. Mathematical modeling indicated that the linear-cubic (LC) model was optimal for HV, TV, AV, and TOTV (R2: 97.3%, 97.2%, 98.1% and 99.4%) while the linear-quadratic (L-Q) model was optimal for LV (R2: 98.4%). Significant individual variation was suggested by the high coefficients of variation (CV) obtained for the optimal model coefficients. Inspection of individual growth curves revealed the presence of three types, "linear," "concave," and "convex" with the "concave" type predominating. The variability was less than that seen in the groups as a whole for most subgroups but was still greater than that observed with linear parameters. These results indicated that although volume growth curves can be obtained, their individual variability is significant and thus more fetuses must be studied before standard curves can be defined.
Abdomen↗
Mathematical modeling of fetal growth: I. Basic principles.
Quantitative characterization of fetal growth requires the selection of measurement parameters and a growth curve model. For such studies we propose two new parameters (the head cube and the abdominal cube) and a new growth curve model [P = c(t)k+s(t)]. These parameters are relatively insensitive to shape changes and are related to three-dimensional parameters even though they can be calculated from profile diameter measurements. The growth curve model is capable of adequately describing a wide variety of growth curves and its coefficients may be associated with specific biological variables. The properties of these parameters and the growth curve model are discussed.
Abdomen↗
Mathematical modeling of fetal growth: II. Head cube (A), abdominal cube (B) and their ratio (A/B).
Growth of the fetal head and abdomen have been monitored by measurement of the head cube (A), the abdominal cube (B) and A/B, from 12 to 41 weeks menstrual age. Growth curves for these parameters have been determined using a specially developed growth curve model [P = c(t)k+s(t)]. R2 values of 98.0%, 96.6%, and 56.2% were obtained for A, B, and A/B, respectively. Similar results were obtained when this model was used with HC and AC data from a previous study. Variability analysis indicated a progressive increase in variability with menstrual age for both A and B while the variability of A/B decreased. The variability in the 12- to 17-week interval was significantly greater for all three parameters and the A deviation distribution was asymmetric (shifted toward negative values) after 36 weeks. Variability data were used with the growth curve models to determine standard curves for A, B and A/B.
Abdomen↗
Longitudinal studies of thigh circumference growth in normal fetuses.
To characterize the growth of the thigh circumference (ThC) in individual fetuses, longitudinal studies of ThC growth were carried out in 20 fetuses between 19 (+/- 1.8) and 38 (+/- 1.5) weeks, menstrual age. Because of measurement uncertainties, analysis of growth patterns was limited to the data collected after 22 weeks. The Rossavik growth model fit the data well [R2: 95.8(+/- 2.9 SD)%], but considerable coefficient variability was seen, particularly for the coefficient k. Use of the coefficient k-value (1.138) derived from a cross-sectional data set reduced the variability of the coefficient c by 95% and made the results of the longitudinal and cross-sectional studies consistent with each other. This k-value was taken as the appropriate one for ThC growth curves. Studies of ThC growth in individual fetuses revealed considerable variability in growth curve shape, although the majority of curves could be approximated by a straight line. No differences between growth curves for males and females could be detected. The average longitudinal ThC growth curve was found to be very similar to the growth curve obtained in a cross-sectional study of ThC growth. ThC growth after 26.1 weeks could be predicted with an accuracy of +/- 15% from growth models derived from the data obtained before 26.1 weeks. These results indicate that ThC growth after 22 weeks (as with other parameters) can be followed in individual fetuses. However, because of the greater inherent variability in growth patterns, using each fetus as its own control may be more important.
Embryonic and Fetal Development↗
Evaluation of fetal growth by ultrasonography in twin pregnancy: a comparison between individual and cross-sectional growth curve standards.
Cross sectional curves and individual fetal growth curves standards from the Rossavik growth model [P = c(t)(k + s(t]] were generated for abdominal and head circumferences, femur diaphysis length and estimated fetal weight from a sample of 59 women with twin pregnancy. These curves were compared to their counterparts in singleton pregnancies. Cross sectional curves of the four fetal anatomic parameters under study fell progressively below the curves for singletons during the last trimester of gestation. In contrast, there were few differences between individual fetal groWth curve standards for twin and singleton pregnancies. In 11 of the 59 patients, both methods were used to evaluate fetal growth in the last trimester of gestation. In 5 of these patients, fetal growth was normal by both methods in all 10 fetuses. In the 6 other patients, there were 3 fetuses with abormal estimated fetal weights (EFWs) by both population and individual standards. However, 3 fetuses had abnormal EFW's by populations standards but not by individual standards while the EFW of another fetus was abnormal by individual standards but not by population standards. These results illustrate that the cross-sectional approach to the assessment of growth in twins can be misleading and may lead to incorrect conclusions concerning the growth of these fetuses.
Embryonic and Fetal Development↗
Individual growth curve standards in twins: growth in the second trimester.
To provide a more detailed assessment of the growth of twins, the individual second trimester growth patterns of six fetal parameters [HC, AC, FDL, ThC, head cube (A) and abdominal cube (B)] were studied in fourteen sets of normal twins (six monozygotic and eight dizygotic) and sixteen normal singletons using the Rossavik growth model [P = c(t)(k + s(t)]. Comparisons of start points and coefficient c values indicated no statistically significant differences in the growth processes of twins and singletons in early pregnancy and no detectable effect of zygocity. Comparisons of second trimester growth within sets of twins and randomly paired singletons revealed the presence of differences in feto-placental support. A significant effect of differences in genetic growth potential or maternal support could not be demonstrated, however. These results suggest that with respect to growth, normal twins in the second trimester can be treated as two singletons in the same mother.
Embryonic and Fetal Development↗
Fetal heart rate influence on the pulsatility index in the middle cerebral artery.
In 1300 Doppler assessments performed on the fetal cerebral arteries, 5 cases of heart rate deceleration were recorded while studying the middle cerebral artery. There were 3 normal fetuses (mean menstrual age +/- standard deviation: 28.6 +/- 2.1 weeks), one growth-retarded fetus (34 weeks, menstrual age) and 1 fetus with red cell alloimmunization (27 weeks, menstrual age). The magnitude of decline in the heart rate during the deceleration ranged from 44 to 93 bpm (67 +/- 18 bpm). Pulsatility index values were calculated on 44 waveforms and correlated with the heart rate. Linear regression analysis showed a statistically significant inverse correlation between the heart rate and the pulsatility index in the middle cerebral artery of 4 fetuses. These results indicate that heart rate will affect the pulsatility index of the middle cerebral artery.
Cerebral Arteries↗
Reduction of soft tissue deposition in normal triplets.
In a previous study, birth weight projections obtained with Rossavik growth models were systematically greater than actual birth weights in triplets but not in singletons. To investigate the cause of this overestimation, average mean percent deviations for head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), and weight (WT) at different times in the third trimester were studied in 13 normal triplet and 20 normal singleton fetuses using individual growth curve standards. Average mean percent deviation values for HC in both singletons and triplets were close to zero throughout the third trimester. Average mean percent deviation values for AC in both singletons and triplets were similar, and remained relatively constant. Average mean percent deviation values for ThC in triplets decreased toward the end of the third trimester, but those for singletons increased. Average mean percent deviation values for estimated weight did not change during the third trimester in singletons whereas those in triplets decreased. The difference in average mean percent deviation values for estimated weight between singletons and triplets in the 32- to 36-week interval was statistically significant. There were no significant differences between actual and predicted measurements for HC in both singletons and triplets at birth. However, actual birth measurements were systematically less than predicted birth measurements for AC and ThC in singletons, and for AC, ThC, and WT for triplets. These systematic differences were significantly larger in triplets for ThC and WT. Nutrition Score values, direct measures of subcutaneous tissue, were significantly lower in triplets compared to singletons.(ABSTRACT TRUNCATED AT 250 WORDS)
Birth Weight↗
A review of fetal organ measurements obtained with ultrasound: normal growth.
This review article presents fetal organ measurements obtained with ultrasound. Data derived from measurements of the brain, heart, lung, thymus, liver, spleen, pancreas, stomach, gallbladder, kidney, adrenal glands, intestine, and bladder are summarized, compared and evaluated critically. The selection of optimal parameters, development of valid measurement procedures, and use of mathematical modeling and descriptive statistics are necessary for quantitative studies by ultrasound of fetal organ growth.
Abdomen↗
Growth standards for anatomic measurements and growth rates derived from longitudinal studies of normal fetal growth.
A statistical procedure for deriving growth standards for anatomic measurements and their growth rates from longitudinal studies of fetal growth was evaluated using Rossavik growth models for the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur diaphysis length (FDL) determined in a previous study of normal fetal growth. For each anatomic parameter, the coefficients c and s of the model was used to define a set of growth curves that constituted the boundary growth curves of a region containing 95% of the growth curves of this data set. The set of boundary growth curves was used to specify the mean, lower limit, and upper limit values for the anatomic parameter and its growth rate at weekly intervals between 14 and 38 weeks, menstrual age. Comparison of these values to those determined from cross-sectional studies of fetal growth gave differences of -1.9% to 4.8% (SD: +/- 0.9 to +/- 2.6) for mean vs. predicted value of the anatomic measurements. For the lower limit, similar values were 0.4% to 13.8% (SD: +/- 1.7 to +/- 8.8); for the upper limit the values were 8.3% to 18.0% (SD: +/- 1.5 to +/- 7.0). Comparisons of HC growth rates determined using polynomial and Rossavik growth models gave values of -3.4% (SD: +/- 4.4) for mean vs. predicted value, -12.6% (SD: +/- 10.6) for the lower limit and 5.2% (SD: +/- 9.3) for the upper limit. The degree of agreement was similar for AC growth rates.(ABSTRACT TRUNCATED AT 250 WORDS)
Anthropometry↗
Detection of intrauterine growth retardation in twins using individualized growth assessment: I. Evaluation of growth outcome at birth.
The growth of 17 sets of twins was evaluated at 2 to 3 week intervals from 15 weeks to delivery by measurement of the head circumference, abdominal circumference, and thigh circumference, and estimation of weight. The birth characteristics of these twins were compared to those predicted by Rossavik growth models, derived from second-trimester ultrasound measurements, using the Growth Potential Realization Index (GPRI) and by comparison to population standards. Newborns were classified as normal or intrauterine growth retarded (IUGR) based on their Neonatal Growth Assessment Score, determined from GPRI values. All normal twins had birth weights that were appropriate-for-gestational-age and had few abnormal birth measurements. The birth weight differences between normal twin fetuses were all < 20%. IUGR twins were both small for gestational age (78%) and appropriate-for-gestational-age (22%), and all had 3 or 4 abnormal GPRI values. In only 40% of the cases was the birth-weight difference between a normal and an IUGR twin > 20%. No single anatomic parameter evaluated at birth adequately separated the normal twins from those with IUGR. These results indicate the need for multiple parameter Individualized Growth Assessment in the detection of IUGR in twins.
Adult↗
Detection of intrauterine growth retardation in twins using individualized growth assessment. II. Evaluation of third-trimester growth and prediction of growth outcome at birth.
Second- and third-trimester growth in 34 twin fetuses was evaluated with ultrasonography by measurement of five anatomic parameters. Rossavik growth models, derived from second-trimester measurements, were used to specify expected third-trimester growth curves. Actual measurements were compared to predicted measurements by calculation of the percent deviations. Growth outcome at birth [normal, intrauterine growth retardation (IUGR)] was determined from Neonatal Growth Assessment Scores. Growth in the second trimester was similar in normal and IUGR twins. In the third trimester, abnormal negative deviations were larger and more numerous in IUGR twins. However, there was considerable individual variability and normal twins also had abnormal negative deviations. In IUGR twins, the first appearance of an abnormal negative deviation was quite variable (range: 28.6 weeks to 35.1 weeks), as was the parameter to show such a deviation. Prediction of neonatal outcome was poor using individual anatomic parameters but improved considerably with use of all five parameters. However, some fetuses were misclassified when only the number of abnormal negative deviations was used. The Prenatal Growth Assessment Score (PGAS), determined by both the number and magnitude of abnormal negative deviations, predicted neonatal outcomes with a sensitivity of 100% and specificity of 100%. On average, PGAS values were abnormal 5 weeks before delivery. These results indicate that normal and IUGR twins can be separated, using third-trimester growth patterns, if multiple parameter Individualized Fetal Growth Assessment is employed.
Diseases in Twins↗
An evaluation of two methods for measuring fetal head and body circumferences.
Head and abdominal circumference measurements of 166 fetuses (15-40 weeks) were made by three different examiners using two measurement techniques. In method 1 the actual circumferences were measured using an electronic digitizer, while in method 2 the circumference measurements were estimated using the formula for calculating the circumference for an ellipse. Evaluation of the entire data set as a whole demonstrated no significant mean errors (P > 0.05), and only a small degree of variability (2 SD = 6 per cent). Evaluation of the data for each examiner demonstrated no significant differences (P > 0.05) in the observed variability, but small statistically significant mean errors (1.7-4.1 per cent) were observed. The latter finding is thought not to be a limitation of the ellipse approximation technique, since similar findings have been observed when experienced sonographers make actual circumference measurements on the same fetus using the same equipment.
Embryonic and Fetal Development↗