Biomedical subjects
N V Simon
Publications and source records attributed to N V Simon.
The prediction of fetal lung maturity by amniotic fluid fluorescence polarization in diabetic pregnancy.
Amniotic fluid fluorescence polarization was determined in 105 pregnant diabetic women who delivered between 31 and 41 weeks gestation within 48 hours of an amniocentesis. Seventy-seven of these 105 women had lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) determinations. Seven (6.6%) of the 105 neonates suffered from hyaline membrane disease (HMD). Fluorescence polarization at any cutoff value between 0.310 and 0.330 excluded reasonably well the possibility of HMD (false mature prediction rate, 2.7-3.4%). At these cutoff values, there was no difference in sensitivity and false mature prediction rate between fluorescence polarization and L/S ratio. However, PG determination was the most sensitive method and carried no false mature predictions.
Minicomputer-based system for obstetric ultrasound analysis, with multi-user and networking capability.
A computer-assisted approach to the dating of gestation and the evaluation of fetal growth by ultrasonography that relies on a computer-based information management system of a general hospital is described. The system processes, stores, retrieves, and compares ultrasound data, and a report can be generated by the ultrasonographer while the patient is still on the examining table. A major feature is that the system can be accessed by any authorized user from any terminal within the hospital where obstetric ultrasound examinations are performed and from off-site physicians' offices. The large memory capacity, the networking among several data bases, and the statistical manipulation capabilities of the system make it ideal for clinical research.
Influence of gestational age on prediction of fetal lung maturity by fluorescence polarization of amniotic fluid.
Compared are the amniotic fluid fluorescence polarization values and the neonatal outcomes of 201 pregnant women who delivered from 28 through 37 weeks of gestation within 48 hours of the fluorescence polarization determinations. Thirty-five neonates developed hyaline membrane disease. The corresponding fluorescence polarization values ranged from 0.275 to 0.391. Eight of those 35 tests results were less than 0.325. The predictiveness of the method was studied using different threshold fluorescence polarization values. At the authors' own threshold of less than or equal to 0.325, the overall predictive value was as follows: false mature predictions: 6.2%, false immature predictions: 62.5%, sensitivity: 77.1%, and specificity: 72.8%. However, the false mature prediction rate was 21 to 40% from week 28 through week 33 versus 3.4 to 5.8% from week 34 through week 37, depending on the selected cutoff fluorescence polarization value. The sensitivity and specificity before, at, or after week 34 were significantly different at all tested fluorescence polarization values (P less than .05 to P less than .01) with the exception of the sensitivity at 0.310 and at 0.316 (P = .057). Caution is advised against relying on the fluorescence polarization method to predict fetal lung maturity at least before 34 weeks of gestation.
Evaluation of the dating of gestation via the growth adjusted sonographic age method.
We compared the actual delivery dates of 248 normal pregnant women to the estimated dates of confinement (EDC) calculated from one biparietal diameter measurement (BPD) between 18 and 26 weeks of gestation and to the EDCs corrected by the growth adjusted sonographic age ( GASA ) method. The dating of gestation by those two ultrasound methods also was compared to the calculation of the gestational age from the last menstrual period in a subgroup of 61 women with highly reliable clinical data. The GASA method had no advantage over the dating of gestation using one single BPD measurement obtained before 26 weeks, nor over the dating of gestation using reliable menstrual data.
Sensitivity and specificity of the L/S ratio in relation to gestational age.
A review of the literature was made, and 762 titles relating to fetal lung maturity were screened. From these, 195 articles or abstracts on the L/S ratio were reviewed. Five articles met the following criteria: (1) L/S ratio by the method of Borer and Gluck including acetone precipitation; and silica-gel-H plates, (2) interval of the L/S ratio to delivery of 72 hours or less, (3) exclusion of diabetics (except for one patient with an L/S ratio greater than or equal to 2 whose baby developed hyaline membrane disease (HMD) who may have been diabetic), (4) HMD well defined and documented, and (5) a breakdown of the data by gestational age. From these five articles, the sensitivity, specificity, and predictive values were calculated for less than 34 weeks, 34 to 37 weeks, and greater than 37 weeks of gestational age. The sensitivity of the L/S ratio was good regardless of gestational age. The specificity was very poor before 34 weeks, somewhat better between 34 and 37 weeks, and best after 37 weeks. The predictive value of a negative test result was moderate before 34 weeks and became excellent after 37 weeks. The predictive value of a positive test result was moderate before 34 weeks and became very poor after 37 weeks. In conclusion, after 34 weeks, an L/S ratio of 2 or greater was a reliable indication of fetal lung maturity. However, an L/S ratio of less than two was only slightly better than an accurate assessment of gestational age at predicting HMD.
Relationship between Grade III placentas and biparietal diameter determinations.
Grade III placentas were found in 133 (12 per cent) of 1,082 pregnant women evaluated ultrasonographically after 20 weeks of gestation. Associated biparietal diameter measurements ranged from 7.2 to 10 cm. In 11 women with no complications known to accelerate fetal lung maturity or to induce premature placental maturation, grade III placentas were observed between 30 and 33 weeks of gestation. Gestational ages determined according to the growth adjusted sonographic age method of Sabbagha were accurate within one to three days. Considering the risk of hyaline membrane disease at those gestational ages, a grade III placenta cannot be equated with fetal lung maturity. Criteria other than placental grading should be used to assess the pulmonary status of the fetus.
Fetal lung maturity in complicated pregnancy, as predicted from microviscosity of amniotic fluid.
We measured the microviscosity of amniotic fluid between 28 and 40 weeks of gestation in 252 normal pregnancies and in 172 pregnancies complicated by factors known to influence fetal lung maturation, including chronic high blood pressure, pregnancy-induced hypertension, diabetes mellitus, and therapy with betamethasone. Comparison of the microviscosity value distributions and regression analysis indicated significantly lower microviscosity values in hypertensive disorders, in Class D and Classes F or R diabetes, and after 48 h of treatment with betamethasone. Few changes were observed in Classes A, B, or C diabetes. These observations are consistent with the accelerated maturation of surfactant observed in chronic intrauterine stress and the lower incidence of hyaline membrane disease reported after glucocorticoids.
Microviscosity of amniotic fluid as an index of fetal lung maturity.
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Effect of centrifugation on fluorescence polarization of amniotic fluid.
Fluorescence polarization was measured on amniotic fluids of different gestational ages before and after centrifugation at relative centrifugal forces of 34 to 4955 x g. Centrifugation significantly increased the fluorescence polarization values over those of uncentrifuged amniotic fluids. The greatest increase was observed in the most "mature" fluids centrifuged at 34 to 230 x g. Almost without exception, use of centrifugal forces greater than 1239 x g did not further increase fluorescence polarization values.
Prediction of fetal lung maturity by amniotic fluid fluorescence polarization, L:S ratio, and phosphatidyl glycerol.
The relation of amniotic fluid fluorescence polarization (FP) to fetal lung maturity was examined in 186 pregnancies terminating within 48 hours of the fluid collection. Among the 9 babies who developed hyaline membrane disease (HMD), 8 were associated with FP values of 0.340 or more, and 1 had an FP value of 0.329. In 95 of these patients, the lecithin:sphingomyelin (L:S) ratio and the presence or absence of phosphatidyl glycerol (PG) were also determined. All 9 infants with HMD had L:S ratios less than 2.00 and no PG detectable in the amniotic fluid. Using an FP value of 0.325 or less, an L:S ratio of 2.00 or more, and the presence of PG as criteria for lung maturity, FP, L:S ratio, and PG did not differ significantly in the number of false predictions of HMD. Each test detected some mature infants who would have been incorrectly classified by at least 1 of the other tests. The status of all infants born at 33 weeks' gestation or later who did not develop HMD would have been correctly predicted by FP, L:S ratio, or both. These 3 tests, therefore, are complementary and can be used in combination to reduce the number of false predictions of HMD.
Studies on the growth-inhibiting property of amniotic fluids from two United States population groups.
This study attempted to determine if lack of antimicrobial activity in amniotic fluid is the reason United States blacks have more amniotic fluid bacterial infection than whites. No significant interracial differences were found in a study of 111 fluids from whites and 56 fluids from blacks. It has been claimed that the phosphate:zinc ratio in amniotic fluid is an accurate predictor of antimicrobial activity. The present study found this often to be untrue. Amniotic fluids that lacked antimicrobial activity gained such activity when zinc was added, but the in vitro zinc levels required were usually higher than observed physiologic concentrations. Previous studies have claimed that antimicrobial activity first appears in the amniotic fluid in the third trimester of gestation. We found such activity in the majority of fluids by the end of the first trimester, with a Staphylococcus aureus indicator; in contrast, with Escherichia coli and Streptococcus agalactiae as test organisms, greater inhibition was observed after 35 weeks.
Clinical evaluation of a "short" supine pressor test for pregnancy-induced hypertension.
A modified supine pressor test was performed on 304 apparently normal primigravidas between 28 and 32 weeks' gestation. The blood pressure was measured with the patient first in lateral position and within 2 minutes thereafter in the supine position. Of those patients showing an increase of at least 20 mmHg in the diastolic blood pressure while in the supine position, 13 of 76 (17%) developed pregnancy-induced hypertension. Of those patients without an increase of at least 20 mmHg in the diastolic blood pressure, 33 of 228 (14%) became hypertensive. The results of this study do not substantiate the use of the "short" supine pressor test as an accurate predictor of pregnancy-induced hypertension.
Closing the Rh immune globulin utilization gap.
A simple and effective system, designed to achieve 100% utilization of Rh immune globulin in a general hospital, is presented. During a one-year period, all Rh-negative women exposed to events capable of inducing Rh sensitization were identified. In every case the protection of these women was verified. Four major oversights were discovered and immediately corrected, resulting in adequate protection of all Rh-negative women at risk of Rh sensitization. The system is compared with two other successful programs currently in use. The role of the Pathology Department, as a fail-safe mechanism to close potential loopholes in a Rh prophylaxis program, is emphasized.
Detection of large fetal--maternal transfusions.
Two hundred consecutive Rh-negative women at risk of Rh sensitization were screened postpartum for large fetal--maternal transfusion by two acid elution techniques. The Nierhaus modification of the Betke-Kleihauer method and the Fetaldex test were compared. In 194 of 200 women, both procedures indicated the absence of significant fetal--maternal transfusion. In 6 women a large fetal--maternal hemorrhage was detected by the Betke-Kleihauer method and in 5 of these 6 by the Fetaldex test. The overall correlation between the two techniques was 99.5%. The Fetaldex test has advantages over the Betke-Kleihauer method and is well suited for routine use postpartum and for other situations where identification or quantitation of fetal cells is desirable.
Measurement of fetal cells in the maternal circulation.
There is evidence that the quantitation of fetal-maternal hemorrhage may be useful in reducing some of the RhoGAM failures in preventing Rh sensitization. The Betke-Kleihauer technique is a well-established method that has been used to estimate the amount of transplacental hemorrhage. Recently, a kit (Fetaldex) has become available for use in the detection and quantitation of fetal-maternal hemorrhage. Using control blood smears, we compared the results of the Fetaldex kit with those results obtained by the Betke-Kleihauer technique. The data indicate that the Fetaldex method is as accurate as the Betke-Kleihauer technique in detecting and measuring fetal red cells in the maternal circulation.
Influence of fetal growth patterns on sonographic estimation of fetal weight.
Six published fetal weight estimating regression models proposed for clinical use were evaluated in 259 pregnant women who delivered within 72 h of an ultrasound evaluation performed with sector scanner. The patient sample included 89 (33.2%) fetal weights that were below the 10th or above the 90th percentile for menstrual age. The actual mean percent error (systematic error), standard deviation (random error), and the number of large errors of prediction for all equations were greatest in fetuses that were small- and large-for-gestational age. Whereas there were no significant differences between equations for the patient sample as a whole, equation AC,BPD (Shepard) had the smallest systematic error in intrauterine growth retarded, premature, and normal-term fetuses less than 4000 g. Conversely, the systematic error of the models that included femur length was smallest at the upper end of the weight scale and in macrosomic fetuses in general. In that regard, the accuracy of fetal weight prediction could be increased by selecting the appropriate model for the proper clinical indications. Although these findings can be explained by the limitations of the current regression models in estimating fetal soft tissue mass, a subtle effect of the use of the sector scanner on the results of this study cannot be completely excluded and requires further investigation.
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.