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Biomedical subjects

R O Davis

Publications and source records attributed to R O Davis.

At least 55 records · Page 3Linked to original sources
PubMed1992

Accuracy and precision of the CellForm-Human automated sperm morphometry instrument.

OBJECTIVE: To evaluate the accuracy and precision of the CellForm-Human (CFH) automated sperm morphometry instrument (Motion Analysis Corp., Santa Rosa, CA). SETTING: Clinical and research andrology and in vitro fertilization laboratories. PATIENTS: Individuals undergoing semen evaluation and infertility work-up. RESULTS: Coefficients of variation for repeated measures of the same sperm were 1%. Coefficients of variation of normal sperm measurements were 7.4% to 12.8%, depending on the measure. Of the objects recognized as sperm by the instrument, 6.8% were debris; hence, the sperm recognition algorithms need improvement. Mean values for all CFH measures of normal sperm from specimens clinically classified as having predominantly normal, tapered, or amorphous sperm were not different; hence, the morphometry of normal sperm from normal specimens was similar to normal sperm from specimens with two different abnormalities. The instrument classified sperm as abnormal if their length or width fell outside a critical range of values recommended by the World Health Organization. Using this method, manual and CFH classification agreed unambiguously 60% of the time. When disagreement occurred, length or width marginally exceeded the range by no more than 0.1 microns. In these cases, the technician classified sperm as normal 25% of the time and classified them as abnormal 6% of the time. Because this disagreement between methods is well below the resolution of manual methods, the overall accuracy of CFH was 91% for cell type classification. CONCLUSION: At its present stage of development, the CFH instrument exceeds the accuracy and precision of most manual approaches. With improvements in sperm recognition and type classification algorithms, it could significantly improve the reliability of morphology assays in clinical and research laboratories.

Equipment Design↗
PubMed1992

The role of digital image analysis in reproductive biology and medicine.

The use of high-speed computers, direct digitization of video images, and new methods to probe soft tissues has revolutionized our view of biology. Many of these new techniques are now commonly used in several areas of medicine, but their use in reproductive biology has just begun. At present, digital image processing is limited to a few applications in reproductive medicine, including digital colposcopy and the laboratory analysis of spermatozoon motility and cellular morphology. Early implementations of digital image processing experienced problems typical of any newly introduced high technology. Today, however, with careful attention to operational details, digital image processing instruments can be productively used in the clinical diagnosis of cervical cancer, in the laboratory diagnosis of male infertility, and in more basic cell biological research. Such instruments also promise to play a significant role in laboratory quality assurance and control and in technologist training and education. In the near future, digital image processing instruments will also be applied to other areas of reproductive laboratory medicine, such as oocyte evaluation and embryo monitoring in the in vitro fertilization laboratory.

Embryo, Mammalian↗
PubMed1992

The relationships among psychosocial profile, maternal size, and smoking in predicting fetal growth retardation.

OBJECTIVE: We explored the relationships among measures of psychosocial well-being, maternal size, and smoking in predicting infant size at birth. METHODS: Participants in this population-based cohort study were drawn from public health prenatal clinics in Jefferson County, Alabama during 1985-1988. Para 1 and 2 women were screened for 11 risk factors for low birth weight, including small stature, a previous low birth weight infant, and smoking. RESULTS: Poor scores on five of six psychosocial scales, as well as on a combined profile, were associated with a significantly higher relative risk of fetal growth retardation (FGR) only in thinner women, defined as having a body mass index less than the median (relative risk [RR] 2.11, 95% confidence interval [CI] 1.47, 3.04). A significant association between the psychosocial profile and birth weight was demonstrated for thin women in a multivariate analysis adjusting for gestational age, race, infant sex, and smoking (P = .0003). The relationship remained significant when hypertension, alcohol and drug use, and weight gain were added to the model (P = .003). In women with a body mass index above the median, a poor psychosocial profile showed little association with FGR (RR 1.20, 95% CI 0.73, 1.98) and did not have a significant association with birth weight. A poor profile had a greater association with FGR in non-smokers (RR 2.04, 95% CI 1.29, 3.22) than in smokers (RR 1.4, 95% CI 0.95, 2.06). CONCLUSIONS: Greater pre-pregnancy weight for height appears to protect against the adverse effects of a poor psychosocial profile in a population of poor, primarily black women. In thinner women, both smoking and a poor psychosocial profile were associated with a substantially increased rate of FGR, indicating a subgroup of women who may receive greater benefits from intervention programs.

Body Mass Index↗
PubMed1992

Accuracy and precision of computer-aided sperm analysis in multicenter studies.

STUDY OBJECTIVES: To develop methods of instrument calibration and standardization that enable the use of computer-aided sperm analysis (CASA) technology in multicenter studies of sperm motility. SETTING: Clinical semen evaluation for the andrology laboratory and in vitro fertilization programs. PATIENTS: Semen specimens were selected from the videotape archives of the University of California at Davis Andrology Laboratory and used to produce a videotape reference standard for CASA instrument testing and calibration. Four identical CASA instruments, two each at two sites, were used to analyze the videotape. Machine accuracy was verified by manual analysis of the videotape. RESULTS: The coefficient of variation (CV) for repeated measures was between 1% and 8% for each variable on all CASA instruments. Mean values for CASA parameters varied as a function of the digitization threshold. A minimum CV was obtained at a particular threshold setting, suggesting an optimum for each machine. Because of high within-machine precision, slight differences in mean values between machines were statistically significant for some variables and some specimens; such differences are probably not biologically significant. CONCLUSION: Multicenter standardization of CASA instrumentation is possible, but threshold settings are one source of variation that must be controlled using CVs or another means of objective calibration. One method is to adjust the threshold of each instrument until the count obtained by CASA equals the count obtained by the manual method used to determine the dilution requirements for neat semen.

Computers↗
PubMed1991

Movement characteristics of human epididymal sperm used for fertilization of human oocytes in vitro.

STUDY OBJECTIVE: To develop mathematical models using kinematic parameters from Computer-Aided Sperm Analysis (CASA) that predict the fertilization rate of sperm recovered from the caput epididymidis and to test the hypothesis that fertilization was enhanced by the presence of specific sperm subpopulations in the inseminate. SETTING: In vitro fertilization (IVF) program. PATIENTS: Thirteen patients with congenital absence of the vas deferens provided epididymal sperm for IVF as well as for CASA. RESULTS: The mathematical model that was most predictive of fertilization rates included kinematic parameters of the epididymal aspirate (percent motility), the inseminate used for IVF (curvilinear velocity [VCL]), and the change in sperm movement after in vitro processing by the mini-Percoll technique (difference in amplitude of lateral head displacement [ALH]). Multivariate cluster analysis revealed that inseminates that resulted in higher fertilization rates had subpopulations of sperm that were characterized by high VCL and high mean angular displacement, as well as a greater change in ALH after processing. CONCLUSION: In vitro fertilization with epididymal sperm was more likely to succeed when the sperm population that was initially aspirated had a higher proportion of motile cells and when these sperm were capable of capacitation in vitro as indicated by the appearance of sperm subpopulations with motility that resembled hyperactivation.

Diagnosis, Computer-Assisted↗
PubMed1991

Management of prenatally detected nonlethal fetal anomalies: is a karyotype of benefit?

The pregnancy outcomes of 155 women who underwent an amniocentesis for a prenatal karyotype after being diagnosed by ultrasound as having one or more nonlethal structural anomalies are presented. Thirty-three (21%) patients were found to have an abnormal karyotype. Knowledge of the prenatal karyotype was useful in the subsequent management of these pregnancies. A pregnancy with a fetal anomaly diagnosed prior to 24 weeks was more likely to be terminated if an abnormal karyotype was also present. In women who were diagnosed as having a fetal anomaly with an abnormal karyotype at 24 weeks or later, only 3 of 13 (23%) infants survived the neonatal period. Knowledge of the karyotype results influenced decisions regarding the place, timing, and route of delivery in these fetuses. In 32 women, (21%) a karyotype was beneficial by avoiding maternal transport, cesarean delivery, and neonatal expenses at a Level III perinatal center.

Abortion, Induced↗
PubMed1991

Maternal serum alpha 2-macroglobulin and fetal growth retardation.

Maternal serum alpha 2-macroglobulin levels were measured twice, at approximately 18 and 30 weeks' gestation, in 289 pregnant women who later delivered at or after 37 weeks. Levels were elevated as early as 18 weeks' gestation in women destined to have a growth-retarded infant, and this elevation persisted through 30 weeks' gestational age. Furthermore, levels were higher in white women than black, in smokers than in non-smokers, and in thin than in heavier women. When the effect of alpha 2-macroglobulin on birth weight was evaluated in a multiple regression analysis adjusting for gestational age, race, body size, smoking, fetal sex, and a history of a low birth weight infant, high alpha 2-macroglobulin levels were associated with a statistically significant decrease in birth weight. The effect was greater in women who smoked. This relationship did not appear to be associated with differences in serum zinc or hematocrit levels.

Adult↗
PubMed1991

Fetal obstructive uropathies. Importance of chromosomal abnormalities and associated anomalies to perinatal outcome.

The ultrasound records of 30 fetuses suspected of having an obstructive uropathy were reviewed retrospectively. A prenatal karyotype was obtained with amniocentesis on each patient. After delivery, neonatal urologic records, renal ultrasound reports and autopsy information were reviewed and compared to the ultrasound records and fetal karyotype results. Chromosomal defects were found in 23% of fetuses with a suspected obstructive fetal uropathy. In five patients the chromosomal abnormality was lethal and caused 45% of the perinatal deaths in this series. If a fetus with an obstructive uropathy was female, there was a significant likelihood of an extrarenal anomaly or a complex genitourinary tract malformation. Seventeen percent of patients with an obstructive uropathy had a coexistent extrarenal defect. A prenatal karyotype should be obtained if a fetal obstructive uropathy is suspected antenatally since lethal chromosomal defects are an important cause of perinatal death. A female karyotype may indicate a fetus at higher risk of extrarenal anomalies or complex genitourinary malformations.

Adult↗
PubMed1991

Black-white differences in newborn anthropometric measurements.

The mean birth weight of black infants is consistently less than that of white infants. In 1518 low-income multiparous women, the mean difference in singleton births was 171 g, of which 38 g was partitioned to preterm births and another 35 g reflected lower gestational ages in term births. A series of regression analyses were used to determine the effect of black race on various newborn measurements in 1205 term newborns, adjusting for other known risk factors. In this model, black race accounted for a mean decrease of 148 g in weight and 0.52 cm in length. There were also significant decreases in mean head (0.44 cm), chest (0.66 cm), and abdominal (0.56 cm) circumferences. Arm and leg lengths were not different, but black arm circumferences (0.14 cm) were significantly larger. Triceps and thigh skin fold measurements were not statistically different, but black subscapular skin fold values were significantly smaller (0.17 mm). The ponderal index in blacks was significantly less than in whites. These data suggest that in this population, intrinsic and/or extrinsic factors associated with race account for most smaller black newborn measurements and for much of the racial difference in birth weight.

Alabama↗
PubMed1991

Etiologies of preterm birth in an indigent population: is prevention a logical expectation?

To assess the expectations of preterm birth prevention, we determined the causes of preterm birth in a population of indigent women. We studied 13,119 singleton births in a predominantly black, indigent population occurring between November 1982 and April 1986 to identify the proportion of preterm births that may have been prevented using current treatment modalities. Forty-four percent of the preterm births occurred at 35 to 36 weeks' gestational age, a time when most practitioners do not attempt tocolysis. Of the remainder, 17% occurred before 35 weeks but were indicated for maternal medical or obstetric complications, and another 17% occurred before 35 weeks but followed spontaneous premature rupture of the membranes. Therefore, of the 1445 preterm births, we calculated that only 336 (23.2%) were theoretically preventable. A fourth of these presented at less than 3 cm cervical dilatation and were treated appropriately with tocolytics, but delivered anyway. Therefore, most of the potentially preventable births occurred in the group that presented with cervical dilatation of more than 3 cm. We conclude that improving the preterm birth rate significantly below current levels may be difficult to achieve.

Black People↗
PubMed1990

Smoking, maternal age, fetal growth, and gestational age at delivery.

The relationship between smoking and maternal age and their combined effects on birth weight, intrauterine growth retardation, and preterm delivery were studied. Smoking lowers birth weight both by decreasing fetal growth and by lowering gestational age at delivery. However, the effect of smoking on both fetal growth and gestational age is significantly greater as maternal age advances. In a multiple logistic regression model adjusting for race, parity, marital status, maternal weight, weight gain, and alcohol use, smoking was associated with a fivefold increased risk of growth retardation in women older than 35 but less than a twofold increased risk in women younger than 17. Smoking reduced birth weight by 134 gm in young women but 301 gm in women older than 35. Smoking in older women also was associated with more instances of preterm delivery and a lower mean gestational age when compared to women 25 or younger.

Birth Weight↗
PubMed1990

Warning symptoms, uterine contractions, and cervical examination findings in women at risk of preterm delivery.

The presence of various reputed warning signs of preterm labor, the frequency of contractions, and the presence of cervical examination findings and their value in predicting preterm labor and spontaneous preterm delivery were assessed. The frequency of contractions and all cervical examination findings increased during pregnancy, as did backache, pressure, and cramping. The frequency of diarrhea, discharge, and bleeding remained constant. Of the various warning signs, only diarrhea and discharge were associated with the diagnosis of preterm labor. None of the warning signs were associated with spontaneous preterm delivery. Various patterns of contractions tended to be associated with higher rates of preterm labor and preterm delivery, but results were generally not statistically significant. Most cervical examination findings were statistically associated with both preterm labor and preterm delivery.

Adult↗
PubMed1990

Is indicated or spontaneous preterm delivery more advantageous for the fetus?

We performed a case-control study to determine whether fetuses delivered prematurely because of pregnancy complications (primarily pregnancy-associated hypertensive disease) had a different neonatal course than that of those born after either spontaneous preterm labor or after premature rupture of the membranes. Two case-control populations were matched by gestational age at delivery, fetal sex, and race. There was no perinatal survival advantage in babies delivered from "stressed" pregnancies. Selected neonatal morbidities were generally similar, but there was an increased incidence of necrotizing enterocolitis in babies born after preterm labor and a higher incidence of both necrotizing enterocolitis and neonatal sepsis after premature rupture of the membranes. We conclude that a "stressed" pregnancy confers a negligible survival advantage to the fetus.

Adult↗
PubMed1990

Evaluation of a risk scoring system as a predictor of preterm birth in an indigent population.

A risk scoring system designed to predict spontaneous preterm birth was implemented in a large, indigent population as part of a multicenter trial of preterm birth prevention. A total of 7478 women with singleton gestations were screened and followed up prospectively at the Birmingham project center. Patients who had an indicated preterm delivery or a fetal anomaly were excluded from the study population. Analysis by assigned risk score and parity showed that, whereas the sensitivity and positive predictive value were better in multiparous women than in nulliparous women, overall the values were low. Logistic regression analyses of the multiparous and nulliparous populations showed independent sets of significant (p less than or equal to 0.05) risk variables. A history of preterm delivery and a low prepregnancy weight were the most predictive risk factors in the multiparous and nulliparous models, respectively. We conclude that the clinical usefulness of a risk scoring system to predict spontaneous preterm birth in an indigent population is limited.

Age Factors↗
PubMed1990

The relationship between maternal serum and amniotic fluid alpha-fetoprotein in women undergoing early amniocentesis.

alpha-Fetoprotein levels were measured on 148 paired samples from the maternal serum and amniotic fluid in women greater than or equal to age 35, who were undergoing early amniocentesis (12 to 14 weeks) for chromosomal analysis. These 148 women were white, weighed less than 200 pounds, had no serious medical problems, and did not have a fetal abnormality detected by ultrasonography or karyotype analysis. There was a significant rise in the maternal serum alpha-fetoprotein concentration from 12 to 14 weeks' gestation. Amniotic fluid alpha-fetoprotein peaked at 13 weeks and then significantly declined by 14 weeks' gestation. Similar to reports from normal pregnancies at 16 and 17 weeks, we found no correlation between the maternal serum and amniotic fluid alpha-fetoprotein levels between 12 and 14 weeks. Amniotic fluid alpha-fetoprotein levels cannot be predicted by levels in the maternal serum in pregnancies between 12 and 14 weeks' gestation.

Adult↗
PubMed1990

Screening tests for intrauterine growth retardation: a comparison of umbilical artery Doppler to real-time ultrasound.

In a study designed to compare Doppler umbilical artery velocimetry to ultrasound morphometric measurements in the prediction of intrauterine growth retardation, 636 paired ultrasound and Doppler umbilical artery examinations were performed between 24 and 40 weeks gestational age. Intrauterine growth retardation was defined as birth weight less than the tenth percentile per gestational age and 25 (9.2%) of the infants born in our study met this criteria. In general, when the gestational age was limited to less than 30 weeks, none of the tests were highly predictive of intrauterine growth retardation. Doppler umbilical artery systolic-to-diastolic ratios of greater than 3 had the highest sensitivity. However, due to inclusion of a large number of false-positives, it was considered a poor test. After 30 weeks, fetal abdominal circumference less than the tenth percentile had a greater sensitivity (45%) and positive predictive value (28%) than Doppler systolic-to-diastolic ratios greater than 3 (36% and 18%, respectively). Doppler ultrasound umbilical artery systolic-to-diastolic ratios are not more predictive of intrauterine growth retardation than ultrasound morphometric measurements.

Birth Weight↗
PubMed1990

The Alabama preterm birth prevention project.

A preterm birth prevention program consisting of risk scoring, intensive weekly observation including cervical examinations, and detailed education about preterm labor signs and symptoms was tested in a predominantly black, indigent population. One thousand high-risk women were randomized to treatment or control groups. Although more preterm labor was diagnosed and treated in the treatment group, there were no significant differences between the groups with respect to mean birth weight or gestational age, spontaneous preterm delivery rates, or low or very low birth weight rates. The rates of respiratory distress syndrome and fetal and neonatal mortality, although greater in the treatment group, were not statistically different. However, the treatment-group infants had significantly more intracranial hemorrhages and spent more days on ventilators. At this institution, the preterm birth prevention program was not effective.

Adolescent↗