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Biomedical subjects

R O Davis

Publications and source records attributed to R O Davis.

At least 37 records · Page 2Linked to original sources
PubMed1994

Relationship between amniotic fluid and maternal blood nutrient levels.

To study the relationships between amniotic fluid and maternal blood nutrient concentrations, we obtained amniotic fluid and blood samples simultaneously from 76 pregnant women at around 17 weeks gestation. Folate and vitamin B-12 levels were measured by microbiological assay and radioassay, respectively, and zinc, copper and iron levels by atomic absorption spectrophotometry. Mean concentrations of plasma and red blood cell (RBC) folate and plasma copper of the pregnant women were 38 (+/- 1, SD), 1,501 (+/- 374) nmol/L, and 32.7 (+/- 4.8) mumol/L, respectively, all of which were higher than those of healthy non-pregnant controls (p < 0.001). Mean concentrations of plasma vitamin B-12, zinc and iron levels and RBC zinc were 320 (+/- 130) pmol/L, 12.2 (+/- 2.3), 21.7 (+/- 6.1) and 177 (+/- 30) mumol/L and these were similar to those of non-pregnant controls. Amniotic fluid folate, zinc, copper and iron concentrations were 21 (+/- 13) nmol/L, 1.4 (+/- 0.6), 1.7 (+/- 0.6) and 6.8 (+/- 2.1) mumol/L, respectively, which were significantly lower than plasma levels (p < 0.001). However, this relationship was reversed for vitamin B-12 (650 +/- 420 pmol/L). Significant correlations were found between amniotic fluid and maternal plasma and RBC for folate, and between amniotic fluid and maternal plasma for vitamin B-12 (p < 0.001). No such correlations were observed for zinc, copper and iron. There was no correlation between amniotic fluid and/or blood nutrient concentrations and pregnancy outcome including birth weight of infants.

Adult↗
PubMed1994

Unexplained elevation in maternal serum alpha-fetoprotein and subsequent fetal loss.

OBJECTIVE: To examine the frequency and timing of fetal death and its association with maternal serum alpha-fetoprotein (MSAFP) levels. METHODS: Pregnancy outcomes were evaluated in 6927 predominantly middle-class women (83% white, 17% black) who had second-trimester MSAFP determinations performed in our laboratory. All cases of multiple gestation, preexisting fetal death, and fetal malformation were excluded. RESULTS: The overall fetal death rate was 13 per 1000 (n = 90). Black women had a higher fetal death rate than white women (35.6 per 1000 versus 8.4 per 1000; P < .001). One hundred forty-eight women (2.1%) had an adjusted MSAFP multiples of the median (MoM) value of at least 2.5, which was not explained by multiple gestation, congenital anomaly, or preexisting fetal death. As the MSAFP increased, the fetal death rate increased (MoM less than 2.0, 11 per 1000; MoM 2-2.49, 29 per 1000; MoM 2.5 or greater, 95 per 1000; P < .001). Despite the increased risk of fetal death in the elevated MSAFP group, most fetal deaths (84%) occurred in women with levels below 2.5 MoM. Furthermore, the timing of fetal loss was significantly different between the group less than 2.5 MoM and the group at or above 2.5 MoM. Fetal death occurred at or after 26 weeks in 45% of the women with normal MSAFP, compared with only 14% of women with high MSAFP (at least 2.5 MoM) (P = .023). CONCLUSIONS: Women with unexplained elevations in MSAFP are at increased risk for fetal loss, with most of the losses occurring in the second trimester. Because many of these fetal deaths occur at gestational ages when the neonatal survival is very low, it is unlikely that antepartum fetal surveillance aimed at early delivery would substantially increase fetal salvage.

Chi-Square Distribution↗
PubMed1994

Risk factors for fetal death in white, black, and Hispanic women. Collaborative Group on Preterm Birth Prevention.

OBJECTIVE: To document the relation between stillbirth and various demographic, obstetric, and medical risk factors. METHODS: We analyzed the risk factors and medical origins of 403 stillbirths. The population studied included 34,350 births occurring during the March of Dimes Preterm Birth Prevention Trial. All births occurring in five perinatal centers from 1982-1986 were included in the analysis. Stillbirth was defined as those infants born at 20 weeks' gestation or later whose Apgar score was 0 at 1 and 5 minutes. RESULTS: Stillbirth occurred in 1.2% of all births. Fifty-one percent occurred before 28 weeks and only 18% were at term. Blacks had a greater risk of stillbirth when compared to other women. Prior preterm delivery yielded nearly a two-fold increase in the risk of stillbirth. Preeclampsia, chronic hypertension, and class A or class B-R diabetes were not associated with an increased risk of stillbirth. Other medical factors (hemoglobinopathies, Rh sensitization) resulted in a greater than sixfold increase in the rate of stillbirth, and congenital anomalies resulted in a fivefold increase. Abruption was associated with a 12-fold increase in the risk of stillbirth; nearly 14% of all stillbirths were associated with abruption. CONCLUSION: Eighty-two percent of all stillbirths occurred before term, and more than 50% occurred before 28 weeks. The majority of stillbirths were not explained by medical complications, but instead were often associated with other risk factors related to preterm birth. Further investigations are needed to understand the complex etiology of stillbirth.

Adolescent↗
PubMed1993

Maternal risk factors and their influence on fetal anthropometric measurements.

OBJECTIVE: Our purpose was to determine if and when maternal risk factors and fetal sex have an impact on specific fetal anthropometric measurements assessed by ultrasonography. STUDY DESIGN: Serial ultrasonographic examinations were performed on 1205 fetuses of indigent multiparous women who ultimately gave birth at term. Femur length, abdominal circumference, and head circumference measurements were obtained at mean gestational ages of 18, 25, 31, and 36 weeks, and an estimated fetal weight was calculated. At birth the infant was weighted and head circumference, abdominal circumference, femur length, and crown-heel length measurements were made. Regression analyses were used to determine the effect on each measurement of maternal race, height, body mass index, hypertension, weight gain, smoking, previous low birth weight, and fetal sex. RESULTS: Acting through their effect on head circumference, abdominal circumference, and fetal length, each of the risk factors and female sex were shown to have a negative effect on fetal weight. The timing of the impact, its magnitude, and the specific anthropometric measurement affected were different for each of the risk factors. CONCLUSIONS: The impact of maternal risk factors and fetal sex on estimated fetal weight has been demonstrated to occur first in specific gestational age windows and is mediated through effects on specific fetal anthropometric measurements.

Anthropometry↗
PubMed1993

Albumin levels in pregnancy: a hypothesis--decreased levels of albumin are related to increased levels of alpha-fetoprotein.

Serum albumin levels decrease during pregnancy while the concentration of most other maternal serum proteins of hepatic origin remain stable or increase. In a study of 289 women, most maternal characteristics such as race, age, smoking, a history of previous low birth-weight, infant sex and gestational age at delivery were not related to maternal serum albumin levels at 18 or 30 weeks' gestational age. The degree of maternal obesity significantly correlated with the concentration of albumin. There was a significant negative correlation in individual women between maternal serum levels of albumin and alpha-fetoprotein, with high levels of maternal serum alpha-fetoprotein predicting lower levels of albumin. We hypothesize that there may be a negative feedback effect of alpha-fetoprotein of fetal origin on the maternal production of albumin during pregnancy.

Body Mass Index↗
PubMed1993

A multicenter study of preterm birth weight and gestational age-specific neonatal mortality.

OBJECTIVE: This analysis was performed to present updated neonatal mortality data by age and birth weight for preterm newborns and to demonstrate the influence of plurality, ethnicity, and infant sex on mortality. STUDY DESIGN: Preterm birth weight and gestational age-specific mortality rates were compiled from the five centers that participated in the March of Dimes Multicenter Preterm Birth Prevention Project. In each center gestational age was assessed by standardized methods. A birth weight and gestational age-specific mortality chart for preterm births was created with live-birth data. RESULTS: In each birth weight group mortality decreased as the gestational age advanced; for each gestational age group heavier infants had less mortality. Female infants < 29 weeks survived better than male infants, and singletons < 29 weeks survived better than twins. Survival for black preterm newborns was better than that of whites but differences were not significant. Mortality for black term infants was significantly higher. The largest improvement in survival occurred between 25 and 26 weeks. At 30 weeks survival was > 90% and improved < 1% per week thereafter. CONCLUSIONS: When compared with rates in previous reports, mortality rates appear to have improved, especially at gestational ages < 29 weeks. These data may be useful in decision-making and in counseling patients at risk for preterm delivery.

Black or African American↗
PubMed1993

Standardization of specimen preparation, staining, and sampling methods improves automated sperm-head morphometry analysis.

OBJECTIVES: To evaluate the accuracy and performance of the CellForm-Human automated sperm morphometry instrument (Motion Analysis Corp., Santa Rosa, CA) using different specimen preparation, staining, and analysis techniques. SETTING: Clinical and research andrology and in vitro fertilization laboratories. PATIENTS: Individuals who were undergoing semen evaluation and infertility work-up. RESULTS: The percentage of normal sperm detected by CellForm-Human was not different for washed specimens compared with nonwashed controls. Washing and resuspension to a standard concentration in medium significantly increased spermatozoan density and homogeneity on the slide. Comparison of digitization errors and morphometric measures of sperm stained by the Papanicolaou (PAP) method, the hematoxylin portion of the PAP method, and a new method developed by us, GZIN (pronounced Gee-ZIN), showed that GZIN produced larger measures for length, width, area, and perimeter, but not for width/length, and also produced less variability for most measures than PAP or hematoxylin. The number of digitization errors was significantly less for GZIN than for PAP. Visual inspection revealed that GZIN produced a more consistent stain over the entire sperm head than hematoxylin. The number of sperm analyzed affected the percentage of normal sperm detected. The % normal stabilized only after at least 200 sperm had been analyzed for each man. CONCLUSIONS: Technical variability arising from semen preparation and slide staining methods can be reduced when specimens are washed and resuspended to a standard concentration before smearing. At least 200 sperm should be analyzed to obtain a stable estimate of the percentage of normal sperm. More sperm should be analyzed if the % normal is < 50%. Morphometric measurements are more accurate and precise when sperm are stained with GZIN than when stained with PAP or hematoxylin.

Cytological Techniques↗
PubMed1993

Automated morphometric analysis of stallion spermatozoa.

Tissue variation in microscope slides made for spermatozoon analysis and variation introduced by the subjective techniques used to analyze these slides reduce the statistical power of studies that seek to use spermatozoon morphology to predict fertility. A simple specimen preparation method was developed to standardize stallion spermatozoon morphologic smears, and a new, automated spermatozoa morphometry instrument was used to objectively analyze the efficacy of the specimen preparation technique. The method achieved a standard spermatozoon concentration and reduced field-to-field variation in the number of spermatozoa analyzed. Metric measurements of spermatozoon head dimensions from clinically normal, fertile stallions revealed small, but highly significant, differences between stallions. The variation in metric measurements between replicate slides within stallions was small, indicating that replicate slide analysis probably is not necessary for clinically normal stallions. Coefficients of variation were generally < 11% for metric measurements between stallions, and were < 4% within stallions. This study revealed that a high degree of statistical power can be achieved when using these new, standardized specimen preparation and objective analysis techniques. Such power makes possible the detection of subtle differences between clinically normal stallions, and may facilitate accurate detection of abnormal fertility (ie, subfertility) in stallions.

Animals↗
PubMed1993

Anthropometric assessment of body size differences of full-term male and female infants.

OBJECTIVE: To determine gender-specific differences in anthropometric characteristics of full-term male and female infants. METHODS: Twelve hundred five term newborn infants were examined. All measures of length and skinfold thickness were performed in a standardized manner. RESULTS: After adjusting for confounding variables by regression analysis, we found that nearly all length and circumference measurements were significantly smaller in female infants than in male infants but that subcutaneous fat deposition in female infants was significantly increased. However, there was no difference in the ponderal index between male and female newborns, indicating that this measure does not correlate with newborn fat deposition across the sexes. CONCLUSIONS: Despite being shorter and having smaller circumferences, female infants have more subcutaneous fat than male infants. The ponderal index is not useful as a measure of fatness when the sexes are compared. We speculate that the greater subcutaneous fat deposition in female infants may be related to their better neonatal outcomes.

Birth Weight↗
PubMed1993

Fetal biparietal diameter, head circumference, abdominal circumference and femur length. A comparison by race and sex.

Biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) were compared by race and sex in 5,405 ultrasound examinations done on 2,831 women. Black fetuses had significantly longer FL than white fetuses; male fetuses had larger BPD, HC and AC than females. The differences in BPD, HC and AC correlated with the different birth weights observed between male and female infants, 3,253 vs. 3,153 g. The difference in birth weight between black and white infants, 3,152 vs. 3,331 g, did not correlate with differences in their respective BPD, HC and AC. Earlier delivery accounted for some but not all of the birth weight difference between black and white infants. Our data suggest that there may be differences in body length proportions (longer legs and shorter trunks in black infants) that are important factors in understanding the birth weight difference between black and white infants. Furthermore, fetal race and sex differences could account for some degree of error in the ultrasound estimation of gestational age.

Abdomen↗
PubMed1992

Laboratory methods for assessing human semen in epidemiologic studies: a consensus report.

It is clear that additional methodologic work needs to be performed. Some data gaps described above are being actively investigated. Other standards were not addressed at this meeting; statistical handling of the data, differences among CASA machines, and factors to consider as potential confounders in analysis are just a few. These may be the subject of future workshops, which will also review progress made in the existing knowledge base. For now, this effort represents a first attempt to share information and to use it to encourage investigators in different laboratories to employ similar methods. In this way more direct comparisons among studies can be made, and our collective data base can be strengthened.

Computers↗
PubMed1992

Elevated levels of midtrimester maternal serum alpha-fetoprotein are associated with preterm delivery but not with fetal growth retardation.

OBJECTIVE: Our objective was to determine if the low birth weight associated with unexplained elevations of midtrimester maternal serum alpha-fetoprotein levels is due to prematurity or to fetal growth retardation. STUDY DESIGN: Rates of preterm delivery and fetal growth retardation were analyzed according to incremental maternal serum alpha-fetoprotein levels in 5555 women, predominantly white, who were screened for neural tube defects (group 1) and 843 women, predominantly black, with risk factors for low birth weight (group 2). Statistical methods included chi 2, t tests, analysis of variance, and regression analysis. RESULTS: In both groups increasing levels of maternal serum alpha-fetoprotein are significantly associated with preterm delivery but not with fetal growth retardation. The preterm delivery rate increased in each group from 8% at levels less than 0.5 multiples of the median to 18.1% (p less than 0.001) at levels greater than or equal to 2.5 multiples of the median in group 1 and 28.1% (p = 0.01) in group 2. CONCLUSIONS: Women with unexplained elevations of maternal serum alpha-fetoprotein are at increased risk for preterm delivery but not fetal growth retardation. Because of the wide availability of maternal serum alpha-fetoprotein screening, women at increased risk for preterm delivery can be identified in the midtrimester of pregnancy.

Black People↗
PubMed1992

Neonatal periventricular-intraventricular hemorrhage after maternal beta-sympathomimetic tocolysis. The March of Dimes Multicenter Study Group.

OBJECTIVE: Our objective was to determine if the rate of periventricular-intraventricular hemorrhage is increased in the offspring of women who received a beta-sympathomimetic agent as part of the management of preterm labor. STUDY DESIGN: This retrospective study consists of 2827 women who were delivered of a singleton, live infant free of congenital neurologic anomalies between 25 and 36 completed weeks of gestation during a multicenter preterm birth prevention trial. The data were analyzed, adjusting for type of tocolytic agent, race, infant sex, gestational age, birth weight, health care center, route of delivery, indication for delivery, intrapartum fetal distress, respiratory distress syndrome, and neonatal sepsis. RESULTS: The overall incidence of periventricular-intraventricular hemorrhage in this population was 5.6%. In a univariate analysis in which no adjustment was made for potentially confounding variables, beta-sympathomimetic tocolysis was found to be associated with nearly a fourfold increase in the incidence of periventricular-intraventricular hemorrhage when compared with the use of either magnesium sulfate or no tocolytic agent. The results of a multivariate regression analysis revealed that beta-sympathomimetic agents were associated with a statistically significant increase in the overall incidence of periventricular-intraventricular hemorrhage (odds ratio 2.47, 95% confidence interval 1.34 to 4.56, p = 0.004) and a similar, but not significant, increase in the incidence of grades 3 and 4 periventricular-intraventricular hemorrhage (odds ratio 2.50, 95% confidence interval 0.96 to 6.48, p = 0.06). CONCLUSION: beta-Sympathomimetic tocolytic therapy may be associated with a more than twofold increase in the incidence of neonatal periventricular-intraventricular hemorrhage.

Birth Weight↗
PubMed1992

Transverse uterine incision closure: one versus two layers.

OBJECTIVE: Closure of a low transverse cesarean incision with one layer of suture results in less operating time, better hemostasis, and less infectious morbidity than a two-layer closure. STUDY DESIGN: At our institution 906 women were randomized to closure of a low transverse cesarean incision with either one continuous layer of a locking No. 1 chromic suture and a CTX needle (n = 457) or two continuous layers of No. 1 chromic suture with the first layer locked (n = 449). The Student t test, chi 2 test of proportion, and Wilcoxon rank sum test were used to compare groups of patients. RESULTS: A one-layer closure required less operative time, 43.8 versus 47.5 minutes (p = 0.0003). Fewer additional uterine hemostatic sutures were required in 369 women in whom either the one- (n = 179) or the two-layer (n = 190) closure did not achieve hemostasis (p = 0.046). Endometritis was similar in both groups, 83 (22%) in the one-layer group versus 65 (18%) in the two-layer group (p = 0.17). In no outcome assessment was the two-layer closure superior to the one-layer closure. CONCLUSION: We recommend a one-layer closure when its use is anatomically feasible.

Adult↗
PubMed1992

Blood pressure, growth retardation, and preterm delivery.

The effect of various levels of both diastolic and systolic blood pressure at various times during pregnancy on the rates of intrauterine growth retardation (IUGR) and preterm delivery (PTD) were determined. Low systolic and diastolic pressures were associated with both IUGR and PTD, as were high pressures. Low pressures tended to be associated with spontaneous preterm deliveries, whereas high pressures were associated with more indicated preterm deliveries.

Blood Pressure Determination↗
PubMed1992

Nutrient levels in amniotic fluid from women with normal and neural tube defect pregnancies.

We analyzed nutrient levels in amniotic fluid obtained during the second trimester of normal, uncomplicated pregnancies from 221 women who delivered apparently healthy infants and from 8 with neural tube defect (NTD) pregnancies. Folate was measured by microbiological assay, vitamin B12 by a radiobinding method, and zinc, copper and iron by atomic absorption spectrophotometry. We found that the mean amniotic fluid nutrient levels of normal pregnancies were 24.7 nmol/l for folate, 600 pmol/l for vitamin B12, and 1.7, 1.9, and 9.0 mumol/l for zinc, copper and iron, respectively. Amniotic fluid folate, zinc, copper and iron levels of NTD pregnancies were similar to those found during normal pregnancy, however, vitamin B12 levels were markedly lower than those of normal pregnancies.

Adolescent↗
PubMed1992

Prenatal differentiation of ventral abdominal wall defects. Are amniotic fluid markers useful adjuncts?

We retrospectively reviewed 29 cases of ventral abdominal wall defects to evaluate the usefulness of amniotic fluid markers in the prenatal assessment of those disorders. Amniotic fluid alpha-fetoprotein (AF-AFP) values were available in 17 cases diagnosed prior to 22 weeks' gestation and acetylcholinesterase (AF-ACE) values, in 21 cases. All 7 fetuses with a gastroschisis had an elevated AF-AFP, while only 2 of the 10 fetuses with an omphalocele had elevated values (P = .002). ACE was present in 80% of the cases of gastroschisis versus 27.3% of the cases of omphalocele (P = .03). With equivocal sonographic findings, a normal AF-AFP and negative AF-ACE may be more compatible with an omphalocele.

Acetylcholinesterase↗