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Biomedical subjects

D D Baird

Publications and source records attributed to D D Baird.

At least 19 recordsLinked to original sources
PubMed2006

Bleeding following pregnancy loss before 6 weeks' gestation.

BACKGROUND: Pregnancy loss before 6 weeks' gestation is common, but little has been reported about the associated bleeding. We compared women's bleeding following a pregnancy loss before 6 weeks' gestation with their typical menstruation. METHODS: Women provided daily urine samples while trying to become pregnant and recorded the number of pads and tampons used each day. Thirty-six women had complete bleed data for a loss before 6 weeks' gestation and one or more non-pregnant cycles. RESULTS: Mean bleed length following a pregnancy loss was 0.4 days longer than the woman's average menstrual bleed (P = 0.01), primarily because of more days of light bleeding. Although there was no overall increase in the total number of pads plus tampons used, women with losses bled less than their typical menses following pregnancies of very short duration and more than usual for the pregnancies lasting the longest. CONCLUSIONS: Overall, the bleeding associated with pregnancy loss before 6 weeks' gestation is similar to menstrual bleeding and unlikely to be recognized as pregnancy loss. The intriguing finding that pregnancies of very short duration were associated with less bleeding than the woman's typical menses might reflect endometrial factors associated with loss.

Abortion, Spontaneous↗
PubMed2006

Fertility and exposure to solvents among families in the Agricultural Health Study.

BACKGROUND: Several studies have reported associations between solvent exposure and reduced female fertility, but the evidence is inconclusive for male fertility. OBJECTIVES: To investigate the impact of solvent exposure on subfertility among families of male licensed pesticide applicators in the Agricultural Health Study cohort. METHODS: The couples enrolled between 1993 and 1997. Cross-sectional questionnaire information on work tasks was used to assess exposure to solvents. The data were limited to couples (wife aged less than 40 years) with an attempt at pregnancy in the last four years (n = 2112). RESULTS: Twenty eight per cent of the couples were defined as subfertile (not conceiving a pregnancy after at least 12 months of unprotected intercourse, regardless of whether or not a pregnancy ultimately occurred). Adjusted subfertility odds ratios (OR) for exposure to solvents were calculated with logistic regression. Female (OR 1.42, 95% CI 1.15 to 1.75) and male exposure to solvents (OR 1.21 (95% CI 0.93 to 1.57) for monthly exposure and 1.40 (95% CI 0.97 to 2.03) for daily or weekly exposure) were associated with subfertility. In farming, spouses may share or exchange jobs. To account for potential dual exposure, variables for parental exposure (either parent exposed or both parents exposed) were also defined. Both were strongly associated with subfertility (OR 1.62 (95% CI 1.20 to 2.17) and OR 2.10 (95% CI 1.22 to 3.60), respectively). CONCLUSIONS: Solvents may impair fertility of either gender, though the evidence for female effects is stronger than for male effects.

Adult↗
PubMed2005

Biomarkers of oxidative stress study II: are oxidation products of lipids, proteins, and DNA markers of CCl4 poisoning?

Oxidation products of lipids, proteins, and DNA in the blood, plasma, and urine of rats were measured as part of a comprehensive, multilaboratory validation study searching for noninvasive biomarkers of oxidative stress. This article is the second report of the nationwide Biomarkers of Oxidative Stress Study using acute CCl4 poisoning as a rodent model for oxidative stress. The time-dependent (2, 7, and 16 h) and dose-dependent (120 and 1200 mg/kg i.p.) effects of CCl4 on concentrations of lipid hydroperoxides, TBARS, malondialdehyde (MDA), isoprostanes, protein carbonyls, methionine sulfoxidation, tyrosine products, 8-hydroxy-2'-deoxyguanosine (8-OHdG), leukocyte DNA-MDA adducts, and DNA-strand breaks were investigated to determine whether the oxidative effects of CCl4 would result in increased generation of these oxidation products. Plasma concentrations of MDA and isoprostanes (both measured by GC-MS) and urinary concentrations of isoprostanes (measured with an immunoassay or LC/MS/MS) were increased in both low-dose and high-dose CCl4-treated rats at more than one time point. The other urinary markers (MDA and 8-OHdG) showed significant elevations with treatment under three of the four conditions tested. It is concluded that measurements of MDA and isoprostanes in plasma and urine as well as 8-OHdG in urine are potential candidates for general biomarkers of oxidative stress. All other products were not changed by CCl4 or showed fewer significant effects.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2005

Biomarkers of oxidative stress study III. Effects of the nonsteroidal anti-inflammatory agents indomethacin and meclofenamic acid on measurements of oxidative products of lipids in CCl4 poisoning.

Plasma and urinary levels of malondialdehyde-like products (MDA) and isoprostanes were identified as markers of in vivo lipid peroxidation in an animal model of CCl4 poisoning. We sought to determine the extent to which the formation of these oxidation products is influenced by inhibition of the cyclooxygenase enzymes which catalytically generate proinflammatory lipid peroxidation products known as prostaglandins and thromboxane. In the present studies, after induction of oxidant stress in rats with CCl4, lipid peroxidation products measured in plasma and urine demonstrate that isoprostanes and MDA can be partially inhibited by cyclooxygenase inhibitors, albeit to different extents. The lowering of isoprostane and MDA formation, however, may not to due primarily to the diminution of catalytic generation of isoprostanes or MDA by the cyclooxygenases but, rather, may be the result of the suppression of nonenzymatic lipid peroxidation. This is suggested since 8,12-iso-iPF2alpha-VI is also reduced by indomethacin, yet, unlike other isoprostanes and MDA, it is not generated catalytically by the cyclooxygenase. Thus, although the two cyclooxygenase inhibitors we tested have statistically significant effects on the measurements of both isoprostanes and MDA in this study, the results provide evidence that these lipid-degradation products primarily constitute markers of oxidative stress.

Animals↗
PubMed2003

Vaginal bleeding in very early pregnancy.

INTRODUCTION: Little is known about the occurrence and patterns of vaginal bleeding during the earliest stages of pregnancy. We explore this in a prospective study of early pregnancy. METHODS: A total of 221 healthy women kept daily diaries and provided daily urine samples while trying to become pregnant. Of these, 151 women became clinically pregnant [i.e. pregnancy that lasted >/=6 weeks beyond last menstrual period (LMP)] during the study. Diaries provided information on days with vaginal bleeding and sexual intercourse. Urine hormone assays were used to identify ovulation and implantation. Women were interviewed about their medical histories and lifestyle factors. RESULTS: A total of 14 women (9%) recorded at least 1 day of vaginal bleeding during the first 8 weeks of pregnancy. Twelve of these 14 pregnancies continued to a live birth. Bleeding tended to occur around the time when women would expect their periods, although rarely on the day of implantation. Bleeding was not associated with intercourse. CONCLUSIONS: Early bleeding in clinical pregnancies is generally light, and not likely to be mistaken for LMP. Thus, early bleeding is unlikely to contribute to errors in LMP-based gestational age. We found no support for the hypothesis that implantation can produce vaginal bleeding. Similarly, intercourse did not cause bleeding. Nearly all women with bleeding went on to have successful pregnancies.

Adult↗
PubMed2001

Natural limits of pregnancy testing in relation to the expected menstrual period.

CONTEXT: Pregnancy test kits routinely recommend testing "as early as the first day of the missed period." However, a pregnancy cannot be detected before the blastocyst implants. Due to natural variability in the timing of ovulation, implantation does not necessarily occur before the expected onset of next menses. OBJECTIVE: To estimate the maximum screening sensitivity of pregnancy tests when used on the first day of the expected period, taking into account the natural variability of ovulation and implantation. DESIGN AND SETTING: Community-based prospective cohort study conducted in North Carolina between 1982 and 1986. PARTICIPANTS: Two hundred twenty-one healthy women 21 to 42 years of age who were planning to conceive. MAIN OUTCOME MEASURES: Day of implantation, defined by the serial assay of first morning urine samples using an extremely sensitive immunoradiometric assay for human chorionic gonadotropin (hCG), relative to the first day of the missed period, defined as the day on which women expected their next menses to begin, based on self-reported usual cycle length. RESULTS: Data were available for 136 clinical pregnancies conceived during the study, 14 (10%) of which had not yet implanted by the first day of the missed period. The highest possible screening sensitivity for an hCG-based pregnancy test therefore is estimated to be 90% (95% confidence interval [CI], 84%-94%) on the first day of the missed period. By 1 week after the first day of the missed period, the highest possible screening sensitivity is estimated to be 97% (95% CI, 94%-99%). CONCLUSIONS: In this study, using an extremely sensitive assay for hCG, 10% of clinical pregnancies were undetectable on the first day of missed menses. In practice, an even larger percentage of clinical pregnancies may be undetected by current test kits on this day, given their reported assay properties and other practical limitations.

Adult↗
PubMed2001

Measures of menopausal status in relation to demographic, reproductive, and behavioral characteristics in a population-based study of women aged 35-49 years.

The purpose of this cross-sectional analysis of women aged 35-49 years from the Third National Health and Nutrition Examination Survey, conducted between 1988 and 1994, was to assess associations with menopausal status based either on menstrual cycle patterns or on elevated (>20 IU/liter) follicle-stimulating hormone. Menstrual cycle-based menopausal status was defined for women who had not had surgical menopause by months since the last period (<2, 2-12, and >12 months for pre-, peri-, and postmenopause, respectively). Logistic regression was adjusted for age, smoking, and unilateral oophorectomy. Higher body mass index (> or =30 kg/m(2) compared with < 25.0 kg/m(2)) was associated with a lower likelihood of elevated follicle-stimulating hormone (odds ratio (OR)=0.6, 95% confidence interval (CI): 0.4, 0.9) but this association was not seen with the menstrual measure of menopause. Exercise (three or more times per week) was associated with a lower likelihood of being postmenopausal on the basis of menstrual (OR = 0.3, 95% CI: 0.2, 0.7) and hormonal (OR = 0.6, 95% CI: 0.4, 1.0) measures. Alcohol use also tended to be associated with postmenopausal status by either measure, but not significantly so. There was little evidence of associations with ethnicity, education, age at menarche, number of livebirths, and oral contraceptive use. Menstrual-based definitions of menopause can be misclassified for women with menstrual irregularity. This might explain why obese women were classified menstrually as menopausal while remaining hormonally premenopausal.

Adult↗
PubMed2001

Assessing human fertility using several markers of ovulation.

In modelling human fertility one ideally accounts for timing of intercourse relative to ovulation. Measurement error in identifying the day of ovulation can bias estimates of fecundability parameters and attenuate estimates of covariate effects. In the absence of a single perfect marker of ovulation, several error prone markers are sometimes obtained. In this paper we propose a semi-parametric mixture model that uses multiple independent markers of ovulation to account for measurement error. The model assigns each method of assessing ovulation a distinct non-parametric error distribution, and corrects bias in estimates of day-specific fecundability. We use a Monte Carlo EM algorithm for joint estimation of (i) the error distribution for the markers, (ii) the error-corrected fertility parameters, and (iii) the couple-specific random effects. We apply the methods to data from a North Carolina fertility study to assess the magnitude of error in measures of ovulation based on urinary luteinizing hormone and metabolites of ovarian hormones, and estimate the corrected day-specific probabilities of clinical pregnancy. Published in 2001 by John Wiley & Sons, Ltd.

Algorithms↗
PubMed2001

Likelihood of conception with a single act of intercourse: providing benchmark rates for assessment of post-coital contraceptives.

Emergency post-coital contraceptives effectively reduce the risk of pregnancy, but their degree of efficacy remains uncertain. Measurement of efficacy depends on the pregnancy rate without treatment, which cannot be measured directly. We provide indirect estimates of such pregnancy rates, using data from a prospective study of 221 women who were attempting to conceive. We previously estimated the probability of pregnancy with an act of intercourse relative to ovulation. In this article, we extend these data to estimate the probability of pregnancy relative to intercourse on a given cycle day (counting from onset of previous menses). In assessing the efficacy of post-coital contraceptives, other approaches have not incorporated accurate information on the variability of ovulation. We find that the possibility of late ovulation produces a persistent risk of pregnancy even into the sixth week of the cycle. Post-coital contraceptives may be indicated even when intercourse has occurred late in the cycle.

Coitus↗
PubMed2001

No evidence for lipid peroxidation in severe preeclampsia.

OBJECTIVE: This study was undertaken to address the role of oxidative stress in preeclampsia. STUDY DESIGN: We measured urinary 8,12-iso-iPF(2alpha)-VI, a chemically stable, free-radical catalyzed product, in a case control study of severe preeclampsia nested within the trial of Calcium for Preeclampsia Prevention. Cases included 29 women who developed severe preeclampsia and from whom urine had been obtained 10 to 20 weeks before the diagnosis of preeclampsia, 3 to 9 weeks before, and 1 day before through delivery. Controls did not develop hypertension or proteinuria and were matched to cases by center, gestational age at each of 3 corresponding urine collections, and date of enrollment. RESULTS: Urinary 8,12-iso -iPF(2alpha)-VI did not differ significantly between cases and controls before or at diagnosis of preeclampsia, nor did it vary with gestational age. CONCLUSIONS: These results call into question the importance of oxidative stress in the disease and the biochemical rationale for clinical trials of antioxidants to prevent and treat preeclampsia.

Adult↗
PubMed2001

A flexible parametric model for combining current status and age at first diagnosis data.

In some cross-sectional studies of chronic disease, data consist of the age at examination, whether the disease was present at the exam, and recall of the age at first diagnosis. This article describes a flexible parametric approach for combining current status and age at first diagnosis data. We assume that the log odds of onset by a given age and of detection by a given age conditional on onset by that age are nondecreasing functions of time plus linear combinations of covariates. Piecewise linear models are used to characterize changes across time in the baseline odds. Methods are described for accommodating informatively missing current status data and inferences based on the age-specific incidence of disease prior to a landmark event (e.g., puberty, menopause). Our formulation enables straightforward maximum likelihood estimation without requiring restrictive parametric or Markov assumptions. The methods are applied to data from a study of uterine fibroids.

Adult↗
PubMed2000

The timing of the "fertile window" in the menstrual cycle: day specific estimates from a prospective study.

OBJECTIVES: To provide specific estimates of the likely occurrence of the six fertile days (the "fertile window") during the menstrual cycle. DESIGN: Prospective cohort study. PARTICIPANTS: 221 healthy women who were planning a pregnancy. MAIN OUTCOME MEASURES: The timing of ovulation in 696 menstrual cycles, estimated using urinary metabolites of oestrogen and progesterone. RESULTS: The fertile window occurred during a broad range of days in the menstrual cycle. On every day between days 6 and 21, women had at minimum a 10% probability of being in their fertile window. Women cannot predict a sporadic late ovulation; 4-6% of women whose cycles had not yet resumed were potentially fertile in the fifth week of their cycle. CONCLUSIONS: In only about 30% of women is the fertile window entirely within the days of the menstrual cycle identified by clinical guidelines-that is, between days 10 and 17. Most women reach their fertile window earlier and others much later. Women should be advised that the timing of their fertile window can be highly unpredictable, even if their cycles are usually regular.

Estrogens↗
PubMed2000

Biomarkers of oxidative stress study: are plasma antioxidants markers of CCl(4) poisoning?

Antioxidants in the blood plasma of rats were measured as part of a comprehensive, multilaboratory validation study searching for noninvasive biomarkers of oxidative stress. For this initial study an animal model of CCl(4) poisoning was studied. The time (2, 7, and 16 h) and dose (120 and 1200 mg/kg, intraperitoneally)-dependent effects of CCl(4) on plasma levels of alpha-tocopherol, coenzyme Q (CoQ), ascorbic acid, glutathione (GSH and GSSG), uric acid, and total antioxidant capacity were investigated to determine whether the oxidative effects of CCl(4) would result in losses of antioxidants from plasma. Concentrations of alpha-tocopherol and CoQ were decreased in CCl(4)-treated rats. Because of concomitant decreases in cholesterol and triglycerides, it was impossible to dissociate oxidation of alpha-tocopherol and the loss of CoQ from generalized lipid changes, due to liver damage. Ascorbic acid levels were higher with treatment at the earliest time point; the ratio of GSH to GSSG generally declined, and uric acid remained unchanged. Total antioxidant capacity showed no significant change except for 16 h after the high dose, when it was increased. These results suggest that plasma changes caused by liver malfunction and rupture of liver cells together with a decrease in plasma lipids do not permit an unambiguous interpretation of the results and impede detection of any potential changes in the antioxidant status of the plasma.

Animals↗
PubMed2000

Age at menopause and childbearing patterns in relation to mortality.

Several studies have reported increased mortality risk with early natural menopause. More recently, mortality risk was reported to be reduced among women who gave birth at age > or =40 years. The association between reproductive history and mortality was explored among 826 women in a prospective study involving 18,959 person-years of follow-up (from age 50 to 1990-1991) and 108 deaths. After adjustment for age and other covariates, the risk ratio among parous women was 1.53 (95% confidence interval: 0.58, 4.07) for natural menopause at age < or =45 years compared with > or =51 years. In contrast to a previous report, however, the highest estimated mortality risk was seen among women who gave birth in their forties (adjusted risk ratio = 2.14, 95% confidence interval: 1.05, 4.38) compared with having a last birth at ages 30-34 years.

Adolescent↗
PubMed2000

The associations of adolescent cigarette smoking, alcoholic beverage consumption, environmental tobacco smoke, and ionizing radiation with subsequent breast cancer risk (United States).

OBJECTIVES: Studies of breast cancer among survivors of the World War II atomic bomb blasts over Japan suggest that the adolescent breast may be particularly sensitive to carcinogenic insult. To further explore that possibility we examined the relationships of cigarette smoking, alcohol consumption, environmental tobacco smoke (ETS) exposure, and medical treatment with ionizing radiation during adolescence with subsequent breast cancer risk. METHODS: Data from the Carolina Breast Cancer Study, a population-based, case-control study of breast cancer in North Carolina women aged 20-74 years (864 cases, 790 controls), were analyzed. RESULTS: A modest increase in breast cancer risk was suggested for women who began to smoke cigarettes between the ages of 10 and 14 years (OR: 1.5, CI: 0.9-2.5), and for women exposed to ionizing radiation between ages 10 and 19 years to treat or monitor a medical condition (OR: 1.6, CI: 0.5-2.5). Neither exposure to ETS at home prior to age 18 years (OR: 1.1, CI: 0.9-1.3) nor initiation of alcoholic beverage consumption between ages 10 and 15 years (OR: 1.1, CI: 0.6-1.8) appeared to increase risk. CONCLUSIONS: Our results are consistent with previous evidence suggesting that some adolescent exposures could influence future breast cancer risk.

Adolescent↗
PubMed2000

Urinary oestrogen patterns in long follicular phases.

Long menstrual cycles have been associated with reduced risk of breast cancer and increased risk of osteoporosis. These observations have led to assumptions about the endogenous oestrogen exposure of women with long cycles. However, daily oestrogen profiles in long menstrual cycles have not been described. This paper examines daily urinary oestrogen profiles during the follicular phases of 416 conception and non-conception cycles. Women were aged 21-42 years, had no history of infertility and were not under treatment. Twenty-eight cycles were defined as long, with a follicular phase that lasted 24 days or more. Five patterns were observed among these long cycles, the most common being a pattern consistent with delayed emergence of a dominant follicle. Other patterns were a pattern consistent with demise and replacement of a dominant follicle, one consistent with delayed follicular recruitment, one showing a prolonged initial drop in oestrogen and one with an extended oestrogen peak. Average follicular phase oestrogen concentrations were highest in cycles with short follicular phases (7-11 days). Oestrogen concentrations from long follicular phases (24-59 days) did not differ substantially from follicular phases of usual length (12-17 days). The oestrogen profiles in long follicular phases are heterogeneous and not necessarily hypo-oestrogenic.

Adult↗
PubMed2000

Epidemiologic contributions to understanding the etiology of uterine leiomyomata.

Uterine leiomyomata are hormonally dependent tumors that are a major source of gynecologic morbidity among women of reproductive age. Relatively few studies have attempted to identify specific risk factors for these neoplasms. In this review of epidemiologic contributions to the etiology of uterine leiomyomata, we begin by outlining methodologic issues in epidemiologic studies that arise from the fact that a large proportion of uterine leiomyomata does not come to medical attention. We then review the major findings from published epidemiologic studies, which to date have focused primarily on menstrual and childbearing history, exogenous hormone use, obesity, cigarette smoking, and other lifestyle and behavioral characteristics that may in part reflect aspects of a woman's hormonal milieu. None of the potential risk factors studied have demonstrated sufficiently consistent associations to guide decisions on the primary prevention of uterine leiomyomata. Clarifying the etiology and natural history of uterine leiomyomata will require studies designed to address methodologic issues and test hypotheses involving environmental and lifestyle influences on endocrine function, as well as on other possible etiologic mechanisms. Recent advances in molecular genetics present opportunities for epidemiologic studies of uterine leiomyomata to incorporate biomarkers of somatic changes found in these tumors and to examine inherited genetic factors related to possible causal physiologic mechanisms.

Disease Progression↗