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D D Baird

Publications and source records attributed to D D Baird.

At least 73 records · Page 4Linked to original sources
PubMed1991

Using the ratio of urinary oestrogen and progesterone metabolites to estimate day of ovulation.

We have developed a method of estimating day of ovulation using urinary ovarian hormone data. The method identifies a day of luteal transition that occurs at the shift from production of follicular oestrogen to luteal progesterone. The algorithm for identifying this shift was evaluated and judged better than specified alternatives in that it resulted in (1) a high concordance between the day of luteal transition and peaks in urinary luteinizing hormone (LH) for cycles with well-defined peaks, (2) a low variance in the length of the luteal phase of the menstrual cycle, which presumably reflects a low measurement error in estimating day of ovulation, and (3) a high proportion of cycles for which an approximate day of ovulation could be determined. To validate the new algorithm, it was applied to an independent data set. The algorithm identified a day of luteal transition in 88 per cent of these cycles, and the identified day occurred within two days of the urinary LH peak for all the cycles with clear LH peaks. Determination of the day of luteal transition to estimate ovulation requires only first-morning urine specimens, requires no correction for day-to-day variations in urine concentration, and can be applied to a mid-cycle window of data.

Algorithms↗
PubMed1991

Hormonal profiles of natural conception cycles ending in early, unrecognized pregnancy loss.

Loss of a conceptus early in development can be detected by very sensitive assays specific for hCG. We examined 20 menstrual cycles ending in early loss of a conceptus in order to identify hormonal correlates of loss. Each loss cycle was compared to a successful conception cycle in the same woman, using daily concentration of urinary estrone-3-glucuronide and pregnanediol-3-glucuronide (PdG). The estrone-3-glucuronide and PdG profiles in cycles of early pregnancy loss were very similar to those in successful conception cycles until late in the luteal phase. Early pregnancy loss was not related to a midluteal deficiency in PdG. hCG tended to be detected later in cycles of early pregnancy loss than in successful conception cycles, presumably indicating later implantation. Ten of the early pregnancy losses implanted after luteal-day-10; only one of the successful pregnancies implanted that late. The corpus luteum responded to the conception in only 2 of the 10 loss cycles with late implantation. In contrast, the corpus luteum responded in 8 of 10 loss cycles with normally timed implantation. The similarity of preimplantation hormonal profiles in cycles of early pregnancy loss and in cycles with successful conceptions suggests that most early losses in reproductively normal women do not result directly from deficiencies in ovarian steroid production.

Abortion, Spontaneous↗
PubMed1990

Increased risk of preterm birth for women with inflammatory bowel disease.

The reproductive histories of 177 women with Crohn's disease and 84 women with ulcerative colitis were compared with those of healthy control subjects. Inflammatory bowel disease was associated with reduced fertility as measured by number of pregnancies, but measures of childlessness, infertility, fecundability, and methods of birth control suggested that this reduced fertility was the patients' choice rather than a consequence of disease-mediated biological impairments. There was no evidence of increased risk of pregnancy loss, but the risk of preterm birth was significantly elevated for patients with Crohn's disease (odds ratio, 3.1; 95% confidence interval, 1.8-5.4) and for those with ulcerative colitis (odds ratio, 2.7; 95% confidence interval, 1.8-5.4). Several plausible biological mechanisms that could explain the link between preterm birth and inflammatory bowel disease are suggested. These results may be useful when counseling patients who desire pregnancy. Physicians can reassure patients about potential fertility problems but should also encourage close obstetrical monitoring during the third trimester of pregnancy.

Adult↗
PubMed1990

Risk factors for early pregnancy loss.

We looked at risk of early pregnancy loss among 171 women who conceived while participating in study. Twenty-five percent of biochemically detected pregnancies ended within six weeks of the last menstrual period; all but two of these losses were clinically unrecognized. While our sample is small, it is the first to allow description of possible associations between risk of early pregnancy loss and maternal characteristics or exposures. We looked at risk in relation to a woman's age, pregnancy history, weight, education, prenatal DES exposure, cigarette smoking, use of caffeinated and alcoholic beverages, marijuana, cigarette smoking by baby's father, and other variables. None of these factors was definitely associated with early pregnancy loss. Still, the possibility of real effects cannot be excluded and deserves further study.

Abortion, Spontaneous↗
PubMed1989

Reduced fecundability in women with prenatal exposure to cigarette smoking.

Animal studies have suggested that fertility may be impaired by transplacental exposures, but little is known about human prenatal exposures and subsequent adult reproduction. A possible relation between prenatal exposure to cigarette smoking and adult fecundability in women was explored, with the use of data from a prospective study of 221 North Carolina couples. These couples were recruited during 1983-1985, at the time they stopped using birth control in order to become pregnant. The relative fecundability of exposed compared with unexposed women was estimated by applying a discrete-time proportional probabilities model to the cycle-by-cycle conception rates. Women with prenatal exposure to their mother's cigarette smoking had reduced fecundability. The fecundability ratio associated with prenatal exposure to mother's smoking, adjusted for age, frequency of intercourse, current smoking status, age at menarche, and childhood exposure to cigarette smoking, was 0.5 (95% confidence interval 0.4-0.8). This association was not changed by further adjustment for other possible confounding variables, including educational level, reproductive history, body weight, and consumption of alcohol and caffeine. Thus, women whose mothers smoked while pregnant with them may be on average substantially less fecund than women whose mothers did not smoke during pregnancy.

Adult↗
PubMed1989

Do women with childhood exposure to cigarette smoking have increased fecundability?

The authors earlier conducted a retrospective study of time to pregnancy among a group of pregnant women in Minnesota, in order to investigate the relation between cigarette smoking and fecundability. Further analysis of these data shows that women who had been exposed as children to cigarette smokers had increased fertility. This finding lacks biologic plausibility. However, the authors found a similar association in a group of North Carolina women whose fecundability had been measured prospectively. Furthermore, both groups showed an apparent dose-response effect. The authors briefly describe this unexpected finding so that it might be more fully explored in other studies.

Fathers↗
PubMed1988

Incidence of early loss of pregnancy.

We studied the risk of early loss of pregnancy by collecting daily urine specimens from 221 healthy women who were attempting to conceive. Urinary concentrations of human chorionic gonadotropin (hCG) were measured for a total of 707 menstrual cycles with use of an immunoradiometric assay that is able to detect hCG levels as low as 0.01 ng per milliliter, with virtually 100 percent specificity for hCG in the presence of luteinizing hormone. Our criterion for early pregnancy--an hCG level above 0.025 ng per milliliter on three consecutive days--was determined after we compared the hCG levels in the study group with the levels in a comparable group of 28 women who had undergone sterilization by tubal ligation. We identified 198 pregnancies by an increase in the hCG level near the expected time of implantation. Of these, 22 percent ended before pregnancy was detected clinically. Most of these early pregnancy losses would not have been detectable by the less sensitive assays for hCG used in earlier studies. The total rate of pregnancy loss after implantation, including clinically recognized spontaneous abortions, was 31 percent. Most of the 40 women with unrecognized early pregnancy losses had normal fertility, since 95 percent of them subsequently became clinically pregnant within two years.

Abortion, Spontaneous↗
PubMed1988

Using time-to-pregnancy data to study occupational exposures: methodology.

Occupational and environmental influences on fertility are for the most part unstudied, partly because sensitive methods for studying them have not been developed. We are developing a measure of fecundability, the monthly probability of pregnancy, by studying time to pregnancy, the number of noncontracepting menstrual cycles each couple requires to conceive. The relationship of this measure of reproductive impairment with others, such as spontaneous abortion, is not known. Preliminary data from two sources suggest that reduced fertility is not highly correlated with increased risk of spontaneous abortion, despite predictions to the contrary from the toxicology literature. A current study of occupational exposures of dental assistants will address questions of data quality by providing comparisons of brief responses from mail questionnaires and telephone interviews with very detailed data from telephone interviews. This study also will allow estimation of the magnitude of two potential selection biases: selection of only planned pregnancies (time-to-pregnancy data for accidental pregnancies are not meaningful), and selection against highly infertile and sterile couples (when studying currently or previously pregnant women, sterile couples are not represented at all and highly infertile couples are underrepresented).

Female↗
PubMed1987

The use of biochemical assays in epidemiologic studies of reproduction.

Recent progress in the assay of urinary hormones has opened new opportunities for epidemiologists to study hormones and health outcomes. This is especially true for studies of female reproduction. The cyclic nature of female reproduction can be fully described only by continuous frequent measurements that, in order to be practical, require easily collected biological specimens. We describe our experience in collecting and analyzing daily urine specimens from 301 healthy women. We conclude that this approach is not only feasible but potentially of great value to epidemiologists for studying fertility, early pregnancy, the effects of toxic exposures on reproduction, and the relationships between reproduction and later risk of chronic diseases.

Adult↗
PubMed1986

Use of time to pregnancy to study environmental exposures.

There is need in reproductive epidemiology for sensitive and convenient screening tools that can be used to study environmental and occupational exposures. The measurement of fecundability (the probability of pregnancy in each cycle) by ascertaining how long it takes couples to conceive, may be useful for this purpose. Theoretically, exposures that interfere with any of the biologic processes involved in achieving pregnancy could lower fecundability among exposed men or women. To evaluate problems with collecting data on time to pregnancy, telephone interviews were conducted with nearly 700 pregnant women who reported having planned their pregnancies. Power curves were developed based on the distribution of time to pregnancy in the interviewed population. These curves indicate that relatively small sample sizes are sufficient for investigating an exposure. For example, the authors estimate that to detect a given 50% drop in mean fecundability with 80% power would require data from 55 exposed and 55 unexposed women who are pregnant. Disadvantages of using time to pregnancy as a reproductive endpoint include susceptibility to selection bias and need for data on several potential confounding variables. The next step in evaluating time to pregnancy as a reproductive endpoint is to apply it in studies of environmental or occupational exposures.

Adult↗
PubMed1986

Future fertility after prenatal exposure to cigarette smoke.

The authors tested the hypotheis that prenatal exposure to cigarette smoke is associated with impaired fertility in adulthood. Fertility for nearly 600 couples was quantified by counting the number of noncontraception cycles required to conceive. Exposure in utero was assessed by asking couples about their parents' cigarette smoking. In contrast to data on laboratory animals, husbands and wives prenatally exposed to cigarette smoke showed no evidence of reduced fertility. In exploratory analyses, prenatal exposure to cigarette smoke was associated with semen abnormalities. Although this observation was based on small numbers, it has biologic plausibility and warrants further investigation.

Behavior↗
PubMed1986

Future fertility after prenatal exposure to cigarette smoke.

We tested the hypothesis that prenatal exposure to cigarette smoke is associated with impaired fertility in adulthood. Fertility for nearly 600 couples was quantified by counting the number of noncontraception cycles required to conceive. Exposure in utero was assessed by asking couples about their parents' cigarette smoking. In contrast to data on laboratory animals, husbands and wives prenatally exposed to cigarette smoke showed no evidence of reduced fertility. In exploratory analyses, prenatal exposure to cigarette smoke was associated with semen abnormalities. Although this observation was based on small numbers, it has biologic plausibility and warrants further investigation.

Adolescent↗
PubMed1985

Menopausal change in serum cholesterol. Black/white differences in Evans County, Georgia.

The relationship between menopausal status and total serum cholesterol was examined cross-sectionally in a population of 40- to 54-year-old black and white women of Evans County, Georgia. The relationship differed in blacks and whites as assessed by a significant interaction term in linear regression. Controlling for age, Quetelet index, and smoking status, white postmenopausal women showed an estimated increase in total serum cholesterol of 25 mg/dl (p less than 0.001) compared with premenopausal whites, whereas black postmenopausal women showed no significant increase in total serum cholesterol compared with premenopausal blacks. The authors were unable to attribute the lack of menopausal effect in blacks to selection or measurement bias, nor did confounding or effect modification by obesity or social status negate their findings. Of six other populations in which menopausal influence on total serum cholesterol has been examined, only Pima Indians failed to show a significant increase.

Adult↗
PubMed1985

Bilateral distribution of implantation sites in small mammals of 22 North American species.

The distribution of activity between the left and right sides of the reproductive tract, as measured by numbers of CL, embryos and placental scars, was studied in small mammals of 22 species. Shrews ovulate from the two ovaries in a distribution that does not differ from the binomial. Implantation of blastocysts in the two uterine horns is more nearly even ('balanced') than would be predicted from the binomial distribution. Balance in this group apparently is achieved by transuterine migration of blastocysts, perhaps in conjunction with some spacing mechanism within the uterus. Some cricetid rodents show little or no balance, but in others the distribution of activity sites (embryos, CL and placental scars) departs significantly from the binomial distribution. Reproductive activity sites of heteromyid and geomyid rodents (Geomyoidea) are highly balanced; uterine balance apparently is achieved by means of ovarian rather than uterine control. We know of no previous reports of ovarian balance and suggest that physiological mechanisms controlling numbers of ovulations in the species exhibiting this characteristic may differ from those in species exhibiting a random distribution of ovulation sites. Hypotheses regarding evolutionary aspects of balance are considered in phylogenetic and ecological terms, generating several testable research questions for physiologists, anatomists, and evolutionary ecologists.

Animals↗
PubMedDate not supplied

Sources of bias in studies of time to pregnancy.

Among sexually active couples who are not using contraception, there is considerable heterogeneity in fertility, even among those who eventually achieve pregnancy. The number of menstrual cycles required, measured in integer time, is greatly overdispersed compared to the geometric, suggesting that the per cycle probability of conception varies considerably among couples. Some of this variability may reflect the effect of reproductive toxicants on fertility, and studies of time to pregnancy can be useful in identifying such toxic effects. We describe models for analysing time-to-pregnancy data, and discuss seven sources of bias that can lead the reproductive epidemiologist to spurious conclusions. Certain analytic and design strategies can help protect against some of the pitfalls.

Adult↗
PubMedDate not supplied

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. II. Female reproductive disorders.

Members of the workgroup on female reproductive disorders discussed methods to evaluate five principal functions: menstrual dysfunction, infertility, pregnancy loss, lactation disorders, and pregnancy complications. To test each function, a nested strategy was considered, based on progressive levels of effort available to conduct field investigations. This strategy was analogous to the three-tier classification of biomarkers used by other workshops. The lowest level of effort, corresponding to Tier 1, consists only of questionnaires, diaries, and reviews of maternal and infant medical records. The medium level of effort (Tier 2) collects data from questionnaires and diaries, and some biologic specimens. Suggested laboratory analyses included measurement of progesterone in saliva and several glycoprotein hormones in urine that evaluate menstrual dysfunction, infertility, and pregnancy loss. The highest level of effort (Tier 3) involves prospective collection of diary information and simultaneous collection of biological specimens.

Abortion, Spontaneous↗