Biomedical subjects

D D Baird

Publications and source records attributed to D D Baird.

At least 55 records · Page 3Linked to original sources

PubMed1995

Fertility in men exposed prenatally to diethylstilbestrol.

BACKGROUND: Prenatal exposure to diethylstilbestrol causes infertility in male mice and has been associated with malformations of the genital tract in men. However, little is known about the fertility of men who have been exposed prenatally to diethylstilbestrol. METHODS: In 1950 through 1952, 1646 pregnant women were enrolled in a randomized, placebo-controlled clinical trial of diethylstilbestrol at Chicago Lying-in Hospital. We interviewed men who were born to the women during that study about their fertility. RESULTS: Four decades after their birth, we were able to trace 548 of the surviving sons (68 percent). Ninety percent consented to be interviewed (253 who had been exposed to diethylstilbestrol in utero and 241 who had not been exposed). Congenital malformations of the genitalia were reported three times as often by the diethylstilbestrol-exposed men as by the sons of the women in the placebo group. Within the exposed group, malformations were reported twice as often among those exposed to diethylstilbestrol before the 11th week of gestation as among those exposed later (P = 0.05). Men with genital malformations were nonetheless as fertile as other men. The diethylstilbestrol-exposed men (with or without genital malformations) had no impairment of fertility by any measure, including whether they had ever impregnated a women, age at the birth of their first child, average number of children, medical diagnosis of a fertility problem, or length of time to conception in the most recent pregnancy of the female partner. Finally, diethylstilbestrol-exposed men had no impairment of sexual function, as indicated, for example, by the frequency of intercourse or reported episodes of decreased libido. CONCLUSIONS: High doses of diethylstilbestrol did not lead to impairment of fertility or sexual function in adult men who had been exposed to the drug in utero.

Abnormalities, Drug-Induced↗

PubMed1995

A study of milk and calcium supplement intake and subsequent preeclampsia in a cohort of pregnant women.

To test the hypothesis that high calcium intake protects against preeclampsia, the relation between milk intake and preeclampsia was examined in a cohort of 9,291 pregnant women (7,104 white women and 2,187 black women) selected from the Child Health and Development Study population assembled by the University of California, Berkeley, during 1959-1966. Exposure was based on glasses of milk per day with and without calcium supplements. Data from both white and black women displayed a U-shaped distribution of preeclampsia risk in relation to milk and milk plus supplement intake. Logistic regression analysis showed that women who drank two glasses of milk per day had the lowest risk (reference category). The relative risk (RR) for those drinking one glass of milk per day was similarly low (RR = 1.2; 95 percent confidence interval (CI) 0.7-2.0), but risk for those drinking less than one glass of milk per day was substantially higher (RR = 1.9; 95 percent CI 1.2-2.9). Women drinking three or more glasses of milk per day also showed increased risk (RR = 2.0; 95 percent CI 1.2-3.4) as did those drinking four or more glasses per day (RR = 1.8; 95 percent CI 1.1-3.0). The increased risk associated with low milk intake is consistent with studies showing reduced blood pressure with increased calcium intake. The increased risk with high milk intake has not been demonstrated previously.

Adult↗

PubMed1995

Nitrous oxide and spontaneous abortion in female dental assistants.

The relation between anesthetic gas exposure and spontaneous abortion remains unresolved. We examined the effect of nitrous oxide on spontaneous abortion among female dental assistants. Questionnaires were sent to 7,000 dental assistants aged 18-39 years who were registered in California in 1987; 4,856 (69%) responded. Analysis was based on 1,465 respondents whose most recent pregnancy was conceived while working full time. Women were asked how many hours a week they worked with nitrous oxide during this pregnancy and whether the excess gas was scavenged (vented). Relative risk of spontaneous abortion (through week 20) was calculated using a person-week model. This allowed women with current pregnancies (13%) or induced abortions (10%) to be included for appropriate time periods of risk. A total of 101 pregnancies (7%) ended as spontaneous abortions. An elevation in risk of spontaneous abortion was seen among women who worked with nitrous oxide for 3 or more hours per week in offices not using scavenging equipment (relative risk = 2.6, 95% confidence interval 1.3-5.0, adjusted for age, smoking, and number of amalgams prepared per week), but not among those using nitrous oxide in offices with scavenging equipment. This relation changed little when analyses were restricted to confirmed pregnancies or examined for several types of potential bias. Scavenging equipment appears to be important in protecting the reproductive health of women working with nitrous oxide.

Abortion, Spontaneous↗

PubMed1995

Follicle-stimulating hormone concentrations in relation to active and passive smoking.

OBJECTIVE: To determine the association between various forms of tobacco exposure and ovarian status, as measured by FSH concentrations, in women 38-49 years old. METHODS: Two hundred ninety women between 38-49 years old, who had not had hysterectomy or oophorectomy, completed a self-administered questionnaire that included information on tobacco exposure and had serum FSH levels measured on days 2-4 of the menstrual cycle. Linear regression was used to assess the relation between FSH and tobacco exposure. RESULTS: Controlling for age and other factors, FSH concentrations were 66% higher among current smokers (geometric mean FSH 14.0 mIU/mL) and 39% higher among nonsmokers with passive smoke exposure (11.7 mIU/mL), compared to nonsmoking women without passive smoke exposure (8.4 mIU/mL). The estimated increase in FSH for each year of age was greater for current smokers than for nonsmokers (16 versus 6%, respectively). Ex-smokers did not have higher FSH concentrations, and there was no association between prenatal exposure to tobacco smoke and FSH. CONCLUSION: Both active and passive smoking are associated with elevated FSH concentrations in women 38-49 years old. The effect, limited to women with current exposure, is consistent with a shorter duration of the menopausal transition period.

Adult↗

PubMed1995

The sex of the baby may be related to the length of the follicular phase in the conception cycle.

In a prospective study of normal couples discontinuing contraception to begin a pregnancy, the days of ovulation were estimated by hormonal assay of daily urine specimens. No hormonal interventions were used. Length of the follicular phase (from onset of menses to ovulation) was found to be related to the sex of the baby among 133 pregnancies that survived to delivery. Conception cycles with short follicular phases (early ovulation) tended to produce boys, while those with long follicular phases tended to produce girls. This relationship is consistent with other data and could explain sex-related differences in the length of gestation and the observed excess of same-sex pairs among dizygotic twins.

Adult↗

PubMed1995

Application of a method for estimating day of ovulation using urinary estrogen and progesterone metabolites.

Longitudinal epidemiologic studies of menstrual and reproductive function are more informative if one can identify day of ovulation. We previously developed a method for estimating day of ovulation that is feasible for epidemiologic studies. The method relies on the relative concentrations of estrogen and progesterone metabolites in daily first-morning urine specimens and does not require creatinine adjustment. This paper describes results of applying this method to a large study with 724 menstrual cycles from 217 women. The method estimated a credible day of ovulation in 88% of cycles. Missing data accounted for most of the failures. When we excluded anovulatory cycles (1%) and cycles with missing data, the method estimated a day of ovulation in 97% of cycles. Variance in luteal phase length was small for our sample, suggesting that this method of identifying a day of ovulation introduces no more measurement error than when day of ovulation is determined by plasma luteinizing hormone (LH), the standard clinical method.

Adult↗

PubMed1995

The use of questionnaire data to classify peri- and premenopausal status.

We assessed how well questionnaire data could classify peri- vs premenopausal status in 280 women, ages 38-49 years. Sixty-seven per cent of those who reported use of hormone replacement therapy begun when menstrual periods were irregular, or who had hot flashes at least once a day, or whose last menstrual period was at least 60 days in length, were perimenopausal by hormonal assay (early follicular phase serum follicle-stimulating hormone > or = 15 international units per liter), with a sensitivity of 0.56 [95% confidence interval (CI) = 0.41-0.72] and a specificity of 0.95 (95% CI = 0.93-0.98). In the classification of premenopausal status, the criterion of no menstrual cycle length changes in the past 5 years yielded the highest sensitivity (0.61; 95% CI = 0.54-0.67) and specificity (0.81; 95% CI = 0.68-0.93). With these few items, researchers can improve the classification of peri- and premenopausal status when longitudinal or hormonal assessments cannot be obtained.

Adult↗

PubMed1995

Dietary intervention study to assess estrogenicity of dietary soy among postmenopausal women.

We tested the hypothesis that postmenopausal women on a soy-supplemented diet show estrogenic responses. Ninety-seven postmenopausal women were randomized to either a group that was provided with soy foods for 4 weeks or a control group that was instructed to eat as usual. Changes in urinary isoflavone concentrations served as a measure of compliance and phytoestrogen dose. Changes in serum FSH, LH, sex hormone binding globulin, and vaginal cytology were measured to assess estrogenic response. The percentage of vaginal superficial cells (indicative of estrogenicity) increased for 19% of those eating the diet compared with 8% of controls (P = 0.06 when tested by ordinal logistic regression). FSH and LH did not decrease significantly with dietary supplementation as hypothesized, nor did sex hormone binding globulin increase. Little change occurred in endogenous estradiol concentration or body weight during the diet. Women with large increases in urinary isoflavone concentrations were not more likely to show estrogenic responses than were women with more modest increases. On the basis of published estimates of phytoestrogen potency, a 4-week, soy-supplemented diet was expected to have estrogenic effects on the liver and pituitary in postmenopausal women, but estrogenic effects were not seen. At most, there was a small estrogenic effect on vaginal cytology.

Aged↗

PubMed1994

Selection bias associated with contraceptive practice in time-to-pregnancy studies.

In studies of subfertility using data on time to pregnancy (the number of noncontracepting menstrual cycles required to conceive), many pregnancies are not included in analyses because time-to-pregnancy data cannot always be collected. Birth control failures are one such group (couples who are using birth control regularly or sporadically, but become pregnant anyway). The more fecund couples are more likely to have birth control failures, and consequently, more likely to be excluded from analyses. If an exposure of interest is associated with irregular use of birth control or with the choice of less effective methods of birth control, the fecundability in the exposed (based on data from couples who can provide adequate time to pregnancy data) will be underestimated. Such bias may account for the findings in the literature showing reduced fecundability among smokers. More generally, when a subset of couples who differ in their fecundability are excluded from analysis, there will be opportunity for selection bias to produce under or overestimation of the strength of an association between an exposure and fecundability. This problem affects both retrospective and prospective studies. Time-to-pregnancy studies need to be designed to minimize this potential bias and to collect data to evaluate it adequately.

Contraception↗

PubMed1994

Bias in retrospective studies of spontaneous abortion based on the outcome of the most recent pregnancy.

In a retrospective studies of spontaneous abortion, bias can arise if the investigator restricts attention to the outcome of the most recent pregnancy. Bias happens because couples tend to replace spontaneous abortions with other pregnancies until they achieve a live birth, after which they may avoid conception for a long time. Consequently, the proportion of most recent conceptions ending in loss might be very low compared to what would be seen in a prospective study. Also, time since conception is negatively correlated with apparent risk, because most pregnancies which occurred relatively long ago and ended in loss have been replaced by subsequent pregnancies. If the exposure of interest may also have changed over time, then time since conception should be considered a potential confounder. In addition, the consistency with which couples use birth control varies. Some couples are planners who use effective contraception and plan the growth of their family with deliberation; others have most of their pregnancies unintentionally. As a result, the most recent pregnancy is less likely to be a spontaneous abortion for a planner than for a nonplanner. If planners and nonplanners also differ in their exposures, then bias will result. Other factors which affect the interpregnancy interval, such as fecundability, breastfeeding, and desired family size can distort the relative sampling fraction for spontaneous abortions compared to live births and, to the extent that such factors are associated with the exposure, can bias estimates of relative risks.

Abortion, Spontaneous↗

PubMed1994

Placental arsenic and cadmium in relation to lipid peroxides and glutathione levels in maternal-infant pairs from a copper smelter area.

Arsenic exposure may enhance oxidative damage causing adverse health effects in pregnant women. The purposes of this paper are: (i) to evaluate placental arsenic concentration as a biomarker of arsenic exposure for pregnant women; and (ii) to examine the relationship between metal exposure from a copper smelter area in Bulgaria and oxidative damage during pregnancy (as measured by glutathione and lipid peroxides) in 49 maternal-infant pairs. Placental levels of arsenic were highest in areas with the highest environmental contamination, and environmental variables (residency, smoking and occupational exposure) explained a large portion of the observed variability in placental arsenic levels (linear regression R2 = 0.71). The combined exposures of smoking and living in the smelter area were associated with lower glutathione antioxidant protection. The per cent maternal and cord blood glutathione in reduced form was significantly lower for smokers compared to non-smokers in the smelter area (47 versus 66 per cent in maternal blood, P < 0.01, and 60 versus 75 per cent in cord blood, P < 0.05). Higher concentrations of lipid peroxides in maternal blood, cord blood and placenta, though not statistically significant, suggested that pregnant women with both exposures may be at higher risk of oxidative damage.

Adult↗

PubMed1994

The effect of occupational exposure to mercury vapour on the fertility of female dental assistants.

Exposure to mercury vapour or inorganic mercury compounds can impair fertility in laboratory animals. To study the effects of mercury vapour on fertility in women, eligibility questionnaires were sent to 7000 registered dental assistants in California. The final eligible sample of 418 women, who had become pregnant during the previous four years, were interviewed by telephone. Detailed information was collected on mercury handling practices and the number of menstrual cycles without contraception it had taken them to become pregnant. Dental assistants not working with amalgam served as unexposed controls. Women with high occupational exposure to mercury were less fertile than unexposed controls. The fecundability (probability of conception each menstrual cycle) of women who prepared 30 or more amalgams per week and who had five or more poor mercury hygiene factors was only 63% of that for unexposed women (95% CI 42%-96%) after controlling for covariates. Women with low exposure were more fertile, however, than unexposed controls. Possible explanations for the U shaped dose response and limitations of the exposure measure are discussed. Further investigation is needed that uses biological measures of mercury exposure.

Adolescent↗

PubMed1994

Galactose consumption, metabolism, and follicle-stimulating hormone concentrations in women of late reproductive age.

OBJECTIVE: To test the hypothesis that high galactose consumption and low activity of galactose-1-phosphate uridyl transferase (transferase) is associated with early ovarian senescence among nongalactosemic women. DESIGN: Cross-sectional study. Data collection consisted of a self-administered questionnaire with sections on diet (food frequency data to measure galactose consumption), reproductive, and medical histories. One blood sample was collected to measure FSH and transferase activity; FSH was used as a measure of ovarian senescence. Among women who were having menstrual periods at least every 8 weeks, the blood sample was drawn in the early follicular phase (days 2 to 4) of a menstrual cycle. PARTICIPANTS: Two hundred ninety-five women volunteers ages 38 to 49 years who had not had a hysterectomy or oophorectomy were recruited through posters and advertisements. MAIN OUTCOME MEASURE: Serum FSH concentrations. RESULTS: Controlling for age, smoking, and body mass, transferase activity and FSH were unrelated. However, FSH levels were 29% higher (95% confidence intervals, 9% to 52%) among women who reported consuming > or = 6 g galactose/d. CONCLUSION: These data do not support the hypothesis that low transferase activity represents a genetic predisposition for early ovarian senescence, as measured by FSH levels in women ages 38 to 49 years. However, the hypothesized positive association between galactose consumption and FSH was supported.

Adult↗

PubMed1994

Is there a seasonal pattern in risk of early pregnancy loss?

We recruited 221 women with no known fertility problems who were discontinuing contraception to conceive a pregnancy. The primary objective of this prospective study was to estimate the incidence of very early pregnancy loss by using a highly sensitive and specific assay to detect the pregnancy hormone chorionic gonadotropin in first morning urine specimens. We found the risk of early pregnancy loss, defined as loss within 6 weeks of the last menstrual period, to vary by season of conception, with a large amplitude and some consistency across the 3 years of the study. Such a seasonal pattern may reflect the contribution of an environmental factor that varies with season. The peaks in risk ranged from early September to early December. A seasonal pattern of early pregnancy loss should contribute to a corresponding lagged seasonal pattern in livebirths. Accordingly, we looked for corroborative evidence in regional birth data from the same years. There was some correspondence, but this was largely limited to the first year of the study.

Abortion, Spontaneous↗

PubMed1993

Pitfalls inherent in retrospective time-to-event studies: the example of time to pregnancy.

Retrospective studies of time from initiation of risk (for example, transfusion of HIV-infected blood) to the occurrence of an endpoint of interest are useful in epidemiology. One example is studies of time to pregnancy, which have evaluated exposures that may affect human fertility. One can reconstruct the non-contracepting interval required for each woman's most recent pregnancy and then treat the data as if the couples had been studied prospectively. As we illustrate, however, failure-time models can be dangerously misleading when there have been trends over calendar time in exposures under study. We propose an ad hoc method for evaluating possible effects on fertility despite this bias, by making use of external data on trends in the exposure over time. This approach applies a prospective model and generates an empirical p-value, based on comparing the data-based estimated exposure coefficient with its null distribution estimated by simulation. A second method maximizes a conditional likelihood, and we show that this is equivalent to logistically modelling the relative odds for the subject's exposure as related to the reported time she required to achieve pregnancy.

Bias↗

PubMed1992

Reduced fertility among women employed as dental assistants exposed to high levels of nitrous oxide.

BACKGROUND: Fertility is reduced in female rats exposed to levels of nitrous oxide similar to those found in some dental offices. Epidemiologic studies have suggested an association between exposure to mixed anesthetic gases and impaired fertility. We investigated the effects of occupational exposure to nitrous oxide on the fertility of female dental assistants. METHODS: Screening questionnaires were mailed to 7000 female dental assistants, ages 18 to 39, registered by the California Department of Consumer Affairs. Sixty-nine percent responded. Four hundred fifty-nine women were determined to be eligible, having become pregnant during the previous four years for reasons unrelated to the failure of birth control, and 91 percent of these women completed telephone interviews. Detailed information was collected on exposure to nitrous oxide and fertility (measured by the number of menstrual cycles without contraception that the women required to become pregnant). RESULTS: After controlling for covariates, we found that women exposed to high levels of nitrous oxide were significantly less fertile than women who were unexposed or exposed to lower levels of nitrous oxide. The effect was evident only in the 19 women with five or more hours of exposure per week. These women were only 41 percent (95 percent confidence interval, 23 to 74 percent; P less than 0.003) as likely as unexposed women to conceive during each menstrual cycle. CONCLUSIONS: Occupational exposure to high levels of nitrous oxide may adversely affect women's ability to become pregnant.

Adolescent↗

PubMed1992

Efficiency and bias in studies of early pregnancy loss.

Recent advances in laboratory techniques for measuring the pregnancy hormone human chorionic gonadotropin have allowed detection of occult very early pregnancy losses based on assaying urine. We used data from the Early Pregnancy Study carried out in North Carolina to develop a simplified collection protocol for reducing costs and improving compliance in similar studies conducted in less-selected populations of women. Collection of specimens only during menses would have caused some decrease in sensitivity but would nevertheless have allowed detection of at least 75% of the losses detected in the North Carolina study. Reduced-collection protocols would also result in some loss in specificity. Simulations suggest that moderate losses in sensitivity and specificity, as would result from reduced-collection protocols, produce only moderate loss of power for detecting associations between risk factors and early pregnancy loss. A "fertility bias" exists, however, which can produce seriously misleading results when specificity is less than perfect. We therefore recommend use of a baseline group of sterile women, so that criteria for "pregnancy" can achieve specificity close to 1.0.

Abortion, Spontaneous↗

PubMed1991

Reporting errors in time-to-pregnancy data collected with a short questionnaire. Impact on power and estimation of fecundability ratios.

Few tools exist in reproductive epidemiology for studying adverse effects on fertility. Data on time to pregnancy (the number of menstrual cycles required to conceive) can be used to estimate fecundability ratios, a sensitive endpoint for identifying factors associated with reduced fertility. Time-to-pregnancy data can be collected in detailed interviews. The accuracy of data collected on brief, self-administered questionnaires is not known. In a study of occupational exposures to dental assistants conducted in 1987-1988, 523 women provided time-to-pregnancy data both on a short, mailed questionnaire and in a detailed telephone interview. The correlation between the two measures was 0.82. Assuming that the detailed data were accurate, reporting errors in data from the short form were distributed nondifferentially with respect to most covariates of interest in fecundability analyses. Simulation studies were conducted to estimate bias and loss of power from the misclassification. Bias was toward the null. Substantial power was lost in detecting weak exposures. However, exposures that reduce fecundability by 50 percent (equivalent to adding about three cycles to the median time to pregnancy) could still be detected with 80 percent power in samples of about 100 women (half of them exposed to a possible toxin). The authors conclude that time-to-pregnancy data collected with a few self-administered questions can be useful in a variety of epidemiologic studies, including occupational and environmental surveillance programs.

Bias↗