Biomedical subjects

L Z Heidam

Publications and source records attributed to L Z Heidam.

5 recordsLinked to original sources

PubMed1985

Self-reported data on spontaneous abortions compared with data obtained by computer linkage with the hospital registry.

In a study of occupational causes of spontaneous abortions, based upon self-reported data and data from the hospital registry, evidence of differential misclassification was noted. Among those exposed a larger proportion of the self-reported spontaneous abortions were identified in the hospital registry, compared with what was found in the control group. This could be due to recall bias of the questionnaire data masking an effect of exposure, or a lower threshold for hospitalization among those exposed vis-à-vis controls, which would exaggerate the effect of exposure, if any. The analysis tended to support the idea of a less accurate recall of spontaneous abortions among controls, especially for abortion that occurred more than 3 years before the questionnaires were sent out. A second questionnaire was sent out to a subset of the participants 3 1/2 years after the first questionnaire. 17% reported fewer spontaneous abortions in this second questionnaire compared with the situation in the first questionnaire, for the period 1973 to 1980.

Abortion, Spontaneous↗

PubMed1984

Spontaneous abortions among laboratory workers; a follow up study.

An investigation was conducted among all female laboratory workers in the county of Funen to test the hypothesis that work in laboratories during pregnancy increases the risk of spontaneous abortion. Laboratory workers from hospital, university, and other public laboratories and from laboratories in industry were investigated. A socially comparable reference group less exposed to chemicals at work included office workers, technical assistants and designers, physiotherapists, and occupational therapists. Information was obtained through a postal questionnaire study in May 1980 and from hospital records. Neither the occupation in any single category of laboratory nor the alleged exposure to any single chemical during pregnancy showed a significant increase in the odds ratio for spontaneous abortion. A selection bias was found among the non-respondents with respect to both occupation and outcome of pregnancy, but the influence on the results was slight, owing to the small number of non-respondents. The higher rates of hospital admission for spontaneous abortion among the cases compared with the controls indicates that register data are not more valid than self reported data. This leads to several methodological problems that ought to be studied in further detail.

Abortion, Spontaneous↗

PubMed1984

Spontaneous abortions among dental assistants, factory workers, painters, and gardening workers: a follow up study.

This investigation was conducted to test the hypothesis that exposure of pregnant women to chemicals increases the risk of spontaneous abortion. The chemical risk factors under study to which dental assistants, factory workers, painters, and gardening workers were exposed were nitrous oxide, inorganic mercury, organic solvents, and pesticides. The study was carried out within the Danish county of Funen. It included all dental assistants employed in private or public dentistry. A comparable reference group was made up by employees less exposed to chemicals. Further study groups included all women painters within the county, women factory workers from selected factories, and about 50% of the women gardening workers within the county. Shop assistants and packers formed their control group. Information was obtained through a postal questionnaire study in May 1980 and from hospital records. Only among factory workers and painters was the odds ratio of spontaneous abortion found to be significantly increased. Neither among these women nor among dental assistants and gardening workers, however, was the reported exposure to any single chemical during pregnancy associated with a significantly increased odds ratio of spontaneous abortion.

Abortion, Spontaneous↗

PubMed1983

Analysis of pathological outcome of pregnancy.

A series of publications have demonstrated that women undergoing numerous pregnancies during their reproductive lives show considerably higher pregnancy order-specific abortion rates or perinatal mortality rates than women who have been pregnant less often. This gives rise to a statistical problem of control in connection with analytical epidemiology, especially since these differences are far greater than those expected for rates of abortion or perinatal mortality, for example between various occupational categories. The present article is concerned with statistical control problems of this nature. On the basis of computer simulations, the extent and direction of the bias which inadequate statistical control may bring about is calculated for situations in which the presumed deleterious effect is reflected in gravidity- and pregnancy order-specific relative risks.

Abortion, Spontaneous↗

PubMed1983

Spontaneous abortions among factory workers. The importance of gravidity control.

The purpose of this study were twofold. First to demonstrate the impact of gravidity control on the crude odds ratio (OR), the risk estimate of the total number of spontaneous abortions among all chemically exposed women in comparison with non-exposed women. Second, to discuss whether the increased proportion of higher gravidities among the exposed subjects did compensate for an increased risk of spontaneous abortion provoked by the chemical exposure. The study included 262 factory workers occupationally exposed predominantly to organic solvents and 241 reference women who were socially comparable and relatively free from chemical exposure of their work. The subjects are included in a historical prospective survey of 6 730 women representing 12 selected occupations in the Danish county of Funen. The data were collected by postal questionnaires in May 1980. The crude OR of spontaneous abortions among factory workers was significantly increased, but when controlled for gravidity, it was no longer statistically significant. The childbearing behaviour of the two groups of women was compared in a logistic regression analysis which suggested that the increased proportion of higher gravidities among the factory workers was not only due to a compensatory behaviour. A desire for more children among the factory workers, or a less careful use of contraception compared to the reference group might explain the findings. Consequently, gravidity should probably be controlled.

Abortion, Spontaneous↗