Populations and methods

The foundation of data is two research databases that are used or developed as part of the development of the national research network:

The Danish National Birth Cohort (DNBC) includes approximately 100,000 pregnant women and their children from all over Denmark in the period 1995-2004. The women were interviewed twice during their pregnancies and three times after birth. The women were asked about profession and psychologically and ergonomically stress of work. For selected occupations, there are data on occupational exposure (such as painting and varnishing, dry-cleaning, horticulture and agriculture, hospitals, laboratories, graphic industry). Data on pregnancy course and children's health is collected partly by interview and partly from the Medical Birth Register (MFR; birth weight, gestational age and birth defects) and the Danish Hospital Register (LPR; hospital admissions with illness during childhood and malformations). The cohort is moderated by researchers at the Epidemiological Basic Research Centre with Professor Jørn Olsen as chairman. Occupational medical clinic in Aarhus has developed occupational classification (DSCO-88) and has contributed to the development of specific questions about exposures in the workplace. There is in the context of a PhD project published several studies based on data from DNBC on the working environment, but so far the working environment is only studied in about 12% of the publications in DNBC (see www.ssi.dk).

Occupation and Birth Register (EFR) will be developed by supplementing the information from the Medical Birth Registers on all births in Denmark from 1973 (including birth weight, malformations, pregnancy duration, birth complications) with nationwide data on parental occupation from Labor Classification Module (AKM) and the child's medical contacts from the Danish Hospital Register (LPR). Data on migration and deaths are included from the CPR register. The Medical Birth Register (MFR) was in the period 1973 to 1995 based on the reporting from the National Board of Health. From 1995 births in hospitals were reported electronically via LPR. The register also indicates smoking status of the mother. Since 1995, all hospital contacts in the LPR are included (previously only admissions). It is thought that the EFR should cover birth data, etc. from 1995 and onwards, together with data on occupation from 1994. Earlier periods can be a possibility. Statistics Denmark administers AKM, which has existed since 1975. The National Board of Health manages LPR and MFR. Establishment of the EFR requires approval from Statistics Denmark, the National Board of Health and the Danish Data Protection Agency. The register gives the opportunity to link both parents' occupations with reproductive damages - like the Occupation and Hospital Register.