Introduction: The Danish Civil Registration System (CRS) was established in 1968, and all persons alive and living in Denmark were registered for administrative use. Content: CRS includes individual information on the unique personal identification number, name, gender, date of birth, place of birth, citizenship, identity of parents and continuously updated information on vital status, place of residence and spouses. Validity and coverage: Since 1968, CRS has recorded current and historical information on all persons living in Denmark. Among persons born in Denmark in 1960 or later it contains complete information on maternal identity. For women born in Denmark in April 1935 or later it contains complete information on all their children. CRS contains complete information on immigrations and emigrations from 1969 onwards, permanent residence in a Danish municipality from 1971 onwards, and full address in Denmark from 1977 onwards. Conclusion: CRS in connection with other registers and biobanks will continue to provide the basis for significant knowledge relevant to the aetiological understanding and possible prevention of human diseases.

https://journals.sagepub.com/doi/pdf/10.1177/1403494810387965

The Danish civil registration system

BACKGROUND Semen quality is taken as a surrogate measure of male fecundity in clinical andrology, male fertility, reproductive toxicology, epidemiology and pregnancy risk assessments. Reference intervals for values of semen parameters from a fertile population could provide data from which prognosis of fertility or diagnosis of infertility can be extrapolated. METHODS Semen samples from over 4500 men in 14 countries on four continents were obtained from retrospective and prospective analyses on fertile men, men of unknown fertility status and men selected as normozoospermic. Men whose partners had a time-to-pregnancy (TTP) of < or =12 months were chosen as individuals to provide reference distributions for semen parameters. Distributions were also generated for a population assumed to represent the general population. RESULTS The following one-sided lower reference limits, the fifth centiles (with 95th percent confidence intervals), were generated from men whose partners had TTP < or = 12 months: semen volume, 1.5 ml (1.4-1.7); total sperm number, 39 million per ejaculate (33-46); sperm concentration, 15 million per ml (12-16); vitality, 58% live (55-63); progressive motility, 32% (31-34); total (progressive + non-progressive) motility, 40% (38-42); morphologically normal forms, 4.0% (3.0-4.0). Semen quality of the reference population was superior to that of the men from the general population and normozoospermic men. CONCLUSIONS The data represent sound reference distributions of semen characteristics of fertile men in a number of countries. They provide an appropriate tool in conjunction with clinical data to evaluate a patient's semen quality and prospects for fertility.

/pdf/world-health-organization-reference-values-for-human-semen-3qu21s6tqf.pdf

World Health Organization reference values for human semen characteristics

Background The Danish Civil Registration System (CRS) was established in 1968, where all persons alive and living in Denmark were registered. Among many other variables, it includes individual information on personal identification number, gender, date of birth, place of birth, place of residence, citizenship, continuously updated information on vital status, and the identity of parents and spouses. Methods To evaluate the quality and completeness of the information recorded on persons in the CRS, we considered all persons registered on November 4, 2005, i.e. all persons who were alive and resident in Denmark at least one day from April 2, 1968 to November 4, 2005, or in Greenland from May 1, 1972 to November 4, 2005. Results A total of 8,176,097 persons were registered. On November 4, 2005, 5,427,687 (66.4%) were alive and resident in Denmark, 56,920 (0.7%) were alive and resident in Greenland, 2,141,373 (26.2%) were dead, 21,160 (0.3%) had disappeared, and 528,957 (6.5%) had emigrated. Among persons born in Denmark 1960 or later the CRS contains complete information on maternal identity. Among persons born in Denmark 1970 or later the CRS contains complete information on paternal identity. Among women born in Denmark April 1935 or later the CRS contains complete information on all their children. Among males born in Denmark April 1945 or later the CRS contains complete information on all their children. The CRS contains complete information on: a) immigrations and emigrations from 1971 onwards, b) permanent residence in a Danish municipality from 1971 onwards, c) permanent residence in a municipality in Greenland from May 1972 onwards, and d) full address in Denmark from 1977 onwards. Conclusion Data from the CRS is an important research tool in epidemiological research, which enables Danish researchers to carry out representative population-based studies on e.g. the potential clustering of disease and death in families and the potential association between residence and disease and death.

The Danish Civil Registration System. A cohort of eight million persons.

Clefts of the lip and/or palate (CLP) are common birth defects of complex aetiology. CLP can occur in isolation or as part of a broad range of chromosomal, Mendelian or teratogenic syndromes. Although there has been marked progress in identifying genetic and environmental triggers for syndromic CLP, the aetiology of the more common non-syndromic (isolated) forms remains poorly characterized. Recently, using a combination of epidemiology, careful phenotyping, genome-wide association studies and analysis of animal models, several distinct genetic and environmental risk factors have been identified and confirmed for non-syndromic CLP. These findings have advanced our understanding of developmental biology and created new opportunities for clinical translational research.

/pdf/cleft-lip-and-palate-understanding-genetic-and-environmental-1z63y69qrr.pdf

Cleft lip and palate: understanding genetic and environmental influences.

How the mind works

Previous analyses of period fertility suggest that the trends of the Nordic countries are sufficiently similar to speak of a common "Nordic fertility regime". We investigate whether this assumption ...

/pdf/cohort-fertility-patterns-in-the-nordic-countries-47qwnzyntk.pdf

Cohort Fertility Patterns in the Nordic Countries

Using the Danish Fertility Database, we investigate intergenerational fertility transmission, including the relationship between the number of children born to those aged 25 and 26 years in 1994 and the number of their full sibs and half-sibs. We find that the fertility behaviour of parents and their children is positively correlated, and that half-sibs and full sibs have broadly similar effects. We do not find, in this complete national population, the strong birth order effects reported in some earlier studies. Nor do we find evidence of a weakening of intergenerational fertility transmission over time, perhaps because the greater flexibility of lifestyles in this post-transitional phase provides the extended social space within which intergenerational continuities can manifest themselves. We show that members of large families are over-represented in subsequent generations - that they have far more kin than those from smaller families - and that intergenerational continuities in fertility behaviour play a substantial role in keeping fertility higher than it would be in the absence of such transmission.

https://evolution.binghamton.edu/evos/wp-content/uploads/2009/08/hacker02.pdf

The intergenerational transmission of fertility in contemporary Denmark: the effects of number of siblings (full and half), birth order, and whether male or female

Background—Some malformations are clearly associated with older maternal age, but the effect of older age of the father is less certain. The aim of this study is to determine the degree to which maternal age and paternal age independently influence the risk of having a child with oral clefts. Methods—Among the 1,489,014 live births in Denmark during 1973–1996, there were 1920 children with nonsyndromic cleft lip with or without cleft palate and 956 children with nonsyndromic cleft palate. We used logistic regression to assess the impact of parental age on the occurrence of cleft lip with or without cleft palate and cleft palate. Interaction between mother’s and father’s age was included in the analysis. Results—Separate analyses of mother’s and father’s age showed that older age was associated with increased risk of both cleft lip with or without cleft palate and cleft palate only. In a joint analysis, both maternal and paternal ages were associated with the risk of cleft lip with or without cleft palate, but the contribution of each was dependent on the age of the other parent. In the analysis of cleft palate only, the effect of maternal age disappeared, leaving only paternal age as a risk factor. Conclusion—Both high maternal age and high paternal age were associated with cleft lip with or without cleft palate. Higher paternal age but not maternal age increased the risk of cleft palate only. Oral cleft is one of the most common congenital malformations with prevalence between 1 and 2 per 1000 live births. 1 Family studies suggest that cleft lip with or without cleft palate and cleft palate only are etiologically distinct malformations. 2 The etiology of both defects is thought to be multifactorial with genes playing the major role. Several potential risk factors have been studied, but no strong risk factor has yet been identified. 3–5 Increased maternal age is a risk factor for both chromosomal 6 and nonchromosomal abnormalities. 7 There have been conflicting reports on whether older maternal or paternal ages are associated with risk of oral clefts. Only a few studies were conducted according to the recommendation of the International Consortium for Oral Clefts Genetics, 8 population-based, distinguishing between cleft lip with or without cleft palate and cleft palate only, and excluding cases with associated anomalies. Furthermore, few controlled for the age of the other parent, which is known to be correlated. Ascertaining whether older parental age is associated with oral cleft is not only of interest for clarifying the etiology of oral clefts, but is also important

/pdf/parent-s-age-and-the-risk-of-oral-clefts-57qlkcwz15.pdf

Parent's age and the risk of oral clefts.

Introduction: The establishing of three Danish population-based registers, namely the Fertility Database, the Register of Legally Induced Abortions, and the In Vitro Fertilisation register, aimed at providing data for surveying of reproductive outcome. Content: The registers include information on births, abortions, and assisted reproduction as well as selected characteristics of the women (and men) involved. Validity and coverage: Both the validity and coverage of each register are considered of high quality. Conclusion: These registers provide, both individually and in combination, unique opportunities for undertaking detailed and comprehensive research in the field of reproduction.

https://journals.sagepub.com/doi/pdf/10.1177/1403494811399957

Danish registers on aspects of reproduction.

Background The Fertility Database (FTDB) in Statistics Denmark is solely based on data from other registers, which comprise data on a different number of birth cohorts and different time spans. The FTDB was established during 1989-1992 in order to provide a better tool for socio-demographic research on the developments in fertility. The variables included also make the register a valuable tool in medical research regarding reproductive outcome and characterization of parents. Results Based on the Register of Population Statistics, the FTDB comprises at present annual information on any woman and man in the fertile age in Denmark for the period 1980-1993, approximately 1.2 and 1.4 million persons, respectively. Their children are identified through various registers and for all children born 1973-1993 specific information on the birth was available from the Medical Register of Vital Statistics. The adult populations are described annually as regards education, occupation, income, social benefit and housing conditions. Conclusion The FTDB has been used in a number of research projects; in some cases data from the FTDB have been linked with data from other registers. The FTDB is a valuable tool in demographic as well as medical research.

Lisbeth B. Knudsen

Papers

Cohort Fertility Patterns in the Nordic Countries

The intergenerational transmission of fertility in contemporary Denmark: the effects of number of siblings (full and half), birth order, and whether male or female

Parent's age and the risk of oral clefts.

Danish registers on aspects of reproduction.

The Danish Fertility Database.