Annette Wind Olesen

The Danish National Birth Cohort - its background, structure and aim

Background: It is well known that the time from conception to early childhood has importance for health conditions that reach into later stages of life. Recent research supports this view, and diseases such as cardiovascular morbidity, cancer, mental illnesses, asthma, and allergy may all have component causes that act early in life. Exposures in this period, which infl uence fetal growth, cell divisions, and organ functioning, may have long-lasting impact on health and disease susceptibility. Methods: To investigate these issues the Danish National Birth Cohort (Better health for mother and child) was established. A large cohort of pregnant women with long-term follow-up of the offspring was the obvious choice because many of the exposures of interest cannot be reconstructed with sufficient validity back in time. The study needs to be large, and it is aimed to recruit 100,000 women early in pregnancy, and to continue follow-up for decades. The Nordic countries are better suited for this kind of research than most other countries because of their population-based registers on diseases, demography and social conditions, linkable at the individual level by means of the unique ID-number given to all citizens. Exposure information is mainly collected by computer-assisted telephone interviews with the women twice during pregnancy and when their children are six and 18 months old. Participants are also asked to fill in a self-administered food frequency questionnaire in mid-pregnancy. Furthermore, a biological bank has been set up with blood taken from the mother twice during pregnancy and blood from the umbilical cord taken shortly after birth. Data collection started in 1996 and the project covered all regions in Denmark in 1999. By August 2000, a total of 60,000 pregnant women had been recruited to the study. It is expected that a large number of gene-environmental hypotheses need to be based on case-control analyses within a cohort like this.

Risk of recurrence of prolonged pregnancy

Paternal genes as expressed by the fetus play a role in the timing of birth and in the risk of repeating a prolonged pregnancy Prolonged pregnancy—a pregnancy with a gestational length of 294 days or more—occurs in about 5% of all births. It is associated with a higher frequency of obstetric complications and perinatal morbidity,1 and little is known about its aetiology.2 We studied the risk of recurrence of prolonged pregnancy as a function of change in partner or change in social conditions. We obtained data recorded in the Danish medical birth registry on all women with a prolonged pregnancy in the first delivery and in a subsequent delivery, during 1980-94, and a 5% sample of all women with two or more pregnancies recorded in the period 1980-92 (only the first two deliveries were used for analysis). The information on gestational age in the registry was obtained from birth records that had been …

Prenatal risk indicators of a prolonged pregnancy. The Danish Birth Cohort 1998-2001

Background. Few prenatal risk factors of prolonged pregnancy, a pregnancy of 42 weeks or more, are known. The objective was to examine whether sociodemographic, reproductive, toxicologic, or medical health conditions were associated with the risk of prolonged pregnancy. Methods. Data from the Danish Birth Cohort in Denmark were used. Interview data from 53,392 participants with live‐born singleton deliveries in the period 1998–2001 were available at the time of this study. The participants were interviewed by telephone at 12 and 30 weeks’ gestation, and 6 and 18 months after delivery. Statistical analyses were done using logistic regression. Results. Women with a pre‐pregnancy body mass index of 25 kg/m2 or more had a high risk of prolonged pregnancy. If the pre‐pregnancy body mass index was 35 kg/m2 or more the odds ratio was 1.52 (95% CI 1.28–1.82). Nulliparity also increased the risk of prolonged pregnancy (OR (95% CI) = 1.35 (1.27–1.44)). Conclusions. The risk of post‐term delivery was high in women with a pre‐pregnancy body mass index of 25 kg/m2 or more, and in nulliparous women.

A continuous decline in menarcheal age in Denmark

We report a renewed decline in mean menarcheal age in a large Danish sample after a period with a halt in the trend towards earlier age at menarche in many North European countries. In our study based on retrospective data from six different samples constituting 42784 women, we find a continuously declining mean menarcheal age in Denmark among women born in the years 1964-1973. In a sample of textile workers born in the years 1939-1968 (n = 12605) we find a 1 year higher mean menarcheal age. This indicates that menarcheal age is still delayed in certain groups in Denmark. This leaves the possibility that the menarcheal age could fall even further in the future.We report a renewed decline in mean menarcheal age in a large Danish sample after a period with a halt in the trend towards earlier age at menarche in many North European countries. In our study based on retrospective data from six different samples constituting 42784 women, we find a continuously declining mean menarcheal age in Denmark among women born in the years 1964-1973. In a sample of textile workers born in the years 1939-1968 (n = 12605) we find a 1 year higher mean menarcheal age. This indicates that menarcheal age is still delayed in certain groups in Denmark. This leaves the possibility that the menarcheal age could fall even further in the future.

The Danish Fetal Medicine Database: establishment, organization and quality assessment of the first trimester screening program for trisomy 21 in Denmark 2008–2012

To describe the establishment and organization of the Danish Fetal Medicine Database and to report national results of first‐trimester combined screening for trisomy 21 in the 5‐year period 2008–2012.

Correlation between self-reported gestational age and ultrasound measurements.

Background.  We studied the agreement between different measurements of gestational age, i.e. self‐reported gestational age in the Danish National Birth Cohort Study, ultrasound‐estimated gestational age from the medical records in one Danish county and gestational age from the Danish National Hospital Discharge Register.

Prediction of delivery date by sonography in the first and second trimesters

To compare the dates of delivery predicted by last menstrual period (LMP), crown–rump length (CRL) and biparietal diameter (BPD) with the actual date of delivery in a population of pregnant women divided into those with certain and those with uncertain LMP.

Risk for developmental coordination disorder correlates with gestational age at birth.

BACKGROUND Studies suggest that children born very preterm have a high risk of developmental coordination disorder (DCD). We examined the relation between the larger spectrum of gestational age at birth and the risk of DCD. METHODS   We used the 7-year follow-up data from 22898 singletons in the Danish National Birth Cohort. We calculated a total score from the Developmental Coordination Disorder Questionnaire (DCDQ), incorporated in the 7-year follow-up, and defined children with a score of 46 or below as having probable DCD. Information on gestational age was obtained from the Medical Birth Register. RESULTS   Gestational age at birth was inversely associated with the risk of DCD; a decline in gestational age by a week was associated with a 19% [95% confidence interval 14%, 25%] increased risk of DCD screening positive among children delivered before 40 weeks. No significant increased risk of DCD was seen for children born post-term. CONCLUSION Our data indicate that short gestational age at birth in a range up to gestational week 37 is related to an increased risk of DCD.

Neonatal BCG vaccination has no effect on recurrent wheeze in the first year of life: A randomized clinical trial

Background: Recurrent wheeze (RW) is frequent in childhood. Studies have suggested that BCG vaccination can have nonspecific effects, reducing general nontuberculosis morbidity, including respiratory tract infections and atopic diseases. The mechanisms behind these nonspecific effects of BCG are not fully understood, but a shift from a TH2 to a TH1 response has been suggested as a possible explanation. Objective: We hypothesized that BCG at birth would reduce the cumulative incidence of RW during the first year of life. Methods: The Danish Calmette Study is a multicenter randomized trial conducted from 2012–2015 at 3 Danish hospitals. The 4262 newborns of 4184 included mothers were randomized 1:1 to BCG (SSI strain 1331) or to a no‐intervention control group within 7 days of birth; siblings were randomized together as one randomization unit. Exclusion criteria were gestational age of less than 32 weeks, birth weight of less than 1000 g, known immunodeficiency, or no Danish‐speaking parent. Information was collected through telephone interviews and clinical examinations at 3 and 13 months of age; data collectors were blind to randomization group. RW was defined in several ways, with the main definition being physician‐diagnosed and medically treated RW up to 13 months of age. Results: By 13 months, 211 (10.0%) of 2100 children in the BCG group and 195 (9.4%) of 2071 children in the control group had received a diagnosis of RW from a medical doctor and received antiasthma treatment (relative risk, 1.07; 95% CI, 0.89–1.28). Supplementary analyses were made, including an analysis of baseline risk factors for development of RW. Conclusion: Neonatal BCG had no effect on the development of RW before 13 months of age.

Neonatal BCG has no effect on allergic sensitization and suspected food allergy until 13 months

Vaccination with Bacillus Calmette‐Guérin (BCG) is used in many countries as protection against tuberculosis. Studies have suggested that BCG may also have non‐specific effects, reducing non‐tuberculosis mortality, morbidity, and atopic manifestations. In this study, we evaluated the effect of neonatal BCG vaccination on allergic sensitization and suspected food allergy at 13 months of age.