BACKGROUND: Two British cohort studies have reported birth weight to be associated with self-reported depression in adulthood, even after adjustment for socio-economic factors. AIMS: To examine the relationship between birth dimensions and discharge from a psychiatric ward with a depression diagnosis in adulthood. METHOD: A cohort of 10 753 male singletons born in Copenhagen, Denmark in 1953 and for whom birth certificates had been traced in 1965 were followed from 1969 until 2002, with record linkage for date of first admission to a psychiatric ward that led to a discharge diagnosis of depression. RESULTS: A total of 190 men, corresponding to 1.8% of the cohort, had a discharge diagnosis of depression. The Cox's regression analyses failed to show any association between birth dimensions (birth weight and ponderal index) and risk of psychiatric ward diagnosis of depression in adult life, before or after adjustment for social indicators at birth. CONCLUSIONS: This study does not support the existence of a relation between birth dimensions and psychiatric ward admission for depression in adult men.
BACKGROUND: Birthweight has, in several studies, been associated with mortality in adult age, even after adjustment for available socioeconomic factors. This association has been explained as a biological result of fetal undernutrition (fetal programming), by genetic predisposition, as a result of confounding by factors related to social position and lifestyle, or by a combination of these mechanisms. This study examines the relationship between birth dimensions and all-cause and cause-specific mortality in early adulthood, taking parental lifespan and social position at time of birth into account. Furthermore, the relationship between offspring birth dimensions and parental mortality is addressed. METHODS: In all 10 753 male singletons born in the metropolitan area of Copenhagen, Denmark in 1953 whose birth certificates had been traced manually in 1965 were followed from 1968 to 2002 for information on parents' and own vital status by linkage with the Civil Registration System. Causes of death for the cohort members were identified by record linkage with the Cause-of-Death Registry. Hazard ratios and 95% CI were calculated using Cox regression models. RESULTS: Low birthweight and especially short birth length were strongly associated with adult mortality risk, but no relationship between low ponderal index at birth and mortality was found. The relationship between birth size and early adult mortality was only slightly attenuated after adjustment for early-life social position and/or maternal and paternal lifespan. The associations between birthweight/birth length and mortality were stronger for the age group 35-49 years compared with the age group 15-34 years. Cause-specific mortality was inversely related to small birth dimensions for all causes of death, but strongest and graded for death from liver cirrhosis. Offspring birth dimensions showed an inverse association with parental mortality, which was most pronounced for maternal mortality. CONCLUSIONS: The strong inverse association between birth dimensions and adult mortality, but lack of association between ponderal index and mortality, indicates that more complicated mechanisms than a general long-term detrimental effect of intrauterine growth retardation explain the association between birth size and adult mortality. The heterogeneous associations between birth dimensions and mortality in young and later adulthood, the minor differences in relative risk of cause-specific mortality, and the heterogeneity in the association between birth dimensions and maternal and paternal mortality, respectively, indicate that several mechanisms (factors related to social position, common genetic factors, and specific organ programming) may account for the relation between birth measures and later mortality.
To study the association between birth weight and polycystic ovary syndrome (PCOS) in adult life in Danish women born 1973-1991.
Data were extracted from the Danish Medical Birth Register and the Danish National Patient Register (NPR).
All female children born of Danish mothers in Denmark between 1973 and 1991 were included (n = 523,757) and followed for a total of 4,739,547 person-years at risk.
Information on birth weight was extracted from the Danish Medical Birth Register. The cohort was followed up in the NPR for PCOS diagnoses from age 15 years until the end of 2006. Furthermore, information on maternal diabetes diagnoses was extracted from the NPR.
The risk of PCOS was significantly increased in women with birth weight =4,500 g (incidence rate ratio, 1.57; 95% confidence interval 1.21-2.03) compared to women with birth weight 3,000-3,499 g. All women with birth weight =4,500 g were born large for gestational age and a birth weight of 4,500 g represented the 98.5th percentile of the birth weights. Women born of mothers diagnosed with diabetes were at increased risk of PCOS. In these women the risk of PCOS increased with decreasing birth weight.
The risk of PCOS was increased in women born with birth weight =4,500 g. In women of diabetic mothers we found an increased risk of PCOS, which was inversely related to birth weight.
The aim of this study was to determine antibody titres against Campylobacter, Salmonella, and Yersinia in a population-based cohort of pregnant women in Denmark in order to evaluate adverse pregnancy outcomes (miscarriage, preterm birth, and small for gestational age) in relation to occupational exposure to animals in women exposed to food producing animals.
We used data and blood samples from the Danish National Birth Cohort. Serum samples collected during the first trimester from 192 pregnant women who were occupationally exposed to domestic animals and 188 randomly selected unexposed pregnant women were analysed for IgG, IgM, and IgA antibodies against Campylobacter, Salmonella, and Yersinia. Pregnancy outcomes of interest were identified through the Danish National Patient Register.
Women with occupational exposure to animals had significantly higher IgG antibody concentrations against Campylobacter, Salmonella, and Yersinia, whereas they had lower concentrations of IgM and IgA antibodies.
Serological markers were not identified as risk factors for adverse pregnancy outcomes, with the exception of elevated concentrations of Salmonella antibodies, which were found to be associated with an increased risk of preterm birth.
While recent studies have reported an inverse relation between childhood intelligence test scores and all-cause mortality in later life, the link with disease-specific outcomes has been rarely examined. Furthermore, the potential confounding effect of birthweight and childhood social circumstances is unknown. We investigated the relation of childhood intelligence with coronary heart disease (CHD) and stroke risk in a cohort of 6910 men born in 1953 in the Copenhagen area of Denmark. Events were ascertained from 1978 to 2000 using a cause-of-death register and hospital discharge records. There were 150 CHD (19 fatal; 131 non-fatal) and 93 stroke (4 fatal; 89 non-fatal) events during follow-up into mid-life. Childhood intelligence was inversely related to CHD with the highest rate apparent in adults with low childhood test scores (HR(lowest vs. highest quartile), 2.70; 95% confidence interval: 1.60, 4.57; P(trend) = 0.0001). After adjustment for paternal social class and birthweight, this association was attenuated only marginally. There was little evidence of a IQ-stroke relationship. The cognitive characteristics captured by IQ testing in the present study, such as communication and problem solving ability, appear to be associated with risk of CHD. Health promotion specialists and clinical practitioners may wish to consider these skills in their interactions with the general public. Replication of these results using studies which hold data on intelligence and socio-economic position across the life course is required.
Socio-economic disparities in preterm delivery have often been attributed to socially patterned smoking habits. However, most existing studies have used methods that potentially give biased estimates of the mediating effect of smoking. We used a contemporary mediation approach to study to which extent smoking during pregnancy mediates educational disparities in preterm delivery.
We performed a comparative analysis of data from three large birth cohort studies: the Danish National Birth Cohort (DNBC), the Dutch Generation R Study, and the Norwegian Mother and Child Cohort Study (MoBa). Risk of preterm delivery by maternal education is reported as risk differences and decomposed into a part explained by smoking and a part explained by other pathways.
Proportions of preterm singleton deliveries were 4.8%-4.9% in all three cohorts. Total effects of maternal education were 2.0 (95% confidence interval [CI] 1.4, 2.5), 3.2 (95% CI 0.8, 5.2) and 2.0 (95% CI 0.9, 3.0) excess preterm deliveries per 100 singleton deliveries in DNBC, Generation R and MoBa when comparing primary/lower secondary education to an academic degree or equivalent. Smoking mediated, respectively, 22%, 10% and 19% of the excess risk in the DNBC, Generation R and MoBa cohorts. Adjustment for potential misclassification of smoking only increased mediated proportions slightly.
Smoking during pregnancy explains part of educational disparities in preterm delivery, but the mediated proportion depends on the educational gradient in smoking, emphasising that educational disparities in preterm birth may be mediated by different risk factors in different countries.
BACKGROUND: Exercise in pregnancy is recommended in many countries, and swimming is considered by many to be an ideal activity for pregnant women. Disinfection by-products in swimming pool water may, however, be associated with adverse effects on various reproductive outcomes. We examined the association between swimming in pregnancy and preterm and postterm birth, fetal growth measures, small-for-gestational-age, and congenital malformations. METHODS: We used self-reported exercise data (swimming, bicycling, or no exercise) that were prospectively collected twice during pregnancy for 74,486 singleton pregnancies. Recruitment to The Danish National Birth Cohort took place 1996-2002. Using Cox, linear and logistic regression analyses, depending on the outcome, we compared swimmers with physically inactive pregnant women; to separate a possible swimming effect from an effect of exercise, bicyclists were included as an additional comparison group. RESULTS: Risk estimates were similar for swimmers and bicyclists, including those who swam throughout pregnancy and those who swam more than 1.5 hours per week. Compared with nonexercisers, women who swam in early/mid-pregnancy had a slightly reduced risk of giving birth preterm (hazard ratio = 0.80 [95% confidence interval = 0.72-0.88]) or giving birth to a child with congenital malformations (odds ratio = 0.89 [0.80-0.98]). CONCLUSIONS: These data do not indicate that swimming in pool water is associated with adverse reproductive outcomes.
Q fever caused by Coxiella burnetii is transmitted to humans by inhalation of aerosols from animal birth products. Q fever in pregnancy is suspected to be a potential cause of fetal and maternal morbidity and fetal mortality but the pathogenesis is poorly understood, and even in Q fever endemic areas, the magnitude of a potential association is not established.We aimed to examine if presence of antibodies to C. burnetii during pregnancy or seroconversion were associated with adverse pregnancy outcomes.
The Danish National Birth Cohort collected blood samples and interview data from 100,418 pregnant women (1996-2002). We sampled 397 pregnant women with occupational or domestic exposure to cattle or sheep and a random sample of 459 women with no animal exposure. Outcome measures were spontaneous abortion, preterm birth, birth weight and Small for Gestational Age (SGA).Blood samples collected in pregnancy were screened for antibodies against C. burnetii by enzyme-linked immunosorbent assay (ELISA). Samples positive for IgG or IgM antibodies in the ELISA were confirmed by immunofluorescence antibody test (IFA).
Among the 856 women, 169 (19.7%) women were IFA positive; 147 (87%) of these had occupational or domestic contact with livestock (IFA cutoff?>?=1:128).Two abortions were IFA positive vs. 6 IFA negative (OR: 1.5; 95%CI: 0.3-7.6). Three preterm births were IFA positive vs. 38 IFA negative (OR: 0.4; 95% CI: 0.1-1.1). There was a significant difference in birth weight of 168?g (95% CI: 70-267?g) with IFA positive being heavier, and the risk of being SGA was not increased in the newborns of IFA positive women (OR: 0.4; 95%CI: 0.8-1.0).Most seropositive women were IgG positive indicating previous exposure. Seroconversion during pregnancy was found in 10 women; they all delivered live babies at term, but two were SGA.
We found no increased risk of adverse pregnancy outcome in women with verified exposure to C. burnetii.To our knowledge, this is the first population-based seroepidemiologic study evaluating pregnancy outcome in women with serologically verified exposure to C. burnetii against a comparable reference group of seronegative women.
It has been suggested that the handling of heavy loads during pregnancy is associated with impaired fetal growth. We examined the association between quantity and frequency of maternal occupational lifting and the child's size at birth, measured by weight, length, ponderal index, small-for-gestational-age (SGA), abdominal circumference, head circumference, and placental weight.
We analyzed birth size from the Danish Medical Birth Registry of 66 693 live-born children in the Danish National Birth Cohort according to the mother's self-reported information on occupational lifting from telephone interviews around gestational week 16. Data were collected in the period 1996-2002. We used linear and logistic regression models and adjusted for confounders.
In the fully adjusted models, most of the mean differences in birth size measures had values indicating a smaller size of offspring among women with occupational lifting versus women with no lifting, but the differences were very small, and there was a statistically significant trend only for placental weight showing lighter weight with increasing number of kilos lifted per day. In jobs likely to include person-lifting, we found increased odds of SGA among children of women who lifted 501-1000 kilos per day [odds ratio (OR) 1.34, 95% confidence interval (95% CI) 0.98-1.83] and >1000 kilos per day (OR 1.51, 95% CI 0.83-2.76) compared to no lifting. In jobs with no person-lifting, occupational lifting was not associated with SGA.
Overall, we observed no strong support for an association between maternal occupational lifting and impaired size at birth. Our data indicated a potential association between lifting and SGA among offspring of women in occupations that are likely to include person-lifting. These results should, however, be interpreted with caution due to limited statistical power, and we suggest that future studies include detailed, individual information on job functions and ergonomic routines of lifting procedures.