Secular change in size at birth from 1973 to 2003: national data from Denmark

New Danish reference values for height, weight and body mass index of children aged 0-5 years

AIM

To derive new reference values for height, weight and body mass index (BMI) of children aged 0-5 years in Denmark and to compare them with the national reference from the 1970s and the 2006 WHO standard.

METHODS

The height and weight of 4105 healthy singleton children born in 1995 were obtained from a cohort study. Children were measured at birth and at seven regular health examinations by a general practitioner up to 5 years of age. Generalized additive models for location, scale and shape were used to construct percentile curves.

RESULTS

Mean length, weight and BMI at birth and during the first months of life increased significantly, but the differences diminished thereafter, and at 1 year BMI had decreased. In boys, weight and BMI had decreased by 2 years of age but had increased, together with height, at 5 years. Children were taller, heavier and had a higher BMI than that referred to in the WHO standard.

CONCLUSION

New references for length or height, weight and BMI by age were constructed for children in Denmark. Since the 1970s, weight, length and BMI at birth increased, and growth during the first year of life appears to be healthier.

Body size at birth and same-sex marriage in young adulthood

An unexplained excess of overweight has been reported among lesbians. In contrast, reports suggest that gay men may be, on average, slightly lighter and shorter than heterosexual men. We studied associations between weight, length, and body mass index (BMI) at birth and same-sex marriage in young adulthood among 818,671 Danes. We used linear regression to calculate differences in mean body measures at birth and Poisson regression analysis to calculate confounder-adjusted incidence rate ratios (IRR) of same-sex marriage according to body measures at birth. Overall, 739 persons entered same-sex marriage at age 18-32 years during 5.6 million person-years of follow-up. Birth year-adjusted mean body measures at birth were similar for same-sex married and other women. However, same-sex marriage rates were 65% higher among women of heavy birth weight (IRR = 1.65; 95% CI = 1.18-2.31, for > or =4000 vs. 3000-3499 g, p = .02), and rates were inversely associated with birth length (p (trend) = .04). For same-sex married men, birth year-adjusted mean weight (-72 g, p = .03), length (-0.3 cm, p = .04), and BMI (-0.1 kg/m(2), p = .09) at birth were lower than for other Danish men. Same-sex marriage rates were increased in men of short birth length (IRR = 1.45; 95% CI = 1.01-2.08, for < or =50 vs. 51-52 cm), although not uniformly so (p (trend) = .16). Our population-based findings suggest that overweight in lesbians may be partly rooted in constitutional factors. Novel findings of smaller average body measures at birth in same-sex marrying men need replication. Factors affecting intrauterine growth may somehow influence sexual and partner-related choices in adulthood.

Trends in birth size and macrosomia in Queensland, Australia, from 1988 to 2005

The objectives of this study were to explore temporal changes in birth measures in Queensland, Australia, and examine whether secular trends are similar to those in other countries. This study used data from the Queensland Perinatal Data Collection, including singleton livebirths (n = 831 375) from 1988 to 2005. Recorded birthweight (BW, g), birth length (BL, cm), gestational age (weeks), maternal age, ethnic origin and calculated ponderal index (PI, kg/m(3)) were used. Temporal trends were assessed over the intervals 1988-2005 for BW and 2001-2005 for BW, BL and PI. Mean BW increased during the 17-year interval by approximately 1.9 g/year at a relatively low rate compared with reports from other countries. The proportion of high BW infants (> or = 4000 g) rose by 0.8% per year. Stratification by Indigenous status indicated that the increase in mean BW and prevalence of high BW was confined to non-Indigenous newborns only. The secular increase in BW was further modified by gestational age, and maternal age. The increase in BW was larger in term infants (4.2 g/year) than in preterm infants (1.8 g/year), and larger in infants of younger mothers than in those of older mothers (5.0 g/year vs. 3.1 g/year). There were no trends in mean BL and mean PI at birth from 2001 to 2005. In Queensland, mean BW increased moderately in the last 17 years, as did the proportion of high BW infants. The trend in rising BW remained after controlling for other perinatal characteristics. Birth measures per se and related trends differed by Indigenous status and warrant further investigation.

Temporal trends in pregnancy weight gain and birth weight in Bavaria 2000-2007: slightly decreasing birth weight with increasing weight gain in pregnancy

AIMS

To assess temporal trends in birth weight and pregnancy weight gain in Bavaria from 2000 to 2007.

METHODS

Data on 695,707 mother and infant pairs (singleton term births) were available from a compulsory reporting system for quality assurance, including information on birth weight, maternal weight at delivery and at booking, maternal smoking, age, and further anthropometric and lifestyle factors. Pregnancy weight gain was defined as: weight prior to delivery minus weight at first booking minus weight of the newborn.

RESULTS

Although mean weight gain during pregnancy increased considerably from 10.10 to 10.73 kg in seven years, the mean birth weight in mature singletons decreased slightly from 3433 to 3414 g. These trends could not be explained by concurrent changes in the rates of primiparity, smoking and gestational diabetes.

CONCLUSIONS

These German data confirm an increased weight gain during pregnancy with adjustment for potential confounders.

Conference on "Multidisciplinary approaches to nutritional problems". Symposium on "Diabetes and health". Challenges in the study of causation of obesity

Use of the energy balance equation for understanding the causation of obesity is discussed. Its basis on the thermodynamic laws is expressed in mathematical models for body-weight changes. Only a very small net energy surplus per time unit constitutes the energy deposition during weight gain, making measurements of its components difficult. The physical laws provide exact quantitative relationships between energy intake, energy expenditure and deposition of energy, but cannot disentangle the initiating and driving forces of the energy imbalance, which may also be an active storage of fat in adipose tissue. These and various other limitations of the energy balance model warrant cautiousness in using the model in studies of obesity causation. Weight gain may be self-promoting and mathematical feedback models allowing estimation of such effects show that they are realistic. Predisposition and susceptibility should be distinguished, and susceptibility as a modifiable predisposition, the genetic and environmental contribution to predisposition and its usefulness as targets for prevention and treatment are discussed. Current progress in unravelling genetic predisposition, the complex genetically-determined mechanisms, the slower progress in unravelling the environmental influences, the different nature of genetic and environmental influences, the possible pathways of environmental influences and the environmental influences as mediators of genetic effects are addressed. The evidence behind the prevailing concept of the 'obesogenic' environment is critically analysed. Finally, particular opportunities for the identification of the causes of the obesity epidemic by detailed analysis of an observed irregular development of the epidemic over long time periods are presented, and evidence for predisposition as a result of postnatal environmental influences is inferred from these studies.

Birth size and breast cancer risk: re-analysis of individual participant data from 32 studies

BACKGROUND

Birth size, perhaps a proxy for prenatal environment, might be a correlate of subsequent breast cancer risk, but findings from epidemiological studies have been inconsistent. We re-analysed individual participant data from published and unpublished studies to obtain more precise estimates of the magnitude and shape of the birth size-breast cancer association.

METHODS AND FINDINGS

Studies were identified through computer-assisted and manual searches, and personal communication with investigators. Individual participant data from 32 studies, comprising 22,058 breast cancer cases, were obtained. Random effect models were used, if appropriate, to combine study-specific estimates of effect. Birth weight was positively associated with breast cancer risk in studies based on birth records (pooled relative risk [RR] per one standard deviation [SD] [= 0.5 kg] increment in birth weight: 1.06; 95% confidence interval [CI] 1.02-1.09) and parental recall when the participants were children (1.02; 95% CI 0.99-1.05), but not in those based on adult self-reports, or maternal recall during the woman's adulthood (0.98; 95% CI 0.95-1.01) (p for heterogeneity between data sources = 0.003). Relative to women who weighed 3.000-3.499 kg, the risk was 0.96 (CI 0.80-1.16) in those who weighed < 2.500 kg, and 1.12 (95% CI 1.00-1.25) in those who weighed > or = 4.000 kg (p for linear trend = 0.001) in birth record data. Birth length and head circumference from birth records were also positively associated with breast cancer risk (pooled RR per one SD increment: 1.06 [95% CI 1.03-1.10] and 1.09 [95% CI 1.03-1.15], respectively). Simultaneous adjustment for these three birth size variables showed that length was the strongest independent predictor of risk. The birth size effects did not appear to be confounded or mediated by established breast cancer risk factors and were not modified by age or menopausal status. The cumulative incidence of breast cancer per 100 women by age 80 y in the study populations was estimated to be 10.0, 10.0, 10.4, and 11.5 in those who were, respectively, in the bottom, second, third, and top fourths of the birth length distribution.

CONCLUSIONS

This pooled analysis of individual participant data is consistent with birth size, and in particular birth length, being an independent correlate of breast cancer risk in adulthood.

Outcomes of pregnancy in women with tetralogy of Fallot

BACKGROUND

Surgical results after repair of tetralogy of Fallot have remained excellent for the last decades, with current long-term rates of survival over 95%. Since functional capacity, quality of life, and social interactions are basically normal in this large group of patients, pregnancy obviously becomes a relevant issue for the female subgroup. In consequence, adequate obstetrical and cardiological management of pregnancy is particularly important.

OBJECTIVE

To describe the outcomes of pregnancy, and fertility, in a series of women who underwent surgery for tetralogy of Fallot in a single centre.

METHODS AND RESULTS

We obtained data from hospital records, national registries, and questionnaires on 78 women who underwent surgical correction of tetralogy of Fallot between 1972 and 1992. Of 58 women who reached an age of at least 18 years, with 45 of this cohort currently surviving, 13 having died as adults, there were 54 pregnancies in 25 women. The recorded rate of spontaneous abortion was 15%, and infertility rate was 3.4%. There have been 41 life births, with a median weight at birth of 3.2 kg. Only 1 newborn was small for gestational age, and no one was born before the 36th week. The recurrence rate of congenital heart disease was high, at 9.8%. Cardiac complications during or after pregnancy were not observed, and only one woman had pre-eclampsia.

CONCLUSIONS

Pregnancy is well tolerated in women with tetralogy of Fallot, and an excellent neonatal outcome is expected. The recurrence risk of congenital cardiac disease, most often tetralogy of Fallot, is high.

Weight at birth and all-cause mortality in adulthood

BACKGROUND

Small size at birth is associated with subsequent cardiovascular disease and diabetes, and large size is associated with obesity and cancer. The overall impact of these opposing effects on mortality throughout the lifespan is unclear because causes of death change with age.

METHODS

We investigated the association of birth weight with adult all-cause mortality using a Danish school-based cohort of 216,464 men and women born from 1936 through 1979. The cohort was linked to vital statistic registers. The main outcome was all-cause mortality from ages 25 through 68 years. Associations with death from cancer, circulatory disease, and all other causes were also examined.

RESULTS

During 5,205,477 person-years of follow-up, 11,149 deaths occurred among men and 6609 among women. The cumulative hazard ratios of the association between birth weight categories and all-cause mortality was constant for all ages investigated and did not differ between men and women. Compared with subjects having birth weights in the reference category (3251-3750 g), those with the lowest birth weights (2000-2750 g) had 17% higher mortality (95% confidence interval = 1.11-1.22), and those with the highest birth weights (4251-5500 g) had 7% higher mortality (1.01-1.15) from all causes. The association of birth weight with cancer increased linearly, whereas the association of birth weight with circulatory disease and all other causes was U-shaped.

CONCLUSIONS

To the degree that the association of birth weight with adult survival is causal, the U-shaped association between birth weight and adult mortality suggests that population increases in birth weight may not necessarily lead to improved health in adulthood.