Birth weight has increased over a generation

Secular Trends of Birth Weight in Twins and Singletons in South Korea from 2000 to 2020

Whether the decline of birth weight (BW) reported in developed countries in the early 2000s is ongoing remains unknown. Furthermore, despite recent sharp increases in twin births, comparing secular trends of BW between singletons and twins is difficult, as studies have rarely examined secular trends of BW in twins and singletons simultaneously. Therefore, this study aimed to investigate the most recent 20-year trends (2000-2020) of BW in twins and singletons in South Korea. Annual natality files from 2000 to 2020 obtained from the Korean Statistical Information Service were analyzed. A yearly decrease of BW was 3 g among singletons and 5 to 6 g in twins from 2000 to 2020, indicating a widening gap of BW between twins and singletons with increasing years. Gestational age (GA) also decreased in twins and singletons with yearly decreases of 0.28 days in singletons and 0.41 days in twins. Whereas BW decreased in term (GA ≥ 37 weeks), and very preterm groups (28 weeks ≤ GA < 32 weeks) from 2000 to 2020 in twins and singletons, it increased in moderate to late preterm (32 weeks ≤ GA < 37 weeks) groups, indicating a non-linear relationship between BW and GA. The prevalence of macrosomia (BW > 4000 g) in singletons decreased from 2000 to 2020, whereas low birth weight (LBW; BW < 2500 g) increased in twins and singletons. LBW is associated with adverse health outcomes. Effective public health strategies aiming at reduction in the incidence of LBW in the population should be developed.

Development of birthweight and length for gestational age and sex references in Yucatan, Mexico

OBJECTIVE

To develop sex- and gestational age specific reference percentiles and curves for birth weight and length for Yucatec neonates using data from birth registers of infants born during 2015-2019.

MATERIAL AND METHODS

Observational, descriptive, epidemiologic study in a 5-year period including every registered birth in the state of Yucatan, Mexico using birth registries. A total of 158 432 live, physically healthy singletons (76 442 females and 81 990 males) between 25 and 42 weeks of gestation were included in the analysis. We used the LMS method to construct smoothed reference centiles (3rd, 10th, 25th, 50th, 75th, 95th, and 97th) and curves for males and females separately.

RESULTS

Mean maternal age was 26 (SD = 6.22) years. Fifty-two percent of births occurred by vaginal delivery, 37% were firstborn and similar proportions were second (33%) and third or more (30%) born. 5.5% of newborns included in the references corresponds to neonates born before 37 weeks of gestation (5.9% boys and 5.1% girls). In both sexes, the percentage of infants with a birthweight less than 2500 g was 6.7%. The birthweight at the 50th percentile for males and females at 40 weeks of gestation in this cohort was 3256 and 3167 g, respectively, and the corresponding values for birth length were 50.23 and 49.84 cm (mean differences between sexes: 89 g and 0.40 cm, respectively).

CONCLUSION

The reference percentile and curves developed in this study are useful for research purposes and can help health practitioners to assess the biological status of infants born in Yucatán.

Early life programming of adult ischemic heart disease within and across generations: The role of the socioeconomic context

BACKGROUND

The developmental origins of ischemic heart disease (IHD) have been widely documented but little is known about their persistence across more than one generation. This study aimed to investigate whether the effects of early life disadvantages on adult IHD have changed between generations and are mediated by adult socioeconomic circumstances, and further explore the transgenerational effects of grandparental and parental exposures to disadvantaged circumstances on adult offspring's IHD.

METHODS

We used register-based data from the Uppsala Multigenerational Study, Sweden. The study populations were the parents born 1915-1929 and their offspring born 1932-1972 with available obstetric data. The offspring were further linked to grandparents who had their socioeconomic and demographic data recorded. The outcome was incident IHD assessed at ages 32-75 during a follow-up from January 1, 1964 till December 31, 2008. The exposures included birthweight standardized-for-gestational age, ponderal index, gestational length, and parental socioeconomic position (SEP). Education and income were analyzed as mediators. Potential transgenerational associations were explored by linking offspring IHD to parents' standardized birthweight and gestational length, grandparental SEP, and to grandmothers' age, parity, and marital status at parental birth. All associations were examined in Cox proportional hazard regression models.

RESULTS

Lower standardized birthweight and lower parental SEP were found to be associated with higher IHD rates in both generations, with no evidence of effect modification by generation. Education and income did not mediate the association between standardized birthweight and IHD. Disadvantaged grandparental SEP, younger and older childbearing ages of grandmothers, and paternal preterm birth affected offspring's IHD independent of parental education, income, or IHD history.

CONCLUSIONS

The findings point to similar magnitudes of IHD inequalities by early life disadvantages across two historical periods and the existence of transgenerational effects on IHD. Epigenetic dysregulation involving the germline is a plausible candidate mechanism underlying the transgenerational associations that warrant further research.

The Biological and Social Determinants of Childhood Obesity: Comparison of 2 Cohorts 50 Years Apart

OBJECTIVE

To determine whether the same relationships between early-life risk factors and socioeconomic status (SES) with childhood body mass index (BMI) are observed in a modern cohort (2000) compared with a historic cohort (1947).

STUDY DESIGN

The relationships between early-life factors and SES with childhood BMI were examined in 2 prospective birth cohorts from the same region, born 50 years apart: 711 children in the 1947 Newcastle Thousand Families Study (NTFS) and 475 from the 2000 Gateshead Millennium Study (GMS). The associations between birth weight, breastfeeding, rapid infancy growth (0-12 months), early-life adversity (0-12 months), and parental SES (birth and childhood) with childhood BMI z-scores and whether overweight/obese (BMI >91st percentile using UK 1990 reference) aged 9 years were examined using linear regression, path analyses, and logistic regression.

RESULTS

In the NTFS, the most advantaged children were taller than the least (+0.91 height z-score, P = .001), whereas in GMS they had lower odds of overweight/obese than the least (0.35 [95% CI 0.14-0.86]). Rapid infancy growth was associated with increased BMI z-scores in both cohorts, and with increased likelihood of overweight/obese in GMS.

CONCLUSIONS

This study suggests that children exposed to socioeconomic disadvantage or who have rapid infancy growth in modern environments are now at lower risk of growth restriction but greater risk of overweight.

Secular trends of birthweight in boys from 1950 to 2010

BACKGROUND

Birthweight is an indicator of fetal development and intrauterine conditions and is associated with future health outcomes. Secular birthweight trends prior to the 1970s are mostly unknown. Our aim was to explore secular birthweight trends in Swedish boys from 1950 to 2010.

METHODS

We have collected detailed growth data including birthweight from archived School Health Care records for children born in Gothenburg from 1946 and onwards and established a unique population-based cohort, the Body Mass Index Epidemiology Study (BEST). The birthweight cohort spans six decades (1950-2010) and includes 46,548 boys.

RESULTS

The mean birthweight of the complete study cohort was 3580 ± 562 g. Linear regression analysis of the entire period revealed a minimal negative secular trend for birthweight (BETA = -0.4 g/year; p < 0.01). However, three distinct trends appeared during sub-periods: a decrease 1950-80, an increase 1980-2000 and another decrease 2000-2010.

CONCLUSION

We demonstrate that birthweight in boys has undergone periodic decreases and subsequent increases, but the overall trend from the 1950s to the present is stable.

Childhood Health Outcomes in Term, Large-for-Gestational-Age Babies With Different Postnatal Growth Patterns

Large-for-gestational-age (LGA) babies have a higher risk of metabolic disease later in life, and their postnatal growth in early childhood may be associated with long-term adverse outcomes. This study aimed to determine childhood health outcomes of term LGA babies with different growth patterns. Data were obtained from the US Collaborative Perinatal Project for the years between 1959 and 1976. The growth trajectories of 3,316 term LGA babies were identified and odds ratios of obesity, growth restriction, low intelligence quotient (IQ), and high blood pressure (HBP) were calculated by logistic regression. Compared with term appropriate-for-gestational-age infants, term LGA babies without catch-down growth had increased risks of obesity (adjusted odds ratio (aOR) = 6.37, 95% confidence interval (CI): 5.24, 7.73) and HBP (aOR = 1.67, 95% CI: 1.37, 2.03). Those with high catch-down growth had higher risks of growth restriction (aOR = 2.21, 95% CI: 1.66, 2.95) and low IQ (aOR = 1.61, 95% CI: 1.04, 2.49). Nevertheless, infants with small catch-down growth had lower risks of obesity (aOR = 0.78, 95% CI: 0.63, 0.95), growth restriction (aOR = 0.28, 95% CI: 0.17, 0.46), low IQ (aOR = 0.66, 95% CI: 0.41, 1.06), and HBP (aOR = 0.89, 95% CI: 0.77, 1.04). According to our data, term LGA infants with small catch-down growth had no increased risks of adverse outcomes.

Ponderal index at birth associates with later risk of gestational diabetes mellitus

PURPOSE

Low birth weight (BW) and low ponderal index (PI) are associated with increased risk of type 2 diabetes mellitus. This study has two purposes: first to investigate the influence of PI on the risk of gestational diabetes mellitus (GDM); second, to study the association between glucose metabolism and BW in women with previous GDM.

METHODS

GDM cohort: 185 women with GDM in 1978-1996, attending a follow-up study in 2000-2002. Control cohort: 1137 women from a population-based diabetes screening study (Inter99) in a neighbouring county in 1999-2001. BW and birth length were collected from the original midwifery records. BW and PI were stratified into tertiles for analysis.

RESULTS

PI in the lower tertiles was associated with an increased risk of GDM [odds ratio 1.59 (95% confidence interval 1.07-2.36, p = 0.021)]. Among women with previous GDM, the area under the curve (AUC) for plasma levels of glucose and insulin during an OGTT was highest for the lower tertiles of BW (for AUCglucose p = 0.048, for AUCinsulin p = 0.047 adjusted for age and BMI).

CONCLUSIONS

Lower PI is associated with increased risk of GDM. In women with previous GDM, lower BW is associated with a more severe impairment of glucose metabolism one to two decades after the pregnancy complicated by GDM.

Anthropometrics at birth and risk of a primary central nervous system tumour: A systematic review and meta-analysis

BACKGROUND

The aetiology of primary central nervous system (CNS) tumours remains largely unknown, but their childhood peak points to perinatal parameters as tentative risk factors. In this meta-analysis, we opted to quantitatively synthesise published evidence on the association between birth anthropometrics and risk of primary CNS tumour.

METHODS

Eligible studies were identified via systematic literature review; random-effects meta-analyses were conducted for the effect of birth weight and size-for-gestational-age on childhood and adult primary CNS tumours; subgroup, sensitivity, meta-regression and dose-response by birth weight category analyses were also performed.

RESULTS

Forty-one articles, encompassing 53,167 CNS tumour cases, were eligible. Birth weight >4000 g was associated with increased risk of childhood CNS tumour (OR: 1.14, [1.08-1.20]; 22,330 cases). The risk was higher for astrocytoma (OR: 1.22, [1.13-1.31]; 7456 cases) and embryonal tumour (OR: 1.16, [1.04-1.29]; 3574 cases) and non-significant for ependymoma (OR: 1.12, [0.94-1.34]; 1374 cases). Increased odds for a CNS tumour were also noted among large-for-gestational-age children (OR: 1.12, [1.03-1.22]; 10,339 cases), whereas insufficient data for synthesis were identified for other birth anthropometrics. The findings remained robust across subgroup and sensitivity analyses controlling for several sources of bias, whereas no significant heterogeneity or publication bias were documented. The limited available evidence on adults (4 studies) did not reveal significant associations between increasing birth weight (500-g increment) and overall risk CNS tumour (OR: 0.99, [0.98-1.00]; 1091 cases) or glioma (OR: 1.03, [0.98-1.07]; 2052 cases).

CONCLUSIONS

This meta-analysis confirms a sizeable association of high birth weight, with childhood CNS tumour risk, particularly astrocytoma and embryonal tumour, which seems to be independent of gestational age. Further research is needed to explore underlying mechanisms, especially modifiable determinants of infant macrosomia, such as gestational diabetes.

Fit to WHO weight standard of European infants over time

OBJECTIVES

The 2006 WHO growth charts were created to provide an international standard for optimal growth, based on healthy, breastfed populations, but it has been suggested that Northern European children fit them poorly. This study uses infant weight data spanning 50 years to determine how well-nourished preschool children from different eras fit the WHO standard, and discuss the implications of deviations.

DESIGN

Four longitudinal datasets from the UK and one from Finland were used comprising over 8000 children born between 1959 and 2003. Weights from birth to 2 years were converted to age-sex-adjusted Z scores using the WHO standard and summarised using Generalized Additive Models for Location, Scale and Shape.

RESULTS

Weights showed a variable fit to the WHO standard. Mean weights for all cohorts were above the WHO median at birth, but dipped by up to 0.5 SD to a nadir at 8 weeks before rising again. Birth weights increased in successive cohorts and the initial dip became slightly shallower. By age 1 year, cohorts were up to 0.75 SD above the WHO median, but there was no consistent pattern by era.

CONCLUSIONS

The WHO standard shows an acceptable, but variable fit for Northern European infants. While birth weights increased over time, there was, unexpectedly, no consistent variation by cohort beyond this initial period. Discrepancies in weight from the standard may reflect differences in measurement protocol and trends in infant feeding practice.

Race Disparities and Decreasing Birth Weight: Are All Babies Getting Smaller?

The mean infant birth weight in the United States increased for decades, but it might now be decreasing. Given race disparities in fetal growth, we explored race-specific trends in birth weight at Magee-Womens Hospital, Pittsburgh, Pennsylvania, from 1997 to 2011. Among singleton births delivered at 37-41 weeks (n = 70,607), we evaluated the proportions who were small for gestational age and large for gestational age and changes in mean birth weights over time. Results were stratified by maternal race/ethnicity. Since 1997, the number of infants born small for their gestational ages increased (8.7%-9.9%), whereas the number born large for their gestational ages decreased (8.9%-7.7%). After adjustment for gestational week at birth, maternal characteristics, and pregnancy conditions, birth weight decreased by 2.20 g per year (P < 0.0001). Decreases were greater for spontaneous births. Reductions were significantly greater in infants born to African-American women than in those born to white women (-3.78 vs. -1.88 per year; P for interaction = 0.010). Quantile regression models indicated that birth weight decreased across the entire distribution, but reductions among infants born to African-American women were limited to those in the upper quartile after accounting for maternal factors. Limiting the analysis to low-risk women eliminated birth weight reductions. Birth weight has decreased in recent years, and reductions were greater in infants born to African-American women. These trends might be explained by accumulation of risk factors such as hypertension and prepregnancy obesity that disproportionately affect African-American women. Our results raise the possibility of worsening race disparities in fetal growth.

A retrospective cohort study of factors relating to the longitudinal change in birth weight

BACKGROUND

Recent reports have shown a decrease in birth weight, a change from prior steady increases. Therefore we sought to describe the demographic and anthropometric changes in singleton term fetal growth.

METHODS

This was a retrospective cohort analysis of term singleton deliveries (37-42 weeks) from January 1, 1995 to January 1, 2010 at a single tertiary obstetric unit. We included all 43,217 neonates from term, singleton, non-anomalous pregnancies. Data were grouped into five 3-year intervals. Mean and median birth weight (BW), birth length (BL), and Ponderal Index (PI) were estimated by year, race and gestational age. Our primary outcome was change in BW over time. The secondary outcomes were changes in BL and PI over time.

RESULTS

Mean and median BW decreased by 72 and 70 g respectively (p < 0.0001) over the 15 year period while BL also significantly decreased by 1.0 cm (P < 0.001). This contributed to an increase in the neonatal PI by 0.11 kg/m(3) (P < 0.001). Mean gestational age at delivery decreased while maternal BMI at delivery, hypertension, diabetes, and African American race increased. Adjusting for gestational age, race, infant sex, maternal BMI, smoking, diabetes, hypertension, and parity, year of birth contributed 0.1 % to the variance (-1.7 g/year; 26 g) of BW, 1.8% (-0.06 cm/year; 0.9 cm) of BL, and 0.7% (+0.008 kg/m(3)/year; 0.12 kg/m(3)) of PI. These findings were independent of the proportional change in race or gestational age.

CONCLUSIONS

We observed a crude decrease in mean BW of 72 g and BL of 1 cm over 15 years. Furthermore, once controlling for gestational age, race, infant sex, maternal BMI, smoking, diabetes, hypertension, and parity, we identified that increasing year of birth was associated with a decrease in BW of 1.7 g/year. The significant increase in PI, despite the decrease in BW emphasizes the limitation of using birth weight alone to define changes in fetal growth.

Divergent Patterns of Incidence in Peripheral Neuroblastic Tumors

BACKGROUND

Prior research on trends in neuroblastoma incidence has conflicted. We aimed to compare how ganglioneuroblastoma and neuroblastoma incidence have changed.

PROCEDURE

Using the Surveillance Epidemiology and End Results (SEER) 9 population-based registry, we identified 2081 malignant peripheral neuroblastic tumors in patients 0 to 14 years from 1973 to 2009. Age-adjusted annual incidence rates were calculated using SEER*Stat, and Joinpoint Regression Program was used to calculate annual percent change (APC) and analyze trends. Data were stratified by histology, age, and stage.

RESULTS

Overall peripheral neuroblastic tumor incidence increased by an APC of 0.47 (P=0.045). However, ganglioneuroblastoma incidence decreased (APC=-1.48; P=0.003), whereas neuroblastoma incidence increased (APC=0.79; P=0.008). When divided by age and stage, locoregional neuroblastoma incidence increased in infants until a significant inflection point in 1996 (APC=4.19; P<0.001) and then decreased sharply (APC=-6.80; P=0.160).

CONCLUSIONS

Ganglioneuroblastoma incidence has decreased, whereas neuroblastoma incidence has increased. These changes could be real, or reflect bias from classification changes or increased detection. Neuroblastoma incidence increased most markedly in infants with locoregional disease only until 1996, then declined, which may reflect changes in tumor ascertainment and folate supplementation.

The childhood obesity epidemic as a result of nongenetic evolution: the maternal resources hypothesis

Over the past century, socioenvironmental evolution (eg, reduced pathogenic load, decreased physical activity, and improved nutrition) led to cumulative increments in maternal energy resources (ie, body mass and adiposity) and decrements in energy expenditure and metabolic control. These decrements reduced the competition between maternal and fetal energy demands and increased the availability of energy substrates to the intrauterine milieu. This perturbation of mother-conceptus energy partitioning stimulated fetal pancreatic β-cell and adipocyte hyperplasia, thereby inducing an enduring competitive dominance of adipocytes over other tissues in the acquisition and sequestering of nutrient energy via intensified insulin secretion and hyperplastic adiposity. At menarche, the competitive dominance of adipocytes was further amplified via hormone-induced adipocyte hyperplasia and weight-induced decrements in physical activity. These metabolic and behavioral effects were propagated progressively when obese, inactive, metabolically compromised women produced progressively larger, more inactive, metabolically compromised children. Consequently, the evolution of human energy metabolism was markedly altered. This phenotypic evolution was exacerbated by increments in the use of cesarean sections, which allowed both the larger fetuses and the metabolically compromised mothers who produced them to survive and reproduce. Thus, natural selection was iatrogenically rendered artificial selection, and the frequency of obese, inactive, metabolically compromised phenotypes increased in the global population. By the late 20th century, a metabolic tipping point was reached at which the postprandial insulin response was so intense, the relative number of adipocytes so large, and inactivity so pervasive that the competitive dominance of adipocytes in the sequestering of nutrient energy was inevitable and obesity was unavoidable.

The contribution of maternal birth cohort to term small for gestational age in the United States 1989-2010: an age, period, and cohort analysis

BACKGROUND

After decades of steady increase, mean birthweight in the US declined throughout the 1990s and early 2000s, a trend not fully explained by changes in length of gestation, medical practice, demographics, or maternal behaviours. We hypothesised that secular changes in health or social factors across women's life courses may have contributed to this unexplained trend and examined maternal birth cohort as a proxy measure of life-course determinants of fetal growth in the US.

METHODS

We used the age, period, and cohort (APC) intrinsic estimator (IE) approach to estimate the contribution of maternal birth cohort (independent of maternal age and period of birth) to small for gestational age (SGA), overall and among term births, in the US from 1989 to 2010. We conducted analyses separately among foreign- and US-born Hispanic, non-Hispanic black (NHB), and non-Hispanic white mothers.

RESULTS

We found evidence of a U-shaped relationship between maternal birth cohort and SGA among NHB women only. After accounting for maternal age and period of birth, risk of SGA among NHB women born in 1950 was 21.1% and decreased to 15.9% in 1970. However, NHB women born after 1970 experienced increasing risk (19.6% by the 1986 birth cohort).

CONCLUSIONS

Our findings suggest that NHB women born after 1970 have experienced increasing risk of SGA. Declining risk of SGA across NHB maternal birth cohorts from 1950 to 1970, however, suggests the potential to reverse this trend. Results illustrate the need for research on health and social risk factors for SGA across the pre-pregnancy life course.

Intrauterine growth restriction: effects of physiological fetal growth determinants on diagnosis

The growth of the fetus, which is strongly associated with the outcome of pregnancy, reflects interplay of several physiological and pathological factors. The assessment of fetal growth is based on comparison of birthweight (BW) or estimated fetal weight (EFW) to standards which define reference ranges at a spectrum of gestational ages. Most birthweight standards do not take into account effects of physiological determinants of fetal growth. Additionally, gestational age in many standards is based on the menstrual history and is often inaccurate. Fetal growth norms should be based on an early ultrasound estimate of gestational age. Customized standards, which have included only ultrasound-dated pregnancies, seem to be superior to population-based birthweight norms in predicting perinatal mortality and morbidity. Adjustment for individual variation in customized growth curves reduces false-positive diagnosis of IUGR and may lead to a very significant reduction in intervention for suspected IUGR. Customized growth potential identifies better the risk for adverse outcome than the currently used national standards, but customized charts may fail in detecting growth-restricted stillbirth. An individual's birthweight is the sum of physiological and pathological influences operating during pregnancy. Growth potential norms are a better discriminator of aberrations of fetal growth than population, ultrasound, and customized norms.

Is fetal macrosomia related to blood pressure among adolescents? A birth cohort study in China

Birth weight (BW) has effects on blood pressure (BP). In order to explore the effects of macrosomia on BP in childhood and in adolescence, a longitudinal cohort study was conducted in Wuxi, China. Subjects with BW ≥4000 g, born in 1993-1995, were the exposed group; the unexposed comparisons were matched by year of birth and sex of infant, with BW of 2500-4000 g. Follow-ups in 2005-6 and 2011-12 were conducted, and height, weight and BP were measured by trained doctors. Multi-mixed models in SAS were used to control for repeated measures to explore the effects of fetal macrosomia on BP. At the inception of the cohort, 1595 pairs of participants were recruited. At the end, 1112 in the exposed group and 1126 in the unexposed group finished both follow-ups. Among adolescents, mean (s.d.) of systolic BP (SBP) was 110.83 (9.43)  mm  Hg, which was statistically significantly higher than that in the unexposed group (mean ± s.d.: 109.33 ± 9.26)  mm  Hg (P=0.0002). After adjusting the repeated measures and birth year, sex, mother's occupation and delivery age, adding weight during pregnancy, hypertension during delivery, gestational age and parity, being a picky eater in childhood, the macrosomia group had higher SBP than the normal BW group; the parameter estimate value was 1.03 (s.e.=0.30). When BMI in childhood and BMI in adolescence were added in the multi-model, the estimated β was 0.71 (s.e.=0.29). No statistically significant effect of macrosomia was found on diastolic BP among adolescents in the multianalysis.

Maternal Prenatal Nutrition and Health in Grandchildren and Subsequent Generations

This review focuses on how maternal prenatal nutritional states may affect the health of grandchildren and later generations. We first summarize the limited current data in human populations relating to the potential transmission of phenotypes across multiple generations that result from the nutritional experience of a pregnant woman. We then discuss findings from other species, especially mammals, that provide important clues as to whether, and if so how, such transmission could occur in humans. Finally, we consider how studies of human populations could be best designed to detect transmission across multiple generations. We argue that just as epidemiologists embraced a life-course perspective to human health and disease in the twentieth century, we must now seek to better understand how health and disease could be shaped across multiple generations.

Sex-specific effect of first-trimester maternal progesterone on birthweight

STUDY QUESTION

Are maternal progesterone levels in early pregnancy associated with fetal birthweight?

SUMMARY ANSWER

Low levels of first-trimester maternal progesterone are significantly associated with a reduction in birthweight in girls, but not boys.

WHAT IS ALREADY KNOWN

Progesterone in the third trimester of pregnancy has previously been related to birthweight in humans.

STUDY DESIGN, SIZE, DURATION

Pregnant women between gestational weeks 4 and 12 were recruited by 99 obstetricians in private practice and enrolled in a prospective cohort study. A follow-up took place at birth. Women younger than 18 years, who had undergone fertility treatments or were diagnosed with infectious diseases, were excluded from the study. A subgroup of 906 participants in whom progesterone had been measured was then selected retrospectively based on the following criteria: no miscarriages, elective abortions or pregnancy complications, infections or multiple births. Data from the follow-up were available for 623 women, who were included in the analyses.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study was coordinated at the Charité University Medicine in Berlin, Germany. Anthropometric, medical and psychosocial information were collected and serum progesterone and estradiol levels were measured in women during the first trimester of pregnancy, followed by the documentation of the pregnancy outcome at birth. Univariable and multivariable regression analyses were performed to identify maternal markers, among them progesterone, affecting birthweight and to determine environmental and maternal factors that are associated with maternal progesterone levels during pregnancy.

MAIN RESULTS AND THE ROLE OF CHANCE

In the multivariable regression model, each increase in maternal progesterone by 1 ng/ml during the first trimester increased girls' birthweight by 10.17 g (95% CI: 2.03-18.31 g). If the mother carried a boy, maternal smoking and perceived worries during early pregnancy predicted a reduced birthweight, irrespective of progesterone levels. Maternal body mass index over 25 and maternal age <21 years significantly correlated with the reduced levels of progesterone. Correlations between environmental challenges and maternal progesterone did not reach levels of significance. Since the analyses were exploratory, the likelihood that results may be due to chance is increased.

LIMITATIONS, REASONS FOR CAUTION

Due to the exploratory nature of the analyses, results need to be independently confirmed in a larger sample. Furthermore, our findings pertain to pregnant women without pregnancy complications or fertility treatments.

WIDER IMPLICATIONS OF THE FINDINGS

Maternal progesterone during early pregnancy is an indicator of subsequent fetal development in female children. Future studies should confirm this relationship and determine whether maternal progesterone is a useful tool in predicting pregnancies at risk resulting in the birth of a girl with low birthweight. Detailed identification of environmental factors modulating maternal progesterone levels should be addressed in future studies.

STUDY FUNDING/POTENTIAL COMPETING INTERESTS

Financial support was provided by the Alexander von Humboldt Foundation, Excellence Initiative of the Hamburg Foundation for Research and the Association for Prevention and Information for Allergy and Asthma (Pina e.V.). The authors have no conflict of interest.

Eighty-year trends in infant weight and length growth: the Fels Longitudinal Study

OBJECTIVES

To investigate secular trends in weight and length growth from birth to 3 years of age in infants born from 1930 to 2008, and to assess whether these trends were associated with concurrent trends in pace of infant skeletal maturation and maternal body mass index.

STUDY DESIGN

Longitudinal weight and length data from 620 infants (302 girls) were analyzed with mixed effects modeling to produce growth curves and predicted anthropometry for infants born from 1930 to 1949, 1950 to 1969, 1970 to 1989, and 1990 to 2008.

RESULTS

The most pronounced differences in growth occurred in the first year of life. Infants born after 1970 were approximately 450 g heavier and 1.4 cm longer at birth, but demonstrated slower growth to 1 year of age than infants born before 1970. Growth trajectories converged after 1 year of age. There was no evidence that relative skeletal age, maternal body mass index, or maternal age together mediated associations between cohort and growth.

CONCLUSIONS

Recent birth cohorts may be characterized not only by greater birth size, but also by subsequent catch-down growth. Trends over time in human growth do not increase monotonically, and growth velocity in the first year may have declined compared with preceding generations.

Birth weight patterns by gestational age in Brazil

BACKGROUND AND OBJECTIVES

We present an updated birth weight-for-gestational-age portrait, based on nearly 8 million observations of an ethnic-mixed population. It comprises the first comprehensive charts with Brazilian data. This contribution intends to assist clinicians in classifying fetal growth, to provide a reference for investigations of predictors and to show the consequences of small and large patterns for gestational age delivery. Most of the reference data for assessing birth weight for gestational age deal with insufficient sample size, especially at low gestational age. Population-based studies with considerably large sample size refer to data collected more than 15 years ago.

METHODS

We accomplished a population-based study on births in all the Brazilian states from 2003 to 2005. Results were based on 7,993,166 singletons. We constructed the 3(rd), 5(th), 10(th), 25(th), 50(th), 90(th), 95(th) and 97(th) smoothed percentiles curves and gender-specific tables from 22 to 43 completed weeks.

RESULTS

The resulting tables and graphical representation provide a gender-specific reference to access the birth weights distribution according to the gestational age in the Brazilian population.

CONCLUSIONS

This is the first population-based reference constructed on a developing country data. These charts could provide an important tool to improve clinical assessment of growth in newborns.

Discordant time trends in maternal body size and offspring birthweight of term deliveries in France between 1972 and 2003: data from the French National Perinatal Surveys

We investigated time trends in maternal weight before and during pregnancy and in infant birthweight in France, from 1972 to 2003, using data on singleton live term births from the representative National Perinatal Surveys of 1972, 1981, 1995, 1998 and 2003 (n=8,664, 4,494, 11,445, 12,006, 12,692, respectively). Mothers were interviewed a few days after delivery and data on delivery and the newborn were extracted from hospital records. Maternal prepregnancy weight, height, body mass index and pregnancy weight gain all increased from 1972 to 2003; however, birthweight did not show a parallel trend. After taking gestational age, maternal age, parity, country of origin, newborn gender and maternal smoking during pregnancy into account, mean birthweight increased between 1972 and 1995 but decreased thereafter and, consistently, there was an increase in small-for-gestational age (SGA) and a decrease in large-for-gestational age newborns. Further adjustment for induced delivery, an indicator of obstetric practice, did not change the results. A similar variation has been observed very recently in the US and in Germany. Further research is needed to identify the factors responsible for these discordant changes and especially the factors responsible for the recent increase in SGA since this has been shown to be associated with poorer health in later life.

Glycemic index and pregnancy: a systematic literature review

Background/Aim. Dietary glycemic index (GI) has received considerable research interest over the past 25 years although its application to pregnancy outcomes is more recent. This paper critically evaluates the current evidence regarding the effect of dietary GI on maternal and fetal nutrition. Methods. A systematic literature search using MEDLINE, EMBASE, CINAHL, Cochrane Library, SCOPUS, and ISI Web of Science, from 1980 through September 2010, was conducted. Results. Eight studies were included in the systematic review. Two interventional studies suggest that a low-GI diet can reduce the risk of large-for-gestational-age (LGA) infants in healthy pregnancies, but one epidemiological study reported an increase in small-for-gestational-age (SGA) infants. Evidence in pregnancies complicated by gestational diabetes mellitus (GDM), though limited (n = 3), consistently supports the advantages of a low-GI diet. Conclusion. There is insufficient evidence to recommend a low-GI diet during normal pregnancy. In pregnancy complicated by GDM, a low-GI diet may reduce the need for insulin without adverse effects on pregnancy outcomes. Until larger-scale intervention trials are completed, a low-GI diet should not replace the current recommended pregnancy diets from government and health agencies. Further research regarding the optimal time to start a low-GI diet for maximum protection against adverse pregnancy outcomes is warranted.

Intergenerational transmission of programmed effects: public health consequences

Epidemiological studies have shown that the environment experienced in early life can 'programme' susceptibility to later disease. Furthermore, there is increasing evidence that these effects can be transmissible to subsequent generations through non-genomic mechanisms, with profound implications for human populations. Several mechanisms can underpin the intergenerational transmission of the programmed phenotype, including persistence of the abnormal environment across generations, maternal effects and the transmission of epigenetic information through the germline. In this review, we discuss the evidence for these mechanisms in human and animal studies and the potential importance of this field for human health.

Trends in birth weight and gestational length among singleton term births in the United States: 1990-2005

OBJECTIVE

To estimate changes over time in birth weight for gestational age and in gestational length among term singleton neonates born from 1990 to 2005.

METHODS

We used data from the U.S. National Center for Health Statistics for 36,827,828 singleton neonates born at 37-41 weeks of gestation, 1990-2005. We examined trends in birth weight, birth weight for gestational age, large and small for gestational age, and gestational length in the overall population and in a low-risk subgroup defined by maternal age, race or ethnicity, education, marital status, smoking, gestational weight gain, delivery route, and obstetric care characteristics.

RESULTS

In 2005, compared with 1990, we observed decreases in birth weight (-52 g in the overall population, -79 g in a homogenous low-risk subgroup) and large for gestational age birth (-1.4% overall, -2.2% in the homogenous subgroup) that were steeper after 1999 and persisted in regression analyses adjusted for maternal and neonate characteristics, gestational length, cesarean delivery, and induction of labor. Decreases in mean gestational length (-0.34 weeks overall) were similar regardless of route of delivery or induction of labor.

CONCLUSION

Recent decreases in fetal growth among U.S., term, singleton neonates were not explained by trends in maternal and neonatal characteristics, changes in obstetric practices, or concurrent decreases in gestational length.

LEVEL OF EVIDENCE

III.

Birth weight, postnatal growth, and age at menarche

Larger body size in childhood is correlated with earlier age at menarche; whether birth and infant body size changes are also associated with age at menarche is less clear. The authors contacted female participants enrolled in the New York site of the US National Collaborative Perinatal Project born between 1959 and 1963 (n = 262). This racially and ethnically diverse cohort (38% white, 40% African American, and 22% Puerto Rican) was used to investigate whether maternal (body size, pregnancy weight gain, age at menarche, smoking) and birth (birth weight, birth length, placental weight) variables and early infant body size changes were associated with age at menarche even after considering later childhood body size. Higher percentile change in weight from ages 4 months to 1 year was associated with earlier age at menarche even after adjustment for later childhood growth (beta = -0.15, 95% confidence interval: -0.27, -0.02 years per 10-percentile change in weight from ages 4 months to 1 year). The association was in the same direction for all 3 racial/ethnic groups but was largest for the white group. These New York Women's Birth Cohort Adult Follow-up data (2001-2006) suggest that infant weight gain, in addition to childhood weight gain, may be associated with earlier age at menarche.

Maternal risk factors for abnormal placental growth: the national collaborative perinatal project

Background

Previous studies of maternal risk factors for abnormal placental growth have focused on placental weight and placental ratio as measures of placental growth. We sought to identify maternal risk factors for placental weight and two neglected dimensions of placental growth: placental thickness and chorionic plate area.

Methods

We conducted an analysis of 24,135 mother-placenta pairs enrolled in the National Collaborative Perinatal Project, a prospective cohort study of pregnancy and child health. We defined growth restriction as < 10^th percentile and hypertrophy as > 90^th percentile for three placental growth dimensions: placental weight, placental thickness and chorionic plate area. We constructed parallel multinomial logistic regression analyses to identify (a) predictors of restricted growth (vs. normal) and (b) predictors of hypertrophic growth (vs. normal).

Results

Black race was associated with an increased likelihood of growth restriction for placental weight, thickness and chorionic plate area, but was associated with a reduced likelihood of hypertrophy for these three placental growth dimensions. We observed an increased likelihood of growth restriction for placental weight and chorionic plate area among mothers with hypertensive disease at 24 weeks or beyond. Anemia was associated with a reduced likelihood of growth restriction for placental weight and chorionic plate area. Pre-pregnancy BMI and pregnancy weight gain were associated with a reduced likelihood of growth restriction and an increased likelihood of hypertrophy for all three dimensions of placental growth.

Conclusion

Maternal risk factors are either associated with placental growth restriction or placental hypertrophy not both. Our findings suggest that the placenta may have compensatory responses to certain maternal risk factors suggesting different underlying biological mechanisms.

Mortality risk of small infants varies with their mother's birthweight and race

We analysed a transgenerational linked birth file to investigate the relationship between maternal birthweight and infant birthweight-specific mortality risk for white and African American infants. Birth records of 267,303 infants born between 1989 and 1991 were linked to records of their mothers, born between 1956 and 1976, and to their own death certificates for those dying in the first year. The means, standard deviations and z-scores were calculated for each race- and generation-specific birthweight distribution. Investigators then analysed the mortality of very small infants (birthweight at least two standard deviations below their mean) for three maternal birthweight categories. Over half of the infant deaths involved births with weights more than two standard deviations below the relevant population mean birthweight (comprising 4.2% of white and 6.9% of African American births respectively). African American infants experienced higher mortality rates at all levels of standardised birthweight, from z-scores of -3 to +3. The relative risk of mortality associated with very small infant size was less for infants delivered to smaller birthweight mothers when compared with those whose mothers were average sized or large at birth. This differential effect was confined to neonatal deaths and was more prominent in the white subpopulation.

Centile charts for birthweight for gestational age for Scottish singleton births

BACKGROUND

Centile charts of birthweight for gestational age are used to identify low birthweight babies. The charts currently used in Scotland are based on data from the 1970s and require updating given changes in birthweight and in the measurement of gestational age since then.

METHODS

Routinely collected data of 100,133 singleton births occurring in Scotland from 1998-2003 were used to construct new centile charts using the LMS method.

RESULTS

Centile charts for birthweight for sex and parity groupings were constructed for singleton birth and compared to existing charts used in Scottish hospitals.

CONCLUSION

Mean birthweight has been shown to have increased over recent decades. The differences shown between the new and currently used centiles confirm the need for more up-to-date centiles for birthweight for gestational age.

Disparities in infant mortality: what's genetics got to do with it?

Since 1950, dramatic advances in human genetics have occurred, racial disparities in infant mortality have widened, and the United States' international ranking in infant mortality has deteriorated. The quest for a "preterm birth gene" to explain racial differences is now under way. Scores of papers linking polymorphisms to preterm birth have appeared in the past few years. Is this strategy likely to reduce racial disparities? We reviewed broad epidemiological patterns that call this approach into question. Overall patterns of racial disparities in mortality and secular changes in rates of prematurity as well as birth-weight patterns in infants of African immigrant populations contradict the genetic theory of race and point toward social mechanisms. We postulate that a causal link to class disparities in health exists.

Low birth weight across generations

OBJECTIVES

This study sought to determine the relationship between maternal birth weight, prenatal care usage, and infant birth weight.

METHODS

Stratified and logistic regression analyses were performed on a dataset of computerized Illinois vital records of White (N = 187, 074) and African-American (N = 58,856) infants born between 1989 and 1991 and their mothers born between 1956 and 1975.

RESULTS

Among White mothers who received adequate prenatal care, the low birth weight (<2500 g) rate was 4% for infants of former low birth weight mothers (N = 5230) compared to 2.1% for infants of former nonlow birth weight mothers (N = 93,011), relative risk equaled 1.9(1.7-2.2); the population attributable risk of maternal low birth weight was 4.1%. Among African American mothers who received adequate prenatal care, the low birth weight rate was 15% for infants of former low birth weight mothers (N = 2196) compared to 7.2% for infants of former nonlow birth weight mothers (N = 14,607), relative risk equaled 2.1(1.9-2.4); the population attributable risk of maternal low birth weight was 10.9%. The maternal-infant birth weight associations were consistent across all maternal age, education, marital status, and prenatal care categories.

CONCLUSIONS

Maternal low birth weight is a risk factor for infant low birth weight independent of risk status during the current pregnancy. A greater percentage of low birth weight African American (compared to White) infants are attributable to maternal low birth weight.

Physical characteristics of newborn babies after vaginal delivery: a 25-year study from Vienna

This retrospective analysis evaluated whether the gestational age, mean birth weight, length and shoulder width of vaginally delivered newborns have increased during the last 25 years in Vienna, Austria. Women who have given birth at the University of Vienna Medical School Hospital were divided into four age groups: under 20 years, 20-24 years, 25-29 years, and 30 years of age or over. Patient data collected between 1976 to 2000 were grouped into five periods: 1976-1979, 1980-1984, 1985-1989, 1990-1994, and 1995-2000. A highly significant increase of all four parameters was observed for all age groups between 1976 and 2000. The changes were most marked in the 25-29 year age group.

Birth weight and perinatal mortality: a comparison of "optimal" birth weight in seven Western European countries

BACKGROUND

Previous studies have suggested that a population's entire birth weight distribution may be shifted towards higher or lower birth weights, and that optimal birth weight may be lower in populations with a lower average birth weight. We evaluated this hypothesis for seven western European countries.

METHODS

We obtained data on all singleton births (N = 1,372,092) and extended perinatal deaths (stillbirths plus neonatal deaths; N = 7,900) occurring in Finland, Sweden, Norway, Denmark, Scotland, the Netherlands, and Flanders (Belgium) in 1993-1995. We assessed whether countries differed in the mode of their birth weight distribution and in the birth weight associated with the lowest perinatal mortality, and then correlated the two.

RESULTS

Substantial international differences were found in the mode of the birth weight distribution, which ranged between 3384 gm in Flanders and 3628 gm in Finland. The position of the minimum of the perinatal mortality curve also differed considerably, ranging between 3755 gm in Flanders and 4305 gm in Norway. There was a strong relation between the two: for every 100 gm increase in modal birth weight, optimal birth weight was 170 gm higher (95% confidence interval = 104-236 gm).

CONCLUSIONS

Our results confirm those of previous studies that compared two populations. To improve the identification of small babies at high risk of perinatal death, population-specific standards for birth weight should be developed and used.

The increase in very-low-birthweight infants in Germany: artefact or reality?

Earlier findings have shown that after unification with the Federal Republic of Germany (FRG) in October 1990 the proportion of very-low-birthweight infants in the former German Democratic Republic (GDR) increased. This study seeks to explore this observation in more detail at the regional level. The analysis of aggregate data of live births in Germany between 1991 and 1997 shows an increasing proportion of very-low-birthweight infants as well as a general trend towards heavier babies in both east and west. The growing proportion of live born infants at very low birthweights in the east, however, seems to be due, in part, to increased registration, most likely reflecting the introduction of the more comprehensive (western) definition of a live birth with unification in October 1990. A fairly distinct east-west pattern in the birthweight distribution present in 1991 had almost disappeared by 1997 and given way to a north-south one.

Risk factors for the increasing trend in low birth weight among live births born by vaginal delivery, Brazil

OBJECTIVE

To identify risk factors for low birth weight (LBW) among live births by vaginal delivery and to determine if the disappearance of the association between LBW and socioeconomic factors was due to confounding by cesarean section.

METHODS

Data were obtained from two population-based cohorts of singleton live births in Ribeirão Preto, Southeastern Brazil. The first one comprised 4,698 newborns from June 1978 to May 1979 and the second included 1,399 infants born from May to August 1994. The risks for LBW were tested in a logistic model, including the interaction of the year of survey and all independent variables under analysis.

RESULTS

The incidence of LBW among vaginal deliveries increased from 7.8% in 1978--79 to 10% in 1994. The risk was higher for: female or preterm infants; newborns of non-cohabiting mothers; newborns whose mothers had fewer prenatal visits or few years of education; first-born infants; and those who had smoking mothers. The interaction of the year of survey with gestational age indicated that the risk of LBW among preterm infants fell from 17.75 to 8.71 in 15 years. The mean birth weight decreased more significantly among newborns from qualified families, who also had the highest increase in preterm birth and non-cohabitation.

CONCLUSIONS

LBW among vaginal deliveries increased mainly due to a rise in the proportion of preterm births and non-cohabiting mothers. The association between cesarean section and LBW tended to cover up socioeconomic differences in the likelihood of LBW. When vaginal deliveries were analyzed independently, these socioeconomic differences come up again.

Low-income African-American mothers' perception of exposure to racial discrimination and infant birth weight

We performed a hospital-based case-control study of African-American mothers to explore the relation between a mother's perception of exposure to racial discrimination during pregnancy and very low birth weight. We administered a structured questionnaire to low-income mothers of very low birth weight (<1500 gm; N = 25) and non-low birth weight (>2500 gm; N = 60) infants. The unadjusted and adjusted odds ratio of very low birth weight for maternal exposure to racial discrimination were 1.9 (0.5-6.6) and 3.2 (0.9-11.3), respectively. We conclude that maternal perception of exposure to racial discrimination during pregnancy may be associated with very low birth weight in their infants.