Familial aggregation of low birth weight among whites and blacks in the United States

In Search of the Promised Land: County-Level Disadvantage and Low Birth Weight among Black Mothers of the Great Migration

The Great Migration was a movement of roughly eight million Black Southerners relocating to the North and West from 1910 to 1980. Despite being one of the most significant mass internal migrations during the twentieth century, little is known about the health outcomes resulting from migration and whether migrators' destination choices were potential mechanisms. This study measured the association between destination county disadvantage and odds of low birth weight during the last decade of the Great Migration. We used the US Census from 1970 as well as the birth records of first-time Black mothers who migrated from the South collected through the National Center of Health Statistics from 1973 to 1980 (n = 154,145). We examined three measures of area-based opportunity: Black male high school graduation rate, Black poverty rate, and racialized economic residential segregation. We used multilevel logistic regression, where mothers were nested within US counties, to quantify the relationship between county disadvantage and low birth weight. After adjusting for individual risk and protective factors for infant health, there was no relationship between county opportunity measures and low birth weight among migrators. Although high socioeconomic opportunity is typically associated with protection of low birth weight, we did not see these outcomes in this study. These results may support that persistent racial discrimination encountered in the North inhibited infant health even as migrators experienced higher economic opportunity relative to the South.

Moving to opportunity? Low birth weight outcomes among Southern-born Black mothers during the Great Migration

OBJECTIVE

The Great Migration was a mass movement in the United States during the twentieth century of roughly eight million Black Southerners to the Northeast, Midwest, and West. Despite its significance, little is known about the health outcomes associated with this internal migration. This study assessed the relationship between migration and low birth weight among mothers born in the South between 1950 and 1969.

METHODS

We used approximately 1.4 million birth records of Black infants maintained by the US National Center for Health Statistics. To tease out the roles of the healthy migrant bias and of destination contexts, we compared two migration groups to Southern non-migrators: (1) migrators moving to the North and (2) migrators moving within the South. Non-migrants were matched to migrants using coarsened exact matching. We estimated the relationship between migration status and low birth weight stratified by birth year cohorts using logistic regression models.

RESULTS

There was positive selection in education and marriage among migrants moving out of the South and within the South. Results showed lower odds of low birth weight in both migration groups compared to Southern non-migrants. The odds ratios of low birth weight were similar in both comparisons.

CONCLUSION

We found evidence consistent with a healthy migrant bias in infant health among mothers during the last decades of the Great Migration. Despite better economic opportunity, migrating to the North may not have offered additional protection for infant birth weight outcomes.

Incidence and familial clustering of infantile hemangiomas: A multicenter study

BACKGROUND

The exact incidence of infantile hemangiomas (IH) in the Chinese population is still unknown. A positive family history of IH was considered as a risk factor for the development of IH.

OBJECTIVES

This study aims to investigate the incidence of IH in the Chinese population and the mechanism of family history increases the risk for IH development.

METHODS

2489 women and their newborns were enrolled in the prospective study. All newborns were followed up for 12 months to determine whether they developed IH. In addition, 213 IH probands and their 174 siblings were enrolled in the study. The incidence of IH in siblings of the IH probands was investigated. Information regarding risk factors for IH and demographic data were collected on all children.

RESULTS

Of the 2572 newborns, 58 IH were identified in 56 (2.2%) newborns. The majority of IH were located on the trunk (46.6%). Siblings of the IH probands were at increased risk for the development of IH (P = 0.024, relative risk 2.451), and the occurrence of prenatal risk factors for IH(P = 0.003) compared with the general population.

CONCLUSIONS

Our study showed that the incidence of IH is 2.2% in the Chinese population. Siblings of the individuals with IH were at increased risk for the development of IH may be related to the family clustering of prenatal risk factors for IH. Further exploration of the mechanisms and common features of these prenatal risk factors may help to disclosure the origin and pathogenesis of IH.

Gaining a deeper understanding of social determinants of preterm birth by integrating multi-omics data

In the US, high rates of preterm birth (PTB) and profound Black-White disparities in PTB have persisted for decades. This review focuses on the role of social determinants of health (SDH), with an emphasis on maternal stress, in PTB disparity and biological embedding. It covers: (1) PTB disparity in US Black women and possible contributors; (2) the role of SDH, highlighting maternal stress, in the persistent racial disparity of PTB; (3) epigenetics at the interface between genes and environment; (4) the role of the genome in modifying maternal stress-PTB associations; (5) recent advances in multi-omics studies of PTB; and (6) future perspectives on integrating multi-omics with SDH to elucidate the Black-White disparity in PTB. Available studies have indicated that neither environmental exposures nor genetics alone can adequately explain the Black-White PTB disparity. Preliminary yet promising findings of epigenetic and gene-environment interaction studies underscore the value of integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women. In an era of rapid advancements in biomedical sciences and technologies and a growing number of prospective birth cohort studies, we have unprecedented opportunities to advance this field and finally address the long history of health disparities in PTB. IMPACT: This review provides an overview of social determinants of health (SDH) with a focus on maternal stress and its role on Black-White disparity in preterm birth (PTB). It summarizes the available literature on the interplay of maternal stress with key biological layers (e.g., individual genome and epigenome in response to environmental stressors) and significant knowledge gaps. It offers perspectives that such knowledge may provide deeper insight into how SDH affects PTB and why some women are more vulnerable than others and underscores the critical need for integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women.

Racial disparities in the transgenerational transmission of low birthweight risk

Objective: To examine the association of maternal low birthweight (LBW) with infant LBW and infant LBW subgroups (i.e. moderate and very LBW), overall and among non-Hispanic (NH) white and NH black mothers. Design: We conducted a population-based cohort study in Allegheny County, Pennsylvania, using linked birth record data of NH white and NH black mother-infant pairs (N = 6,633) born in 1979-1998 and 2009-2011, respectively. The exposure of interest was maternal LBW (birthweight <2500 grams) while the outcomes were infant LBW and LBW subgroups - moderate LBW (1,500-2,499 grams) or very LBW (<1,500 grams). Logistic regression (binomial and multinomial) models were used to estimate adjusted Odds Ratios (ORs), Relative Risk Ratios (RRRs), and related 95% confidence intervals (CI). Stratified analyses were conducted to assess effect modification by mothers' race. Results: Maternal LBW was associated with 1.53 (95%CI: 1.15-2.02) and 1.75 (95%CI: 1.29-2.37) -fold increases in risk of infant LBW and MLBW, respectively, but not VLBW (RRR = 0.86; 95%CI: 0.44-1.70). In race-stratified models, maternal LBW-infant LBW associations were observed among NH blacks (OR = 1.88; 95%CI: 1.32-2.66) and not among NH whites (OR = 1.03; 95%CI: 0.62-1.73) (P for interaction = 0.07). Among NH blacks, maternal LBW was associated with a 2.18 (95%CI: 1.49, 3.20) -fold increase in risk of infant MLBW, but not VLBW (RRR = 1.12; 95%CI: 0.54, 2.35). Among NH whites, LBW subgroup analyses could not be performed due to small numbers of VLBW infants among LBW mothers. Conclusion: Mothers who were LBW at their own birth were more likely to have MLBW infants. Maternal race modified associations of maternal LBW with infant LBW, particularly infant MLBW. Further research is needed in this area to understand the potential mechanisms involved in the transgenerational transmission of LBW risk and race-specific differences in the transmission.

History of the establishment of the Preterm Birth international collaborative (PREBIC)

INTRODUCTION

The primary aim of PREBIC is to assess the underlying mechanisms and developing strategies for preterm birth (PTB) prevention.

MATERIALS AND METHODS

We used concept mapping and logic models to track goals. This paper reviews our progress over 13 years using working group activities, research developments, guest speakers, and publications.

RESULTS

Using interactions between genetics, environment, and behaviors we identified complex interactions between biological systems. PREBIC determined that epidemiology and biomarkers should be an initial focus. In 2005, we initiated presentations by young investigators, yearly satellite meetings, working groups including nutrition and inflammation, assessment of clinical trials, and accepted an invitation by the WHO to begin yearly meetings in Geneva.

DISCUSSION

PREBIC used epidemiology to identify PTB factors and complex pathways. Candidate genes are associated with the environment, behavior (stress), obesity, inflammation and insulin resistance. Epigenetic changes and production of proteins can be used as biomarkers to define risk. Subsequently, we found risk factors for PTB that were also associated with the risk of cardiovascular disease (CVD) of the mother. Tanz et al. (2017) found that a history of PTB is independently predictive of CVD later in life and suggested that a modest proportion of PTB-CVD association was accounted by CVD risk factors, many of which have been identified in this paper.

CONCLUSION

Our findings support a relationship between genes, environment, behaviors and risk of CVD in women. The next several years must assess which factors are modifiable early in life and before pregnancy to prevent PTB.

The Impact of Kidney Development on the Life Course: A Consensus Document for Action

Hypertension and chronic kidney disease (CKD) have a significant impact on global morbidity and mortality. The Low Birth Weight and Nephron Number Working Group has prepared a consensus document aimed to address the relatively neglected issue for the developmental programming of hypertension and CKD. It emerged from a workshop held on April 2, 2016, including eminent internationally recognized experts in the field of obstetrics, neonatology, and nephrology. Through multidisciplinary engagement, the goal of the workshop was to highlight the association between fetal and childhood development and an increased risk of adult diseases, focusing on hypertension and CKD, and to suggest possible practical solutions for the future. The recommendations for action of the consensus workshop are the results of combined clinical experience, shared research expertise, and a review of the literature. They highlight the need to act early to prevent CKD and other related noncommunicable diseases later in life by reducing low birth weight, small for gestational age, prematurity, and low nephron numbers at birth through coordinated interventions. Meeting the current unmet needs would help to define the most cost-effective strategies and to optimize interventions to limit or interrupt the developmental programming cycle of CKD later in life, especially in the poorest part of the world.

Familial Factors, Low Birth Weight, and Development of ESRD: A Nationwide Registry Study

BACKGROUND

Previous studies have demonstrated that low birth weight (LBW) is associated with higher risk for end-stage renal disease (ESRD). However, both LBW and ESRD cluster in families. The present study investigates whether familial factors explain the association between LBW and ESRD.

STUDY DESIGN

Retrospective registry-based cohort study.

SETTING & PARTICIPANTS

Since 1967, the Medical Birth Registry of Norway has recorded medical data for all births in the country. Sibling data are available through the Norwegian Population Registry. Since 1980, all patients with ESRD in Norway have been registered in the Norwegian Renal Registry. Individuals registered in the Medical Birth Registry with at least 1 registered sibling were included.

PREDICTOR

LBW in the participant and/or LBW in at least 1 sibling.

OUTCOME

ESRD.

RESULTS

Of 1,852,080 included individuals, 527 developed ESRD. Compared with individuals without LBW and with no siblings with LBW, individuals without LBW but with a sibling with LBW had an HR for ESRD of 1.20 (95% CI, 0.91-1.59), individuals with LBW but no siblings with LBW had an HR of 1.59 (95% CI, 1.18-2.14), and individuals with LBW and a sibling with LBW had an HR of 1.78 (95% CI, 1.26-2.53). Similar results were observed for individuals who were small for gestational age (SGA). Separate analyses for the association of age 18 to 42 years and noncongenital ESRD showed stronger associations for SGA than for LBW, and the associations were not statistically significant for age 18 to 42 years for LBW.

LIMITATIONS

Follow-up only until 42 years of age.

CONCLUSIONS

LBW and SGA are associated with higher risk for ESRD during the first 40 years of life, and the associations were not explained by familial factors. Our results support the hypothesis that impaired intrauterine nephron development may be a causal risk factor for progressive kidney disease.

Developing a maternally linked birth dataset to study the generational recurrence of low birthweight in Virginia

This paper examined the generational recurrence of low birthweight (LBW) among first-born singletons using a statewide maternally-linked birth dataset. An intergenerational dataset was created by linking 2005-2009 to 1960-1997 Virginia resident live birth data. Maternal information from the recent birth cohort was linked to infant information in the historic birth file using various combinations of mother's name and birthdate. The linked dataset contained 170,624 records (87 % of all eligible records). The analysis dataset was limited to non-Hispanic black and non-Hispanic white first-born singleton infants linked to their mother's own birth record (n = 69,702). Maternal birthweight was a significant predictor of LBW for first-born singletons. The birthweight distribution for both non-Hispanic black and non-Hispanic white infants was shifted toward lower birthweights for infants whose mothers were born LBW. Even after adjusting for known maternal risk factors in the current pregnancy, non-Hispanic black (AOR = 1.6 [95 % CI 1.4, 1.8]) and non-Hispanic white (AOR = 2.0 [95 % CI 1.8, 2.3]) infants had increased odds of being born LBW if their mother was born LBW. A mother's early life experiences can impact the health of her children. These findings underscore the importance of applying a life course perspective to the prevention of LBW. Routine linkage of maternal and infant birth data is needed to strengthen the evidence base for policies and programs that address issues affecting maternal and child health throughout the life course.

Newborn infant characteristics and risk of future rheumatoid arthritis: a twin-control study

Low birth weight has been proposed as a risk factor for rheumatoid arthritis (RA). The twin-control study design provides an opportunity to investigate the significance of potential prenatal determinants for adult morbidity by accounting for maternal characteristics and early environmental and genetic factors. We investigated the association between birth weight and RA in a sample of 42 twin pairs discordant for rheumatoid arthritis in which valid information on birth weight, birth length, and order was available from midwife records. Difference plot and conditional logistic regression were used to investigate the relationship between RA and birth weight or birth order adjusting for birth length and sex. The intra-pairwise birth weight differences, i.e., RA twin minus co-twin, ranged from -750 to 1,100 g, mean 78 g (95 % CI -13 to 70), 146 g (95 % CI (-36 to 329) in monozygotic, 32 g (95 % CI -90 to 154) in dizygotic, same sex and 69 g (95 % CI -122 to 260) in dizygotic, opposite sex twin pairs. The odds ratio for birth weight as risk factor for RA was 1.00 (95 % CI 0.997-1.003) when adjusting for birth length, birth order, and sex, irrespective of ACPA status. The odds ratio for developing RA as first born twin was 2.33 (95 % CI 0.97-5.60) when adjusting for birth length, birth weight, and sex, irrespective of ACPA status. In this twin-control study, birth weight was not associated with the development of RA in adult life. Being born first may predispose to RA.

Genetics of pediatric obesity

Onset of obesity has been anticipated at earlier ages, and prevalence has dramatically increased worldwide over the past decades. Epidemic obesity is mainly attributable to modern lifestyle, but family studies prove the significant role of genes in the individual's predisposition to obesity. Advances in genotyping technologies have raised great hope and expectations that genetic testing will pave the way to personalized medicine and that complex traits such as obesity will be prevented even before birth. In the presence of the pressing offer of direct-to-consumer genetic testing services from private companies to estimate the individual's risk for complex phenotypes including obesity, the present review offers pediatricians an update of the state of the art on genomics obesity in childhood. Discrepancies with respect to genomics of adult obesity are discussed. After an appraisal of findings from genome-wide association studies in pediatric populations, the rare variant-common disease hypothesis, the theoretical soil for next-generation sequencing techniques, is discussed as opposite to the common disease-common variant hypothesis. Next-generation sequencing techniques are expected to fill the gap of "missing heritability" of obesity, identifying rare variants associated with the trait and clarifying the role of epigenetics in its heritability. Pediatric obesity emerges as a complex phenotype, modulated by unique gene-environment interactions that occur in periods of life and are "permissive" for the programming of adult obesity. With the advent of next-generation sequencing techniques and advances in the field of exposomics, sensitive and specific tools to predict the obesity risk as early as possible are the challenge for the next decade.

Maternal and infant factors associated with neonatal adiposity: results from the Tasmanian Infant Health Survey (TIHS)

OBJECTIVE

To examine the maternal and neonatal factors associated with offspring adiposity and the role of birth and placental weight as potential mediators in such associations.

DESIGN

The Tasmanian Infant Health Survey was a prospective cohort study conducted between 1988 and 1995 in Australia to investigate the cause of Sudden Infant Death Syndrome. This large infant cohort provides measurement of skinfolds on 7945 mothers and their offspring.

SUBJECTS

Participants included singletons born ≥37 weeks gestation who were at high risk of sudden infant death syndrome identified through a composite score that included birth weight, maternal age, neonatal gender, season of birth, duration of second-stage labor and intention to breastfeed.

MEASUREMENTS

Neonatal adiposity was assessed from skinfold measurements of the subscapular (SSF) and triceps folds (TSF) taken at birth. Maternal early-pregnancy body mass index (BMI) was calculated from self-reported height and weight. Neonatal data were extracted from birth records. Data relating to other environmental exposures were obtained from questionnaires administered when neonates were ∼4-days old.

RESULTS

In multivariable models, higher maternal adiposity, increasing maternal age, gestation age, delivery by Caesarian section and female gender were associated with larger SSF independent of placental and birth weight (P<0.001). Maternal age and delivery by Caesarian section were significantly associated with larger TSF, whereas gestational age and male gender were associated with thinner TSF independent of placental and birth weight. Higher early-pregnancy BMI, maternal weight gain, maternal age, parity and gestational age were significantly associated with larger placental and birth weight. Smoking during pregnancy was associated with smaller birth weight but not with placental weight.

CONCLUSION

In addition to birth weight, maternal adiposity and placental weight were important additional factors associated with neonatal adiposity.

Clustering of fecundability within women

Adverse pregnancy outcomes have long been observed to cluster within women resulting in the inclusion of past reproductive history in clinical assessments and perinatal scoring systems. However, limited study has focused on the clustering of fecundability as measured by time to pregnancy (TTP), despite growing evidence suggestive of a possible association with adverse pregnancy outcomes known to cluster within women. We sought to empirically evaluate the clustering of conception delay, and TTP more globally, in one of the few existing prospective pregnancy cohort studies that captured women's successive pregnancies. The study cohort comprised 544 women who contributed 1119 pregnancies in the U.S. Collaborative Perinatal Project. We used a discrete Cox frailty model to estimate the degree and significance of within-woman clustering of TTP. Women with an initial conception delay (TTP > 6 months) were older, less educated and had higher body mass indices than women not experiencing delays (TTP ≤ 6 months). Our analysis indicates that there is significant within-woman clustering of TTP (variance of the frailty = 0.80, [95% confidence interval 0.49, 1.11]) after adjusting for baseline maternal age, body mass index and education level. Similar to many other reproductive and perinatal outcomes, our findings suggest that TTP clusters within women. Identifying exposures or behaviours that affect TTP may offer strategies for reducing conception delay in future pregnancy attempts.

Polymorphisms in maternal and fetal genes encoding for proteins involved in extracellular matrix metabolism alter the risk for small-for-gestational-age

OBJECTIVE

To examine the association between maternal and fetal genetic variants and small-for-gestational-age (SGA).

METHODS

A case-control study was conducted in patients with SGA neonates (530 maternal and 436 fetal) and controls (599 maternal and 628 fetal); 190 candidate genes and 775 SNPs were studied. Single-locus, multi-locus and haplotype association analyses were performed on maternal and fetal data with logistic regression, multifactor dimensionality reduction (MDR) analysis, and haplotype-based association with 2 and 3 marker sliding windows, respectively. Ingenuity pathway analysis (IPA) software was used to assess pathways that associate with SGA.

RESULTS

The most significant single-locus association in maternal data was with a SNP in tissue inhibitor of metalloproteinase 2 (TIMP2) (rs2277698 OR = 1.71, 95% CI [1.26-2.32], p = 0.0006) while in the fetus it was with a SNP in fibronectin 1 isoform 3 preproprotein (FN1) (rs3796123, OR = 1.46, 95% CI [1.20-1.78], p = 0.0001). Both SNPs were adjusted for potential confounders (maternal body mass index and fetal sex). Haplotype analyses resulted in associations in α 1 type I collagen preproprotein (COL1A1, rs1007086-rs2141279-rs17639446, global p = 0.006) in mothers and FN1 (rs2304573-rs1250204-rs1250215, global p = 0.045) in fetuses. Multi-locus analyses with MDR identified a two SNP model with maternal variants collagen type V α 2 (COL5A2) and plasminogen activator urokinase (PLAU) predicting SGA outcome correctly 59% of the time (p = 0.035).

CONCLUSIONS

Genetic variants in extracellular matrix-related genes showed significant single-locus association with SGA. These data are consistent with other studies that have observed elevated circulating fibronectin concentrations in association with increased risk of SGA. The present study supports the hypothesis that DNA variants can partially explain the risk of SGA in a cohort of Hispanic women.

Effects of current size, postnatal growth, and birth size on blood pressure in early childhood

OBJECTIVE

In a prospective study, we investigated the impact of early growth on blood pressure at 3 years of age.

METHODS

We measured systolic blood pressure (SBP) and diastolic blood pressure (DBP) for 590 children 3 years of age and related measurements to current size and size at birth, 6 months, 1 year, and 2 years of age.

RESULTS

SBP was related positively to weight at 3 and 2 years and, after adjustment for current size, negatively to weight at birth and 6 months but not at 1 or 2 years. No effect was observed for DBP. A family history of hypertension was associated with higher maternal blood pressure, greater weight, and gestational hypertension (P = .05). Mothers with a history of gestational hypertension had higher SBP and DBP values (P < .001). In multivariate linear regression analyses, SBP was influenced positively by weight at 3 years and family history of hypertension and negatively by weight at 6 months. None of the factors was associated with DBP.

CONCLUSIONS

For 3-year-old children, current weight was a determinant of SBP and postnatal growth to 6 months of age was more predictive than birth weight. A family history of hypertension is important in determining maternal blood pressure. These observations suggest a window in which postnatal growth might be modified.

A meta-analysis of depression during pregnancy and the risk of preterm birth, low birth weight, and intrauterine growth restriction

CONTEXT

Maternal depressive symptoms during pregnancy have been reported in some, but not all, studies to be associated with an increased risk of preterm birth (PTB), low birth weight (LBW), and intrauterine growth restriction (IUGR).

OBJECTIVE

To estimate the risk of PTB, LBW, and IUGR associated with antenatal depression.

DATA SOURCES AND STUDY SELECTION

We searched for English-language and non-English-language articles via the MEDLINE, PsycINFO, CINAHL, Social Work Abstracts, Social Services Abstracts, and Dissertation Abstracts International databases (January 1980 through December 2009). We aimed to include prospective studies reporting data on antenatal depression and at least 1 adverse birth outcome: PTB (<37 weeks' gestation), LBW (<2500 g), or IUGR (<10th percentile for gestational age). Of 862 reviewed studies, 29 US-published and non-US-published studies met the selection criteria.

DATA EXTRACTION

Information was extracted on study characteristics, antenatal depression measurement, and other biopsychosocial risk factors and was reviewed twice to minimize error.

DATA SYNTHESIS

Pooled relative risks (RRs) for the effect of antenatal depression on each birth outcome were calculated using random-effects methods. In studies of PTB, LBW, and IUGR that used a categorical depression measure, pooled effect sizes were significantly larger (pooled RR [95% confidence interval] = 1.39 [1.19-1.61], 1.49 [1.25-1.77], and 1.45 [1.05-2.02], respectively) compared with studies that used a continuous depression measure (1.03 [1.00-1.06], 1.04 [0.99-1.09], and 1.02 [1.00-1.04], respectively). The estimates of risk for categorically defined antenatal depression and PTB and LBW remained significant when the trim-and-fill procedure was used to correct for publication bias. The risk of LBW associated with antenatal depression was significantly larger in developing countries (RR = 2.05; 95% confidence interval, 1.43-2.93) compared with the United States (RR = 1.10; 95% confidence interval, 1.01-1.21) or European social democracies (RR = 1.16; 95% confidence interval, 0.92-1.47). Categorically defined antenatal depression tended to be associated with an increased risk of PTB among women of lower socioeconomic status in the United States.

CONCLUSIONS

Women with depression during pregnancy are at increased risk for PTB and LBW, although the magnitude of the effect varies as a function of depression measurement, country location, and US socioeconomic status. An important implication of these findings is that antenatal depression should be identified through universal screening and treated.

Obesity and diabetes genes are associated with being born small for gestational age: results from the Auckland Birthweight Collaborative study

Background

Individuals born small for gestational age (SGA) are at increased risk of rapid postnatal weight gain, later obesity and diseases in adulthood such as type 2 diabetes, hypertension and cardiovascular diseases. Environmental risk factors for SGA are well established and include smoking, low pregnancy weight, maternal short stature, maternal diet, ethnic origin of mother and hypertension. However, in a large proportion of SGA, no underlying cause is evident, and these individuals may have a larger genetic contribution.

Methods

In this study we tested the association between SGA and polymorphisms in genes that have previously been associated with obesity and/or diabetes. We undertook analysis of 54 single nucleotide polymorphisms (SNPs) in 546 samples from the Auckland Birthweight Collaborative (ABC) study. 227 children were born small for gestational age (SGA) and 319 were appropriate for gestational age (AGA).

Results and Conclusion

The results demonstrated that genetic variation in KCNJ11, BDNF, PFKP, PTER and SEC16B were associated with SGA and support the concept that genetic factors associated with obesity and/or type 2 diabetes are more prevalent in those born SGA compared to those born AGA. We have previously determined that environmental factors are associated with differences in birthweight in the ABC study and now we have demonstrated a significant genetic contribution, suggesting that the interaction between genetics and the environment are important.

Effects of Prenatal Poverty on Infant Health: State Earned Income Tax Credits and Birth Weight

This study estimates the effects of prenatal poverty on birth weight using changes in state Earned Income Tax Credits (EITC) as a natural experiment. We seek to answer two questions about poverty and child wellbeing. First, are there associations between prenatal poverty and lower birth weights even after factoring out unmeasured potential confounders? Because birth weight predicts a range of outcomes across the life course, lower birth weights that result from poverty may have lasting consequences for children’s life chances. Second, how have recent expansions of a work-based welfare program (i.e., the EITC) affected maternal and infant health? In recent decades, U.S. poverty relief has become increasingly tied to earnings and labor markets, but the consequences for children’s wellbeing remain controversial. We find that state EITCs increase birth weights and reduce maternal smoking. However, results related to AFDC/TANF and varying EITC effects across maternal ages raise cautionary messages.

Recurrence of fetal growth restriction in singleton and twin gestations

OBJECTIVE

Patterns of recurrence of restricted fetal growth provide important insights to understand the relative contributions of genetic versus environmental influences. Although there is evidence of increased tendency of small for gestational age (SGA) births to recur, whether similar patterns of recurrence in twins among women that delivered a prior singleton SGA birth remains poorly studied.

METHODS

We used Missouri's maternally-linked data (1978-1997), and restricted the analysis to women that delivered their first two consecutive live births. SGA (birthweight <10th and <5th centile for gestational age) recurrence was examined in two distinct analyses: women that delivered their first two singleton live births (n = 305,654) and those that delivered their first singleton live birth followed by twin live births (n = 8594). Sib-sib pairwise odds ratio (pOR) were estimated from bivariate logistic regression with robust variance estimation after adjustments for confounders.

RESULTS

Risks of SGA were 24.3% and 6.1% in the second singleton birth among women with and without a previous singleton SGA, respectively (pOR 3.9, 95% CI 3.7-4.0). The corresponding risks among twins with and without a previous singleton SGA birth were 16.9% and 6.7%, respectively (pOR 2.3, 95% CI 1.8-2.8). In the singleton-singleton cohort, the highest recurrence risk for SGA occurred around the same gestational age window as the first singleton SGA birth. These associations were stronger for more severe forms of SGA (<5th centile).

CONCLUSIONS

The likelihood of SGA to recur within sibships is strong, with varying magnitude of risks between singleton-singleton and singleton-twin births.

Factors predicting ante- and postnatal growth

Human growth is a continuous process. Studies defining factors influencing growth focus on discrete time points (e.g., birth), overlooking the conditional nature of the process. One thousand six hundred fifty Caucasian mothers who gave birth at term after an uncomplicated singleton pregnancy were studied using conditional analysis. Infant height, weight, and head circumference were obtained at birth and 6 mo of age. Data analysis, conditional upon birth size, was conducted as a stepped consideration of factors influencing phases of fetal and infant growth beginning with determinants of placental size. Placental weight was related to birth size. Seven percent of the variance in placental weight was explained by a combination of gestation at delivery, maternal size at first prenatal visit, paternal height (all positive), and increasing parity (negative). When centered on birth weight, 41% of the variance in placental weight was explained by birth weight, length of gestation, smoking during pregnancy (all positive), and a female baby (negative). Maternal and paternal stature equally influenced newborn and infant size. Conditional analysis reveals a series of modifiable (parity, length of gestation, and smoking) and nonmodifiable factors at different stages of the growth process.

Early pregnancy lipid concentrations and spontaneous preterm birth

OBJECTIVE

Women who deliver preterm infants may be at increased risk for cardiovascular disease, perhaps related to dyslipidemia.

STUDY DESIGN

In a nested case control study of women with spontaneous preterm birth, cholesterol, high-density lipoprotein, low-density lipoprotein, and triglycerides were evaluated. Lipid concentrations and gestational changes, as well as risk for preterm birth, were evaluated in women who delivered <34 (n = 23), >or=34-<37 (n = 67), and >or=37 weeks (n = 199).

RESULTS

High cholesterol or triglycerides <or=15 weeks were associated with a 2.8-fold (1.0-7.9) and 2.0-fold (1.0-3.9) increased risk for preterm birth <34 weeks and >or=34-<37 weeks, respectively. Overweight women who delivered <34 weeks had particularly elevated early pregnancy concentrations of cholesterol and low-density lipoprotein; lean women with moderate preterm birth had elevated triglycerides. There was a reduced triglyceride response in the first half of pregnancy among women who delivered <34 weeks.

CONCLUSION

Our results indicate the presence of dyslipidemia in women with spontaneous preterm birth.

Association between small for gestational age and paternally inherited 5' insulin haplotypes

OBJECTIVE

To test the association between small for gestational age and polymorphisms in the insulin gene in newborns and their mothers, as well as the effect of the parental transmission of haplotypes.

SUBJECTS

Pairs of healthy African-American full-term newborns (N=207) and mothers were recruited from Memphis TN and Jackson MS with birth weights ranging from 2210 to 4735 g.

METHODS

Six single nucleotide polymorphisms (SNPs) located in the insulin (INS) and insulin-like growth factor 2 (IGF2) genes were genotyped in mothers and newborns. Haplotypes composed of three SNPs in the 5' region of the INS-IGF2 locus were computationally inferred. Odds ratios for risk of small for gestational age (SGA) birth were calculated for individual SNPs and inferred haplotypes in the newborns and in the mothers using logistic regression. For 162 mother--newborn pairs the parental transmission of the haplotypes could be inferred, and the risks for SGA birth were calculated for the three common haplotypes in this sample.

RESULTS

Three INS SNPs exhibited significant association with risk for SGA birth. The SNP alleles associated with increased risk for SGA were opposite in the maternal and newborn genomes, implying opposing influences on the rate of fetal growth. Consistent with these results, haplotypes composed of complementary nucleotide sequences (CAC at rs3842738, rs689 and rs3842748, respectively, in the newborn versus GTG in the mother) were significantly associated with risk for SGA birth. In analyses of haplotypes according to parental transmission, the same trend in risk for SGA was observed for both maternally and paternally transmitted haplotypes, although a significant difference in risk was observed only for paternally transmitted haplotypes.

CONCLUSION

Polymorphisms near the 5' end of the INS-IGF2 locus are significantly associated with risk for SGA birth with a major effect due to the paternally transmitted haplotype, which is preferentially expressed due to imprinting.

Studying genetic predisposition among small-for-gestational-age newborns

The objective of this report is to provide a summary overview of genetic association studies for the small-for-gestational-age (SGA) pregnancy outcome. Only the thrombophilia and xenobiotic-metabolizing genetic pathways were studied with any frequency. Most studies used case-control designs and analyzed only the maternal genotype. A brief critique of some features of the published studies is presented: it addresses mainly the selection of controls, study power, the need to evaluate gene-environment interaction, and the potential for population stratification bias, believed likely to affect such studies. Alternative designs, not vulnerable to the population structure bias, are also discussed; they include case-parental trios and a mixture of both case trios and case-control data. Aspects that have almost never been considered in the published studies, but that are particularly relevant for adverse pregnancy outcomes, are maternally mediated and parent-of-origin effects. These are defined and methods to evaluate them are briefly presented.

Obstetrician-assessed maternal health at pregnancy predicts offspring future health

Background

We aimed to examine the association between obstetrician assessment of maternal physical health at the time of pregnancy and offspring cardiovascular disease risk.

Methods and Principal Findings

We examined this association in a birth cohort of 11,106 individuals, with 245,000 person years of follow-up. We were concerned that any associations might be explained by residual confounding, particularly by family socioeconomic position. In order to explore this we used multivariable regression models in which we adjusted for a range of indicators of socioeconomic position and we explored the specificity of the association. Specificity of association was explored by examining associations with other health related outcomes. Maternal physical health was associated with cardiovascular disease: adjusted (socioeconomic position, complications of pregnancy, birthweight and childhood growth at mean age 5) hazard ratio comparing those described as having poor or very poor health at the time of pregnancy to those with good or very good health was 1.55 (95%CI: 1.05, 2.28) for coronary heart disease, 1.91 (95%CI: 0.99, 3.67) for stroke and 1.57 (95%CI: 1.13, 2.18) for either coronary heart disease or stroke. However, this association was not specific. There were strong associations for other outcomes that are known to be related to socioeconomic position (3.61 (95%CI: 1.04, 12.55) for lung cancer and 1.28 (95%CI:1.03, 1.58) for unintentional injury), but not for breast cancer (1.10 (95%CI:0.48, 2.53)).

Conclusions and Significance

These findings demonstrate that a simple assessment of physical health (based on the appearance of eyes, skin, hair and teeth) of mothers at the time of pregnancy is a strong indicator of the future health risk of their offspring for common conditions that are associated with poor socioeconomic position and unhealthy behaviours. They do not support a specific biological link between maternal health across her life course and future risk of cardiovascular disease in her offspring.

Low birth weight is not associated with thyroid autoimmunity: a population-based twin study

CONTEXT

Low birth weight has been proposed as a risk factor for the development of antibodies toward thyroid peroxidase (TPOAb) and thyroglobulin (TgAb) in adult life. However, the association could also be due to genetic or environmental factors affecting both birth weight and the development of thyroid autoantibodies. The effect of these confounders can be minimized through investigation of twin pairs.

OBJECTIVE AND DESIGN

To examine the impact of low birth weight on the development of thyroid autoimmunity, we studied whether within-twin-cohort and within-twin-pair differences in birth weight are associated with differences in the serum concentration of TPOAb and TgAb in adult life.

PARTICIPANTS

We studied 1024 euthyroid twin individuals who were distributed in 512 same-sex twin pairs.

METHODS

Original midwife protocols were traced manually through the Provincial Archives of Denmark. TPOAb and TgAb were measured using solid-phase time-resolved fluoroimmunometric assays.

RESULTS

There were no statistically significant associations between birth weight and serum concentrations of TPOAb [regression coefficient (beta) = 0.003 (95% confidence interval, -0.010 to 0.015); P = 0.67] or TgAb [beta = 0.002 (-0.010 to 0.014); P = 0.77]. When restricting the analysis to twin pairs with a within-pair difference in birth weight of 500 g or greater or to twin pairs born 4 wk or more before term, the regression coefficients were almost unchanged. Controlling for potential confounders (sex, zygosity, gestational age, TSH, and smoking) did not change the findings of nonsignificant regression coefficients.

CONCLUSION

Low birth weight per se has no evident role in the etiology of thyroid autoimmunity.

Accuracy and Reliability of Maternal Recall of Infant Birth Weight Among Older Women

PURPOSE

We assessed the accuracy and reliability of maternal recall of infant birth weight 35 to 70 years after delivery.

METHODS

A total of 120 well functioning women (mean age 80 years; 45% Black) reported the birth weight for each live birth and then provided documentation of birth weights (n = 22) or reported birth weights a second time (n = 98).

RESULTS

Agreement between recalled and documented birth weights was high for first births (ICC = 0.96) but moderate for subsequent births (ICC = 0.59). Maternal recall was highly reliable for first births (r = 0.95) and subsequent births (r = 0.87), and reliability remained high when considered separately by race, education, income, and age.

CONCLUSION

Women report accurate and reliable infant birth-weight data an average of 57 years after delivery, and recall is particularly precise for first births.

Relation of Maternal Low Birth Weight to Infant Growth Retardation and Prematurity

OBJECTIVES

This study sought to determine the relationship between maternal birth weight, infant intrauterine growth retardation, and prematurity.

METHODS

Stratified and logistic regression analyses were performed on a dataset of computerized Illinois vital records of African American (N = 61,849) and White (N = 203,698) infants born between 1989 and 1991 and their mothers born between 1956 and 1975.

RESULTS

Race-specific rates of small-for-gestational age (weight-for-gestational age <10th percentile) and preterm (<37 weeks) infants rose as maternal birth weight declined. The adjusted (controlling for maternal age, education, marital status, parity, prenatal care utilization, and cigarette smoking) odds ratio (95% confidence interval) of small-for-gestational age for maternal low birth weight (<2,500 g) among African Americans and Whites were 1.7 (1.1.4-1.9) and 1.8 (1.7-2.0), respectively. The adjusted odds ratio (95% confidence interval) of prematurity for maternal low birth weight (<2,500 g) among African Americans and Whites were 1.6 (1.3-1.9) and 1.3 (1.0-1.6), respectively. The racial disparity in the rates of small-for-gestational age and prematurity persisted independent of maternal birth weight: adjusted odds ratio equaled 2.2 (2.1-2.4) and 1.5 (1.4-1.7), respectively.

CONCLUSIONS

Maternal low birth weight is a risk factor for infant intrauterine growth retardation and prematurity among African Americans independent of maternal risk status during pregnancy; it is a risk factor for infant intrauterine growth retardation among Whites. Maternal low birth weight fails to explain the racial disparity in the rates of small-for-gestational age and premature infants.

Racial disparity in fetal growth inhibition among singletons and multiples

OBJECTIVE

The purpose of this study was to determine the magnitude of black-white gap in intrauterine fetal growth inhibition among singletons and multiples.

STUDY DESIGN

This was a cross-sectional study on singleton, twin, and triplet live births in the United States from 1995 through 1998. We compared the risk for low and very low-birth-weight, preterm and very preterm, and small-for-gestational age between black and white neonates.

RESULTS

A total of 14,245,865 singletons (blacks = 16.2%), 392,761 twins (blacks = 18.0%), and 21,436 triplets (blacks = 7.7%) were analyzed. Black neonates depicted significantly higher risks for all indices of fetal growth inhibition regardless of plurality. The gestational age of onset of fetal growth lag for black fetuses was earliest among triplets (23 weeks and the gap remained unchanged) then singletons (26 weeks; maximum gap 37-42 weeks), and finally twins (33 weeks; maximum gap 37-40 weeks).

CONCLUSION

Black-white disparity in fetal growth inhibition varied by plurality subtypes. The different gestational ages of onset of black-white fetal growth divergence could potentially be exploited for targeting intervention measures aimed at narrowing the gap.

Association between fetal growth restriction and polymorphisms at sites -1 and +3 of pituitary growth hormone: a case-control study

BACKGROUND: Fetal growth restriction is associated with significantly increased risks of neonatal death and morbidity and with susceptibility to hypertension, cardiovascular disease and NIDDM later in life. Human birth weight has a substantial genetic component, with at least a quarter of the variation attributable to additive genetic effects. METHODS: One hundred twenty-five subjects (83 control and 42 case) were selected using stringent inclusion/exclusion criteria. DNA sequencing was used to identify 26 single nucleotide polymorphisms in the pituitary growth hormone gene (GH1) at which all subjects were genotyped. Association with fetal growth restriction was tested by logistic regression for all sites with minor allele frequencies greater than 5%. RESULTS: Logistic regression identified significant association with fetal growth restriction of C alleles at sites -1 and +3 (relative to the start of transcription) that are in complete linkage disequilibrium. These alleles are present at higher frequency (6% vs. 0.4%) in fetal growth restricted subjects and are associated with an average reduction in birth weight of 152 g in normal birth weight and 97 g in low birth weight subjects. CONCLUSIONS: There is suggestive association between fetal growth restriction and the presence of C alleles at sites -1 and +3 of the pituitary growth hormone gene.

Significant paternal contribution to the risk of small for gestational age

OBJECTIVE

The aim of this study is to investigate both maternal and paternal contributions in the familial aggregation of small for gestational age.

DESIGN

Nested case-control study.

SETTING

Metropolitan area of Haguenau, France.

POPULATION

Data were drawn from a French population-based maternity registry. After selection, 256 cases born either small for gestational age or average for gestational age were included.

METHODS

Controlling for known pregnancy-related risk factors, logistic regression models were used to determine the risk of the child being small for gestational age, given that the mother, father or both were small for gestational age, and to examine interactions between maternal small for gestational age and pregnancy risk factors.

MAIN OUTCOME MEASURES

Specifically, we investigate to what extent having either or both parents born small for gestational age increases the risk of small for gestational age in their offspring, after controlling for the established risk factors of small for gestational age and maternal and paternal characteristics. We also explore the extent to which the intergenerational predictors of small for gestational age may modify the effect of current pregnancy-related risk factors.

RESULTS

The risk of a small for gestational age offspring was 4.7 times greater for mothers and 3.5 times greater for fathers who were small for gestational age, compared with average for gestational age counterparts. Furthermore, the risk of a small for gestational age offspring was 16.3 times greater when both parents were small for gestational age. No significant interactions between maternal small for gestational age and maternal smoking, hypertension or parity were observed.

CONCLUSION

These results indicate that small for gestational age in both mother and father significantly influences the risk of their offspring being small for gestational age. While previous research has indicated that the birth outcome of the mother is an important determinant of the birth outcome of her offspring, these data indicate that the birth outcome of the father plays an equally critical role in determining fetal growth, strongly suggesting a genetic component in the familial aggregation of small for gestational age.

The genetic contribution towards preterm delivery

Indirect evidence supports a possible genetic predisposition towards preterm birth. The recurrence of spontaneous preterm delivery in individual women, families and ethnic groups suggests a long-acting aetiology, consistent with a genetic factor. Genetic contributions from both mother and fetus probably play a role in determining gestational length. Preliminary genetic association studies implicate gene variants of tumor necrosis factor-alpha (TNF-alpha) in preterm birth. Further understanding of a genetic predisposition begins with investigation of the pathogenesis of preterm delivery. Technological advances in the study of the human genome (genomics) and protein complement (proteomics) will allow identification of novel genes and proteins involved in preterm delivery. Insight into the complex gene regulation and protein production in preterm delivery may contribute to an understanding of a genetic basis. A discovered genetic factor may lead to medical breakthroughs and reductions in prematurity, neonatal morbidity and mortality.

Reconsidering risk: adapting public policies to intergenerational determinants and biosocial interactions in health-related needs

According to recent research, interactions between infant health and environment can play crucial roles in clustering health and economic disadvantage among certain families. Researchers have provided a clear example of such intergenerational biosocial cycles when they document that interactions between parental low birth weight status and prenatal environment are associated with the risk of a low birth weight, and that interactions between a child's birth weight status and early childhood environment are associated with adult socioeconomic outcomes. In this article, we consider how existing policies may be revised to more effectively address such interactions between social and biological risk categories. We are particularly concerned in this discussion with revising risk categories so they can encompass biological risk, social risk, and developmental frameworks. A framework of biosocial risk is quite flexible and may be applied to a variety of issues and programs; however, in this article we focus on the single case of low birth weight to illustrate our argument. In considering specific applications, we further explore how attention to biosocial interactions may reshape Medicaid, special education, the Earned Income Tax Credit, and Temporary Assistance for Needy Families.

Maternal/newborn GSTT1 null genotype contributes to risk of preterm, low birthweight infants

OBJECTIVES

Maternal cigarette smoke exposure during pregnancy has been identified as a risk factor for prematurity and low birthweight. However, little is known about genetic susceptibility and possible interactions with cigarette smoking which may increase risk of these events.

METHODS

Maternal peripheral and umbilical cord blood samples from 955 mother/newborn pairs were genotyped for a panel of phase I/II metabolic enzymes responsible for the metabolism of tobacco related mutagens and carcinogens in order to evaluate the association with premature birth.

RESULTS

As reported previously, maternal cigarette smoking during the last trimester was significantly associated with premature birth. In addition, maternal glutathione S-transferase T1 (GSTT1) null genotype also increased risk of premature birth. Risk was further elevated among subjects with the combination of maternal and newborn GSTT1 null genotype with or without maternal cigarette smoke.

CONCLUSIONS

These observations suggest that women and/or newborns with the GSTT1 null genotype who are exposed to cigarette smoke during pregnancy are at elevated risk for premature delivery. The ability to identify high-risk women by genotyping has potential for reducing the frequency of premature births, a major public health concern.

Genetics and drug use as a complex phenotype

Drug use is a complex behavior influenced by multiple biological, family, and sociocultural factors. The concurrent use/misuse of multiple drugs is often seen and drug use also co-occurs with other psychiatric conditions. Behavior and molecular genetic studies support an important posited role of genes in drug use. This posited genetic risk does not appear to be conferred by one or two major genes manifesting large effects, but rather by a number of genes manifesting smaller effects. Genetic factors explain, on average, only about half of the total variability in drug use, with the remaining variability influenced by environmental factors. Also, genetic risk may be differentially expressed in the presence vs. absence of particular environmental conditions. Thus, investigation of environmental factors and their interaction with genetic risk is a necessary component of genetic research. While the full potential of genetic investigations for the prevention of drug misuse has yet to be realized, an example of the impact of risk factor modification under various conditions of gene-environment interaction is provided, and the implications for use of genetic information in drug-misuse prevention are discussed. The multifactorial nature of drug use necessitates coordinated investigation from multiple disciplines and timely dissemination of scientific findings. In addition, this work demands adherence to the highest standards of confidentiality and ethical use of genetic information to best inform future prevention efforts.

An investigation of racial and ethnic disparities in birth weight in Chicago neighborhoods

We examine differences in the mean birth weights of infants born to non-Hispanic black, non-Hispanic white, and Mexican-origin Hispanic mothers (of any race) in Chicago in 1990 using linear regression models with neighborhood fixed effects. Our pooled models accounted for 64% of the black-white difference and 57% of the black/Mexican-origin Hispanic difference. Differences in the relationship between measured characteristics and birth weight accounted for around half the birth-weight gap between non-Hispanic black and other infants. Efforts to close this gap must go beyond programs that aim to reduce the level of risk factors among black women to address the causes of differences in the effects of risk factors.

Birthweight and perinatal mortality: paradoxes, social class, and sibling dependencies

BACKGROUND

Birthweight distributions among second-born infants depend on the birthweights of older siblings, with implications for weight-specific perinatal mortality. We wanted to study whether these relations were explained by socioeconomic levels, and to study time trends in a situation with decreasing perinatal mortality rates.

METHODS

Births in the Norwegian Medical Birth Registry from 1967 to 1998 were linked to their mothers through their national identification numbers. The study population was 546 688 mothers with at least two singletons weighing >/==" BORDER="0">500 g at birth. Weight-specific perinatal mortality for second-born siblings in families with first-born siblings in either the highest or the lowest birthweight quartile was analysed. Maternal education and cohabitation status were used as measures of socioeconomic level.

RESULTS

For all 500-g categories below 3500 g, mortality rates were significantly higher among second-born infants with an older sibling in the highest rather than the lowest weight quartile. This pattern was the same across three educational levels. The exclusion of preterm births did not change the effect pattern. A comparison of perinatal mortality among second siblings in terms of relative birthweight (z-scores) showed a reversal of the relative risks, although these were only significantly different from unity for the smallest infants. Conclusion The crossover in weight-specific perinatal mortality for second siblings by weight of first sibling is largely independent of socioeconomic level, and is not weakened by the decreasing perinatal mortality rates in the population over time. Family data should be taken into consideration when evaluating the risk of adverse pregnancy outcome relating to weight.

Integrated perinatal health framework. A multiple determinants model with a life span approach

BACKGROUND

Despite great strides in improving prenatal care utilization among American women, key perinatal indicators have remained stagnant or worsened in the past decade, and the United States continues to rank near the bottom compared to other developed countries. A new approach is needed if we are to achieve improvements in perinatal health.

METHODS

To propose a new framework that integrates a "life span" approach with a multiple determinants model.

RESULTS

We recognize that (1) powerful influences on outcome occur long before pregnancy begins; (2) pregnancy outcome is shaped by social, psychological, behavioral, environmental, and biological forces; and (3) the demography of pregnancy has changed dramatically in the last few decades with more women delaying their first birth. Approaches that simultaneously consider the entire life span as well as multiple determinants may need to be adopted. We propose a framework that integrates these approaches and is supported by the research literature. The life span perspective focuses attention toward the preconceptional and interconceptional periods as targets for intervention in improving perinatal health. The multiple determinants model distinguishes among concepts of disease, health and functioning, and well-being for both women and their offspring.

CONCLUSIONS

Our intent is to influence how policymakers, public health professionals, clinicians, and researchers approach perinatal health.

Racial and ethnic disparities in birth outcomes: a life-course perspective

BACKGROUND

In the United States, Black infants have significantly worse birth outcomes than do White infants. The cause of these persisting racial disparities remains unexplained. Most extant studies focus on differential exposures to protective and risk factors during pregnancy, such as current socioeconomic status, maternal risky behaviors, prenatal care, psychosocial stress, or perinatal infections. These risk factors during pregnancy, however, do not adequately account for the disparities.

METHODS

We conducted a literature review for longitudinal models of health disparities, and presented a synthesis of two leading models, using a life-course perspective. Traditional risk factors during pregnancy are then reexamined within their life-course context. We conclude with a discussion of the limitations and implications of the life-course perspective for future research, practice, and policy development.

RESULTS

Two leading longitudinal models of health disparities were identified and discussed. The early programming model posits that exposures in early life could influence future reproductive potential. The cumulative pathways model conceptualizes decline in reproductive health resulting from cumulative wear and tear to the body's allostatic systems. We propose a synthesis of these two models, using the life-course perspective. Disparities in birth outcomes are the consequences of differential developmental trajectories set forth by early life experiences and cumulative allostatic load over the life course.

CONCLUSIONS

Future research on racial disparities in birth outcomes needs to examine differential exposures to risk and protective factors not only during pregnancy, but over the life course of women. Eliminating disparities requires interventions and policy development that are more longitudinally and contextually integrated than currently prevail.

Low birth weight and high birth weight infants are both at an increased risk to have type 2 diabetes among schoolchildren in taiwan

OBJECTIVE

To study the effect of birth weight on risk of type 2 diabetes in the schoolchildren in Taiwan.

RESEARCH DESIGN AND METHODS

From 1992 to 1997, all schoolchildren aged 6-18 years were screened for diabetes in Taiwan Province. This cohort consisted of 1,966 patients with diabetes and 1,780 randomly selected subjects with normal fasting glycemia (NFG). Questionnaire interviewing was designed to classify diabetes. The birth weight was obtained from the Taiwan's Birth Registry. After merging the data, there were 978 subjects, including 429 with type 2 diabetes and 549 with of NFG enrolled in the present analyses.

RESULTS

The odds ratios (95% CI) for type 2 diabetes, after adjusting age, sex, BMI, family history of diabetes, and socioeconomic status, were 2.91 (1.25-6.76) for children with low birth weight (<2,500 g) and 1.78 (1.04-3.06) for those with high birth weight (> or =4,000 g) when compared with the referent group (birth weight 3,000-3,499 g). The risk of diabetes was still 64% higher in the high birth weight group [odds ratio (OR) 1.64 (95% CI 0.91-2.96)], even after adjustment for gestational diabetes mellitus (GDM). Patients with type 2 diabetes who were born with high birth weight were more likely to have a higher BMI and diastolic blood pressure as well as a higher family history of diabetes compared with those with low birth weight.

CONCLUSIONS

A U-shaped relationship between birth weight and risk of type 2 diabetes was found in the schoolchildren aged 6-18 years in Taiwan. Schoolchildren with type 2 diabetes who were born with low birth weight had different metabolic phenotypes compared with those born with high birth weight.

Insulin-like growth factor I, epidermal growth factor and transforming growth factor beta expression and their association with intrauterine fetal growth retardation, such as development during human pregnancy

AIM

Fetal intrauterine growth retardation (IUGR) is one of the most common obstetric problems, with a frequency of 12% in Mexico. In the past, investigations have focused on extrinsic causes of IUGR. More recent studies have examined the intrinsic factors that cause fetal intrauterine growth. Maintenance of fetal growth has been attributed to insulin-like growth factor (IGF), epidermal growth factor (EGF) and transforming growth factor beta (TGF-beta). The objective of this study was to assess the levels of these growth factors during pregnancy and to determine whether or not low concentrations are associated with IUGR.

METHODS

Nine women whose pregnancies were complicated by IUGR and a group of nine women whose pregnancies exhibited normal fetal intrauterine growth were studied. IUGR was determined by sonography and confirmed by weight at birth. Venous blood samples were taken from both groups of pregnant women at the end of each trimester. Enzyme-linked immunosorbent assays, immunoradiometric assays and radioimmunoassays were used to process samples, and the results were analysed by anova.

RESULTS

IGF-I levels increased in both groups during pregnancy, but the increase was lower (p < 0.001) in the IUGR group throughout pregnancy and at delivery. EGF did not show any significant changes during pregnancy. Blood TGF-beta levels varied only during the first trimester of pregnancy. The differences were not statistically significant. However, TGF-beta concentrations were higher in the pregnancies with IUGR. Women in the IUGR group were smaller than in the control group (p < 0.05), and, using the covariance test (p < 0.05), this was found to be correlated with IGF-I levels but not with EGF or TGF-beta levels.

CONCLUSIONS

Changes in fetal weight might be explained by the different concentrations of IGF. The structural homology between IGF-1 and insulin could mean that the presence of higher levels of IGF would result in a increased energetic metabolism that could contribute to fetal growth. EGF levels were not related to IUGR, and TGF-beta levels increased only during the first 3 months in the IUGR group. This observation correlates with the in vitro action of TGF-beta as a negative factor of growth, but as a positive support for sustaining early pregnancy. Our data illustrates that low height represents an increased risk factor for IUGR. These data also correlate with the studies involving extrinsic factors.

Race and the inheritance of low birth weight

This paper uses intergenerational data from the Panel Study of Income Dynamics (PSID) to address the black-white difference in propensities toward low birth weight (LBW). We determine that socioeconomic conditions account for some variation in low birth weight across race. Further, while race differences in the risk of low birth weight cannot be explained entirely, we find that the inheritance of parental birth weight status dramatically reduces the black-white gap in low birth weight. Intergenerational legacies of poor infant health explain the largest share of racial disparities in filial birth weight. We then try to assess whether this intergenerational transmission of low birth weight is indeed genetic by using grandparent-fixed effects models to factor out, to a great extent, family socioeconomic circumstances. We find that even within this framework, both father's and mother's birth weight status have an important impact on filial outcomes. However, the degree of inheritance is weaker for African Americans than for other races. Finally, we theorize that the importance of paternal birth weight status implies a genetic association that does not work through the uterine environment but rather through the fetus itself.

Molecular epidemiology of preterm delivery: methodology and challenges

Preterm delivery (PTD) appears to be a complex trait determined by both genetic and environmental factors. Few studies have examined genetic influence on PTD. The overall goal of our study is to examine major candidate genes of PTD and to test gene-environment interactions. Our study includes 500 preterm trios, including 500 preterm babies and their parents and 500 maternal age-matched term controls. We will perform the transmission/disequilibrium test (TDT) on candidate genes thought to be important in each of the four biological pathways of PTD: (1) decidual chorioamionotic inflammation: interleukin 1 (IL-1), IL-6, and tumour necrosis factor (TNF); (2) maternal and fetal stress: corticotropin-releasing hormone (CRH); (3) uteroplacental vascular lesions: methylenetereahydrofolate reductase (MTHFR); and (4) susceptibility to environmental toxins: GSTM1, GSTT1, CYP1A1, CYP2D6, CYP2E1, NAT2, NQO1, ALDH2, and EPHX. We will also perform standard case-control analyses on the 500 preterm cases and 500 term controls to examine gene-environment interactions. The major environmental, nutritional and social factors as well as clinical variables known or suspected to be associated with PTD will be used to test for gene-environment interactions. This study integrates epidemiological and clinical data as well as genetic markers along major pathogenic pathways of PTD. The findings from this study should improve our understanding of genetic influences on PTD and gene-environment interactions.

New standards for birth weight by gestational age using family data

OBJECTIVE

This study was undertaken to provide new standards for birth weight according to gestational age through the addition of family data on maternal birth weight and birth weights of previous siblings.

STUDY DESIGN

The analyses were based on 1.7 million births in Norway from 1967 through 1998. These population data were arranged into sibships and mother-offspring units through unique personal numbers. We categorized first births by sex and maternal birth weight and second births by sex and birth weight of the older sibling.

RESULTS

Standards for birth weight per gestational age percentiles differed by >1100 g when the birth weight of an older sibling was considered and by almost 700 g when maternal birth weight was considered. The value of these new standards for birth weight according to gestational age was demonstrated through variation in perinatal mortality.

CONCLUSION

Maternal birth weight and birth weights of previous siblings allow improved predictions of birth weight according to gestational age and should be used for classification of small-for-gestational-age births.

Does smoking by pregnant women influence IQ, birth weight, and developmental disabilities in their infants? A methodological review and multivariate analysis

Neuropsychologists are asked frequently to address the issue of the cause of a variety of central nervous system problems that may affect higher cortical function. One such issue is the relationship of maternal smoking to adverse reproductive outcomes involving neocortical insult including mental retardation, learning disabilities, attention-deficit hyperactivity disorder, and other insults that may be related to prolonged hypoxic states in utero. The instant paper develops the issue of causation as a scientific inquiry, reviews several traditional, applicable models, and critiques these models. An additional model of motility is proposed and discussed. The issue of the relationship of maternal smoking to adverse reproductive outcomes is then addressed from a review perspective along with new empirical analyses, the latter demonstrating that researchers tend to draw causal conclusions independent of whether the respective design of their studies would support conclusions about the causation of an event. Causal conclusions in the absence of causal designs have often lead to incomplete and incorrect conclusions. It is necessary to match conclusions not only to the outcomes of a research project but also to its design and accompanying limitations.

Does zygosity influence the metabolic profile of twins? A population based cross sectional study

OBJECTIVE

To study the influence of zygosity on the metabolic variables involved in the pathophysiology of type 2 diabetes.

DESIGN

Population based cross sectional study.

SETTING

Odense University Hospital, Denmark.

PARTICIPANTS

125 monozygotic twin pairs and 178 dizygotic twin pairs of the same sex born between 1921 and 1940.

MAIN OUTCOME MEASURES

Clinical characteristics of monozygotic and dizygotic twins with or without a family history of type 2 diabetes.

RESULTS

Absolute prevalences of type 2 diabetes and impaired glucose tolerance according to the World Health Organisation criteria were similar in both the monozygotic and the dizygotic twins as were measurements of height, weight, body mass index, waist to hip ratio, and fasting plasma glucose and insulin concentrations. During the oral glucose tolerance test, monozygotic twins had a higher incremental plasma insulin area under the curve than dizygotic twins (10.05 (SD 0.68) v 9.89 (0.72) pmol/lxminutes, P<0.01) indicating insulin resistance. In twins with normal glucose tolerance and without first degree relatives or co-twins with type 2 diabetes or impaired glucose tolerance, both the glucose and insulin areas under the curve were higher among monozygotic twins (glucose 214.4 (88.3) v 189.8 (78.4) mmol/lxminutes, P<0.05; insulin 20 040 (14 865-32 554) v 17 625 (12 330-23 640) pmol/lxminutes, P=0.08).

CONCLUSION

Zygosity influences both plasma glucose and plasma insulin concentrations during an oral glucose tolerance test. This supports an intrauterine influence on glucose homeostasis and perhaps on insulin resistance in humans.