Exploring weathering: the relation of age to low birth weight among first generation and established United States-born Mexican-American women

Lifetime Upward Economic Mobility and US-Born Latina Women's Preterm Birth Rates

OBJECTIVES

To determine whether Latina women's upward economic mobility from early-life residence in impoverished urban neighborhoods is associated with preterm birth (< 37 weeks, PTB) .

METHODS

Multivariate logistic regression analyses were performed on the Illinois transgenerational birth-file with appended US census income information for Hispanic infants (born 1989-1991) and their mothers (born 1956-1976).

RESULTS

In Chicago, modestly impoverished-born Latina women (n = 1,674) who experienced upward economic mobility had a PTB rate of 8.5% versus 13.1% for those (n = 3,760) with a lifelong residence in modestly impoverished neighborhoods; the unadjusted and adjusted (controlling for age, marital status, adequacy of prenatal care, and cigarette smoking) RR equaled 0.65 (0.47, 0.90) and 0.66 (0.47, 0.93), respectively. Extremely impoverished-born Latina women (n = 2,507) who experienced upward economic mobility across their life-course had a PTB rate of 12.7% versus 15.9% for those (n = 3,849) who had a lifelong residence in extremely impoverished neighborhoods, the unadjusted and adjusted RR equaled 0.8 (0.63. 1.01) and 0.95 (0.75, 1.22), respectively.

CONCLUSIONS FOR PRACTICE

Latina women's upward economic mobility from early-life residence in modestly impoverished urban neighborhoods is associated with a decreased risk of PTB. A similar trend is absent among their peers with an early-life residence in extremely impoverished areas.

Mexican-American Women's Lifelong Residence in the United States Is Associated with an Increased Risk of Gastroschisis: A Population-Based Study

OBJECTIVE

To determine whether nativity is associated with abdominal wall defects among births to Mexican-American women.

STUDY DESIGN

Using a cross-sectional, population-based design, stratified and multivariable logistic regression analyses were performed on the 2014-2017 National Center for Health Statistics live-birth cohort dataset of infants of US-born (n = 1 398 719) and foreign-born (n = 1 221 411) Mexican-American women.

RESULTS

The incidence of gastroschisis was greater among births to US-born compared with Mexico-born Mexican-American women: 36.7/100 000 vs 15.5/100 000, RR = 2.4 (2.0, 2.9). US-born (compared with Mexico-born) Mexican-American mothers had a greater percentage of teens and cigarette smokers, P < .0001. In both subgroups, gastroschisis rates were greatest among teens and decreased with advancing maternal age. Adjusting for maternal age, parity, education, cigarette smoking, pre-pregnancy body mass index, prenatal care usage, and infant sex), OR of gastroschisis for US-born (compared with Mexico-born) Mexican-American women was 1.7 (95% CI 1.4-2.0). The population attributable risk of maternal birth in the US for gastroschisis equaled 43%. The incidence of omphalocele did not vary by maternal nativity.

CONCLUSIONS

Mexican-American women's birth in the US vs Mexico is an independent risk factor for gastroschisis but not omphalocele. Moreover, a substantial proportion of gastroschisis lesions among Mexican-American infants is attributable to factors closely related to their mother's nativity.

Association of Primary Language with Very Low Birth Weight Outcomes in Hispanic Infants in California

OBJECTIVE

To determine the association of Spanish as a primary language for a family with the health outcomes of Hispanic infants with very low birth weight (VLBW, <1500g).

STUDY DESIGN

Data from the California Perinatal Quality Care Collaborative (CPQCC) linked to hospital discharge records were analyzed. Hispanic infants with VLBW born between 2009 and 2018 with a primary language of English or Spanish were included. Outcomes selected were hypothesized to be sensitive to language barriers. Multivariable logistic regression models and mixed models estimated associations between language and outcomes.

RESULTS

Of 18 364 infants meeting inclusion criteria, 27% (n = 4976) were born to families with Spanish as a primary language. In unadjusted analyses, compared with infants of primarily English-speaking families, these infants had higher odds of hospital readmission within 1 year (OR 1.11 [95% CI 1.02-1.21]), higher odds to receive human milk at discharge (OR 1.32 [95% CI 1.23-1.42]), and lower odds of discharge home with oxygen (OR 0.83 [95% CI 0.73-0.94]). In multivariable analyses, odds of readmission and home oxygen remained significant when adjusting for infant but not maternal and hospital characteristics. Higher odds for receipt of any human milk at discharge were significant in all models. Remaining outcomes did not differ between groups.

CONCLUSIONS

Significant differences exist between Hispanic infants with VLBW of primarily Spanish-vs English-speaking families. Exploration of strategies to prevent readmissions of infants of families with Spanish as a primary language is warranted.

Epigenetic age acceleration mediates the relationship between neighborhood deprivation and pain severity in adults with or at risk for knee osteoarthritis pain

An estimated 250 million people worldwide suffer from knee osteoarthritis (KOA), with older adults having greater risk. Like other age-related diseases, residents of high-deprivation neighborhoods experience worse KOA pain outcomes compared to their more affluent neighbors. The purpose of this study was to examine the relationship between neighborhood deprivation and pain severity in KOA and the influence of epigenetic age acceleration (EpAA) on that relationship. The sample of 128 participants was mostly female (60.9%), approximately half non-Hispanic Black (49.2%), and had a mean age of 58 years. Spearman bivariate correlations revealed that pain severity positively correlated with EpAA (ρ = 0.47, p ≤ 0.001) and neighborhood deprivation (ρ = 0.25, p = 0.004). We found a positive significant relationship between neighborhood deprivation and EpAA (ρ = 0.47, p ≤ 0.001). Results indicate a mediating relationship between neighborhood deprivation (predictor), EpAA (mediator), and pain severity (outcome variable). There was a significant indirect effect of neighborhood deprivation on pain severity through EpAA, as the mediator accounted for a moderate portion of the total effect, PM = 0.44. Epigenetic age acceleration may act as a mechanism through which neighborhood deprivation leads to worse KOA pain outcomes and may play a role in the well-documented relationship between the neighborhood of residence and age-related diseases.

Different maternal age patterns of preterm birth: Interplay of race/ethnicity, chronic stress, and marital status

The aim of this study was to examine whether the preterm birth (PTB) risks according to maternal age is altered by a woman's marital status and chronic stress among non-Hispanic (N-H) White, N-H Black, Hispanic, and Asian women. This researcher analyzed the Pregnancy Risk Assessment Monitoring System data for New York City and Washington State linked with the birth certificates for 2004-2007. The sample included 6344 singleton live births without birth defects to women aged 18 years or older identified as N-H White, N-H Black, Hispanic, or Asian. The outcome was PTB. Maternal age-specific PTB rates were calculated according to race/ethnicity, marital status, and chronic stress. Linear trends of PTB rates with maternal age were evaluated by the Mantel-Haenszel χ² test. Marriage had a protective effect against PTB at advancing maternal age across racial/ethnic groups. The health benefit of marriage was strong, particularly among the married N-H Black and Asian women, manifested as a maternal age-related decrease in the PTB rate (reverse-weathering). In contrast, women not married showed a maternal age-related increase in the PTB rate (weathering) across the racial/ethnic groups. Under higher chronic stress, married women generally experienced less weathering about PTB. These patterns were observed with noticeable racial/ethnic variations. Acknowledging the different dynamics among maternal age, marital status, and chronic stress by race/ethnicity could help shed light on the psychosocial mechanisms underlying the racial/ethnic inequalities in PTB in the United States. To that end, future studies should use more nuanced measurements of paternal support and chronic stress.

The Hispanic/Latinx Perinatal Paradox in the United States: A Scoping Review and Recommendations to Guide Future Research

For decades, epidemiologists have documented a health advantage among Hispanic/Latinx individuals who live in the United States, despite their significant socioeconomic barriers. This observation is often described as the "Hispanic paradox." In this scoping review, we aimed to summarize literature published on Hispanic/Latinx perinatal outcomes over the past two decades and place these findings within the context of the overarching "Healthy Immigrant" paradox. Studies were eligible for inclusion if they utilized large population datasets to describe rates of preterm birth, low birth weight and infant mortality among Hispanic/Latinx women living in the United States. To focus on the most recent trends, studies were excluded if they were published prior to the year 2000. Globally, Hispanic/Latinx women appear to continue to have improved perinatal outcomes compared to non-Hispanic Black infants, while rates of adverse outcomes appear similar for Hispanic/Latinx and non-Hispanic White women. However, our review emphasizes the heterogeneity of outcomes experienced by Hispanic/Latinx women. The epidemiologic advantage among Hispanic/Latinx women and their infants may be largely concentrated among specific national origin subgroups or among recently arrived foreign-born Hispanic/Latinx women. Given the disparities that exist among Hispanic/Latinx women, we provide a summary of themes to explore in future research and methodologic recommendations that may assist in identifying important subgroup differences and their determinants.

Maternal Age Patterns of Preterm Birth: Exploring the Moderating Roles of Chronic Stress and Race/Ethnicity

BACKGROUND

Despite the suggested contribution of cumulative chronic stress to the racial/ethnic disparities in preterm birth (PTB), it is unclear how chronic stress, maternal age, and race/ethnicity are linked underlying PTB.

PURPOSE

We investigated the moderating effect of chronic stress on the maternal age-PTB association among non-Hispanic (N-H) White, N-H Black, Hispanic, and Asian women.

METHODS

We analyzed the Washington State's Pregnancy Risk Assessment Monitoring System data linked with birth certificates. The sample included women aged 18 years or older who birthed the first, singleton baby without birth defects. Chronic stress was measured by race/ethnicity-specific chronic stress indices. A maternal age-chronic stress interaction was modeled to predict PTB by logistic regression stratified by race/ethnicity. In subanalysis, the moderating role of racism was investigated in the maternal age-chronic stress interaction among three minority groups combined.

RESULTS

Women's maternal age trajectory of PTB varied by their race/ethnicity and chronic stress level. N-H White and N-H Black women showed a steeper maternal age-related increase in PTB (weathering) under higher chronic stress, indicating a chronic stress' cumulative effect with maternal age. Besides, the extent of weathering was amplified by racism on top of chronic stress, particularly among N-H Black women.

CONCLUSIONS

These results show that both chronic stress and racism may develop accelerated PTB risk among minority women. Future research should use more objective and accurate chronic stress measures to ascertain the complex relationships among chronic stress, racial discrimination, and maternal age underlying the racial/ethnic differentials in PTB.

Association of Acculturation With Adverse Pregnancy Outcomes

OBJECTIVE

To evaluate the relationship between acculturation and adverse pregnancy outcomes, and whether these relationships differ across racial or ethnic groups.

METHODS

This is a planned secondary analysis of the nuMoM2b study (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be), a prospective observational cohort study of 10,038 pregnant women at eight academic health care centers in the United States. Nulliparous pregnant women with singleton gestations were recruited between 6 0/7 and 13 6/7 weeks of gestation from October 2010-September 2013. Acculturation was defined by birthplace (United States vs non-United States), language used during study visits (English or Spanish), and self-rated English proficiency. The adverse pregnancy outcomes of interest were preterm birth (less than 37 weeks of gestation, both iatrogenic and spontaneous), preeclampsia or eclampsia, gestational hypertension, gestational diabetes, stillbirth, small for gestational age, and large for gestational age. Multivariable regression modeling was performed, as was an interaction analysis focusing on the relationship between acculturation and adverse pregnancy outcomes by maternal race or ethnicity.

RESULTS

Of the 10,006 women eligible for this analysis, 8,100 (80.9%) were classified as more acculturated (eg, born in the United States with high English proficiency), and 1,906 (19.1%) were classified as having less acculturation (eg, born or not born in the United States with low proficiency in English or use of Spanish as the preferred language during study visits). In multivariable logistic regression modeling, more acculturation was significantly associated with higher frequency of preterm birth (odds ratio [OR] 1.46, adjusted odds ratio [aOR] 1.50, 95% CI 1.16-1.95); spontaneous preterm birth (OR 1.54, aOR 1.62, 95% CI 1.14-2.24); preeclampsia or eclampsia (OR 1.39, aOR 1.31, 95% CI 1.03-1.67); preeclampsia without severe features (OR 1.44, aOR 1.43, 95% CI 1.03-2.01); and gestational hypertension (OR 1.68, aOR 1.48, 95% CI 1.22-1.79). These associations did not differ by self-described race or ethnicity.

CONCLUSION

In a large cohort of nulliparous women, more acculturation, regardless of self-described race or ethnicity, was associated with increased odds of several adverse pregnancy outcomes.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT01322529.

The weathering hypothesis as an explanation for racial disparities in health: a systematic review

PURPOSE

The weathering hypothesis states that chronic exposure to social and economic disadvantage leads to accelerated decline in physical health outcomes and could partially explain racial disparities in a wide array of health conditions. This systematic review summarizes the literature empirically testing the weathering hypothesis and assesses the quality of the evidence regarding weathering as a determinant of racial disparities in health.

METHODS

Databases (Web of Science, Ovid MEDLINE, PubMed, and Embase) were searched for studies published in English up to July 1, 2017. Studies that tested the weathering hypothesis for any physical health outcome and included at least one socially or economically disadvantaged group (e.g., Blacks) for whom the weathering hypothesis applies were assessed for eligibility. Threats to validity were assessed using the Quality in Prognostic Studies tool.

RESULTS

The 41 included studies were rated as having overall good methodological quality. Most studies found evidence in support of the weathering hypothesis, although the magnitude of support varied by the health outcome and population studied.

CONCLUSIONS

Future evaluations of the weathering hypothesis should include an examination of additional health outcomes and interrogate mechanisms that could link weathering to poor health.

Birth weight and maternal age among American Indian/Alaska Native mothers: A test of the weathering hypothesis

Substantial research has examined birth outcomes by race/ethnicity, noting not only disparities by race/ethnicity, but different maternal age patterns in low birth weight (LBW) prevalence. Few studies have examined these disparities among American Indian/Alaska Native (AI/AN) mothers, whose LBW prevalence is below the national average, despite substantial socioeconomic disadvantage among the population. Prior work has hypothesized that AI/AN mothers should exhibit LBW age patterns similar to those seen in NH black mothers as a result of exposure to cumulative stress, trauma, and socioeconomic disadvantage, but this has not been empirically tested. This paper uses data from the 2014–2016 U.S. Birth File, which contains records of all U.S. births for those years to examine maternal age patterns in birth weight among AI/AN mothers. Importantly, this study also considers high birth weight (HBW) births, given higher prevalence of diabetes in the AI/AN population, and proposes that if “weathering” is occurring in this population, HBW prevalence likely will influence the observed maternal age patterns in birth weight, such that prevalence of births in normal range may resemble NH blacks, even if LBW prevalence does not. Findings suggest modest evidence of weathering in AI/AN populations for LBW. Examination of normal birth weight births suggests that inclusion of HBW to the risk profile of AI/AN births better defines birth outcome risk in this population relative to white mothers. Smoking during pregnancy and gestational diabetes were particularly prevalent among AI/AN mothers and present reason for concern in spite of relatively favorable birth outcomes.

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American Indian/Alaska Native (AI/AN) birth outcomes resemble white mothers, despite substantially higher rates of gestational diabetes.

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Age patterns of low birth weight in AI/AN mothers modestly suggest patterns in line with the weathering hypothesis.

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AI/AN birth outcomes and risks have been ignored in research literature because of relatively small population size.

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AI/AN mothers have higher rates of gestational diabetes than other groups, and higher smoking rates at older ages.

Life-course neighbourhood opportunity and racial-ethnic disparities in risk of preterm birth

BACKGROUND

Neighbourhood opportunity, measured by poverty, income and deprivation, has been associated with preterm birth, however little is known about the contribution of early-life and life-course neighbourhood opportunity to preterm birth risk and racial-ethnic disparities. We examined maternal early-life and adult neighbourhood opportunity in relation to risk of preterm birth and racial-ethnic disparities in a population-based cohort of women under age 30.

METHODS

We linked census tract poverty data to 2 generations of California births from 1982-2011 for 403 315 white, black, or Latina mothers-infant pairs. We estimated the risk of preterm birth, and risk difference (RD) comparing low opportunity (≥20% poverty) in early life or adulthood to high opportunity using targeted maximum likelihood estimation.

RESULTS

At each time point, low opportunity was related to increased preterm birth risk compared to higher opportunity neighbourhoods for white, black and Latina mothers (RDs 0.3-0.7%). Compared to high opportunity at both time points, risk differences were generally highest for sustained low opportunity (RD 1.5, 1.3, and 0.7% for white, black and Latina mothers, respectively); risk was elevated with downward mobility (RD 0.7, 1.3, and 0.4% for white, black and Latina mothers, respectively), and with upward mobility only among black mothers (RD 1.2%). The black-white preterm birth disparity was reduced by 22% under high life-course opportunity.

CONCLUSIONS

Early-life and sustained exposure to residential poverty is related to increased PTB risk, particularly among black women, and may partially explain persistent black-white disparities.

Racial disparity in infant mortality

In the United States, African-American infants have significantly higher mortality than white infants. Previous work has identified associations between individual socioeconomic factors and select community-level factors. In this review, the authors look beyond traditional risk factors for infant mortality and examine the social context of race in this country, in an effort to understand African-American women's long-standing birth outcome disadvantage. In the process, recent insights are highlighted concerning neighborhood-level factors such as crime, segregation, built environment, and institutional racism, other likely causes for the poor outcomes of African-American infants in this country compared with infants in most other industrialized nations.

Diverse Aging and Health Inequality by Race and Ethnicity

Although gerontologists have long embraced the concept of heterogeneity in theories and models of aging, recent research reveals the importance of racial and ethnic diversity on life course processes leading to health inequality. This article examines research on health inequality by race and ethnicity and identifies theoretical and methodological innovations that are transforming the study of health disparities. Drawing from cumulative inequality theory, we propose greater use of life course analysis, more attention to variability within racial and ethnic groups, and better integration of environmental context into the study of accumulation processes leading to health disparities.

Epigenetic Biomarkers of Preterm Birth and Its Risk Factors

A biomarker is a biological measure predictive of a normal or pathogenic process or response. Biomarkers are often useful for making clinical decisions and determining treatment course. One area where such biomarkers would be particularly useful is in identifying women at risk for preterm delivery and related pregnancy complications. Neonates born preterm have significant morbidity and mortality, both in the perinatal period and throughout the life course, and identifying women at risk of delivering preterm may allow for targeted interventions to prevent or delay preterm birth (PTB). In addition to identifying those at increased risk for preterm birth, biomarkers may be able to distinguish neonates at particular risk for future complications due to modifiable environmental factors, such as maternal smoking or alcohol use during pregnancy. Currently, there are no such biomarkers available, though candidate gene and epigenome-wide association studies have identified DNA methylation differences associated with PTB, its risk factors and its long-term outcomes. Further biomarker development is crucial to reducing the health burden associated with adverse intrauterine conditions and preterm birth, and the results of recent DNA methylation studies may advance that goal.

Association of neighborhood context with offspring risk of preterm birth and low birthweight: A systematic review and meta-analysis of population-based studies

Findings from studies investigating associations of residential environment with poor birth outcomes have been inconsistent. In a systematic review and meta-analysis, we examined associations of neighborhood disadvantage with preterm birth (PTB) and low birthweight (LBW), and explored differences in relationships among racial groups. Two reviewers searched English language articles in electronic databases of published literature. We used random effects logistic regression to calculate odds ratios (and 95% confidence intervals) relating neighborhood disadvantage with PTB and LBW. Neighborhood disadvantage, most disadvantaged versus least disadvantaged neighborhoods, was defined by researchers of included studies, and comprised of poverty, deprivation, racial residential segregation or racial composition, and crime. We identified 1314 citations in the systematic review. The meta-analyses included 7 PTB and 14 LBW cross-sectional studies conducted in the United States (U.S.). Overall, we found 27% [95%CI: 1.16, 1.39] and 11% [95%CI: 1.07, 1.14] higher risk for PTB and LBW among the most disadvantaged compared with least disadvantaged neighborhoods. No statistically significant association was found in meta-analyses of studies that adjusted for race. In race-stratified meta-analyses models, we found 48% [95%CI: 1.25, 1.75] and 61% [95%CI: 1.30, 2.00] higher odds of PTB and LBW among non-Hispanic white mothers living in most disadvantaged neighborhoods compared with those living in least disadvantaged neighborhoods. Similar, but less strong, associations were observed for PTB (15% [95%CI: 1.09, 1.21]) and LBW (17% [95%CI: 1.10, 1.25]) among non-Hispanic black mothers. Neighborhood disadvantage is associated with PTB and LBW, however, associations may differ by race. Future studies evaluating causal mechanisms underlying the associations, and racial/ethnic differences in associations, are warranted.

Intergenerational transmission of the healthy immigrant effect (HIE) through birth weight: A systematic review and meta-analysis

This review examines intergenerational differences in birth weight among children born to first-generation and second-generation immigrant mothers and the extent to which they vary by country of origin and receiving country. We searched MEDLINE, EMBASE, Web of Science, PubMed, and ProQuest from inception to October 2014 for articles that recorded the mean birth weight (in grams) or odds of low birth weight (LBW) of children born to immigrant mothers and one subsequent generation. Studies were analyzed descriptively and meta-analyzed using Review Manager 5.3 software. We identified 10 studies (8 retrospective cohort and 2 cross-sectional studies) including 158,843 first and second-generation immigrant women. The United States and the United Kingdom represented the receiving countries with the majority of immigrants originating from Mexico and South Asia. Six studies were meta-analyzed for mean birth weight and seven for low birth weight. Across all studies, there was found to be no statistically significant difference in mean birth weight between first and second-generation children. However, the odds of being LBW were 1.21 [95% CI, 1.15, 1.27] times greater among second-generation children. Second-generation children of Mexican descent in particular were at increased odds of LBW (OR = 1.47 [95% CI, 1.28, 1.69]). In the United States, second-generation children were at 34% higher odds of being LBW (OR = 1.34 [95% CI, 1.13, 1.58]) when compared to their first-generation counterparts. This effect was slightly smaller in the United Kingdom (OR = 1.18 [95% CI, 1.13, 1.23]). In conclusion, immigration to a new country may differentially influence low birth weight over generations, depending on the mother's nativity and the country she immigrates to.

Preconception stress, birth weight, and birth weight disparities among US women

OBJECTIVES

We examined the impact of preconception acute and chronic stressors on offspring birth weight and racial/ethnic birth weight disparities.

METHODS

We included birth weights for singleton live first (n = 3512) and second (n = 1901) births to White, Mexican-origin Latina, other-origin Latina, and Black women reported at wave IV of the National Longitudinal Study of Adolescent Health (2007-2008; ages 24-32 years). We generated factor scores for preconception acute and chronic stressors from wave I (1994-1995; ages 11-19 years) or wave III (2001-2002; ages 18-26 years) for the same cohort of women.

RESULTS

Linear regression models indicated that chronic stressors, but not acute stressors, were inversely associated with birth weight for both first and second births (b = -192; 95% confidence interval = -270, -113; and b = -180; 95% confidence interval = -315, -45, respectively), and partially explained the disparities in birth weight between the minority racial/ethnic groups and Whites.

CONCLUSIONS

Preconception chronic stressors contribute to restricted birth weight and to racial/ethnic birth weight disparities.

Young maternal age and low birth weight risk: An exploration of racial/ethnic disparities in the birth outcomes of mothers in the United States

This study considers how low birth weight (LBW) prevalence varies by race/ethnicity and maternal age and explores mechanisms that explain disparities. Results show that maternal age patterns in LBW risk for African Americans differ from whites and foreign- and U.S.-born Hispanics. Background socioeconomic disadvantage, together with current socioeconomic status and smoking during pregnancy, explain almost all of the LBW disparity between white teenage mothers and their older counterparts. These findings suggest that social disadvantage is a primary driver in unfavorable birth outcomes among white teenage mothers compared to older white mothers. Alternatively, background disadvantage and other social characteristics explain very little of the LBW disparities among African Americans and U.S.- and foreign-born Hispanics. Overall, these results indicate LBW disparities by maternal age are a complex product of socioeconomic disadvantage and current social and behavioral factors, such that LBW risk does not operate uniformly by race/ethnicity or maternal age.

Maternal age and low birth weight: a reinterpretation of their association under a demographic transition in southern Brazil

To evaluate the relationship between changes in fecundity rates and maternal age and the impact of maternal age on low birth weight (LBW) rates in a developed region in southern Brazil. A time series study evaluating birth weight and maternal ages through the born alive information system (SINASC) in Porto Alegre from 1996 to 2008. The Chi-square test for trends was used to evaluate the trend of LBW and fecundity rates at each maternal age. Population attributed risk (PAR) was used to calculate the impact of maternal age on LBW rates. The study included 271,100 newborns. There was a significant reduction in fecundity rates in all age groups younger than 34 years, but especially in the groups between 20 and 29 years. Overall LBW increased from 9.3 to 10.7 % (P < 0.001). The PAR for LBW showed a reduction in the group from 17 to 19 years (from 1.7 % in 1996-1999 to 0.1 % in 2004-2008), and an increase in the groups from 35 to 39 years (from 2.0 % in 1996-1999 to 2.3 % in 2004-2008) and above 40 (from 1.1 % in 1996-1999 to 1.5 % in 2004-2008). There was a significant change in fecundity pattern in the last 12 years in southern Brazil. Adolescent mothers were surpassed by mothers over 30 years of age in terms of vulnerability for LBW babies. The results show a change in the maternal age distribution towards older mothers, accompanied by an increasing incidence of LBW. This demographic transition also involved a paradoxical pattern with a remarkable reduction in fecundity rates in intermediate maternal age groups with concomitant increase in their risk for LBW.