Weight gain during pregnancy and the black-white disparity in preterm birth

Impact of being underweight before pregnancy on preterm birth by race/ethnicity and insurance status in California: an analysis of birth records

BACKGROUND

The US still has a high burden of preterm birth (PTB), with important disparities by race/ethnicity and poverty status. There is a large body of literature looking at the impact of pre-pregnancy obesity on PTB, but fewer studies have explored the association between underweight status on PTB, especially with a lens toward health disparities. Furthermore, little is known about how weight, specifically pre-pregnancy underweight status, and socio-economic-demographic factors such as race/ethnicity and insurance status, interact with each other to contribute to risks of PTB.

OBJECTIVES

The objective of this study was to measure the association between pre-pregnancy underweight and PTB and small for gestational age (SGA) among a large sample of births in the US. Our secondary objective was to see if underweight status and two markers of health disparities - race/ethnicity and insurance status (public vs. other) - on PTB.

STUDY DESIGN

We used data from all births in California from 2011 to 2017, which resulted in 3,070,241 singleton births with linked hospital discharge records. We ran regression models to estimate the relative risk of PTB by underweight status, by race/ethnicity, and by poverty (Medi-cal status). We then looked at the interaction between underweight status and race/ethnicity and underweight and poverty on PTB.

RESULTS

Black and Asian women were more likely to be underweight (aRR = 1.0, 95% CI: 1.01, 1.1 and aRR = 1.4, 95% CI: 1.4, 1.5, respectively), and Latina women were less likely to be underweight (aRR = 0.7, 95% CI: 0.7, 0.7). Being underweight was associated with increased odds of PTB (aRR = 1.3, 95% CI 1.3-1.3) and, after controlling for underweight, all nonwhite race/ethnic groups had increased odds of PTB compared to white women. In interaction models, the combined effect of being both underweight and Black, Indigenous and People of Color (BIPOC) statistically significantly reduced the relative risk of PTB (aRR = 0.9, 95% CI: 0.8, 0.9) and SGA (aRR = 1.0, 95% CI: 0.9, 1.0). The combined effect of being both underweight and on public insurance increased the relative risk of PTB (aRR = 1.1, 95% CI: 1.1, 1.2) but there was no additional effect of being both underweight and on public insurance on SGA (aRR = 1.0, 95% CI: 1.0, 1.0).

CONCLUSIONS

We confirm and build upon previous findings that being underweight preconception is associated with increased risk of PTB and SGA - a fact often overlooked in the focus on overweight and adverse birth outcomes. Additionally, our findings suggest that the effect of being underweight on PTB and SGA differs by race/ethnicity and by insurance status, emphasizing that other factors related to inequities in access to health care and poverty are contributing to disparities in PTB.

Examining demographic and psychosocial factors related to self-weighing behavior during pregnancy and postpartum periods

Black childbearing individuals in the US experience a higher risk of postpartum weight retention (PPWR) compared to their White counterparts. Given that PPWR is related to adverse health outcomes, it is important to investigate predictors of weight-related health behaviors, such as self-weighing (i.e., using a scale at home). Regular self-weighing is an evidence-based weight management strategy, but there is minimal insight into sociodemographic factors related to frequency. The Postpartum Mothers Mobile Study (PMOMS) facilitated longitudinal ambulatory weight assessments to investigate racial inequities in PPWR. Our objective for the present study was to describe self-weighing behavior during and after pregnancy in the PMOMS cohort, as well as related demographic and psychosocial factors. Applying tree modeling and multiple regression, we examined self-weighing during and after pregnancy. Participants (N = 236) were 30.2 years old on average (SD = 4.7), with the majority being college-educated (53.8%, n = 127), earning at least $30,000 annually (61.4%, n = 145), and self-identifying as non-Hispanic White (NHW; 68.2%, n = 161). Adherence to regular self-weighing (at least once weekly) was highest among participants during pregnancy, with a considerable decline after giving birth. Low-income Black participants (earning < $30,000) were significantly less likely to reach a completion rate of ≥ 80% during pregnancy (AOR = 0.10) or the postpartum period (AOR = 0.16), compared to NHW participants earning at least $30,000 annually. Increases in perceived stress were associated with decreased odds of sustained self-weighing after delivery (AOR = 0.79). Future research should consider behavioral differences across demographic intersections, such as race and socioeconomic status, and the impact on efficacy of self-weighing.

Associations of the Neighborhood Built Environment with Gestational Weight Gain

OBJECTIVE

This study aimed to determine whether specific factors of the built environment related to physical activity and diet are associated with inadequate and excessive gestational weight gain (GWG).

STUDY DESIGN

This analysis is based on data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be, a prospective cohort of nulliparous women who were followed from the beginning of their pregnancies through delivery. At each study visit, home addresses were recorded and geocoded. Locations were linked to several built-environment characteristics such as the census tract National Walkability Score (the 2010 Walkability Index) and the number of gyms, parks, and grocery stores within a 3-km radius of residential address. The primary outcome of GWG (calculated as the difference between prepregnancy weight and weight at delivery) was categorized as inadequate, appropriate, or excessive based on weight gained per week of gestation. Multinomial regression (generalized logit) models evaluated the relationship between each factor in the built environment and excessive or inadequate GWG.

RESULTS

Of the 8,182 women in the analytic sample, 5,819 (71.1%) had excessive GWG, 1,426 (17.4%) had appropriate GWG, and 937 (11.5%) had inadequate GWG. For the majority of variables examined, built environments more conducive to physical activity and healthful food availability were associated with a lower odds of excessive or inadequate GWG category. For example, a higher number of gyms or parks within 3 km of a participant's residential address was associated with lower odds of having excessive (gyms: adjusted odds ratio [aOR] = 0.93 [0.89-0.96], parks: 0.94 [0.90-0.98]) or inadequate GWG (gyms: 0.91 [0.86-0.96]; parks: 0.91 [0.86-0.97]). Similarly, a higher number of grocery stores was associated with lower odds of having excessive GWG (0.94 [0.91-0.97]).

CONCLUSION

Among a diverse population of nulliparous women, multiple aspects of the built environment are associated with excessive and inadequate GWG.

KEY POINTS

· There are little data on the association between the built environment and pregnancy outcomes.. · Multiple aspects of the built environment are associated with excessive and inadequate GWG.. · These results suggest the role that neighborhood investment may play in improving pregnancy outcomes..

Are Detailed Behavioral, Psychosocial, and Environmental Variables Necessary to Control for Confounding in Pregnancy Weight Gain Research?

BACKGROUND

Associations between pregnancy weight gain and adverse outcomes may be spurious owing to confounding by factors not typically measured in cohort studies. We determined the extent to which the addition of detailed behavioral, psychosocial, and environmental measurements to commonly available covariates improved control of confounding.

METHODS

We used data from a prospective US pregnancy cohort study (2010-2013, n = 8978). We calculated two propensity scores for low and high pregnancy weight gain (vs. adequate gain) using 11 standard confounders (e.g., age and education). We examined the balance of characteristics between weight gain groups before and after propensity score matching. We used negative binomial regression to estimate the association between weight gain and small- and large-for-gestational-age birth, preterm birth, and unplanned cesarean delivery, controlling for propensity score. To this model, we then added 17 detailed behavioral, psychosocial, and environmental measurements ("fully adjusted"). We calculated the risk ratio owing to confounding as the ratio of the standard confounder-adjusted risk ratio to the fully adjusted risk ratio.

RESULTS

There were minimal imbalances between weight gain groups in detailed measures after matching for a propensity score of standard covariates. Accordingly, the inclusion of detailed covariates had minimal impact on estimated associations between low or high pregnancy weight gain and adverse pregnancy outcomes: risk ratios owing to confounding were null for all outcomes (e.g., 1.1 [95% CI = 1.0, 1.1] for low weight gain and preterm birth).

CONCLUSIONS

Adjustment for detailed behavioral, psychosocial, and environmental measurements had minimal impact on estimated associations between pregnancy weight gain and adverse perinatal outcomes.

African American Women with Cardiometabolic Complications of Pregnancy Have Decreased Serum Abundance of Specialized Pro-Resolving Lipid Mediators and Endocannabinoids

African American (AA) women experience higher rates of maternal morbidity and mortality compared to US women of other racial/ ethnic groups. Cardiometabolic complications of pregnancy (including gestational diabetes, gestational hypertension, and preeclampsia) are leading contributors to maternal morbidity and mortality. Marked changes in circulating lipids are known to accompany cardiometabolic complications of pregnancy. Serum concentrations of docosahexaenoic acid (DHA) have been shown to be inversely correlated with risk for preeclampsia. DHA is a biosynthetic precursor of a class of specialized pro-resolving mediators (SPMs), resolvins, that have anti-inflammatory properties and are also associated with hypertensive disorders of pregnancy. We employed targeted lipidomics to characterize the distribution of DHA-containing phospholipids and SPMs in maternal serum collected in early and late pregnancy (8-14 weeks and 24-30 weeks gestation, respectively) to identify key lipids that are dysregulated during pregnancy in AA women who develop cardiometabolic complications. We identified a lipid signature in early pregnancy serum samples of AA women that is predictive of cardiometabolic complications of pregnancy with 74% accuracy. These are Resolvin D1, Resolvin E1, 2-AG, PGE2-glyerol ester, and 36:6 PC. These findings suggest that there are blood-based markers detectable in early pregnancy that can potentially identify persons at risk and tailor clinical interventions.

Explaining the Black-White Disparity in Preterm Birth: A Consensus Statement From a Multi-Disciplinary Scientific Work Group Convened by the March of Dimes

In 2017-2019, the March of Dimes convened a workgroup with biomedical, clinical, and epidemiologic expertise to review knowledge of the causes of the persistent Black-White disparity in preterm birth (PTB). Multiple databases were searched to identify hypothesized causes examined in peer-reviewed literature, 33 hypothesized causes were reviewed for whether they plausibly affect PTB and either occur more/less frequently and/or have a larger/smaller effect size among Black women vs. White women. While definitive proof is lacking for most potential causes, most are biologically plausible. No single downstream or midstream factor explains the disparity or its social patterning, however, many likely play limited roles, e.g., while genetic factors likely contribute to PTB, they explain at most a small fraction of the disparity. Research links most hypothesized midstream causes, including socioeconomic factors and stress, with the disparity through their influence on the hypothesized downstream factors. Socioeconomic factors alone cannot explain the disparity's social patterning. Chronic stress could affect PTB through neuroendocrine and immune mechanisms leading to inflammation and immune dysfunction, stress could alter a woman's microbiota, immune response to infection, chronic disease risks, and behaviors, and trigger epigenetic changes influencing PTB risk. As an upstream factor, racism in multiple forms has repeatedly been linked with the plausible midstream/downstream factors, including socioeconomic disadvantage, stress, and toxic exposures. Racism is the only factor identified that directly or indirectly could explain the racial disparities in the plausible midstream/downstream causes and the observed social patterning. Historical and contemporary systemic racism can explain the racial disparities in socioeconomic opportunities that differentially expose African Americans to lifelong financial stress and associated health-harming conditions. Segregation places Black women in stressful surroundings and exposes them to environmental hazards. Race-based discriminatory treatment is a pervasive stressor for Black women of all socioeconomic levels, considering both incidents and the constant vigilance needed to prepare oneself for potential incidents. Racism is a highly plausible, major upstream contributor to the Black-White disparity in PTB through multiple pathways and biological mechanisms. While much is unknown, existing knowledge and core values (equity, justice) support addressing racism in efforts to eliminate the racial disparity in PTB.

Does Increasing Access to Prenatal Care Reduce Racial Disparities in Birth Outcomes?

PURPOSE

To examine the effectiveness of early and adequate prenatal care (PNC) in reducing racial disparities in pre-term birth (PTB) among low-income women.

DESIGN AND METHODS

This retrospective study examined birth records for 14,950 low-income Black and White women. The primary outcome of interest was racial disparities in PTB. Exposures of interest were first trimester entry into, and adequacy of, PNC. Maternal residential proximity to nearest PNC provider was calculated. Bivariate analyses were performed for PTB by race. Binary logistic regression was performed, controlling for maternal age, smoking status and racial segregation. Attributable risk of PTB for no or late entry into PNC, and percent difference by race was calculated.

RESULTS

We find that early and adequate PNC significantly decreases the risk of preterm birth, however, we find no evidence that this reduces racial disparities. Low income black females in a large metropolitan county have greater geographic access to and utilization of PNC than low-income white females, yet racial disparities in preterm birth remain. Attributable risk of PTB for no or late entry into PNC was lower for Black women (32.2%) than White women (39.4%).

CONCLUSIONS

Our findings suggest that adequate PNC alone does not reduce the marked racial disparities in preterm birth.

PRACTICE IMPLICATIONS

Public health agencies and health care providers need to look beyond access to care, to achieve racial equity in birth outcomes. Expansion of evidence-based, comprehensive nursing interventions shown to reduce preterm birth, such as the Nurse Family Partnership home visiting program, could contribute to these efforts.

Racial differences in contribution of prepregnancy obesity and excessive gestational weight gain to large-for-gestational-age neonates

OBJECTIVES

To examine the racial differences in the population attributable fraction (PAF) of prepregnancy obesity and excessive gestational weight gain to large-for-gestational-age (LGA) neonates.

METHODS

We conducted a population-based retrospective cohort study among all women who had prenatal screening and had a singleton live birth in a hospital (1 April 2016-31 March 2017) using data from Ontario birth registry in Canada. We used multivariable log-binomial regression models to estimate the PAF and 95% confidence interval (CI) of LGA neonates due to prepregnancy obesity and excessive gestational weight gain. All models were stratified by race (White, Asian, and Black).

RESULTS

Of the 74,402 eligible women, the prevalence of prepregnancy obesity, excessive gestational weight gain, and LGA neonate was 21.1%, 60.0%, and 11.3%, respectively, for Whites; 9.3%, 45.9%, and 5.4%, respectively, for Asians; and 28.6%, 52.4%, and 7.9%, respectively, for Blacks. The association of prepregnancy obesity was greater than that of excessive gestational weight gain on LGA for all racial groups. Excessive gestational weight gain contributed more than prepregnancy obesity in Whites (PAF 32.9%, 95% CI [30.3-35.5%] and 16.6%, 95% CI [15.3-17.9%], respectively, for excessive gestational weight gain and prepregnancy obesity) and in Asians (PAF 32.1%, 95% CI [27.2-36.7%] and 11.8%, 95% CI [9.5-14.1%], respectively, for excessive gestational weight gain and prepregnancy obesity). Prepregnancy obesity (PAF 22.8%, 95% CI [17.1-28.1%]) and excessive gestational weight gain (PAF 20.1%, 95% CI [4.7-33.0%]) contributed to LGA neonates almost the same in Blacks.

CONCLUSIONS

Excessive gestational weight gain contributed more to LGA neonates than prepregnancy obesity in Whites and Asians, while there was no difference between excessive gestational weight gain and prepregnancy obesity in their contributions to the LGA neonates in Blacks. The differences are mostly driven by the differential prevalence of the two risk factors across racial groups.

Neighborhood Racial/Ethnic Composition Trajectories and Black-White Differences in Preterm Birth among Women in Texas

The black-white disparity in preterm birth has been well documented in the USA. The racial/ethnic composition of a neighborhood, as a marker of segregation, has been considered as an underlying cause of the racial difference in preterm birth. However, past literature using cross-sectional measures of neighborhood racial/ethnic composition has shown mixed results. Neighborhoods with static racial/ethnic compositions over time may have different social, political, economic, and service environments compared to neighborhoods undergoing changing racial/ethnic compositions, which may affect maternal health. We extend the past work by examining the contribution of neighborhood racial/ethnic composition trajectories over 20 years to the black-white difference in preterm birth. We used natality files (N = 477,652) from birth certificates for all live singleton births to non-Hispanic black and non-Hispanic white women in Texas from 2009 to 2011 linked to the Neighborhood Change Database. We measured neighborhood racial/ethnic trajectories over 20 years. Hierarchical generalized linear models examined relationships between neighborhood racial/ethnic trajectories and preterm birth, overall and by mother's race. Findings showed that overall, living in neighborhoods with a steady high proportion non-Hispanic black was associated with higher odds of preterm birth, compared with neighborhoods with a steady low proportion non-Hispanic black. Furthermore, while black women's odds of preterm birth was relatively unaffected by neighborhood proportions of the Latinx or non-Hispanic white population, white women had the highest odds of preterm birth in neighborhoods characterized by a steady high proportion Latinx or a steady low proportion non-Hispanic white. Black-white differences were the highest in neighborhoods characterized by a steady high proportion white. Findings suggest that white women are most protected from preterm birth when living in neighborhoods with a steady high concentration of whites or in neighborhoods with a steady low concentration of Latinxs, whereas black women experience high rates of preterm birth regardless of proportion white or Latinx.

The association between gestational weight gain z-score and stillbirth: a case-control study

BACKGROUND

There is limited information on potentially modifiable risk factors for stillbirth, such as gestational weight gain (GWG). Our purpose was to explore the association between GWG and stillbirth using the GWG z-score.

METHODS

We analyzed 479 stillbirths and 1601 live births from the Stillbirth Collaborative Research Network case-control study. Women with triplets or monochorionic twins were excluded from analysis. We evaluated the association between GWG z-score (modeled as a restricted cubic spline with knots at the 5th, 50th, and 95th percentiles) and stillbirth using multivariable logistic regression with generalized estimating equations, adjusting for pre - pregnancy body mass index (BMI) and other confounders. In addition, we conducted analyses stratified by pre - pregnancy BMI category (normal weight, overweight, obese).

RESULTS

Mean GWG was 18.95 (SD 17.6) lb. among mothers of stillbirths and 30.89 (SD 13.3) lb. among mothers of live births; mean GWG z-score was - 0.39 (SD 1.5) among mothers of cases and - 0.17 (SD 0.9) among control mothers. In adjusted analyses, the odds of stillbirth were elevated for women with very low GWG z-scores (e.g., adjusted odds ratio (aOR) and 95% Confidence Interval (CI) for z-score - 1.5 SD versus 0 SD: 1.52 (1.30, 1.78); aOR (95% CI) for z-score - 2.5 SD versus 0 SD: 2.36 (1.74, 3.20)). Results differed slightly by pre - pregnancy BMI. The odds of stillbirth were slightly elevated among women with overweight BMI and GWG z-scores ≥1 SD (e.g., aOR (95% CI) for z-score of 1.5 SD versus 0 SD: 1.84 (0.97, 3.50)).

CONCLUSIONS

GWG z-scores below - 1.5 SD are associated with increased odds of stillbirth.

Gestational Weight Gain and Adverse Birth Outcomes in Twin Pregnancies

OBJECTIVE

To evaluate the association between gestational weight gain in twin pregnancies and small-for-gestational-age (SGA) and large-for-gestational-age (LGA) birth, preterm birth before 32 weeks of gestation, cesarean delivery, and infant death within each prepregnancy body mass index (BMI) category.

METHODS

Data in this population-based study came from Pennsylvania-linked infant birth and death records (2003-2013). We studied 54,836 twins born alive before 39 weeks of gestation. Total pregnancy weight gain (kg) was converted to gestational age-standardized z scores. Multivariable modified Poisson regression models stratified by prepregnancy BMI were used to estimate associations between z scores and outcomes. A probabilistic bias analysis, informed by an internal validation study, evaluated the effect of BMI and weight gain misclassification.

RESULTS

Gestational weight gain z score was negatively associated with SGA and positively associated with LGA and cesarean delivery in all BMI groups. The relation between weight gain and preterm birth was U-shaped in nonobese women. An increased risk of infant death was observed for very low weight gain among normal-weight women and for high weight gain among women without obesity. Most excess risks of these outcomes were observed at weight gains at 37 weeks of gestation that are equivalent to less than 14 kg or more than 27 kg in underweight or normal-weight women, less than 11 kg or more than 28 kg in overweight women, and less than 6.4 kg or more than 26 kg in women with obesity. The bias analysis supported the validity of the conventional analysis.

CONCLUSION

Very low or very high weight gains were associated with the adverse outcomes we studied. If the associations we observed are even partially reflective of causality, targeted modification of pregnancy weight gain in women carrying twins might improve pregnancy outcomes.

Racial Disparities in Obesity Treatment

PURPOSE OF REVIEW

Obesity rates in the USA have reached pandemic levels with one third of the population with obesity in 2015-2016 (39.8% of adults and 18.5% of youth). It is a major public health concern, and it is prudent to understand the factors which contribute. Racial and ethnic disparities are pronounced in both the prevalence and treatment of obesity and must be addressed in the efforts to combat obesity.

RECENT FINDINGS

Disparities in prevalence of obesity in racial/ethnic minorities are apparent as early as the preschool years and factors including genetics, diet, physical activity, psychological factors, stress, income, and discrimination, among others, must be taken into consideration. A multidisciplinary team optimizes lifestyle and behavioral interventions, pharmacologic therapy, and access to bariatric surgery to develop the most beneficial and equitable treatment plans. The reviewed studies outline disparities that exist and the impact that race/ethnicity have on disease prevalence and treatment response. Higher prevalence and reduced treatment response to lifestyle, behavior, pharmacotherapy, and surgery, are observed in racial and ethnic minorities. Increased research, diagnosis, and access to treatment in the pediatric and adult populations of racial and ethnic minorities are proposed to combat the burgeoning obesity epidemic and to prevent increasing disparity.

Gestational Weight Gain-for-Gestational Age Z-Score Charts Applied across U.S. Populations

BACKGROUND

Gestational weight gain may be a modifiable contributor to infant health outcomes, but the effect of gestational duration on gestational weight gain has limited the identification of optimal weight gain ranges. Recently developed z-score and percentile charts can be used to classify gestational weight gain independent of gestational duration. However, racial/ethnic variation in gestational weight gain and the possibility that optimal weight gain differs among racial/ethnic groups could affect generalizability of the z-score charts. The objectives of this study were (1) to apply the weight gain z-score charts in two different U.S. populations as an assessment of generalisability and (2) to determine whether race/ethnicity modifies the weight gain range associated with minimal risk of preterm birth.

METHODS

The study sample included over 4 million live, singleton births in California (2007-2012) and Pennsylvania (2003-2013). We implemented a noninferiority margin approach in stratified subgroups to determine weight gain ranges for which the adjusted predicted marginal risk of preterm birth (gestation <37 weeks) was within 1 or 2 percentage points of the lowest observed risk.

RESULTS

There were minimal differences in the optimal ranges of gestational weight gain between California and Pennsylvania births, and among several racial/ethnic groups in California. The optimal ranges decreased as severity of prepregnancy obesity increased in all groups.

CONCLUSIONS

The findings support the use of weight gain z-score charts for studying gestational age-dependent outcomes in diverse U.S. populations and do not support weight gain recommendations tailored to race/ethnicity.