Preterm birth: the interaction of traffic-related air pollution with economic hardship in Los Angeles neighborhoods

Preterm birth may be affected by the interaction of residential air pollution with neighborhood economic hardship. The authors examined variations in traffic-related pollution exposure--measured by distance-weighted traffic density--using a framework reflecting the social and physical environments. An adverse social environment was conceptualized as low socioeconomic status (SES) neighborhoods--census tracts with concentrated poverty, unemployment, and dependence on public assistance. An adverse physical environment was depicted by the winter season, when thermal inversions trap motor vehicle pollutants, thereby increasing traffic-related air pollution. Los Angeles County, California, birth records from 1994 to 1996 were linked to traffic counts, census data, and ambient air pollution measures. The authors fit multivariate logistic models of preterm birth, stratified by neighborhood SES and third pregnancy trimester season. Traffic-related air pollution exposure disproportionately affected low SES neighborhoods in the winter. Further, in these poorer neighborhoods, the winter season evidenced increased susceptibility among women with known risk factors. Health insurance was most beneficial to women residing in neighborhoods exposed to economic hardship and an adverse physical environment. Reducing preterm births warrants a concerted effort of social, economic, and environmental policies, focused on not only individual risk factors but also the reduction of localized air pollution, expansion of health-care coverage, and improvement of neighborhood resources.     

Traffic-related air pollution, preterm birth and term birth weight in the PIAMA birth cohort study

Background

Maternal exposure to air pollution has been associated with adverse pregnancy outcomes. Few studies took into account the spatial and temporal variation of air pollution levels.

Objectives

To evaluate the impact of maternal exposure to traffic-related air pollution during pregnancy on preterm birth and term birth weight using a spatio-temporal exposure model.

Methods

We estimated maternal residential exposure to nitrogen dioxide (NO₂), particulate matter (PM_2.5) and soot during pregnancy (entire pregnancy, 1st trimester, and last month) for 3853 singleton births within the Dutch PIAMA prospective birth cohort study by means of temporally adjusted land-use regression models. Associations between air pollution concentrations and preterm birth and term birth weight were analyzed by means of logistic and linear regression models with and without adjustment for maternal physical, lifestyle, and socio-demographic characteristics.

Results

We found positive, statistically non-significant associations between exposure to soot during entire pregnancy and during the last month of pregnancy and preterm birth [adj. OR (95% CI) per interquartile range increase in exposure 1.08 (0.88–1.34) and 1.09 (0.93–1.27), respectively]. There was no indication of an adverse effect of air pollution exposure on term birth weight.

Conclusions

In this study, maternal exposure to traffic-related air pollution during pregnancy was not associated with term birth weight. There was a tendency towards an increased risk of preterm birth with increasing air pollution exposure, but statistical power was low.     

Safety of tetanus,diphtheria, and acellular pertussis vaccination among pregnant active duty U.S. military women

BackgroundThe tetanus, diphtheria, and acellular pertussis (Tdap) vaccine was approved for U.S. adults in 2005 and recommended for administration in every pregnancy in 2012, with optimal timing between 27 and 36 weeks’ gestation. In the military, however, a current Tdap vaccination status is compulsory for service, and active duty women may be inadvertently exposed in early pregnancy. Safety data in this population are limited.ObjectivesTo assess safety of inadvertent (0–13 weeks’ gestation) and recommended (27–36 weeks’ gestation) exposure to the Tdap vaccine in pregnancy.MethodsPregnancies and live births from Department of Defense Birth and Infant Health Research program data were linked with military personnel immunization records to determine pregnancy Tdap vaccine exposure among active duty women, 2006–2014. Multivariable Cox and generalized linear regression models estimated associations between Tdap vaccine exposure and adverse pregnancy or infant outcomes.ResultsOf 145,883 pregnancies, 1272 were exposed to the Tdap vaccine in the first trimester and 9438 between 27 and 36 weeks’ gestation. Neither inadvertent nor recommended vaccine exposure were associated with spontaneous abortion, preeclampsia, or preterm labor. Among 117,724 live born infants, 984 were exposed to the Tdap vaccine in the first trimester and 9352 between 27 and 36 weeks’ gestation. First trimester exposure was not associated with birth defects, growth problems in utero, growth problems in infancy, preterm birth, or low birth weight. Tdap vaccine exposure between 27 and 36 weeks’ gestation was not associated with any adverse infant outcome.ConclusionsAmong a population of active duty women in the U.S. military who received the Tdap vaccine during pregnancy, we detected no increased risks for adverse maternal, fetal, or infant outcomes. Our findings corroborate existing literature on the safety of exposure to the Tdap vaccine in pregnancy.     

Ambient air pollution and preterm birth in the environment and pregnancy outcomes study at the University of California, Los Angeles

The authors conducted a case-control survey nested within a birth cohort and collected detailed risk factor information to assess the extent to which residual confounding and exposure misclassification may impact air pollution effect estimates. Using a survey of 2,543 of 6,374 women sampled from a cohort of 58,316 eligible births in 2003 in Los Angeles County, California, the authors estimated with logistic regression and two-phase models the effects of pregnancy period-specific air pollution exposure on the odds of preterm birth. For the first trimester, the odds of preterm birth consistently increased with increasing carbon monoxide exposures and also at high levels of exposure to particulate matter less than or equal to 2.5 microm in diameter (>21.4 microg/m(3)), regardless of type of data (cohort/sample) or covariate adjustment (carbon monoxide exposures of >1.25 ppm increased the odds by 21-25%). Women exposed to carbon monoxide above 0.91 ppm during the last 6 weeks of pregnancy experienced increased odds of preterm birth. Crude and birth certificate covariate-adjusted results for carbon monoxide differed from each other. However, further adjustment for risk factors assessed in the survey did not change effect estimates for short-term pollutant averages appreciably, except for time-activity patterns, which strengthened the observed associations. These results confirm the importance of reducing exposure misclassification when evaluating the effect of traffic-related pollutants that vary spatially.     

Birth outcomes for Australian mother-infant pairs who received an influenza vaccine during pregnancy, 2012–2014: The FluMum study

IntroductionIn Australia, influenza vaccination is recommended for all women who will be pregnant during the influenza season. Vaccine safety and effectiveness are key concerns and influencers of uptake for both vaccine providers and families. We assessed the safety of receiving an influenza vaccination during any trimester of pregnancy with respect to preterm births and infant birthweight.MethodsWe conducted a nested retrospective cohort study of ‘FluMum’ participants (2012–2014). Our primary exposure of interest was influenza vaccination during pregnancy. The primary outcomes of interest were infant birthweight and weeks’ gestation at birth for live singleton infants. Analyses included comparisons of these birth outcomes by vaccination status and trimester of pregnancy an influenza vaccine was given. We calculated means, proportions, and relative risks and performed multivariable logistic regression for potential confounding factors.ResultsIn the 7126 mother-infant pairs enrolled in this study, mean maternal age at infant birth was 31.7 years. Influenza vaccine uptake in pregnancy was 34%. Most mothers with a known date of vaccination received a vaccine in the second trimester (51%). Those mothers with a co-morbidity or risk factor were 13% more likely to have influenza vaccine during pregnancy compared to other mothers (RR 1.13, 95% CI 1.04–1.24, p = 0.007). Mean weeks’ gestation at birth was 38.7 for the vaccinated and 38.8 for the unvaccinated group (p = 0.051). Infants in the vaccinated group weighed 15 g less in birthweight compared to the unvaccinated infants (95% CI −12.8 to 42.2, p = 0.29).ConclusionResults arising from this large Australian cohort study are reassuring with respect to two critical safety outcomes; preterm births and low infant birthweights. Studies examining a broader range of birth outcomes following influenza vaccination during pregnancy are required, particularly now that maternal vaccination in pregnancy has expanded to include pertussis as well as influenza.     

Safety of MenACWY-CRM vaccine exposure during pregnancy

BackgroundAlthough the meningococcal conjugate MenACWY-CRM vaccine is not approved for use in pregnant women, unintentional exposure during pregnancy can occur, especially during early pregnancy among women of child-bearing age. This study provides safety information about inadvertent MenACWY-CRM vaccination during pregnancy.MethodsThe evaluated population consisted of pregnant female members of Kaiser Permanente Southern California who inadvertently received MenACWY-CRM at 11–21 years of age during 09/30/2011-06/30/2013 within 28 days prior to conception or during pregnancy. Chart abstraction was conducted to identify pregnancy and birth outcomes, including spontaneous and induced abortions, preterm births, low weight births, and major congenital malformations (MCMs).ResultsThere were 92 women who received MenACWY-CRM during the pregnancy exposure period, mainly during the first trimester (76.1%). Hispanics represented the largest race/ethnicity category (68.5%). Among the known pregnancy outcomes (n = 66; excluding induced abortions and unknown pregnancy outcomes), the prevalence of spontaneous abortions was 18.2% (n = 12). Among live born infants (n = 55; from 54 pregnancies), 14.5% (n = 8) were born preterm (<37 weeks gestation) and 9.1% (n = 5) had a low birthweight (<2500 g). The prevalence rate of MCMs among live born infants (n = 55) was 1.8% (n = 1).ConclusionsThis study provides baseline prevalence estimates of spontaneous abortions, preterm births, low weight births, and MCMs among women inadvertently exposed to MenACWY-CRM during the pregnancy period. These estimates appear to be comparable with U.S. background prevalence estimates.     

The Impact of Neighborhood Environment,Social Support,and Avoidance Coping on Depressive Symptoms of Pregnant African-American Women

BackgroundAlthough depressive symptoms during pregnancy have been related to negative maternal and child health outcomes such as preterm birth, low birth weight infants, postpartum depression, and maladaptive mother–infant interactions, studies on the impact of neighborhood environment on depressive symptoms in pregnant women are limited. Pregnant women residing in disadvantaged neighborhoods reported higher levels of depressive symptoms and lower levels of social support. No researchers have examined the relationship between neighborhood environment and avoidance coping in pregnant women. Guided by the Ecological model and Lazarus and Folkman's transactional model of stress and coping, we examined whether social support and avoidance coping mediated associations between the neighborhood environment and depressive symptoms in pregnant African-American women.MethodsPregnant African-American women (n = 95) from a medical center in Chicago completed the instruments twice during pregnancy between 15 and 25 weeks and between 25 and 37 weeks. The self-administered instruments measured perceived neighborhood environment, social support, avoidance coping, and depressive symptoms using items from existing scales. Objective measures of the neighborhood environment were derived using geographic information systems.FindingsPerceived neighborhood environment, social support, avoidance coping, and depressive symptoms were correlated significantly in the expected directions. Objective physical disorder and crime were negatively related to social support. Social support at time 1 (20 ± 2.6 weeks) mediated associations between the perceived neighborhood environment at time 1 and depressive symptoms at time 2 (29 ± 2.7 weeks). An increase in avoidance coping between times 1 and 2 also mediated the effects of perceived neighborhood environment at time 1 on depressive symptoms at time 2.ConclusionPregnant African-American women's negative perceptions of their neighborhoods in the second trimester were related to higher levels of depressive symptoms in the third trimester. If these results are replicable in prospective studies with larger sample sizes, intervention strategies could be implemented at the individual level to support pregnant women in their ability to cope with adverse neighborhood conditions and ultimately improve their mental health.     

Exercise during Pregnancy and Risk of Late Preterm Birth,Cesarean Delivery,and Hospitalizations

BackgroundFederal physical activity guidelines recommend at least 150 minutes of moderate-intensity exercise per week during pregnancy. We studied whether regular exercise during pregnancy is associated with preterm birth, cesarean delivery, and hospitalization during pregnancy.MethodsSelf-reported weekly exercise was ascertained in 3,006 women during the third trimester of pregnancy. Using multivariable logistic regression, we report the relationship between regular exercise (≥150 min/wk) and late preterm birth, cesarean delivery, and hospitalization during pregnancy, controlling for age, race, marital status, education, poverty status, prepregnancy body mass index weight category, gestational weight gain, and prepregnancy diabetes or hypertension.ResultsNearly one third of women reported meeting current federal physical activity recommendations during pregnancy. Five percent had late preterm birth, 29% had cesarean deliveries, and 20% reported hospitalization during pregnancy. In multivariable analysis, regular exercise during pregnancy was not associated with late preterm birth or hospitalization during pregnancy. Physical activity of 150 or more minutes per week was associated with reduced odds of cesarean delivery compared with less than 60 minutes per week, but the finding was not significant (adjusted odds ratio, 0.86; 95% confidence interval, 0.69–1.07).ConclusionIn the First Baby Study, physical activity was not associated with late preterm birth or hospitalizations, and may be associated with decreased odds of cesarean delivery.     

Is air pollution a risk factor for low birth weight in Seoul?

Environmental factors contributing to reduced birth weight are of great concern because of the well-known relation of birth weight to infant mortality and adverse effects in later life. We examined the associations between air pollution exposures during pregnancy and low birth weight among all full-term births (gestational age 37-44 weeks) for a 2-year period (January 1996 through December 1997) in Seoul, South Korea. We evaluated these associations with a generalized additive logistic regression adjusting for gestational age, maternal age, parental educational level, parity, and infant sex. We used smoothing plots with generalized additive models to analyze the exposure-response relation for each air pollutant. The adjusted relative risk of low birth weight was 1.08 [95% confidence interval (CI) = 1.04-1.12] for each interquartile increase for carbon monoxide concentrations during the first trimester of pregnancy. The relative risks were 1.07 (95% CI = 1.03-1.11) for nitrogen dioxide, 1.06 (95% CI = 1.02-1.10) for sulfur dioxide, and 1.04 (95% CI = 1.00-1.08) for total suspended particles also for interquartile increase in exposure. Carbon monoxide, nitrogen dioxide, sulfur dioxide, and total suspended particle concentrations in the first trimester of pregnancy period are risk factors for low birth weight.     

Different effects of PM<Subscript>10</Subscript> exposure on preterm birth by gestational period estimated from time-dependent survival analyses

Purpose  We conducted this study to determine if the preterm risks due to PM₁₀ exposure vary with the exposure periods during pregnancy. This study was also conducted to estimate the different effects of PM₁₀ exposure on preterm birth by exposure periods using the extended Cox model with PM₁₀ exposure as a time-dependent covariate. Methods  We studied birth data obtained from the Korea National Statistical office for 374,167 subjects who were delivered between 1998 and 2000 in Seoul, South Korea. We used PM₁₀ data that was measured hourly to give 24-h averages at 27 monitoring stations in Seoul. The extended Cox model with time-dependent exposure was used to determine if the risk of preterm delivery could be associated with PM₁₀ exposures for each trimester during pregnancy. Results  Effect of PM10 exposure prior to the 37 weeks of gestational period was stronger on the risk of premature birth than that posterior to the 37 weeks of gestational weeks. This trend was consistent for each trimester; however, the hazard ratios for preterm delivery associated with PM₁₀ exposure in the first and third trimester were slightly higher than those of the second trimester. Conclusions  The risk of preterm birth associated with exposure to PM₁₀ differed with the exposure period of the neonates. Therefore, when studying the impact of air pollution exposure during pregnancy, the exposure period during pregnancy should be considered.     

Outdoor air pollution, low birth weight, and prematurity

This study tested the hypothesis, suggested by several recent reports, that air pollution may increase the risk of adverse birth outcomes. This study analyzed all singleton live births registered by the Czech national birth register in 1991 in 67 districts where at least one pollutant was monitored in 1990-1991 (n = 108,173). Maternal exposures to sulfur dioxide (SO(2)), total suspended particles (TSP), and nitrous oxides (NO(x)) in each trimester of pregnancy were estimated as the arithmetic means of all daily measurements taken by all monitors in the district of birth of each infant. Odds ratios of low birth weight (< 2,500 g), prematurity (< 37 weeks of gestation), and intrauterine growth retardation (IUGR; < 10th percentile of birth weight for gestational age and sex) were estimated by robust logistic regression. The median (and 25th and 75th percentile) trimester exposures were 32 (18, 56) microg/m(3) for SO(2); 72 (55, 87) microg/m(3) for TSP; and 38 (23, 59) microg/m(3) for NO(x). Low birth weight (prevalence 5.2%) and prematurity (prevalence 4.8%) were associated with SO(2) and somewhat less strongly with TSP. IUGR was not associated with any pollutant. The effects on low birth weight and prematurity were marginally stronger for exposures in the first trimester, and were not attenuated at all by adjustment for socioeconomic factors or the month of birth. Adjusted odds ratios of low birth weight were 1.20 [95% confidence interval (CI), 1.11-1.30] and 1.15 (CI, 1.07-1.24) for a 50 microg/m(3) increase in SO(2) and TSP, respectively, in the first trimester; adjusted odds ratios of prematurity were 1.27 (CI, 1.16-1.39) and 1.18 (CI, 1.05-1.31) for a 50 microg/m(3) increase in SO(2) and TSP, respectively, in the first trimester. Low gestational age accounted for the association between SO(2) and low birth weight. These findings provide further support for the hypothesis that air pollution can affect the outcome of pregnancy.     

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

PurposeTo quantify the relationship between pregnancy weight gain with early and late preterm birth and evaluate whether associations differed between non-Hispanic (NH) black and NH white women.MethodsWe analyzed a retrospective cohort of all live births to NH black and NH white women in the United States 2011–2015 (n = 10,714,983). We used weight gain z-scores in multiple logistic regression models stratified by prepregnancy body mass index (BMI) and race to calculate population attributable risk (PAR) percentages for the contribution of high and low pregnancy weight gain to early and late preterm birth.ResultsPregnancy weight gain was related to early and late preterm birth, but associations varied by BMI and race. For early preterm birth, the PAR percentage for high pregnancy weight gain ranged from 8 to 10% in NH black women and from 6 to 8% in NH white women. There was little evidence of racial differences in late preterm birth: PAR percentages ranged from 2 to 7% in NH black women and from 3 to 7% in NH white women.ConclusionsModerate gestational weight gain is associated with lower rate of preterm birth, with greatest reductions for early preterm birth in NH black women.     

No association between influenza vaccination during pregnancy and adverse birth outcomes

BackgroundPregnant women are recommended to receive inactivated influenza vaccination anytime during pregnancy. Studies have investigated the impact of influenza vaccination during pregnancy on birth outcomes and results on preterm birth have been inconsistent.MethodsWe conducted a retrospective cohort study among children born at a gestational age ≥ 24 weeks from January 1, 2010 to December 31, 2015 at Kaiser Permanente Northern California facilities (KPNC). We evaluated the association between maternal influenza vaccination during pregnancy and risk of preterm birth, small and large for gestational age, admission to the neonatal intensive care unit (NICU), respiratory distress syndrome, low birth weight, and low Apgar score. We ascertained the dates of maternal influenza vaccination, conception, and delivery, as well as birth outcomes from KPNC inpatient and outpatient databases. Conditional multivariate Cox regression and logistic regression analyses were used to determine the association between maternal vaccination during pregnancy and risk of each birth outcome.ResultsThe study included 145,869 children. Maternal influenza vaccination during pregnancy was not associated with risk of small or large for gestational age births, preterm birth, need for mechanical ventilation at birth, respiratory distress syndrome, admission to the NICU, low birth weight, or low Apgar score. However, when we did not control for immortal time bias, the risk of preterm birth (odds ratio [OR] = 0.69, 95% confidence interval [CI] 0.66–0.72) was lower among infants of vaccinated mothers.ConclusionWe found no association between maternal influenza vaccination during pregnancy and adverse birth outcomes. When investigating preterm birth outcome in association with vaccination during pregnancy, immortal time bias should be taken into account in the analysis.     

A cohort study of traffic-related air pollution impacts on birth outcomes

BACKGROUND: Evidence suggests that air pollution exposure adversely affects pregnancy outcomes. Few studies have examined individual-level intraurban exposure contrasts. OBJECTIVES: We evaluated the impacts of air pollution on small for gestational age (SGA) birth weight, low full-term birth weight (LBW), and preterm birth using spatiotemporal exposure metrics. METHODS: With linked administrative data, we identified 70,249 singleton births (1999-2002) with complete covariate data (sex, ethnicity, parity, birth month and year, income, education) and maternal residential history in Vancouver, British Columbia, Canada. We estimated residential exposures by month of pregnancy using nearest and inverse-distance weighting (IDW) of study area monitors [carbon monoxide, nitrogen dioxide, nitric oxide, ozone, sulfur dioxide, and particulate matter < 2.5 (PM2.5) or < 10 (PM10) microm in aerodynamic diameter], temporally adjusted land use regression (LUR) models (NO, NO2, PM2.5, black carbon), and proximity to major roads. Using logistic regression, we estimated the risk of mean (entire pregnancy, first and last month of pregnancy, first and last 3 months) air pollution concentrations on SGA (< 10th percentile), term LBW (< 2,500 g), and preterm birth. RESULTS: Residence within 50 m of highways was associated with a 26% increase in SGA [95% confidence interval (CI), 1.07-1.49] and an 11% (95% CI, 1.01-1.23) increase in LBW. Exposure to all air pollutants except O3 was associated with SGA, with similar odds ratios (ORs) for LUR and monitoring estimates (e.g., LUR: OR = 1.02; 95% CI, 1.00-1.04; IDW: OR = 1.05; 95% CI, 1.03-1.08 per 10-microg/m3 increase in NO). For preterm births, associations were observed with PM2.5 for births < 37 weeks gestation (and for other pollutants at < 30 weeks). No consistent patterns suggested exposure windows of greater relevance. CONCLUSION: Associations between traffic-related air pollution and birth outcomes were observed in a population-based cohort with relatively low ambient air pollution exposure.     

Does lack of multinutrient supplementation during early pregnancy increase vulnerability to alcohol-related preterm or small-for-gestational-age births?

The objective of this study was to assess whether women who do not take multinutrient supplements during early pregnancy are more susceptible to the effects of low-to-moderate alcohol consumption on preterm birth and small-for-gestational-age birth (SGA) compared to women who do take multinutrients. This analysis included 800 singleton live births to mothers from a cohort of pregnant women recruited for a population-based cohort study conducted in the Kaiser Permanente Medical Care Program in Northern California. Participants were recruited in their first trimester of pregnancy and information about their alcohol use and supplement intake during pregnancy was collected. Preterm birth (n = 53, 7%) was defined as a delivery prior to 37 completed weeks of gestation and SGA birth (n = 124, 16%) was defined as birth weight less than the 10th percentile for the infant’s gestational age and sex compared to US singleton live births. A twofold increase in the odds of SGA birth attributed to low-to-moderate alcohol intake was found among multinutrient supplement non-users (95% CI: 1.1, 5.3). Yet, among multinutrient supplement users, there was no increased risk of an SGA birth for women who drank low-to-moderately compared to women who abstained (aOR: 0.97, 95% CI: 0.6, 1.6). Similar results emerged for preterm birth. Our findings provide marginal evidence that multinutrient supplementation during early pregnancy may modify the risk of SGA births and preterm birth associated with alcohol consumption during pregnancy and may have important implications for pregnant women and women of child-bearing age. However, future research needs to be conducted.     

Birth outcomes following immunization of pregnant women with pandemic H1N1 influenza vaccine 2009–2010

BackgroundFollowing the H1N1 influenza pandemic in 2009, pregnant women were recommended to receive both seasonal (TIV) and H1N1 influenza vaccines. This study presents incidence of adverse birth and pregnancy outcomes among a population of pregnant women immunized with TIV and H1N1 vaccines at Kaiser Permanente Northern California during 2009–2010.MethodsWe telephone surveyed pregnant Kaiser Permanente Northern California members to assess non-medically-attended reactions following H1N1, TIV or both vaccines during 2009–2010 (n = 5365) in a separate study. Here we assessed preterm birth (<37 weeks), very preterm birth (<32 weeks), low birth weight (<2500 g, LBW), very low birth weight (<1500 g), small for gestational age, spontaneous abortions, stillbirths and congenital anomalies among this cohort by comparing incidence and 95% confidence intervals between the following immunization groups: TIV only, H1N1 only, H1N1 prior to TIV immunization, TIV prior to H1N1 and both immunizations given at the same time.ResultsResults did not vary significantly between groups. Comparing H1N1 with TIV, incidence were similar for preterm births (6.37 vs 6.28/100 births), very preterm births (5.30 vs 8.29/1000 births), LBW (4.19 vs 2.90/100 births), very LBW (4.54 vs 5.52/1000 births), small for gestational age (9.99 vs 9.24/1000 births), spontaneous abortion (7.10 vs 6.83/1000 pregnancies), stillbirths (7.10 vs 4.57/1000 pregnancies), and congenital anomalies (2.66 vs 2.43/100 births).ConclusionsAlthough constrained by small sample size, complex vaccine groups, and differential vaccine availability during 2009–2010, this study found no difference in adverse birth outcomes between H1N1 vaccine and TIV.     

The effect of vaginal bleeding during pregnancy on preterm and small-for-gestational-age births: US National Maternal and Infant Health Survey, 1988

We examined the effects of vaginal bleeding during pregnancy on preterm and small-for-gestational-age (SGA) births using data from the 1988 US National Maternal and Infant Health Survey. We examined the severity of vaginal bleeding and separated the preterm births into subsets by the degree of prematurity (< 32, 32-33, 34-36 weeks' gestation). We also evaluated associations stratified by race. Multiple logistic regression analysis showed that vaginal bleeding was associated with an increased risk of preterm birth, with a more pronounced elevated risk for preterm birth before 34 weeks' gestation and a notably stronger association for more severe bleeding that occurred in both the first and the second half of pregnancy. Odds ratios, but not risk differences, for birth before 34 weeks' gestation were greater for white women with vaginal bleeding than for black women. There was no association between vaginal bleeding during pregnancy and SGA births.     

The association of daily physical activity and birth outcome: a population-based cohort study

The potential relationship between daily physical activity and pregnancy outcome remains unclear because of the wide variation in study designs and physical activity assessment measures. We sought to prospectively quantify the potential effects of the various domains of physical activity on selected birth outcomes in a large unselected population. The sample consisted of 11,759 singleton pregnancies from the Avon longitudinal study of parents and children, United Kingdom. Information on daily physical activity was collected by postal questionnaire for self-report measures. Main outcome measures were birth weight, gestational age at delivery, preterm birth and survival. After controlling for confounders, a sedentary lifestyle and paid work during the second trimester of pregnancy were found to be associated with a lower birth weight, while ‘bending and stooping’ and ‘working night shifts’ were associated with a higher birth weight. There was no association between physical exertion and duration of gestation or survival. Repetitive boring tasks during the first trimester was weakly associated with an increased risk of preterm birth (<37 weeks) (adjusted odds ratio [OR] = 1.25, 95% CI 1.04–1.50). ‘Bending and stooping’ during the third trimester was associated with a reduced risk of preterm birth (adjusted OR = 0.73, 95% CI 0.63–0.84). Demanding physical activities do not have a harmful effect on the selected birth outcomes while a sedentary lifestyle is associated with a lower birth weight. In the absence of either medical or obstetric complications, pregnant women may safely continue their normal daily physical activities should they wish to do so.     

Cyanobacterial (blue-green algae) contamination in drinking water and perinatal outcomes

OBJECTIVE: The aim of this ecological study was to examine the relationship between potential cyanobacterial exposure through drinking water during pregnancy and birth outcomes. METHOD: One hundred and fifty-six communities in South-Eastern Australia were involved, providing 32,700 singleton live newborn during the period 1992-94. Cyanobacterial occurrence and cell density (alert level) in drinking water sources during the first trimester, the total gestational period for premature births or limited to 36 weeks in term infants, and the last 12 weeks prior to preterm births or up to and including 36 weeks in term infants were used as estimates of exposure. RESULTS: There were statistically significant differences between the proportion of time during the first trimester with cyanobacterial occurrence and the percentage of births that were low birth weight (LBW) and very low birth rate (VLBW). Significant differences were also found among various categories of first trimester exposure based on average cell density and LBW, prematurity and congenital defects. However, the pattern of these results does not suggest a causal link to cyanobacteria. There were no clear dose-response relationships. Analyses based on exposure during the last 12 weeks and total gestation also showed no significant dose-response effects. CONCLUSION: The results of this study provide no clear evidence for an association between cyanobacterial contamination of drinking water sources and adverse pregnancy outcomes.     

Singleton Preterm Birth: Risk Factors and Association with Assisted Reproductive Technology

The objectives of this study were to determine risk factors for early (less than 34 weeks gestation) and late (34–36 weeks gestation) preterm singleton birth, by assisted reproductive technology (ART) status. We linked data from Massachusetts birth records and ART records representing singleton live births from 1997 through 2004. Using multinomial regression models, we assessed risk factors for early and late preterm birth by ART status. From 1997 to 2004 in Massachusetts, among non-ART births, risk factors for early and late preterm birth were similar and included women <15 and ≥35 years of age, those of non-white race or Hispanic ethnicity, those with ≤12 years of education, those with chronic diabetes, those with gestational diabetes, those with gestational hypertension, those who smoked during pregnancy, those who used fertility medications, and those who had not had a previous live birth. Among ART births, risk factors for early and late preterm birth differed and odds of early preterm birth were increased among women with ≤12 years of education while odds of late preterm birth were increased among women with gestational diabetes. Odds of both early and late preterm birth were increased among women of non-white race or Hispanic ethnicity and among women with gestational hypertension. Among non-ART births, increased risk for preterm birth was more strongly related to socioeconomic factors than among ART births. Medical conditions were associated with an increased risk for preterm birth regardless of women’s ART status. Efforts to prevent preterm births should focus on reducing modifiable risk factors.