Preterm Birth Odds Ratio Research Articles

Acute Impact of Hourly Ambient Air Pollution on Preterm Birth

Background:Preterm birth is a major perinatal health problem, but factors leading to it are still not completely understood.Objectives:Our goal was to identify the relation between acute increase in ambient air pollution in a few hours before onset of labor and the risk of preterm birth.Methods:We collected registered birth outcome data and hourly ambient air pollution measurements during 2009‒2013 in Brisbane, Australia. Using a time-stratified case-crossover design and conditional logistic regression models with natural cubic splines, we assessed the shape of air pollution-preterm birth curve, after controlling for potential confounders. We also examined the effect modification of other factors.Results:The association between air pollution [nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO)] and preterm birth was nonlinear. Threshold concentrations for the mean of 0‒24 hr NO2, 24‒48 hr SO2, and 24‒48 hr CO before onset of labor were 7.6 parts per billion (ppb), 3.8 ppb, and 162.5 ppb, respectively. Increases in air pollution concentrations above thresholds were associated with increased risks of preterm birth. The odds ratios of preterm birth at the 95th percentile of NO2, SO2, and CO against the thresholds were 1.17 (95% CI: 1.08, 1.27), 1.01 (95% CI: 0.99, 1.04), and 1.18 (95% CI: 1.06, 1.32), respectively. The associations were modified by demographic factors, such as maternal smoking and socioeconomic status.Conclusion:Acute increases in ambient air pollution concentrations above certain levels before onset of labor may stimulate preterm birth.Citation:Li S, Guo Y, Williams G. 2016. Acute impact of hourly ambient air pollution on preterm birth. Environ Health Perspect 124:1623–1629; http://dx.doi.org/10.1289/EHP200

Indigenous birth outcomes at a Victorian urban hospital, a retrospective 5-year cohort study 2010-2014.

Indigenous people in Australia experience higher rates of preterm birth and low birthweight than their nonindigenous counterparts. There is currently no data on these rates from Victoria, with the data coming from states with higher indigenous proportions. Five years (1st January 2010-31st December 2014) of retrospective data from The Northern Hospital's (Melbourne, Victoria) database were analysed. Mothers and babies were split according to self-reported indigenous status: 13800 nonindigenous mothers, 185 indigenous mothers, 301 indigenous babies and 13843 nonindigenous babies. Primary outcomes measured were low birthweight (LBW) and preterm birth. There was a higher incidence of indigenous babies born preterm (8.8% vs 5.9%, P = 0.034), but the adjusted odds ratios for preterm birth were not significant (indigenous babies OR 1.19, 95% CI: 0.77-1.87, indigenous mothers OR 0.97, CI: 0.52-1.80). There was a similar incidence of LBW among indigenous and nonindigenous babies (6.5% vs 5.4%, P = 0.416). The rate of indigenous women smoking was 29.3% compared to 12.3% of nonindigenous women (P < 0.001), and 40.3% were obese compared to 28.7% (P = 0.001). Indigenous women had lower rates of diabetes (pre-existing or gestational diabetes, 6.1% vs 13.5% P = 0.003). Heterogeneity of indigenous people and geography means that inferences about indigenous health are difficult to make. It appears that Victorian urban indigenous women have similar rates of preterm birth and LBW to nonindigenous women. While there were pleasing results concerning LBW, antenatal care, diabetes and preterm birth, the rates of smoking and obesity remain a challenge in the indigenous population.

Preterm birth and its associations with residence and ambient vehicular traffic exposure

Preterm birth (PTB) is a multifactorial disorder, and air pollution has been suggested to increase the risk of occurrence. However, large population studies controlling for multiple exposure measures in high-density settings with established commuter patterns are lacking. We performed a geospatial analysis with the use of a publicly available database to identify whether residence during pregnancy, specifically with regard to exposure to traffic density and mobility in urban and suburban neighborhoods, may be a contributing risk factor for premature delivery. In our cohort study, we analyzed 9004 pregnancies with as many as 4900 distinct clinical and demographic variables from Harris County, Texas. On the basis of primary residency and occupational zip code information, geospatial analysis was conducted. Data on vehicle miles traveled (VMT) and percentages of inhabitants traveling to work were collected at the zip code level and additionally grouped by the three recognized regional commuter loop high-density thoroughfares resulting from two interstate/highway belts (inner, middle, and outer loops). PTB was categorized as late (34 1/7 to 36 6/7 weeks) and early PTB (22 1/7 to 33 6/7 weeks), and unadjusted odds ratios (OR) and adjusted ORs were ascribed. PTB prevalence in our study population was 10.1% (6.8% late and 3.3% early preterm), which is in accordance with our study and other previous studies. Prevalence of early PTB varied significantly between the regional commuter loop thoroughfares [OR for inner vs outer loop: 0.58 (95% confidence interval, 0.39-0.87), OR for middle vs outer loop, 0.74 (0.57-0.96)]. The ORs for PTB and early PTB were shown to be lower in gravidae from neighborhoods with the highest VMT/acre [OR for PTB, 0.82 (0.68-0.98), OR for early PTB, 0.78 (0.62-0.98)]. Conversely, risk of PTB and early PTB among subjects living in neighborhoods with a high percentage of inhabitants traveling to work over a greater distance demonstrated a contrary tendency [OR for PTB, 1.18 (1.03-1.35), OR for early PTB, 1.48 (1.17-1.86)]. In logistic regression models, the described association between PTB and residence withstood and could not be explained by differences in maternal age, gravidity or ethnicity, tobacco use, or history of PTB. While PTB is of multifactorial origin, the present study shows that community-based risk factors (namely urban/suburban location, differences in traffic density exposure, and need for traveling to work along high-vehicle density thoroughfares) may influence risk for PTB. Further research focusing on previously unrecognized community-based risk factors may lead to innovative future prevention measures.

Relationship of trimester-specific smoking patterns and risk of preterm birth

In 2011, the US national rate of smoking early in pregnancy was 11.5%. Unfortunately, our home state of Ohio had a rate twice as high at 23%. Smoking in pregnancy remains one of the most important modifiable risk factors for pregnancy complications, specifically preterm birth. The objective of the study was to quantify the preterm birth risk to various trimester-specific smoking behaviors. The study was a population-based, retrospective cohort study of singleton non-anomalous live births, using Ohio birth records 2006 to 2012. Preterm birth rates were compared between non-smokers and women who smoked in the preconception period only, those who quit smoking after the 1st and 2nd trimesters, and those who smoked throughout pregnancy. Multivariate logistic regression quantified the risk of smoking with cessation at various times in pregnancy and preterm birth risk, adjusted for maternal race, education, age, Medicaid use, marital status, and parity. A stratified analysis was performed on the basis of preterm birth subtype: spontaneous preterm birth versus indicated preterm birth. We also performed an additional analysis stratifying for maternal race using the 2 largest categories of race (non-Hispanic white and non-Hispanic black). Of the 913,757 birth records analyzed, nearly 25% of the women reported some smoking behavior on the birth certificate data. Of smokers, less than half quit during pregnancy (38.8% vs 61.2% smoked throughout pregnancy). Early quitters had a similar preterm birth rate compared with non-smokers. Women who smoked through the 1st trimester only did not have a significant increase in their overall preterm birth odds ratio <37 weeks; however, it did increase the odds of extreme preterm birth <28 weeks by 20% (adjusted odds ratio, 1.20; 95% confidence interval [CI], 1.02, 1.40). Quitting late in pregnancy resulted in the highest odds ratio increase: 70% for preterm birth <37 weeks (adjusted odds ratio 1.70; CI, 1.60, 1.80), even after adjustment for the confounding influences. Quitting smoking early in pregnancy after the 1st trimester did not increase the overall risk of spontaneous or indicated preterm birth <37 weeks significantly. However, quitting after the 1st trimester was associated with a significant increase in risk of extreme spontaneous preterm birth <28 weeks, an effect not seen with indicated preterm birth <28 weeks. Delaying cessation until late in pregnancy-after the 2nd trimester-was associated with the highest risk increases, 65% increased odds of spontaneous and 78% increase in odds of indicated preterm births. The rate of preterm births to non-Hispanic black mothers was increased in all categories over those of non-Hispanic white mothers. The relative influence of smoking cessation in pregnancy was similar in black compared with white mothers. The effect modification in the regression model was analyzed and revealed no significant interaction between race and smoking patterns on preterm birth risk. Smoking throughout pregnancy is associated with an increased risk of preterm birth. However, quitting early in pregnancy negates this risk. Widespread programs aimed at smoking cessation early in pregnancy could have a significant impact on reducing the rate of preterm birth nationally.

Maternal juvenile rheumatoid arthritis may be associated with preterm birth but not poor fetal growth.

Adverse pregnancy outcomes in mothers with juvenile rheumatoid arthritis (JRA) are not known. The objective of this study was to examine the risk of preterm birth and restricted fetal growth in pregnant mothers diagnosed with JRA, and to examine the impact of race/ethnicity and maternal age on this association. Hospital discharge records for mothers who gave birth in 2011 and 2012 were examined in the National Inpatient Sample (NIS) database. JRA, preterm birth (<37 weeks of gestation), birth weight that is small for gestational age (SGA) and other demographic and clinical variables were identified using ICD-9 (International Classification of Disease--9th revision) diagnostic codes. The associations of JRA with preterm birth and restricted fetal growth were examined controlling for confounding variables. The sample included 8,273,987 birthing mothers, of these 1236 (0.01%) had JRA. The prevalence of preterm birth and SGA was 6.08% and 2.34%, respectively. Preterm birth in mothers with JRA was 12.9% compared with 6.1% in mothers without JRA with an adjusted odds ratio (OR) of 2.1 (confidence interval (CI): 1.74 to 2.42, P<0.001). The incidence of SGA in infants born to mothers with JRA was 3.34% compared with 2.34% in non-JRA mothers, which was not statistically significant. Adjusted OR for preterm birth in association with JRA among White mothers was 1.78 (CI: 1.41 to 2.24, P<0.001). However, Hispanic mothers with JRA (12%) were the ethnicity to suffer the most from preterm birth with an adjusted OR of 4.43 (CI: 2.97 to 6.62, P<0.001). Preterm birth among advanced maternal age (AMA) mothers with JRA was 25% compared with 7% in those without JRA with an adjusted OR of 5.42 (CI: 3.51 to 8.35, P<0.001). JRA is associated with preterm birth but not with SGA. This association is significantly influenced by race/ethnicity and maternal age. More studies are needed to examine these findings in relation to medications used, severity of the disease and exacerbation during pregnancy to understand the genetic/socioeconomic factors behind these racial/ethnic differences.

Dilatation and curettage increases the risk of subsequent preterm birth: a systematic review and meta-analysis.

Could dilatation and curettage (D&C), used in the treatment of miscarriage and termination of pregnancy, increase the risk of subsequent preterm birth? A history of curettage in women is associated with an increased risk of preterm birth in a subsequent pregnancy compared with women without such history. D&C is one of the most frequently performed procedures in obstetrics and gynaecology. Apart from the acknowledged but relatively rare adverse effects, such as cervical tears, bleeding, infection, perforation of the uterus, bowel or bladder, or Asherman syndrome, D&C has been suggested to also lead to an increased risk of preterm birth in the subsequent pregnancy. In the absence of randomized data, we conducted a systematic review and meta-analysis of cohort and case-control studies. We searched OVID MEDLINE and OVID EMBASE form inception until 21 May 2014. We selected cohort and case-control studies comparing subsequent preterm birth in women who had a D&C for first trimester miscarriage or termination of pregnancy and a control group of women without a history of D&C. We included 21 studies reporting on 1 853 017 women. In women with a history of D&C compared with those with no such history, the odds ratio (OR) for preterm birth <37 weeks was 1.29 (95% CI 1.17; 1.42), while for very preterm birth the ORs were 1.69 (95% CI 1.20; 2.38) for <32 weeks and 1.68 (95% CI 1.47; 1.92) for <28 weeks. The risk remained increased when the control group was limited to women with a medically managed miscarriage or induced abortion (OR 1.19, 95% CI 1.10; 1.28). For women with a history of multiple D&Cs compared with those with no D&C, the OR for preterm birth (<37 weeks) was 1.74 (95% CI 1.10; 2.76). For spontaneous preterm birth, the OR was 1.44 (95% CI 1.22; 1.69) for a history of D&C compared with no such history. There were no randomized controlled trials comparing women with and without a history of D&C and subsequent preterm birth. As a consequence, confounding may be present since the included studies were either cohort or case-control studies, not all of which corrected the results for possible confounding factors. This meta-analysis shows that D&C is associated with an increased risk of subsequent preterm birth. The increased risk in association with multiple D&Cs indicates a causal relationship. Despite the fact that confounding cannot be excluded, these data warrant caution in the use of D&C for miscarriage and termination of pregnancy, the more so since less invasive options are available. This study was funded by ZonMw, a Dutch organization for Health Research and Development, project number 80-82310-97-12066.

Maternal Thyroid Disease and Preterm Birth: Systematic Review and Meta-Analysis.

Thyroid disease in pregnancy is increasing with rising average maternal ages in developed countries. The evidence for an association between preterm birth and thyroid disease has been confounded by small studies with varying outcomes and methodology. The aim of this meta-analysis is to review the literature regarding thyroid disease including subclinical and overt hypothyroidism, hyperthyroidism, and isolated hypothyroxinemia and the specific outcome of preterm birth. A search of PubMed and Embase databases was performed in May 2015. A fixed-effects model was used to calculate the overall combined odds ratio (OR) with its corresponding 95% confidence interval (95% CI) to evaluate the relationship between thyroid disease and preterm delivery. Studies were considered eligible if they met the following criteria: prospective cohort study or a case control study; the exposure of interest was maternal thyroid disease, including subclinical hypothyroidism, overt hypothyroidism, hyperthyroidism, or isolated hypothyroxinemia; the outcome of interest was preterm delivery; and data regarding numbers of preterm births in each cohort were reported. Data were recorded in a database evidence table including any incidence data for maternal thyroid disease and preterm birth compared to a reference group. Fourteen cohort studies and one case control study involving 2 532 704 participants were included. The combined OR of preterm delivery for pregnant women with overt hypothyroidism compared with the reference group was 1.19 (95% CI, 1.12-1.26; P < .00001). There was also a significant risk of preterm birth in women with hyperthyroidism (OR, 1.24 [95%, CI 1.17-1.31]; P < .00001). Subclinical hypothyroidism and isolated hypothyroxinemia showed no significant increase in OR. Sensitivity analysis made no change to these results. Both overt hypothyroidism and hyperthyroidism are associated with a small but statistically significant increase in OR for preterm birth not seen in subclinical hypothyroidism or isolated hypothyroxinemia.

Preconception blood pressure and risk of preterm birth: a large historical cohort study in a Chinese rural population

To examine the relationship between preconception blood pressure (BP) and the risk of preterm birth (PTB) using a historical cohort of reproductive-aged women and girls from a Chinese rural population. A historical cohort study established between 2010 and 2013 in People's Republic of China. Local family-planning service agencies and maternal-child care service centers. A total of 367,425 reproductive-aged women and girls who participated in the National Free Pre-pregnancy Checkups in 2010-2012 and subsequently had a live birth before October2013. None. Incidence rates of PTB in reproductive-aged women and girls across preconception BP levels. Preterm births were defined as babies born alive at 28 to 37 weeks of pregnancy. Compared with the participants with a systolic BP of <120 mm Hg, the multivariable-adjusted odds ratio (OR) for PTB was 0.99 (95% confidence interval [CI]: 0.95-1.03]), 1.21 (95% CI: 1.11-1.32), 1.47 (95% CI: 1.22-1.77), 1.80 (95% CI: 1.25-2.59), and 1.81 (95% CI: 1.20-2.73) for the participants with systolic BP of 120-129, 130-139, 140-149, 150-159, and ≥160 mm Hg, respectively. When the participants with normal BP were used as the reference, the adjusted OR for PTB was 1.04 (95% CI: 1.01-1.08), 1.38 (95% CI: 1.25-1.53), and 1.54 (95% CI: 1.21-1.97) for the participants with prehypertension, stage-1 hypertension, and stage-2 hypertension, respectively. In addition, isolated systolic and diastolic hypertension increased the risk of PTB by 55% and 30%, respectively. Our results indicated a strong linear and independent relationship between BP levels and the risk of PTB in Chinese reproductive-aged women and girls. Maternal hypertension before pregnancy can significantly increase the risk of PTB.

Is the increased risk of preterm birth following excision for cervical intraepithelial neoplasia restricted to the first birth post treatment?

ObjectiveTo explore whether the increased risk of preterm birth following treatment for cervical disease is limited to the first birth following colposcopy.DesignNested case–control study.SettingTwelve NHS hospitals in England.PopulationAll nonmultiple births from women selected as cases or controls from a cohort of women with both colposcopy and a hospital birth. Cases had a preterm (20–36 weeks of gestation) birth. Controls had a term birth (38–42 weeks) and no preterm.MethodsObstetric, colposcopy and pathology details were obtained.Main outcome measuresAdjusted odds ratio of preterm birth in first and second or subsequent births following treatment for cervical disease.ResultsA total of 2798 births (1021 preterm) from 2001 women were included in the analysis. The risk of preterm birth increased with increasing depth of treatment among first births post treatment [trend per category increase in depth, categories <10 mm, 10–14 mm, 15–19 mm, ≥20 mm: odds ratio (OR) 1.23, 95% confidence interval (95% CI) 1.12–1.36, P < 0.001] and among second and subsequent births post treatment (trend OR 1.34, 95% CI 1.15–1.56, P < 0.001). No trend was observed among births before colposcopy (OR 0.98, 95% CI 0.83–1.16, P = 0.855). The absolute risk of a preterm birth following deep treatments (≥15 mm) was 6.5% among births before colposcopy, 18.9% among first births and 17.2% among second and subsequent births post treatment. Risk of preterm birth (once depth was accounted for) did not differ when comparing first births post colposcopy with second and subsequent births post colposcopy (adjusted OR 1.15, 95% CI 0.89–1.49).ConclusionsThe increased risk of preterm birth following treatment for cervical disease is not restricted to the first birth post colposcopy; it remains for second and subsequent births. These results suggest that once a woman has a deep treatment she remains at higher risk of a preterm birth throughout her reproductive life.Tweetable abstractRisk of preterm birth following large treatments for cervical disease remains for second and subsequent births.

The role of prenatal care and social risk factors in the relationship between immigrant status and neonatal morbidity: a retrospective cohort study.

Background and AimLiterature evaluating association between neonatal morbidity and immigrant status presents contradictory results. Poorer compliance with prenatal care and greater social risk factors among immigrants could play roles as major confounding variables, thus explaining contradictions. We examined whether prenatal care and social risk factors are confounding variables in the relationship between immigrant status and neonatal morbidity.MethodsRetrospective cohort study: 231 pregnant African immigrant women were recruited from 2007–2010 in northern Spain. A Spanish population sample was obtained by simple random sampling at 1:3 ratio. Immigrant status (Spanish, Sub-Saharan and Northern African), prenatal care (Kessner Index adequate, intermediate or inadequate), and social risk factors were treated as independent variables. Low birth weight (LBW < 2500 grams) and preterm birth (< 37 weeks) were collected as neonatal morbidity variables. Crude and adjusted odds ratios (OR) were estimated by unconditional logistic regression with 95% confidence intervals (95% CI).ResultsPositive associations between immigrant women and higher risk of neonatal morbidity were obtained. Crude OR for preterm births in Northern Africans with respect to nonimmigrants was 2.28 (95% CI: 1.04–5.00), and crude OR for LBW was 1.77 (95% CI: 0.74–4.22). However, after adjusting for prenatal care and social risk factors, associations became protective: adjusted OR for preterm birth = 0.42 (95% CI: 0.14–1.32); LBW = 0.48 (95% CI: 0.15–1.52). Poor compliance with prenatal care was the main independent risk factor associated with both preterm birth (adjusted OR inadequate care = 17.05; 95% CI: 3.92–74.24) and LBW (adjusted OR inadequate care = 6.25; 95% CI: 1.28–30.46). Social risk was an important independent risk factor associated with LBW (adjusted OR = 5.42; 95% CI: 1.58–18.62).ConclusionsPrenatal care and social risk factors were major confounding variables in the relationship between immigrant status and neonatal morbidity.

Downward economic mobility and preterm birth: an exploratory study of Chicago-born upper class White mothers.

A paucity of published data exists on the factors underlying the relatively poor birth outcome of non-Hispanic White women in the United States. To determine whether downward economic mobility is a risk factor for preterm birth (<37 weeks, PTB) among upper class-born White women. Stratified and multilevel logistic regression analyses were performed on an Illinois transgenerational dataset of non-Hispanic White infants (1989-1991) and their women (1956-1976) with appended US census income information. The study sample was restricted to singleton births of Chicago-born upper-class (defined by early-life residence in affluent neighborhoods) non-Hispanic White women. Upper class-born White women (n = 4,891) who did not experience downward economic mobility by the time of delivery had a PTB rate of 5.4 %. Those women who experienced slight (n = 5,112), moderate (n = 2,158), or extreme (n = 339) downward economic mobility had PTB rates of 6.5, 8.5, and 10.1 %, respectively; RR (95 % CI) = 1.2 (1.0-4.0), 1.6 (1.3-1.9), and 1.9 (1.3-2.6), respectively. Maternal downward economic mobility was also associated with an increased prevalence of biologic, medical, and behavioral risk factors. Interestingly, the relationship between moderate to extreme downward mobility and preterm birth was stronger among former low birth weight (<2500 g, LBW) than non-LBW women: 2.8 (1.4-5.8) versus 1.6 (1.3-1.9), respectively. In multilevel logistic regression models, the adjusted odds ratio of preterm birth for former LBW and non-LBW women who experienced any downward mobility (compared to those women with lifelong upper class status) equaled 2.4 (1.1-5.3) and 1.1 (1.0-1.1), respectively. Downward economic mobility is associated with an increased risk of preterm birth among upper class-born White urban women; this phenomenon is strongest among former low birth weight women.

Associations between ozone and preterm birth in women who develop gestational diabetes.

Prenatal exposure to ambient air pollutants might cause adverse birth outcomes; however, there have been few studies in which the association between air pollution and preterm birth was examined after stratifying by pregnancy complications. We conducted a population-based case-control study of 1,510,064 singleton births from the Taiwanese birth registry during 2001-2007. Of the total of 1,510,064 births, we designated all 86,224 preterm births as the case group and then randomly selected an additional 344,896 from the remaining births (equivalent to 4 full-term births for every 1 preterm birth) as the control sample. We used an inverse distance weighting approach to calculate an average exposure parameter for air pollutants. The adjusted odds ratio for preterm birth per 10-ppb increase in ozone was 1.12 (95% confidence interval: 1.01, 1.23) for women with gestational diabetes mellitus who were exposed in the third trimester and 1.02 (95% confidence interval: 1.01, 1.03) for women without gestational diabetes (P for interaction <0.001). These findings suggest that exposure to ozone in pregnancy is associated with an increased risk of preterm birth, particularly for women who have gestational diabetes mellitus.

Increase in Preterm Birth during Demographic Transition in Chile from 1991 to 2012.

Introduction. Universally mothers at 35 years or more have had higher maternal and perinatal risks. This study analyzed the trend of this group in maternal population and determined their risk of having premature children, during the demographic transition period in Chile. Materials and Methods. Epidemiological study conducted in the population of simple live births registered in the Chilean National Database Births of 1991–2012. Analyses were performed in three categories of maternal age: 35 or more, under 35, and 20 to 29 years. The risk of prematurity was measured by crude and Adjusted Odds Ratio from logistic regression model. Results. Mothers aged 35 and older increased in population from 10.6% in 1991 to 16.7% in 2012 and presented an overall prevalence of preterm delivery of 6.7%, higher prevalence than 20–29 age group (4.7%). In aging mothers, the Odds Ratio for preterm birth adjusted for education, marital status, and parity was 1.68 (95% CI (1.66–1.70)) compared to mothers aged 20–29. All differences were significant (p < 0.001). Conclusions. During Chilean demographic transition, mothers aged 35 or older increased steadily and significantly maintaining higher risks of preterm births. Policies to prevent and monitor the late motherhood could contribute to stopping the current trend.

A spectrum project: preterm birth and small-for-gestational age among infants with birth defects.

The aim of this study is to investigate the association between birth defects (BDs), prematurity and small-for-gestational age (SGA) in a population-based sample. Participants were singleton live births enrolled in the National Birth Defects Prevention Study, including 18 737 case infants with one or more BD and 7999 controls. Logistic regression models to evaluate associations between BDs, prematurity and fetal growth were computed while adjusting for covariates. Cases were significantly more likely to be born prematurely than controls, particularly at 24 to 28 weeks of gestation. The highest odds ratios for preterm birth were found for intestinal atresia, anencephaly, gastroschisis and esophageal atresia. Infants with BDs were also significantly more likely to be SGA than controls (17.2 and 7.8%). Infants with BDs are more likely than controls to be born prematurely and SGA. Findings from this study present additional evidence demonstrating a complex interaction between the development of BDs, prematurity and intrauterine growth.

혼외 출생아의 조기분만과 저체중아 발생 위험도에 관한 연구: 2008-2012년 출생통계

The objective of this study was to analyze the risk of preterm birth (PTB) and low birth weight (LBW) in extramarital birth by analyzing 2008-2012 birth certificated data (2,328,719 births) from Korea Statistics. Odds ratio and 95% confidence intervals (95% CI) were calculated from logistic regression analyses to describe the associations between PTB & LBW and extramarital birth adjusted for maternal age, maternal occupation & education, infantile sex, birth order and number of child birth (singleton & multiple birth). The rate of extramarital birth was 1.8 percent and 2.1 percent in 2010-11. The incidence of LBW was 8.1 percent in extramarital birth and 5.0 percent in marital birth. The incidence of PTB in extramarital birth were 8.2 percent and 5.8 percent in marital birth. Compared with marital birth, the odds ratio (OR) for PTB were 1.48 (95% CI: 1.43-1.54) for extramarital birth. Risk of LBW was higher in extramarital birth (OR: 1.70, 95% CI: 1.64-1.76) than that of marital birth. Among mothers younger than 20 years, the odds ratio of PTB among extramarital birth, relative to married birth was 1.69 (1.49-1.91). Among unmarried mothers, those at a higher risk of LBW was aged 20-29 years (1.69: 1.59-1.79). Maternal unmarried status was associated with increased risk of PTB and LBW.

Sources of fine particulate matter and risk of preterm birth in Connecticut, 2000-2006: a longitudinal study.

Background: Previous studies have examined fine particulate matter (≤ 2.5 μm; PM2.5) and preterm birth, but there is a dearth of longitudinal studies on this topic and a paucity of studies that have investigated specific sources of this exposure.Objectives: Our aim was to assess whether anthropogenic sources are associated with risk of preterm birth, comparing successive pregnancies to the same woman.Methods: Birth certificates were used to select women who had vaginal singleton live births at least twice in Connecticut during 2000–2006 (n = 23,123 women, n = 48,208 births). We procured 4,085 daily samples of PM2.5 on Teflon filters from the Connecticut Department of Environmental Protection for six cities in Connecticut. Filters were analyzed for chemical composition, and Positive Matrix Factorization was used to determine contributions of PM2.5 sources. Risk estimates were calculated with conditional logistic regression, matching pregnancies to the same women.Results: Odds ratios of preterm birth per interquartile range increase in whole pregnancy exposure to dust, motor vehicle emissions, oil combustion, and regional sulfur PM2.5 sources were 1.01 (95% CI: 0.93, 1.09), 1.01 (95% CI: 0.92, 1.10), 1.00 (95% CI: 0.89, 1.12), and 1.09 (95% CI: 0.97, 1.22), respectively.Conclusion: This was the first study of PM2.5 sources and preterm birth, and the first matched analysis, that better addresses individual-level confounding potentially inherent in all past studies. There was insufficient evidence to suggest that sources were statistically significantly associated with preterm birth. However, elevated central estimates and previously observed associations with mass concentration motivate the need for further research. Future studies would benefit from high source exposure settings and longitudinal study designs, such as that adopted in this study.Citation: Pereira G, Bell ML, Lee HJ, Koutrakis P, Belanger K. 2014. Sources of fine particulate matter and risk of preterm birth in Connecticut, 2000–2006: a longitudinal study. Environ Health Perspect 122:1117–1122; http://dx.doi.org/10.1289/ehp.1307741

Relationship of Isolated Single Umbilical Artery to Fetal Growth, Aneuploidy, and Perinatal Mortality

The umbilical cord normally contains 2 arteries and a single vein. When an umbilical artery is absent, the condition is called single umbilical artery (SUA). The reported prevalence of SUA varies from 0.5% at the second-trimester prenatal ultrasound and in umbilical cord specimens from live-born infants to 2.1% in fetal deaths, autopsies, or aborted fetuses. Approximately 33% of fetuses with SUA have additional structural anomalies, and 10% are affected with aneuploidy. In ~65% of cases, SUA seems to be an isolated finding. In pregnancies with an apparently isolated SUA (iSUA), aneuploidy or fetal size (small for gestational age [SGA]) may become apparent later in pregnancy or at birth. This systematic review was undertaken to assess outcome of iSUA diagnosed at the midtrimester ultrasound scan and to determine whether data are sufficient to determine appropriate management of pregnancies with diagnosed iSUA. MEDLINE, EMBASE, and the Cochrane Library databases were searched for articles reporting on SUA. Randomized controlled trials, cohort studies, and case-control studies were eligible if they described 30 or more cases of apparent iSUA identified by ultrasound before a mean gestational age of 24 weeks. All studies that allowed construction of a 2 × 2 table were included, with the incidence of the outcome of interest in SUA fetuses and 3-vessel cord fetuses. Quantitative data on the outcome variables included incidence of SGA and perinatal mortality, median or mean birth weight, and frequency of aneuploidy. Odds ratios (ORs) with 95% confidence intervals (CIs) were determined for the occurrence of SGA, perinatal mortality, and frequency of aneuploidy in iSUA fetuses compared with those in 3-vessel cord fetuses. Of 449 articles, the final analysis included 3 cohort and 4 case-control studies, reporting on 68 and 297 cases of apparent iSUA, with a total of 982 patients with an iSUA. The mean gestational age at diagnosis of SUA was 19.0 to 24.3 weeks. A non–statistically significant association was found between iSUA and SGA at birth (OR for SGA in fetuses with iSUA, 1.6; 95% CI, 0.97–2.6; P = 0.06), with ORs in the cohort studies ranging from 1.1 to 3.3. In 3 of the case-control studies, iSUA fetuses did not have significantly lower mean birth weights compared with control fetuses (mean weight, 3154 vs 3176 g; mean difference, 51 g; 95% CI, −154.7 to 52.6 g; P = 0.33). The OR for preterm birth in fetuses with an iSUA compared with control fetuses was 2.1 (95% CI, 1.4–3.2) for delivery before 37 weeks and 3.3 (95% CI, 1.4–7.7) for delivery before 34 weeks. Although there was a positive association between iSUA and increased perinatal mortality, it did not meet statistical significance (OR, 2.0; 95% CI, 0.9–4.2; P = 0.07). Among 695 iSUA cases reported in 16 studies, 4 cases of aneuploidy (0.58%) occurred; the mean maternal age was 30.1 years. These results indicate that iSUA is associated with a nonsignificant trend for increased risk for SGA and perinatal mortality. The relatively low birth weight in iSUA neonates may occur as a result of a relatively high prevalence of preterm birth. On the basis of this review, no firm conclusions can be drawn about the association between iSUA and aneuploidy. More large-scale, prospective cohort studies are necessary to clarify these associations and identify appropriate management protocols for iSUA fetuses.

Preterm Birth and Prenatal Maternal Occupation: The Role of Hispanic Ethnicity and Nativity in a Population-Based Sample in Los Angeles, California

We investigated preterm birth (PTB) in relation to maternal occupational exposure and whether effect measures were modified by Hispanic ethnicity and nativity in a population-based sample with high proportion of Hispanics. We used a case-control study (n = 2543) nested within a cohort of 58,316 births in Los Angeles County, California, in 2003. We categorized prenatal occupations using the US Census Occupation Codes and Classification System and developed a job exposure matrix. Odds ratios for PTB were estimated using logistic regression. Odds ratios for PTB were increased for all women in health care practitioner and technical occupations, but the 95% confidence intervals included the null value; effects were more pronounced among Hispanics. We estimated elevated odds ratios for foreign-born Hispanic women in building and grounds cleaning and maintenance occupations. Shift work and physically demanding work affected births among US-born but not foreign-born Hispanics. Hispanic women are at particular risk for PTB related to adverse prenatal occupational exposure. Nativity may moderate these effects on PTB. Maternal occupational exposures likely contribute to ethnic disparities in PTB.

Is short first‐trimester crown–rump length associated with spontaneous preterm birth?

To assess the association between first-trimester crown-rump length (CRL) and the risk of spontaneous preterm birth before 32 weeks' gestation. We performed a matched case-control study of 129 women with spontaneous preterm birth at < 32 weeks' gestation (cases) and 129 women with term deliveries (controls) using data stored in the ultrasound and obstetric databases of our tertiary referral center. Cases and controls were individually matched based on maternal age, parity, history of preterm birth and medical indication for antenatal care. Fetal CRL measured between 8 + 0 and 13 + 6 weeks was expressed as multiples of the median (MoM) expected CRL, based on last menstrual period. We investigated the association between CRL-MoM and spontaneous preterm birth using logistic regression analysis. CRL-MoM was not associated with spontaneous preterm birth: odds ratio (OR) 1.10 (95% CI, 0.89-1.36) per 0.10 MoM increase in CRL. Timing of measurement did not influence the model (P = 0.59). This was confirmed when restricting the analysis to the 93 pairs with CRL measurements made between 10 + 0 and 13 + 6 weeks: OR for preterm birth 1.07 (95% CI, 0.83-1.37) per 0.10 MoM increase in CRL. A short CRL in the first trimester is not associated with spontaneous preterm birth before 32 weeks' gestation, thus short CRL cannot be used to identify women at increased risk of preterm birth.

Suburban Migration and the Birth Outcome of Chicago-Born White and African–American Women: The Merit of the Healthy Migrant Theory?

The healthy migrant theory posits that women who migrate before pregnancy are intrinsically healthier and therefore have better birth outcomes than those who don't move. Objective. To determine whether migration to the suburbs is associated with lower rates of preterm (<37weeks) birth among Chicago-born White and African-American mothers. We performed stratified and multilevel logistic regression analyses on an Illinois transgenerational dataset of non-Latino White and African-American infants (1989-1991) and their mothers (1956-1976) with appended US census income information. Forty percent of Chicago-born White mothers (N=45,135) migrated to Suburban Cook County and 30% migrated to the more geographically distant collar counties. In contrast, 10% of Chicago-born African-American mothers (N=41,221) migrated to Suburban Cook and only two percent migrated to the collar counties. Chicago-born White and African-American migrant mothers to Suburban Cook County had lower preterm birth rates than their non-migrant counterparts; RR=0.8 (0.8-0.9) and 0.8 (0.7-0.8), respectively. When neighborhood income was singularly taken into account, the protective association of suburban migration and preterm birth disappeared among Chicago-born Whites. In race-specific multilevel multivariate regression models which included neighborhood income, the adjusted odds ratio of preterm birth, low birth weight, and small for gestational-age for Chicago-born White and African-American migrant (compared to non-migrant) mothers approximated unity. Neighborhood income underlies the protective association of suburban migration and birth outcome among Chicago-born White and African-American mothers. These findings do not support the healthy migrant hypothesis of reproductive outcome.