Early Term Birth Research Articles

Acute associations between heatwaves and preterm and early-term birth in 50 US metropolitan areas: a matched case-control study

BackgroundThe effect of heatwaves on adverse birth outcomes is not well understood and may vary by how heatwaves are defined. The study aims to examine acute associations between various heatwave definitions and preterm and early-term birth.MethodsUsing national vital records from 50 metropolitan statistical areas (MSAs) between 1982 and 1988, singleton preterm (< 37 weeks) and early-term births (37–38 weeks) were matched (1:1) to controls who completed at least 37 weeks or 39 weeks of gestation, respectively. Matching variables were MSA, maternal race, and maternal education. Sixty heatwave definitions including binary indicators for exposure to sustained heat, number of high heat days, and measures of heat intensity (the average degrees over the threshold in the past 7 days) based on the 97.5th percentile of MSA-specific temperature metrics, or the 85th percentile of positive excessive heat factor (EHF) were created. Odds ratios (OR) for heatwave exposures in the week preceding birth (or corresponding gestational week for controls) were estimated using conditional logistic regression adjusting for maternal age, marital status, and seasonality. Effect modification by maternal education, age, race/ethnicity, child sex, and region was assessed.ResultsThere were 615,329 preterm and 1,005,576 early-term case-control pairs in the analyses. For most definitions, exposure to heatwaves in the week before delivery was consistently associated with increased odds of early-term birth. Exposure to more high heat days and more degrees above the threshold yielded higher magnitude ORs. For exposure to 3 or more days over the 97.5th percentile of mean temperature in the past week compared to zero days, the OR was 1.027 for early-term birth (95%CI: 1.014, 1.039). Although we generally found null associations when assessing various heatwave definitions and preterm birth, ORs for both preterm and early-term birth were greater in magnitude among Hispanic and non-Hispanic black mothers.ConclusionAlthough associations varied across metrics and heatwave definitions, heatwaves were more consistently associated with early-term birth than with preterm birth. This study’s findings may have implications for prevention programs targeting vulnerable subgroups as climate change progresses.

The Association between Preterm Birth and Ambient Air Pollution Exposure in Shiyan, China, 2015-2017.

Shortening of the gestational duration has been found associated with ambient air pollution exposure. However, the critical exposure windows of ambient air pollution for gestational duration remain inconsistent, and the association between ambient air pollution and early term births (ETB, 37 to 38 weeks) has rarely been studied relative to preterm births (PTB, 28–37 weeks). A time-series study was conducted in Shiyan, a medium-sized city in China. Birth information was collected from the Shiyan Maternity and Child Health Hospital, and 13,111 pregnant women who gave birth between 2015 and 2017 were included. Data of the concentrations of air pollutants, including PM10, PM2.5, NO2, and SO2 and meteorological data, were collected in the corresponding gestational period. The Cox regression analysis was performed to estimate the relationship between ambient air pollution exposure and the risk of preterm birth after controlling the confounders, including maternal age, education, Gravidity, parity, fetal gender, and delivery mode. Very preterm birth (VPTB, 28–32 weeks) as a subtype of PTB was also incorporated in this study. The risk of VPTB and ETB was positively associated with maternal ambient air pollution exposure, and the correlation of gaseous pollutants was stronger than particulate matter. With respect to exposure windows, the critical trimester of air pollutants for different adverse pregnancy outcomes was different. The exposure windows of PM10, PM2.5, and SO2 for ETB were found in the third trimester, with HRs (hazard ratios) of 1.06 (95%CI: 1.04, 1.09), 1.07 (95%CI: 1.04, 1.11), and 1.28 (95%CI: 1.20, 1.35), respectively. However, for NO2, the second and third trimesters exhibited similar results, the HRs reaching 1.10 (95%CI: 1.03, 6.17) and 1.09 (95%CI: 1.03,1.15), respectively. This study extends and strengthen the evidence for a significant correlation between the ambient air pollution exposure during pregnancy and the risk of not only PTB but, also, ETB. Moreover, our findings suggest that the exposure windows during pregnancy vary with different air pollutants and pregnancy outcomes.

Evaluation of Pregnancy Outcomes Among Women With Decreased Fetal Movements

Stillbirth is a devastating pregnancy outcome with far-reaching economic and psychosocial consequences, but despite significant investment, a screening tool for identifying those fetuses at risk for stillbirth remains elusive. Maternal reporting of decreased fetal movements (DFM) has been found to be associated with stillbirth and other adverse perinatal outcomes. To examine pregnancy outcomes of women presenting with DFM in the third trimester at a tertiary Australian center with a clear clinical management algorithm. This cohort study used data on all births meeting the inclusion criteria from 2009 through 2019 at Mater Mothers' Hospital in Brisbane, Australia. This is a tertiary center and Australia's largest maternity hospital. All singleton births without a known congenital anomaly after 28 weeks' gestation were included. Among 203 071 potential participants identified from the hospital database, 101 597 individuals met the eligibility criteria. Data analysis was performed from May through September 2020. Presentation to hospital with DFM after 28 weeks gestation. The primary outcome of this study was the incidence of stillbirth. Multivariate analysis was undertaken to determine the association between DFM and stillbirth, obstetric intervention, and other adverse outcomes, including being born small for gestational age (SGA) and a composite adverse perinatal outcome (at least 1 of the following: neonatal intensive care unit admission, severe acidosis [ie, umbilical artery pH <7.0 or base excess -12.0 mmol/L or less], 5-minute Apgar score <4, or stillbirth or neonatal death). The hypothesis being tested was formulated prior to data collection. Among 101 597 women with pregnancies that met the inclusion criteria, 8821 (8.7%) presented at least once with DFM and 92 776 women (91.3%) did not present with DFM (ie, the control population). Women presenting with DFM, compared with those presenting without DFM, were younger (mean [SD] age, 30.4 [5.4] years vs 31.5 [5.2] years; P < .001), more likely to be nulliparous (4845 women [54.9%] vs 42 210 women [45.5%]; P < .001) and have a previous stillbirth (189 women [2.1%] vs 1156 women [1.2%]; P < .001), and less likely to have a previous cesarean delivery (1199 women [13.6%] vs 17 444 women [18.8%]; P < .001). During the study period, the stillbirth rate was 2.0 per 1000 births after 28 weeks' gestation. Presenting with DFM was not associated with higher odds of stillbirth (9 women [0.1%] vs 185 women [0.2%]; adjusted odds ratio [aOR], 0.54; 95% CI, 0.23-1.26, P = .16). However, presenting with DFM was associated with higher odds of a fetus being born SGA (aOR, 1.14; 95% CI, 1.03-1.27; P = .01) and the composite adverse perinatal outcome (aOR, 1.14; 95% CI, 1.02-1.27; P = .02). Presenting with DFM was also associated with higher odds of planned early term birth (aOR, 1.26; 95% CI, 1.15-1.38; P < .001), induction of labor (aOR, 1.63; 95% CI, 1.53-1.74; P < .001), and emergency cesarean delivery (aOR, 1.18; 95% CI, 1.09-1.28; P < .001). The presence of DFM is a marker associated with increased risk for a fetus. This study's findings of a nonsignificantly lower rate of stillbirth among women with DFM may be reflective of increased community awareness of timely presentation to their obstetric care clinician when concerned about fetal movements and the benefits of tertiary level care guided by a clear clinical management protocol. However, DFM was associated with increased odds of an infant being born SGA, obstetric intervention, early term birth, and a composite of adverse perinatal outcomes.

Association of Preterm Birth With Long-term Risk of Heart Failure Into Adulthood

Preterm birth has been associated with increased risk of heart failure (HF) early in life, but its association with new-onset HF in adulthood appears to be unknown. To determine whether preterm birth is associated with increased risk of HF from childhood into mid-adulthood in a large population-based cohort. This national cohort study was conducted in Sweden with data from 1973 through 2015. All singleton live births in Sweden during 1973 through 2014 were included. Gestational age at birth, identified from nationwide birth records. Heart failure, as identified from inpatient and outpatient diagnoses through 2015. Cox regression was used to determine hazard ratios (HRs) for HF associated with gestational age at birth while adjusting for other perinatal and maternal factors. Cosibling analyses assessed for potential confounding by unmeasured shared familial (genetic and/or environmental) factors. A total of 4 193 069 individuals were included (maximum age, 43 years; median age, 22.5 years). In 85.0 million person-years of follow-up, 4158 persons (0.1%) were identified as having HF (median [interquartile range] age, 15.4 [28.0] years at diagnosis). Preterm birth (gestational age <37 weeks) was associated with increased risk of HF at ages younger than 1 year (adjusted HR [aHR], 4.49 [95% CI, 3.86-5.22]), 1 to 17 years (aHR, 3.42 [95% CI, 2.75-4.27]), and 18 to 43 years (aHR, 1.42 [95% CI, 1.19-1.71]) compared with full-term birth (gestational age, 39-41 weeks). At ages 18 through 43 years, the HRs further stratified by gestational age were 4.72 (95% CI, 2.11-10.52) for extremely preterm births (22-27 weeks), 1.93 (95% CI, 1.37-2.71) for moderately preterm births (28-33 weeks), 1.24 (95% CI, 1.00-1.54) for late preterm births (34-36 weeks), and 1.09 (95% CI, 0.97-1.24) for early term births (37-38 weeks). The corresponding HF incidence rates (per 100 000 person-years) at ages 18 through 43 years were 31.7, 13.8, 8.7, and 7.3, respectively, compared with 6.6 for full-term births. These associations persisted when excluding persons with structural congenital cardiac anomalies. The associations at ages 18 through 43 years (but not <18 years) appeared to be largely explained by shared determinants of preterm birth and HF within families. Preterm birth accounted for a similar number of HF cases among male and female individuals. In this large national cohort, preterm birth was associated with increased risk of new-onset HF into adulthood. Survivors of preterm birth may need long-term clinical follow-up into adulthood for risk reduction and monitoring for HF.

Preventing early births in a regional tertiary maternity unit: Evaluating preterm and early term birth rates before and after implementation of the Preterm Birth Prevention Initiative in the Australian Capital Territory.

A multifaceted preterm birth (PTB) prevention initiative was launched in the Australian Capital Territory (ACT) in 2019. The aim of this initiative was to safely lower the rate of early births across the ACT and the surrounding areas in New South Wales. Modelled on the Western Australian PTB Prevention Initiative, the program included new clinical guidelines and a new PTB prevention clinic at the main tertiary hospital. To evaluate the initiative and its effects on preterm and early term birth rates at the main tertiary hospital after 16months of implementation. A before and after intervention study was conducted. Rates of preterm and early term birth before (previous five years) and after 16months of implementation of the ACT PTB Prevention Initiative were evaluated. At the main tertiary hospital in The Canberra Hospital, the rate of PTB was significantly reduced by 10% after 16months of implementation of the initiative. Rates of PTB were lower than any of the preceding five years and resulted in 45 averted or delayed PTBs. The number of planned early term births with no medical indication was significantly reduced by 34.5% and resulted in 77 averted or delayed early term births. The multifaceted PTB Prevention Initiative safely lowered the rates of early birth in the ACT context. These results highlight the importance of prioritising early birth prevention, education, research and expanding the initiative nationwide.

Medically Indicated Late-Preterm and Early-Term Deliveries: ACOG Committee Opinion Summary, Number 818.

The neonatal risks of late-preterm and early-term births are well established, and the potential neonatal complications associated with elective delivery at less than 39 0/7 weeks of gestation are well described. However, there are a number of maternal, fetal, and placental complications in which either a late-preterm or early-term delivery is warranted. The timing of delivery in such cases must balance the maternal and newborn risks of late-preterm and early-term delivery with the risks associated with further continuation of pregnancy. Deferring delivery to the 39th week is not recommended if there is a medical or obstetric indication for earlier delivery. If there is a clear indication for a late-preterm or early-term delivery for either maternal or newborn benefit, then delivery should occur regardless of the results of lung maturity testing. Conversely, if delivery could be delayed safely in the context of an immature lung profile result, then no clear indication for a late-preterm or early-term delivery exists. Also, there remain several conditions for which data to guide delivery timing are not available. Some examples of these conditions include uterine dehiscence or chronic placental abruption. Delivery timing in these circumstances should be individualized and based on the current clinical situation. This Committee Opinion is being revised to include frequent obstetric conditions that would necessitate delivery before 39 weeks of gestation and to apply the most up-to-date evidence supporting delivery recommendations.

Medically Indicated Late-Preterm and Early-Term Deliveries: ACOG Committee Opinion, Number 818.

The neonatal risks of late-preterm and early-term births are well established, and the potential neonatal complications associated with elective delivery at less than 39 0/7 weeks of gestation are well described. However, there are a number of maternal, fetal, and placental complications in which either a late-preterm or early-term delivery is warranted. The timing of delivery in such cases must balance the maternal and newborn risks of late-preterm and early-term delivery with the risks associated with further continuation of pregnancy. Deferring delivery to the 39th week is not recommended if there is a medical or obstetric indication for earlier delivery. If there is a clear indication for a late-preterm or early-term delivery for either maternal or newborn benefit, then delivery should occur regardless of the results of lung maturity testing. Conversely, if delivery could be delayed safely in the context of an immature lung profile result, then no clear indication for a late-preterm or early-term delivery exists. Also, there remain several conditions for which data to guide delivery timing are not available. Some examples of these conditions include uterine dehiscence or chronic placental abruption. Delivery timing in these circumstances should be individualized and based on the current clinical situation. This Committee Opinion is being revised to include frequent obstetric conditions that would necessitate delivery before 39 weeks of gestation and to apply the most up-to-date evidence supporting delivery recommendations.

468 Long-Term respiratory outcomes in early term born offspring: a systematic review and Meta-Analysis

Newborns exhibit the lowest immediate respiratory morbidity rates when born following 39 completed weeks of gestation. We sought to systematically review the literature and evaluate whether early-term deliveries (370/7-386/7 weeks of gestation) have an impact on long-term respiratory outcomes of offspring up to the age of 18 years, as compared to offspring born at full term or later. This systematic review and meta-analysis was conducted according to the PRISMA guidelines and was registered in PROSPERO. We searched Medline, Embase, and relevant reference lists up to May 31st , 2020, including any observational or randomized trials addressing the association. Two independent reviewers extracted data, and assessed risk of bias. Pooled relative risk (RRs) with their 95% confidence intervals (95% CIs) and heterogeneity were determined. Publication bias was assessed by Funnel plots with Eggers regression line and contours, and sensitivity analyses were performed using Baujat plots. Fifteen studies were included following a screen of nearly 2000 abstracts. Early term birth significantly increased the risk of total respiratory morbidity in the offspring (RR= 1.17, 95%CI= 1.13, 1.22) as compared to full term birth (Figure 1). The increased respiratory morbidity was attributed to obstructive airway diseases (RR=1.14, 95%CI= 1.09, 1.19, Figure 2a) and infectious respiratory diseases (RR= 1.20, 95%CI= 1.11, 1.30, Figure 2b). Compared with full term born offspring, early term delivery poses a significant risk for long term pediatric respiratory morbidity.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Gestational age, mode of delivery, and relation to the day and time of birth in two private health care facilities.

There is a worldwide growing trend of preterm births and C-sections. Our objective was to describe gestational age (GA), mode of delivery, day and time distribution, and the relation between the mode of delivery and the time of birth in two private facilities. Prospective, crosssectional, analytical study. A total of 1500 live newborn infants were included between September 2017 and August 2018 (1465 pregnant women). Of these, 99.4 % had received antenatal care; 66.8 % of pregnancies ended via C-section. The reason was a previous C-section in 36.4 %, lack of progression and descent in 18.9 %, and maternal choice in 9.2 %. The average birth weight was 3232 g ± 561.1 g and the median GA was 39 weeks (range: 38-40) based on the date of the last menstrual period; 88.2 % were term births and, among preterm births, 76.1 % corresponded to late preterm babies. Early term births showed a higher rate of C-sections (p < 0.001). There were 849/1201 (74.5 %) C-sections on weekdays and 173/299 (57.9 %, p < 0.001) on weekends and holidays. A statistically significant relation was observed between the time of birth and the performance of a C-section. The median GA was 39 weeks. C-sections were the most common mode of delivery. Births occurred predominantly Mondays through Fridays between 8 a.m. and 9 p.m.; 82.9 % of C-sections took place on weekdays.

Mortality Among Young Adults Born Preterm and Early Term in 4 Nordic Nations

Adverse long-term outcomes in individuals born before full gestation are not confined to individuals born at extreme gestational ages. Little is known regarding mortality patterns among individuals born in the weeks close to ideal gestation, and the exact causes are not well understood; both of these are crucial for public health, with the potential for modification of risk. To examine the risk of all-cause and noncommunicable diseases (NCD) deaths among young adults born preterm and early term. This multinational population-based cohort study used nationwide birth cohorts from Norway, Sweden, Denmark, and Finland for individuals born between 1967 and 2002. Individuals identified at birth who had not died or emigrated were followed up for mortality from age 15 years to 2017. Analyses were performed from June 2019 to May 2020. Categories of gestational age (ie, moderate preterm birth and earlier [23-33 weeks], late preterm [34-36 weeks], early term [37-38 weeks], full term [39-41 weeks] and post term [42-44 weeks]). All-cause mortality and cause-specific mortality from NCD, defined as cancer, diabetes, chronic lung disease, and cardiovascular disease (CVD). A total of 6 263 286 individuals were followed up for mortality from age 15 years. Overall, 339 403 (5.4%) were born preterm, and 3 049 100 (48.7%) were women. Compared with full-term birth, the adjusted hazard ratios (aHRs) for all-cause mortality were 1.44 (95% CI, 1.34-1.55) for moderate preterm birth and earlier; 1.23 (95% CI, 1.18-1.29) for late preterm birth; and 1.12 (95% CI, 1.09-1.15) for early-term birth. The association between gestational age and all-cause mortality were stronger in women than in men (P for interaction = .03). Preterm birth was associated with 2-fold increased risks of death from CVD (aHR, 1.89; 95% CI, 1.45-2.47), diabetes (aHR, 1.98; 95% CI, 1.44-2.73), and chronic lung disease (aHR, 2.28; 95% CI, 1.36-3.82). The main associations were replicated across countries and could not be explained by familial or individual confounding factors. The findings of this study strengthen the evidence of increased risk of death from NCDs in young adults born preterm. Importantly, the increased death risk was found across gestational ages up to the ideal term date and includes the much larger group with early-term birth. Excess mortality associated with shorter gestational age was most pronounced for CVDs, chronic lung disease, and diabetes.

The Association of COVID-19 Infection in Pregnancy With Preterm Birth: A Retrospective Cohort Study in California

Background: Our understanding of the association of coronavirus disease 19 (COVID-19) and preterm or early term birth among racially and ethnically diverse populations and those with chronic medical conditions is limited. Methods: We examined the relationship between COVID-19 and preterm (PTB) birth among live births documented by California Vital Statistics birth certificates between July 2020 and January 2021 (n=240,147). We used best obstetric estimate of gestational age to classify births as very preterm (VPTB, Findings: COVID-19 diagnoses on birth certificates increased for all racial/ethnic groups between July 2020 and January 2021, and was highest for American Indian/Alaska Native (12.9%), Native Hawaiian/Pacific Islander (11.4%), and Latinx (10.3%) birthing people. COVID-19 diagnosis was associated with an increased risk of VPTB (aRR 1.6, 95% CI [1.4, 1.9]), PTB (aRR 1.4, 95% CI [1.3, 1.4]), and early term birth (aRR 1.1, 95% CI [1.1, 1.2]). There was no effect modification of the overall association by race/ethnicity or insurance status. COVID-19 diagnosis was associated with elevated risk of PTB in people with comorbidities. Interpretation: In a large population-based study, COVID-19 diagnosis increased the risk of VPTB, PTB, and early term birth, particularly among those with medical comorbidities. Prevention measures, including vaccination, should be prioritized for birthing persons. Funding Information: UCSF-Kaiser Department of Research Building Interdisciplinary Research Careers in Women’s Health Program (BIRCWH) National Institute of Child Health and Human Development (NICHD) and the Office of Research on Women’s Health (ORWH) [K12 HD052163] and the California Preterm Birth Initiative, funded by Marc and Lynn Benioff.Declaration of Interests: The authors have no conflicts of interest to disclose.Ethics Approval Statement: The Committee for the Protection of Human Subjects (CPHS) within the Health and Human Services Agency of the State of California approved study protocols.

Early term delivery is associated with increased neonatal respiratory morbidity.

The recent increase in early term birth rates represents a growing challenge to public health given the association between early term birth and neonatal morbidities. We compared the risk of respiratory morbidity between early term and full-term infants. This retrospective cohort population study included infants born at 37-41weeks' gestation in a single tertiary care university hospital between 2014 and 2016. Newborns were categorized as early term (37-38weeks) and full term (39-41weeks). The primary outcome was respiratory morbidity. Of the 4,894 babies born at 37-41weeks gestational age, 31% (n = 1,521) were early term births. The rate of cesarean deliveries, which were often elective, was higher for early term than for full-term newborns (P = 0.001). Compared with full-term newborns, early term newborns, had significantly higher risks of respiratory morbidity (13.2 % vs 6.3 %; odds ratio [OR], 2.28, P = 0.001), respiratory distress syndrome (0.5 % vs 0 %, P = 0.001), transient tachypnea of the newborn (11.2 % vs 4.6 %; OR, 2.72, P = 0.001), continuous positive airway pressure use (9.7 % vs 3.7 %; OR, 2.82, P = 0.001), and ventilation support (1.4% vs 0.4%; OR, 4.11, P = 0.001). The elevated frequency of respiratory morbidity in early term infants emphasizes the importance of early term birth interventions. More than half of the early term births were elective cesarean sections; interventions should therefore focus on reducing elective cesarean procedures at the time of first birth.

Being born and growing up in the Ribeirão Preto and São Luís cohorts.

This thematic issue consists of 14 articles derived from studies of the BRISA birth cohort (Ribeirão Preto, State of São Paulo and São Luís, State of Maranhão, northeastern Brazil, a socially and economically less developed region). In these more than 40 years of existence, these cohorts have been able to document the increase in women's education, the improvement of health conditions, the creation of a public Unified Health System (SUS) that provides universal and free access to health care, eradication of hunger, and transition of the nutritional status characterized by a decrease in malnutrition rates and an increase in obesity in Brazil. Particularly in reproductive health, the country experienced a significant drop in fertility, a decrease in maternal and child mortality, and an increase in breastfeeding rates. Universal access to prenatal care and hospital delivery was accompanied by an excessive number of cesareans without clinical indication and early-term births and premature births, largely due to scheduled cesareans. Articles with a longitudinal and transversal methodological approach are presented, using structural equation analysis and propensity score, together with multivariate regressions, which gave a robust analytical treatment to articles in this thematic issue.

The Acute Effect of Heatwaves on Preterm and Early-term Birth in 53 U.S Metropolitan Areas in the 1980s: A Matched Case-Control Study

Background The effect of heatwaves on adverse birth outcomes is not well understood and may vary by how heatwaves are defined. Objectives To examine acute associations between various heatwave definitions and preterm and early-term birth in 53 metropolitan areas in the U.S during the 1980s. Methods Using national vital records from 53 metropolitan areas between 1982 to 1988, singleton preterm (&lt;37 weeks) and early-term births (37-38 weeks) were matched (1:1) to controls who completed at least 37 weeks or 39 weeks of gestation, respectively. Matching variables included location, maternal race, and maternal education. 40 heatwave definitions were created based on temperature and humidity data, including binary indicators for exposure to sustained heat, number of high heat days, and measures of heat intensity (average degrees over threshold) based on the 97.5%ile of area-specific temperature and apparent temperature, or 85%ile of positive excessive heat factor (EHF). Heatwave exposure in the 7-days preceding birth (for cases) and corresponding gestational window (for controls) was assessed in relation to preterm and early-term birth. Odds ratios for heatwave exposures were estimated using conditional logistic regression adjusting for maternal age, marital status, and seasonality. Results There were a total of 615,329 and 1,293,813 preterm and early-term births in the analyses. Across heatwave definitions, exposure to heatwaves in the week before delivery was consistently associated with increased odds of early-term birth. Odds ratios increased across categories of increasing number of hot days, and minimum consecutive days of heat. For example, exposure to ≥3 days over 97.5%ile of apparent mean temperature in the past week compared to zero days, was associated with a 3.8% (95%CI: 2.6%-5.1%) increase in the odds of early-term birth. Effect estimates for preterm birth were generally consistent with a null association. Conclusions Preliminary results suggest heatwaves were associated with early-term birth but not preterm birth.

Prenatal Exposure to Ambient Air Temperature and Risk of Early Delivery

Background:Preterm birth is a major determinant of adverse health consequences. Often, the specific cause of preterm birth is unclear. However, there are known genetic, behavioral, socioeconomic and environmental risk factors. Considering climate change, temperature is an important factor to consider. Several studies have focused on associations of ambient air temperature (Ta) with risk of preterm birth. Climates studied and methods used varied and results have been inconsistent. Few studies included early-term births.Aims:To investigate the association of prenatal exposure to Ta with preterm and early-term birth in a semi-arid climate in Israel.Methods:All singleton deliveries at the Soroka Medical Center, Be’er Sheva, Israel, with estimated conception dates between May 2004 and March 2013 (N=62,547) were linked to prenatal Ta estimates from a spatiotemporally resolved model, with daily 1 km resolution. We used time-dependent Cox regression models with weekly mean Ta throughout gestation, adjusted for calendar month and year of conception, ethnicity, SES and population density. Effect modification by fetal sex and ethnicity was examined using interaction terms and stratified.Results:Ta was positively associated with late preterm birth (31+0/7 - 36+6/7 weeks of gestation), with increased risk in the upper Ta quintile as compared to the middle Ta quintile, hazard ratio (HR) = 1.31, 95% CI = 1.11 - 1.56. Ta was also associated with early term birth (37+0/6 - 38+6/7 of gestation), with increased risk in the upper Ta quintile as compared to the middle Ta quintile, HR = 1.24, 95% CI = 1.13 - 1.36. Ta was more strongly associated with late preterm birth for female fetuses than for male fetuses (HR = 1.50, 95% CI = 1.17-1.94 and HR = 1.17, 95% CI = 0.97-1.41, respectively).Conclusion:Prenatal exposure to high Ta is associated with a higher risk of early delivery in southern Israel.

Prenatal Exposure to Particulate Air Pollution and Gestational Age at delivery in Massachusetts Neonates 2001-2015 - a Perspective of Causal Modeling and Health Disparities

Background/Aim: Causal evidence of the effects of air pollution on gestational age (GA) at delivery is limited. We aim to estimate the effect of increased trimester-specific PM2.5 levels in neonatal GA at delivery applying causal modeling and identify potential health disparities. Methods: Study population was all Massachusetts live singleton neonates born with a vaginal delivery from 2001 to 2015. Trimester-specific ambient PM2.5 levels at maternal residential address were estimated using a validated ensemble-based model integrating satellite remote sensing, land used data, and meteorology, etc. Outcome of interest was GA at delivery calculated using last menstrual period (LMP). Inverse probability weighted (IPW) quantile regression was applied to derive the causal marginal population-level effect estimates for each GA distribution percentile. Stratified analyses were conducted comparing male vs. female neonates, neonates of younger vs. older mothers, and neonates of African American vs. Caucasian mothers. Low-exposure analyses were conducted by restricting analyses to areas with levels of PM2.5 that met US EPA annual standard of less than 12 μg/m3. Results: For neonates with 0.025, 0.05, 0.10, 0.25, 0.50, 0.75 and 0.975 percentiles of GA at delivery, we estimated adjusted GA reductions of 4.21 days (d) (SE: 0.40), 2.76 d (SE: 0.25), 1.85 d (SE: 0.15), 1.19 d (SE: 0.10), 0.82 d (SE: 0.05), 0.74 d (SE: 0.10) and 0.54 d (SE: 0.20) respectively for each 5 μg/m3 increase of average PM2.5 level in the third trimester. Male neonates and neonates of younger and African American mothers were more vulnerable. Effect estimates were consistently higher at lower percentiles, indicating larger effects for preterm and early-term births. Low-exposure analyses yielded similar results. Conclusions: Prenatal exposure to PM2.5 during third-trimester, even below regulatory standard, reduced GA at delivery among Massachusetts neonates, especially among preterm/early-term births, male neonates, and neonates of younger and African American mothers.

Relationship Between Gestational Age and Outcomes After Congenital Heart Surgery

Previous studies suggest that birth before 39 weeks' gestational age (GA) is associated with higher perioperative mortality and morbidity after congenital heart surgery. The optimal approach to timing of cardiac operation in premature infants remains unclear. We investigated the impact of GA at birth and corrected GA at surgery on postoperative outcomes using the Pediatric Cardiac Critical Care Consortium (PC4) database. Infants undergoing selected index cardiac operations before the end of the neonatal period were included (n= 2298). GA at birth and corrected GA at the time of the index cardiac operation were used as categorical predictors and fitted as a cubic spline to assess nonlinear relationships. The primary outcome was hospital mortality. Multivariable logistic regression models assessed the association between predictors and outcomes while adjusting for confounders. Late-preterm (34-36 weeks) birth was associated with increased odds of mortality compared with full-term (39-40 weeks) birth, while early-term (37-38 weeks) birth was not associated with increased mortality. Corrected GA at surgery of 34 to 37 weeks compared with 40 to 44 weeks was associated with increased mortality. When analyzing corrected GA at surgery as a continuous predictor of outcome, odds of survival improve as patients approach 39 weeks corrected GA. Contrary to previous literature, we did not find an association between early-term birth and hospital mortality at PC4 hospitals. Our analysis of the relationship between corrected GA and mortality suggests that operating closer to full-term corrected GA may improve survival.

Early Term Birth in China and its Association with Universal Two-Child Birth Policy

Background: Early term births (ETB) are related to the morbidity and mortality of infants, and its incidences have not been reported in China. In this study, we aimed to describe the epidemiology of ETB at the national and provincial level, and explore its changes after the implementation of universal two-child policy owing to the timing of policy’s initiation across the research period. Methods: This national multicenter cross-sectional study (n = 75132) used the China Labor and Delivery Survey data collected from 89 hospitals in 25 (out of 34) provinces of mainland China between March 1st 2015 and December 31st 2016. A total of 28,966 low-risk singleton live birth records were included in the analysis of association between universal two-child policy and ETB using a multi-level Poisson regression of sandwich estimation. Findings: The weighted incidence of ETB was 30.1 per 100 all births (95% CI =30.06%, 30.14%) or 29.88 per 100 live births (95% CI = 29.97%, 30.05%) in China. The incidences of ETB were varied by maternal age, parity and previous uterine scars. We found that there were associations between universal two-child policy and ETB when not adjusting for (RR=1.19, p 0.05). Interpretation: The incidence of ETB is high in China and demonstrated practice patterns amenable to improvement. Great importance should be attached to preventing ETB, which risk being more likely after the implementation of the universal two-child policy, especially in young women or women without previous uterine scars. Funding Statement: This study was partly supported by National Natural Science Foundation of China (81673179), the Science and Technology Commission of Shanghai Municipality (18140903100,19140903100), the Shenkang Hospital Development Center (SHDC12016239) Declaration of Interests: We declare no competing interests. Ethics Approval Statement: This study was approved by the Ethics Committees of Xinhua Hosptial (XHECC2015-006) and World Health Organization(A65899). Since only anonymous clinical information were collected, no individual informed consent was obtained.

Preterm birth and nativity among Black women with gestational diabetes in California, 2013\u20132017: a population-based retrospective cohort study

BackgroundDespite the disproportionate prevalence of gestational diabetes (GDM) and preterm birth (PTB) and their associated adverse perinatal outcomes among Black women, little is known about PTB among Black women with GDM. Specifically, the relationship between PTB by subtype (defined as indicated PTB and spontaneous PT labor) and severity, GDM, and nativity has not been well characterized. Here we examine the risk of PTB by severity (early < 34 weeks, late 34 to 36 weeks) and early term birth (37 to 38 weeks) by nativity among Black women with GDM in California.MethodsThis retrospective cohort study used linked birth certificate and hospital discharge data for 8609 of the 100,691 self-identifying non-Hispanic Black women with GDM who had a singleton live birth between 20 and 44 weeks gestation in California in 2013–2017. Adjusted odds ratios (aOR) and 95% confidence intervals (CIs) were examine risks for PTB, by severity and subtype, and early term birth using multivariate regression modeling.ResultsApproximately, 83.9% of Black women with GDM were US-born and 16.1% were foreign-born. The overall prevalence of early PTB, late PTB, and early term birth was 3.8, 9.5, and 29.9%, respectively. Excluding history of prior PTB, preeclampsia was the greatest overall risk factor for early PTB (cOR = 6.7, 95%, CI 5.3 to 8.3), late PTB (cOR = 4.3, 95%, CI 3.8 to 5.0), and early term birth (cOR = 1.8, 95%, CI 1.6 to 2.0). There was no significant difference in the prevalence of PTB by subtypes and nativity (p = 0.5963). Overall, 14.2% of US- compared to 8.9% of foreign-born women had a PTB (early PTB: aOR = 0.56, 95%, CI 0.38 to 0.82; late PTB: aOR = 0.57, 95%, CI 0.45 to 0.73; early term birth: aOR = 0.67, 95%, CI 0.58 to 0.77).ConclusionsForeign-born status remained protective of PTB, irrespective of severity and subtype. Preeclampsia, PTB, and GDM share pathophysiologic mechanisms suggesting a need to better understand differences in perinatal stress, chronic disease, and vascular dysfunction based on nativity in future epidemiologic studies and health services research.

Prenatal exposure to ambient air temperature and risk of early delivery

BackgroundPreterm birth is a major determinant of adverse health consequences, and early term births are also associated with increased risk of various outcomes. In light of climate change, the effect of ambient temperature on earlier delivery is an important factor to consider. Several studies have focused on associations of ambient air temperature (Ta) on preterm birth, but few have examined associations with early term births. AimsTo investigate the association of prenatal exposure to Ta with preterm birth (<37 completed gestation weeks) and with early-term birth (<39 completed gestation weeks) in a semi-arid climate. MethodsAll singleton deliveries at the Soroka Medical Center from the Southern district of Israel, with estimated conception dates between May 1, 2004 and March 31, 2013 (N = 62,547) were linked to prenatal Ta estimates from a spatiotemporally resolved model, with daily 1 km resolution. We used time-dependent Cox regression models with weekly mean Ta throughout gestation, adjusted for calendar month and year of conception, ethnicity, census-level socio-economic status and population density. ResultsTa was positively associated with late preterm birth (31 + 0/7 – 36 + 6/7 weeks), with increased risk in the upper Ta quintile as compared to the third quintile, hazard ratio (HR) = 1.31, 95% confidence interval (CI) = 1.11–1.56. Ta also associated with early term birth (37 + 0/6 – 38 + 6/7), with increased risk in the upper Ta quintile as compared to the third quintile, HR = 1.24, 95% CI = 1.13–1.36. ConclusionExposure to high ambient temperature during pregnancy is associated with a higher risk of preterm and early term birth in southern Israel.