Spatiotemporal Characteristics and Risk Factors for All and Severity-Specific Preterm Births in Southern China, 2014-2021: Large Population-Based Study.

BACKGROUND: The worldwide incidence of preterm births is increasing, and the risks of adverse outcomes for preterm infants significantly increase with shorter gestation, resulting in a substantial socioeconomic burden. Limited epidemiological studies have been conducted in China regarding the incidence and spatiotemporal trends of preterm births. Seasonal variations in risk indicate the presence of possible modifiable factors. Gender influences the risk of preterm birth. OBJECTIVE: This study aims to assess the incidence rates of preterm birth, very preterm birth, and extremely preterm birth; elucidate their spatiotemporal distribution; and investigate the risk factors associated with preterm birth. METHODS: We obtained data from the Guangdong Provincial Maternal and Child Health Information System, spanning from January 1, 2014, to December 31, 2021, pertaining to neonates with gestational ages ranging from 24 weeks to 42 weeks. The primary outcome measures assessed variations in the rates of different preterm birth subtypes over the course of the study, such as by year, region, and season. Furthermore, we examined the relationship between preterm birth incidence and per capita gross domestic product (GDP), simultaneously analyzing the contributing risk factors. RESULTS: The analysis incorporated data from 13,256,743 live births. We identified 754,268 preterm infants and 12,502,475 full-term infants. The incidences of preterm birth, very preterm birth, and extremely preterm birth were 5.69 per 100 births, 4.46 per 1000 births, and 4.83 per 10,000 births, respectively. The overall incidence of preterm birth increased from 5.12% in 2014 to 6.38% in 2021. The incidence of extremely preterm birth increased from 4.10 per 10,000 births in 2014 to 8.09 per 10,000 births in 2021. There was a positive correlation between the incidence of preterm infants and GDP per capita. In more developed economic regions, the incidence of preterm births was higher. Furthermore, adjusted odds ratios revealed that advanced maternal age, multiple pregnancies, and male infants were associated with an increased risk of preterm birth, whereas childbirth in the autumn season was associated with a protective effect against preterm birth. CONCLUSIONS: The incidence of preterm birth in southern China exhibited an upward trend, closely linked to enhancements in the care capabilities for high-risk pregnant women and critically ill newborns. With the recent relaxation of China's 3-child policy, coupled with a temporary surge in advanced maternal age and multiple pregnancies, the risk of preterm birth has risen. Consequently, there is a pressing need to augment public health investments aimed at mitigating the risk factors associated with preterm birth, thereby alleviating the socioeconomic burden it imposes.

Association between preconception anti-androgen therapy and pregnancy outcomes of patients with PCOS: A prospective cohort study.

Background: Polycystic ovary syndrome (PCOS) not only increases fertility challenges for women of reproductive age, but also leads to increased complications during pregnancy and even affects the birth weight of newborns. Also, hyperandrogenemia is associated with lower pregnancy rates and lower live birth rates and may even play a role in preterm delivery and pre-eclampsia in patients with PCOS. However, it is still controversial whether PCOS patients are treated with androgen-lowering therapy before pregnancy. Objective: To assess the effect of anti-androgen therapy prior to ovulation induction on maternal and infant pregnancy outcomes in patients with PCOS. Methods: Prospective cohort study. Results: A total of 296 patients with PCOS were enrolled in the study. The prevalence of adverse pregnancy outcomes, and neonatal complications was lower in DRSP(with drospirenone ethinyl estradiol tablets (II) pretreatment) group than in NO-DRSP(without drospirenone ethinyl estradiol tablets (II) pretreatment) groups (DRSP vs. NO-DRSP: adverse pregnancy outcomes, 12.16% vs. 27.03%, P=0.001; neonatal complications, 17.16% vs. 36.67%, P<0.001). No significant difference was found in maternal complications. Further subgroup analysis revealed that PCOS with pretreatment decreased the risk of preterm delivery (2.99% vs. 10.00%; Adjusted RR, 3.80; 95% CI, 1.19-12.13), pregnancy loss (9.46% vs. 18.92%; Adjusted RR, 2.07; 95% CI, 1.08-3.96), low birth weight (0.75% vs 7.50%; Adjusted RR, 12.08; 95% CI, 1.50-97.31), fetal malformations(1.49% vs. 8.33%; Adjusted RR, 5.63; 95% CI, 1.20-26.33).There were no significant differences in the incidence of DM and PIH as pregnancy complications between the two groups (P>0.05). Conclusion: Our findings suggest that preconception androgen-lowering therapy in patients with PCOS improves pregnancy outcomes and reduces neonatal complications.

Prevalence and risk factors of COVID-19-related generalized anxiety disorder among the general public in China: a cross-sectional study.

Objective: This study aimed to estimate the prevalence of generalized anxiety disorder in China during the coronavirus disease 2019 (COVID-19) pandemic and identify its associated factors. Methods: A cross-sectional study was conducted among the general population in China from March 16 to April 2, 2020. The participants were recruited using stratified random sampling. Data on demographic characteristics and COVID-19 related factors were obtained using self-administered questionnaires. The anxiety score was measured based on the Chinese version of the Generalized Anxiety Disorder 7-item Scale (GAD-7). Results: The study comprised 10,824 participants, of which 37.69% had symptoms of anxiety. The risk factors for anxiety symptoms included poor self-reported health (OR = 1.672, p < 0.001), chronic diseases (OR = 1.389, p < 0.001), and quarantine (OR = 1.365, p < 0.001), while participants' perceptions that COVID-19 would be controlled was a protective factor (OR = 0.774, p < 0.001). The interactions between quarantine and self-reported health (p < 0.001), as well as between perceptions of COVID-19 and self-reported health (p < 0.001) were found to have a significant effect on GAD-7 scores. Conclusions: Self-reported health status, chronic diseases, quarantine, and perceptions of COVID-19 were significantly associated with GAD-7 scores, indicating that mental health interventions are urgently needed during pandemics, especially for high-risk groups.

Association of Interpregnancy Interval With Adverse Birth Outcomes.

Importance: Many studies have reported an association of interpregnancy interval (IPI) between 2 consecutive births with adverse birth outcomes in low- and middle-income countries. However, most of these studies ignore the implications of some unmeasured confounders. Objective: To explore the association of IPI with adverse perinatal outcomes. Design, Setting, and Participants: This large-scale cohort study used the Guangdong Provincial Women and Children Health Information System in Guangdong Province, China, to obtain birth data recorded between January 1, 2014, and December 31, 2020. Matched-sibling design was used. The final cohort included first-born and second-born sibling pairs delivered by mothers who were permanent residents of Guangdong Province. Exposures: The exposure variable was IPI, which was categorized as follows: less than 6, 6 to 11, 12 to 17, 18 to 23, 24 to 29, 30 to 35, and 36 or more months. Main Outcomes and Measures: The outcome variables were adverse birth outcomes: preterm birth (PTB, gestational age <37 weeks), low birth weight (LBW, <2500 g), and small for gestational age (SGA). Adjusted odds ratio (OR) and interaction odds ratio (IOR) associated with IPI were calculated. Results: The study consisted of 725 392 sibling pairs of multiparous mothers. Among these mothers, 718 111 (99.0%) were aged 20 to 34 years, and 715 583 (98.7%) were of Han Chinese ethnicity. Unmatched analysis showed that a short IPI of less than 6 months was associated with higher risks of PTB (adjusted OR, 1.96; 95% CI, 1.87-2.06), LBW (adjusted OR, 1.88; 95% CI, 1.79-1.98), and SGA (adjusted OR, 1.34; 95% CI, 1.30-1.38) compared with an IPI of 18 to 23 months. These associations were attenuated in the matched-sibling analysis. An association of short IPI (<6 months) with PTB (adjusted IOR, 1.40; 95% CI, 1.30-1.51), LBW (adjusted IOR, 1.30; 95% CI, 1.21-1.40), and SGA (adjusted IOR, 1.16; 95% CI, 1.11-1.22) remained in the matched analysis. For IPI of 36 months or more, the odds of PTB (adjusted OR, 1.08; 95% CI, 1.03-1.14) and LBW (adjusted OR, 1.13; 95% CI, 1.07-1.19) in the unmatched analysis were also greater than the reference interval (18-23 months), but not for SGA (adjusted OR, 0.96; 95% CI, 0.93-0.99). Associations between a long IPI (≥36 months) and PTB (adjusted IOR, 1.10; 95% CI, 1.02-1.19) and LBW (adjusted IOR, 1.16; 95% CI, 1.07-1.26) remained through the sibling comparisons. Conclusions and Relevance: Results of this study indicated that mothers with a short (<6 months) or long (≥36 months) IPI had greater odds of adverse birth outcomes. The findings may inform family planning policies and guide individuals and families who are planning for another pregnancy in China.

Spatio-Temporal Distribution and Demographic Characteristics of Congenital Heart Defects in Guangdong, China, 2016-2020.

Background: Congenital heart defects are the most common type of birth defects and bring a heavy disease burden in China. Examining the temporal and spatial trends of congenital heart defects epidemics can give some elementary knowledge for succeeding studies. Objective: To characterize the spatial-temporal patterns of the prevalence of congenital heart defects based on a substantial cohort of the perinatal fetus in south China in 2016-2020. Methods: This study was a retrospective population-based cohort study conducted in Guangdong, China from 2016 to 2020. Pregnant women and their infants received birth defect surveillance during pregnancy and seven days after delivery in more than 1,900 midwifery hospitals in 21 cities. Perinatal infants with congenital heart defects were identified and enrolled. The prevalence of congenital heart defects was calculated according to cities, years, urban and rural areas, regions of Guangdong, categories of maternal age at delivery, seasons of delivery, and infant's gender. Results: A total of 8,653,206 perinatal infants and 53,912 total congenital heart defects were monitored in Guangdong, including 46,716 (86.65%) without other defects and 7,736 (13.35%) with other defects. The average prevalence of total congenital heart defects was 62.30/10,000 (95% CI, 61.78/10,000-62.83/10,000), congenital heart defects without other defects was 53.36/10,000 (95% CI, 52.88/10,000-53.85/10,000), and congenital heart defects with other defects was 8.94/10,000 (95%CI, 8.74/10,000-9.14/10,000). From 2016 to 2020, the prevalence of total congenital heart defects was 54.92/10,000, 54.23/10,000, 63.79/10,000, 73.11/10,000, 68.20/10,000, respectively. We observed geographical variations within the prevalence of congenital heart defects. The prevalence of congenital heart defects was much higher in the Pearl River Delta region than in the non-Pearl River Delta region, as well as higher in urban areas than in rural areas. Conclusion: The findings of this study are helpful to the understanding of the etiology and epidemiology characteristics of congenital heart defects in south China. Our data likely reflect a better estimate of the spatiotemporal trends in congenital heart defects prevalence than reported previously.

The Asian Games, air pollution and birth outcomes in South China: An instrumental variable approach.

We estimate the effects of air-pollution exposure on low birthweight, birthweight, and prematurity risk in South China, for all expectant mothers and by maternal age group and child sex. We do so by exploiting exogenous improvement in air quality during the 2010 Guangzhou Asian Games, when strict regulations were mandated to assure better air quality. We use daily air-pollution levels collected from monitoring stations in Guangzhou, the Asian Games host city, and Shenzhen, a nearby control city, between 2009 and 2011. We first show that air quality during the Asian Games significantly improved in Guangzhou, relative to Shenzhen. Next, using birth-certificate data for both cities for 2009-2011 and using expected pregnancy overlap with the Asian Games as an instrumental variable, we study the effects of three pollutants (PM10, SO2, and NO2) on birth outcomes. Four main conclusions emerge: 1) air pollutants significantly reduce average birthweight and increase preterm risk; 2) for birthweight, late pregnancy is most sensitive to PM10 exposure, but there is not consistent evidence of a sensitive period for other pollutants and outcomes; 3) for birthweight, babies of mothers who are at least 35 years old show more vulnerability to all three air pollutants; and 4) male babies show more vulnerability than female babies to PM10 and SO2, but birthweights of female babies are more sensitive than those of male babies to NO2.

Associations between ambient heat exposure early in pregnancy and risk of congenital heart defects: a large population-based study.

Some epidemiological studies have confirmed the association between environmental factors and congenital heart defects (CHD). While the possibility that maternal ambient heat exposures are related to CHD has received little attention. Our study aims to investigate the association between maternal ambient extreme heat exposure early in pregnancy and the risk of CHD in offspring in China. We conducted a retrospective cohort study of 1,918,105 fetuses between 2 and 8 weeks after gestation from May to October in Guangdong, China, 2015-2019. The main heat exposure was defined as extreme heat events (EHE) by using the 90th (EHE90) or 95th (EHE95) percentile of the daily maximum temperature. For each EHE definition, we further defined four indicators: having EHE or not, frequency, duration, and cumulative days. We used the log-binomial regression models to calculate the prevalence ratios (PR) of CHD with 95% confidence intervals (CI) for the associations between CHD and EHE, adjusted for potentially confounding covariates. There are 1,918,105 infants included in the study, of which 9588 had CHD, with a prevalence rate of 499.9 per 100,000 (95% CI: 489.9, 509.8). We found that all EHE indicators were positively associated with the increased risks of overall CHD, some CHD classes (congenital malformations of cardiac septa, congenital malformations of great arteries, and congenital malformations of great arteries), and some CHD subtypes (atrial septal defect and patent ductus arteriosus). In addition, the PR yielded higher estimates when exposing to EHE95. For instance, the risk of suffering congenital malformations of great arteries was 1.548 (95% CI: 1.401, 1.712) for EHE90 exposure and 1.723 (95% CI: 1.565, 1.898) for EHE95 exposure, respectively. Our study demonstrated that EHE during 2-8 weeks postconception was associated with overall CHD in offspring, particularly atrial septal defects and patent ductus arteriosus. The associations strengthened with the extent and cumulative days of maternal exposure to EHE.

Prevalence of cleft lip and/or cleft palate in Guangdong province, China, 2015-2018: a spatio-temporal descriptive analysis.

OBJECTIVES: This study aimed to investigate the temporal and spatial characteristics of cleft lip and/or palate based on a large-scale birth defect monitoring database. METHODS: Data on perinatal infants and children with cleft lip and/or palate defects from 1 January 2015 to 31 December 2018 in Guangdong province of China were collected. The variables including the demographic data, basic family information (address, education level, etc.), the infant's birth weight, gender and other basic parameters were collected and analysed. RESULTS: During the study period, the prevalence of cleft lip and/or palate was 7.55 per 10 000 perinatal infants. The prevalence of cleft lip, cleft palate and cleft lip and palate were 2.34/10 000, 2.22/10 000 and 2.98/10 000, respectively. The prevalence of cleft lip and/or palate showed a pronounced downward trend, reducing from 8.47/10 000 in 2015 to 6.51/10 000 in 2018. We observed spatial heterogeneity of prevalence of cleft lip and/or palate across the study period in Guangdong. In the Pearl River Delta region, the overall prevalence of cleft lip and/or palate was 7.31/10 000, while the figure (7.86/10 000) was slightly higher in the non-Pearl River Delta region (p<0.05). Concerning infant gender, the prevalence was in general higher in boys than girls (p<0.05). In addition, the higher prevalence was more common in mothers older than 35 years old. For the birth season, infants born in spring tended to have a higher prevalence than those born in other seasons, regardless of the prevalence of cleft lip and palate calculated separately or jointly (p<0.05). The majority of newborns with cleft lip and palate were accompanied by other birth defects. CONCLUSION: This study contributes a better understanding of the characteristics of spatio-temporal trends for birth defects of cleft lip and/or palate in south China.

Congenital anomalies associated with ambient temperature variability during fetal organogenesis period of pregnancy: Evidence from 4.78 million births.

BACKGROUNDS: Evidence for the effects of temperature variability on risk of congenital anomalies is lacking. We aimed to examine the association of temperature variability during fetal organogenesis period (weeks 3-8 post-conception) with major congenital anomalies. METHODS: A retrospective cohort study comprising 4,787,356 singleton live-births and stillbirths in China was performed. We defined two temperature variability indices within gestational week i: the standard deviation (SD) of daily temperature (TVSDi) and the maximum day-to-day temperature difference (TVDi). At 6-week long timescales, we computed the SD of daily temperature (TVSD3-8) and the average value of TVDi (TVD3-8). We matched two temperature variability indices, pollutant exposure levels over entire exposure window and data of each mother-infant pairs. An extended generalized estimating equation log-binomial regression model was constructed to explore their associations after adjusting for individual characters, temperature extremes and air pollutants. Stratified and sensitivity analyses were also performed. RESULTS: 59,571 neonates were registered as major congenital anomalies besides genetic and chromosomal anomalies. At weekly levels, the highest risk estimates of two temperature variability indices occurred at the 5th week for most anomaly groups. All TVSD5, TVD5, and maximum weekly TVSD and TVD were significantly associated with all anomaly groups; with the increment of 1 °C, the estimated risk ratio (RR) and corresponding 95% confidence interval (CI) ranges from 1.03 (1.01-1.05) to 1.19 (1.08-1.31). At 6-week scales, TVSD3-8 and TVD3-8 were associated with most anomaly subgroups. Overall, the strongest associations were estimated for isolated defects among morphology subgroups and cardiac defects among type subgroups. CONCLUSIONS: Exposure to temperature variability during fetal organogenesis period of pregnancy is associated with increased risk of major congenital defects. Our findings provide a research foundation for public health policies, and further mechanism investigation.

Risk Factors for the Development of Intraoperative Hypoxia in Patients Undergoing Nonintubated Video-Assisted Thoracic Surgery: A Retrospective Study from a Single Center.

BACKGROUND Nonintubated video-assisted thoracic surgery (NIVATS) has been demonstrated to be safe and effective in patients. However, the risk factors for intraoperative hypoxia are unclear. This retrospective study aimed to identify the risk factors for the development of intraoperative hypoxia in patients undergoing NIVATS. MATERIAL AND METHODS The study included patients who underwent NIVATS between January 2011 and December 2018. Intraoperative hypoxia was defined as SpO2 ≤93%. Risk factors for hypoxia were identified by binary logistic regression analysis, and the characteristic distribution of patients with and without hypoxia was elaborated. RESULTS Of 2742 included patients, age, anesthesia method, the technical level of surgeons, stair-climbing ability, and type of thoracic procedure were associated with intraoperative hypoxia (P<0.05). The characteristics of patients with hypoxia were older age (P=0.011), higher body mass index and revised cardiac risk index level (P=0.033 and P=0.031), and lower composition of stair-climbing ≥22 m (P<0.001). These patients also had more anatomical lung surgery and mediastinal mass resection (P=0.033) and more epidural anesthesia (P=0.005). The surgeries were more likely to be performed by surgeons with less than 10 years of VATS training (P=0.009) and to have increased intraoperative maximum end-expiratory carbon dioxide partial pressure (P<0.001). These patients had a longer Intensive Care Unit stay (P<0.001), duration of chest-tube drainage (P=0.019), and postoperative hospitalization (P=0.003). CONCLUSIONS The current study suggests that old age and stair-climbing ability of patients, anesthesia method, thoracic procedures, and surgeon experience are risk factors for intraoperative hypoxia in patients undergoing NIVATS.

Prevalence of small for gestational age infants in 21 cities in China, 2014-2019.

Infants who are small for gestational age (SGA) are at increased risk of neonatal and infant death, non-communicable diseases and growth retardation. However, the epidemiological characteristics of SGA remain unclear. We aim to explore the prevalence of SGA and to examine its socioeconomic associations by using data from 21 cities. 10,515,494 single live birth records between 2014 and 2019 from the Guangdong Women and Children Health Information System were included in the study. Descriptive statistical methods were used to analyze the prevalence trend of SGA and its distribution. We also analyze the associations between the prevalence of SGA and per-capita GDP. The prevalence of SGA in Guangdong Province from the years 2014-2019 was 13.17%, 12.96%, 11.96%, 12.72%, 11.45%, 11.30% respectively, and the overall prevalence was 12.28%. The prevalence of term SGA infants in Guangdong Province was 12.50%, which was much higher than that of preterm SGA (7.71%). There was a significant negative correlation between the SGA prevalence and per-capita GDP in 21 cities of Guangdong Province. The level of economic development may affect the prevalence of SGA. The prevalence of SGA in full term infants is significantly higher than in premature infants, suggesting that most SGA infants may be born at a later gestational age.

Impact of the COVID-19 pandemic on intention to use traditional Chinese medicine: A cross-sectional study based on the theory of planned behavior.

OBJECTIVE: Coronavirus disease 2019 (COVID-19) has become an increasingly severe public health emergency. Although traditional Chinese medicine (TCM) has helped to combat COVID-19, public perception of TCM remains controversial. We used the theory of planned behavior (TPB) to identify factors that affect the intention to use TCM. METHODS: A cross-sectional web-based survey of 10,824 individuals from the general public was conducted between March 16 and April 2, 2020. The participants were recruited using a snowball sampling method. Data were collected using a self-administered questionnaire, based on the TPB. The questionnaire consisted of demographic characteristics and TPB structures. Structural equation modeling was used to identify predictors of intention. RESULTS: The results indicated the model explained 77.5% and 71.9% of intention and attitude variance. Intention to use TCM had the strongest relationship with attitude (P < 0.001), followed by past behavior (P < 0.001), subjective norms (P < 0.001) and perceived behavioral control (P < 0.001). Attitudes toward TCM were significantly affected by perceived behavioral control (P < 0.001), subjective norms (P < 0.001) and cognition of TCM (P < 0.001). CONCLUSION: Attitude is a key factor in determining the intention to use TCM, followed by past behaviors, subjective norms and perceived behavioral control. Our results offer important implications for health policy makers to promote the use of TCM.

Association of maternal ozone exposure with term low birth weight and susceptible window identification.

BACKGROUND: Ozone pollution keeps deteriorating in the context of climate change. Maternal ozone exposure may be associated with low birth weight (LBW), but the results are still inconsistent. The identification of the critical exposure windows, a specific period of particular susceptibility during pregnancy, remains unresolved. We aimed to evaluate whether ozone exposure was associated with term LBW and further identify the susceptible exposure windows. METHODS: A retrospective cohort study was conducted in Guangzhou, a megacity in the most populous and economically developed city clusters in China. We included 444,096 singleton live births between January 2015 and July 2017. From 11 fixed stations, we collected daily 1-h maximum and 8-h maximum moving average ozone level (O3-1 h and O3-8 h) and calculated exposures for each participant based on their district of residence during pregnancy. We used traditional Logistic regression to estimate the trimester-specific association between ozone exposure and term LBW, and further estimated monthly- and weekly association by distributed lag models (DLMs) with Logistic regression. Odds ratios (ORs) and 95% confidence intervals (CIs) of term LBW were calculated for an interquartile range (IQR) increase in ozone exposure. Stratified analyses and heterogeneity tests were conducted by maternal age and infant sex. RESULTS: The incidence of term LBW was 1.9%. During the study period, the mean O3-1 h and O3-8 h levels were 112.6 µg/m3 and 84.5 µg/m3, respectively. Increased O3-1 h (IQR: 90 µg/m3) and O3-8 h (73 µg/m3) exposure during the second trimester were associated with increased risk of term LBW. At a monthly level, the term LBW risk was associated with O3-1 h exposure during the 4th-6th month and O3-8 h exposure during the 6th month. By estimating the weekly-specific association, we observed that critical exposure windows were the 15th- 26th gestational weeks for O3-1 h, and the 20th-26th weeks for O3-8 h, respectively. Estimated ORs and 95% CIs ranged from 1.012 (1.000, 1.024) to 1.023 (1.007, 1.039). When examined by subgroups, the effects were present among women ≥ 35 years or < 25 years old and those with female babies. CONCLUSIONS: This study provides compelling evidence that exposure to O3 was associated with increased risk of term LBW, and gestational weeks 15th- 26th was found to be particularly susceptible. These findings provide a research basis for further mechanism examination, public health interventions, and targeted environmental policy-making.

Ambient air pollution and markers of fetal growth: A retrospective population-based cohort study of 2.57 million term singleton births in China.

BACKGROUNDS: Evidence is scarce on the relation between maternal exposure to ambient air pollution during pregnancy and fetal growth in developing countries. Moreover, the current evidence is inconsistent. We aimed to investigate the association of trimester-specific exposure to air pollution with risk of being born small for gestational age (SGA) and birth weight-markers of fetal growth-among Chinese term births. METHODS: This retrospective population-based cohort study consisted of 2,567,457 singleton term live-births from January 1, 2014 to December 31, 2017 across 123 Chinese districts and counties. Personal exposure to ambient air pollutants including carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), particulate matter with aerodynamic diameter < 2.5 µm (PM2.5), and PM10 was assigned using the inverse distance weighting spatial interpolation algorithm. Generalized estimating equations (GEE) logistic regression models were performed to estimate the associations between trimester-specific exposure to air pollution and risk of SGA or low birth weight (LBW), and GEE linear regression to examine the associations between the exposure and term birth weight, adjusting for maternal demographics, maternal cigarette smoking status during pregnancy, mode of delivery, gravidity, gestational age, year and month of conception, neonate's sex, and meteorological factors. Stratified and sensitivity analyses were also performed. RESULTS: When mother exposed to ambient air pollutants over the entire pregnancy, per IQR increment (0.122 mg/m3) in ambient CO concentrations was associated with higher risk of SGA (odds ratio (OR) = 1.04, 95% confidence interval (CI): 1.02, 1.05) and reduced birth weight among term births (-5.95 g, 95% CI: -8.01, -3.89). This association was also pronounced in the second and third trimesters. Term birth weight was negatively associated with per IQR increase of O3 (-3.52 g, 95% CI: -6.23, -0.81), PM2.5 (-5.93 g, 95% CI: -8.36, -3.49) and PM10 (-7.78 g, 95% CI: -10.41, -5.16) during the entire pregnancy, respectively. No significant association was detected between maternal exposure to air pollutants and term LBW. Effect estimates of heterogeneity suggested that maternal age and infant sex modified the impact of air pollution on birth weight. CONCLUSIONS: The findings suggest that maternal exposure to air pollution during pregnancy is adversely affecting fetal growth. Further studies are warranted to integrate these findings and take clinical or public health interventions in pregnancy.

Adverse birth outcomes in Guangdong province, China, 2014-2017: a spatiotemporal analysis of 2.9 million births.

OBJECTIVES: Adverse birth outcomes pose a great threat to the public health and bring a heavy burden of disease in China. A comprehensive examination of the temporal and spatial trends of preterm birth (PTB), low birth weight (LBW) and small for gestational age (SGA) epidemics can provide some elementary information for subsequent aetiological and epidemiological studies. This study aimed to characterise the spatiotemporal features of PTB, LBW and SGA based on a large cohort of live births in China. DESIGN: Spatiotemporal descriptive analysis was performed in Guangdong province, China, from 2014 to 2017. SETTING: Data involving 2 917 098 live births in Guangdong province, China from 2014 to 2017 was collected from Guangdong Birth Certificate System. Information was collected, including the date of birth, gestational age in week, birth weight, sex of the infant, age of the mother and registered residence of the mother. RESULTS: The estimated rate of PTB, LBW and SGA was 4.16%, 4.14% and 12.86%, respectively. For temporal trends, the rates of PTB, LBW and SGA showed seasonal fluctuations, especially for LBW and SGA. In addition, there were regional differences in the rates of PTB, LBW and SGA between the Pearl River Delta and Non-Pearl River Delta regions. From 2014 to 2017, the high rates of PTB and LBW expanded from the Pearl River Delta region to the Non-Pearl River Delta regions. However, compared with the Pearl River Delta region, the rate of SGA was higher in the Non-Pearl River Delta regions on the whole. CONCLUSION: The findings of this study contribute to the understanding of the aetiology and epidemiology of PTB, LBW and SGA in south China.

Birth weight percentiles by sex and gestational age for twins born in southern China.

Mean birth weight of twins is known to be lower than that of singletons, however, southern China lacks a twin-specific birth weight reference. In this paper, we use data from the Birth Certificate System in southern China, collected between January 1st 2014 and December 31st 2017 and including 161,076 twins, to calculate sex- and gestational week-specific birth weight percentiles (the 3rd, 10th, 25th, 50th, 75th, 90th, and 97th). We applied generalized additive models for location, scale and shape (GAMLSS) when calculating the birth weight percentiles, and calculated percentiles for monochorionic and dichorionic twins separately. We next used data collected between Jan 1st 2018 and Apr 30th 2018, encompassing 12,371 live births, to calculate the SGA and LGA ratios using birth weight references in Australia, South Korea and China (based on birth defects surveillance system) and birth weight percentiles calculated in this study. Compared to dichorionic twins, monochorionic twins had lower birth weights at 25 to 42 weeks of gestation. The calculated SGA and LGA ratios were relatively stable compared to the other references.

New birthweight percentiles by sex and gestational age in Southern China and its comparison with the INTERGROWTH-21st Standard.

We first showed the sex- and gestational age (week)-specific birthweight distributions from primiparous and multiparous mothers. Birthweight percentiles were created by using the Lambda Mu Sigma (LMS) method. We established the birthweight percentiles in Southern China and provide clinicians and researchers with up-to-date population norms of birthweight percentiles. Then we use the data from Birth Certificate System between Jan 1st, 2017 and Oct 31st, 2017, which included 1,245,364 live births to calculate SGA and LGA ratio by these three birthweight references- the new INTERGROWTH-21st standard, China's 2015 research standard and our birthweight percentiles. The overall prevalence of SGA estimated by our standards, the China's 2015 research standards and INTERGROWTH-21st standards, were 10.21%, 12.93% and 7.98%, respectively, whereas the overall prevalence of LGA was 9.88%, 4.48% and 8.37%, respectively.

Sample Size for Assessing Agreement between Two Methods of Measurement by Bland-Altman Method.

The Bland-Altman method has been widely used for assessing agreement between two methods of measurement. However, it remains unsolved about sample size estimation. We propose a new method of sample size estimation for Bland-Altman agreement assessment. According to the Bland-Altman method, the conclusion on agreement is made based on the width of the confidence interval for LOAs (limits of agreement) in comparison to predefined clinical agreement limit. Under the theory of statistical inference, the formulae of sample size estimation are derived, which depended on the pre-determined level of α, ß, the mean and the standard deviation of differences between two measurements, and the predefined limits. With this new method, the sample sizes are calculated under different parameter settings which occur frequently in method comparison studies, and Monte-Carlo simulation is used to obtain the corresponding powers. The results of Monte-Carlo simulation showed that the achieved powers could coincide with the pre-determined level of powers, thus validating the correctness of the method. The method of sample size estimation can be applied in the Bland-Altman method to assess agreement between two methods of measurement.

The association between ambient temperature and preterm birth in Shenzhen, China: a distributed lag non-linear time series analysis.

BACKGROUND: A few studies have examined the association between ambient temperature and preterm birth (PTB), and the results have been inconsistent. This study explored the association between ambient temperature and PTB in Shenzhen, China. METHODS: Data of daily singleton PTB, air pollution and meteorological variables from 2005 to 2011 were collected in Shenzhen. A distributed lag non-linear model (DLNM) was used to investigate the association of the low and high temperatures (1st, 5th, 95th, and 99th percentiles) with PTB. RESULTS: The median temperature was 24.5 °C and the 1st, 5th, 95th, and 99th percentiles of daily mean temperatures were 9, 12.5, 29.9 and 30.7 °C, respectively. The prevalence of singleton PTB was 5.61 % in Shenzhen. The association between temperature and PTB was not linear. There was an immediate positive association of low temperature (1st and 5th percentiles) and a negative association of high temperature (95th and 99th percentiles) with PTB. The effect of low temperature 9 °C (1st) on PTB on the current day was stronger than that of 12.5 °C (5th), with a relative risk (RR) of 1.54 (95 % CI: 1.36-1.75) and 1.49 (95 % CI: 1.35-1.63), respectively. The cumulative RR (up to 30 days) of 9 and 12.5 °C was 1.72 (95 % CI: 1.28-2.33) and 1.96 (95 % CI: 1.60-2.39), respectively. The cumulative effects (up to 30 days) of high temperature (95th and 99th percentiles) on PTB were 0.69 (95 % CI: 0.60-0.80) and 0.62 (95 % CI: 0.52-0.74), respectively. The cumulative effect (up to 30 days) of low temperatures on vaginal delivery PTB was lower than that of the cesarean section PTB with an RR of 1.58 (95 % CI: 1.12-2.22) and 1.93 (95 % CI: 1.21-3.08), respectively. CONCLUSIONS: This study suggests that low temperature might be a risk factor, while high temperature might be a protective factor of PTB in Shenzhen.