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[Display omitted] • Aerosol particle phase compositions in HTPs were quantified online for the first time. • Short-lived intermediates during ring opening reactions were observed in gas phase. • Time-mass profile of nicotine release was given within a puff. • Chemical delivery quantity decreased with prolonged puff durations in Close-ended HTPs. To characterize fast and dynamic thermophysical processes of aerosol formation from heated tobacco products (HTPs), a real-time chemical detection and quantification at sub-second time resolution is of great significance. Herein a novel vacuum ultraviolet (VUV) photoionization time-of-flight mass spectrometer (PI-TOFMS) was adapted for on-line chemical analysis of gaseous and particulate aerosol fractions formed from two HTP systems of contrasting designs. The two HTP systems used a battery-powered heating mechanism to heat tobacco rods containing granulated tobacco materials, one puffing air to flow through the tobacco bed and the other with no puffing air going through the tobacco section (termed as open-ended and close-ended, respectively). The on-line PIMS analyzer was able to detect a great number of mass peaks, including nicotine (Nic), glycerin (VG) and propylene glycol (PG) etc in the particulate phase, and flavor components such as 2,3-Butanedione and triethyl citrate in both gaseous and particulate phases. In particular, some short-lived intermediates such as ethenol and propen-2-ol from pyrolysis of the tobacco granules were observed and identified on-line. Nic, VG and PG were quantified with a high time resolution of 0.5 s using their standard calibration curves established with PI-TOFMS. The time-resolved evolving mass profiles of Nic, VG and PG were obtained in near real-time, as well as Nic release rate within a single puff for the first time. In addition, the present results clearly revealed that the change in puffing air flow pathway along the tobacco rod from the open-ended to the close-ended configurations significantly altered the Nic delivery pattern, in which a stable Nic delivery profile in the open-ended HTP at prolonged puff durations was reduced in the close-ended HTP. These findings can be utilized to develop suitable HTPs that could mimic the Nic delivery and hence help smokers to quit smoking. [ABSTRACT FROM AUTHOR]

Background: The optimal threshold of birthweight discordance (BWD) remains controversial. This study aimed to evaluate the associations between BWD at different thresholds and early neonatal outcomes and to assess their predictive accuracy.Methods: This was a retrospective cohort study using a birthweight data with the chorionicity information of 2348 liveborn twin pairs at a gestational age of ≥26 weeks, from 2012 to 2018. The percentage of BWD was calculated by dividing the actual birthweight difference by the weight of the larger twin and multiplying by 100. Outcomes of interest included neonatal intensive care unit (NICU) admission, neonatal respiratory distress syndrome (NRDS), ventilator support and a composite outcome combining major morbidities and neonatal death. Logistic regression models were performed to estimate the association between neonatal outcomes and BWD with different thresholds (≥15.0%, ≥20.0%, ≥25% and ≥ 30%). Generalized estimated equation (GEE) models were used to address intertwin correlation. Restrictive cubic spline (RCS) models were established to draw the dose-response relationship between BWD and the odds ratios of outcomes. Clustered receiver operating characteristic (ROC) curve analyses were performed to assess the predictive accuracy.Results: Of 2348 twin pairs, including 1946 dichorionic twin pairs and 402 monochorionic twin pairs, BWD was significantly associated with NICU admission, regardless of the thresholds used. The incidence of NRDS, ventilator support and the composite outcome were significantly higher when a threshold of ≥20% or greater was chosen. The dose-response relationship showed nonlinear growth in the risk of adverse neonatal outcomes with increasing BWD. ROC analyses showed a low significant AUROC of 0.569 (95% CI: 0.526-0.612) for predicting NICU admission but no significant AUROCs for predicting other outcomes. A BWD of ≥30% provided a moderate increase in the likelihood of NICU admission [positive likelihood ratio (LR+) = 5.77].Conclusion: Although BWD is independently associated with adverse neonatal outcomes, it is not a single predictor for neonatal outcomes given the weak discriminative ability to predict neonatal outcomes. A cutoff of 30% is more practical for risk stratification among twin gestations. [ABSTRACT FROM AUTHOR]

Introduction: Complete placenta previa (CPP) is one of the most problematic types of abnormal placenta, which is further complicated by placenta accreta or percreta that can unexpectedly lead to catastrophic blood loss, infection, multiple complications, emergency hysterectomy, and even death. The present study aimed to assess the efficacy of random placenta margin incision in controlling intraoperative and total blood loss during cesarean section for CPP women. Methods: A prospective cohort study, including a total of 100 consecutive pregnant women with CPP, was performed at a tertiary university-affiliated medical center between March 2016 and July 2017. All of them underwent random placenta margin incision, and intraoperative and total blood loss were analyzed. Through antenatal diagnosis using color Doppler, women were further divided into abnormally invasive placenta (AIP) and non-AIP groups, and anterior and posterior placenta groups. The protocol was registered with the Clinical Trial Registry under registration number NCT02695069. Results: Mean maternal age and gestational age at delivery were 32.26 ± 5.03 years old and 36.21 ± 2.07 weeks, respectively. Total duration of the surgical procedure time was 52.50 (42.43-64.00) min. Median estimated intraoperation blood loss was 746.43 (544.44-1092.86) ml. Total blood loss was 875.00 (604.50-1196.67) ml, and 38 (38.0%) had post-partum hemorrhage. The change from baseline in the median hemoglobin level was -0.33 (6.00-13.20). No women underwent hysterectomy due to massive hemorrhage during the study period. No women had an intraoperative urinary bladder injury, postoperative wound infection, and required relaparotomy, owing to intra-abdominal bleeding. The median hospitalization time was 5.41 (4.18-7.58) d. Conclusion: The random placenta margin incision may be a potentially valuable surgical procedure to control the volumes of intraoperative and postoperative blood loss and reduce the incidence of postpartum hemorrhage among women with complete placenta previa. [ABSTRACT FROM AUTHOR]

Organic aerosol (OA) particles, as important parts of biomass pyrolysis tar, have a negative effect on the quality of pyrolysis oil by coking, while their physical and chemical properties are rarely reported. In this work, the flash and fast pyrolysis of lignocellulosic biomass and its individual components (cellulose, xylan and lignin) were conducted in a microfluidized-bed reactor (MFBR) and a U-shaped fixed-bed reactor (U-FBR), respectively. A vacuum ultraviolet photoionization aerosol mass spectrometer (VUV-PI-AMS) was used for the online characterization of chemical components of OA particles, and their size distributions were determined by a scanning mobility particle size spectrometer (SMPS). The effect of feedstock types, pyrolysis temperatures and heating rates on the properties of OA particles from biomass pyrolysis was investigated and discussed. The experimental results show that the chemical components of OA particles from biomass pyrolysis dominated by carboxylic acids, furans, pyrans, lignin monomers and oligomers. The sizes of biomass-derived OA particles center at about 110 and 240 nm for the flash and fast pyrolysis, respectively. All detected OA particles exist in the form of liquid state. The high heating rate would improve the formation of lignin oligomers in particle phase. • The properties of organic aerosol (OA) from biomass pyrolysis were studied. • MFBR was used to obtain the OA from flash pyrolysis of biomass. • The chemical characterization of OA was conducted by online VUV-PI-AMS. • The effect of pyrolysis conditions on the formation of OA was discussed. [ABSTRACT FROM AUTHOR]

Cigarette smoke and ozone (O 3) are two main pollutants in indoor environments and their mutual reaction can generate substantial detrimental substances having synergistic influences on the environment and human health. The aging process of cigarette smoke in the atmosphere is mainly gone through ozonolysis reaction attracting increasing attention in recent years. Herein, the ozonolysis reaction of cigarette smoke with indoor O 3 concentrations has been investigated in a Teflon chamber. The gas- and particle-phases of cigarette smoke are divided and their individual ozonolysis process can generate ultrafine particles (UFPs) with high number concentrations. The chemical compositions of the gas- and particle-phases of cigarette smoke as well as their nascent UFPs are measured and their differences during the ozonolysis have been clearly observed with vacuum ultraviolet (VUV) photoionization mass spectrometry. In particular, several representative key species of cigarette smoke, i.e. , the gas-phase furan and 2,5-dimethylfuran and the particle-phase nicotine, as well as their ozonolysis products are definitely identified and play an important role in the nucleation formation of UFPs. Their ozonolysis reaction mechanisms are also discussed. In addition, this work demonstrates that the ozonolysis of the particle-phase of cigarette smoke contributes more UFPs than that of the gas-phase. [Display omitted] • Ozonolysis reactions of cigarette smoke with indoor O 3 concentrations investigated. • Gas- and particle-phases of smoke generate ultrafine particles (UFPs) via ozonolysis. • Ozonolysis of particle-phase of smoke generates more UFPs than that of gas-phase. • Key species of smoke and their ozonolysis products are identified in mass spectra. [ABSTRACT FROM AUTHOR]

Introduction: This study aimed to evaluate the preterm birth and additional perinatal outcomes between spontaneous and in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) dichorionic-diamnionic (DCDA) twin pregnancies.Material and Methods: This retrospective cohort study was conducted in a tertiary university-affiliated medical center. All women with DCDA twin pregnancies were considered for inclusion. The primary outcome of interest was preterm birth <37 weeks of gestation and secondary outcomes included spontaneous preterm birth, iatrogenic (induced) preterm birth, gestational diabetes mellitus, pregnancy-induced hypertensive disorder, preeclampsia, preterm premature rupture of membranes (PPROM), intrahepatic cholestasis of pregnancy, placenta previa, neonatal intensive care unit (NICU) admission, birthweight discordance, small for gestational age, neonatal respiratory distress syndrome, ventilator support, and perinatal death and/or severe morbidity. These outcomes were compared between IVF/ICSI and spontaneous twin pregnancies. Multivariable logistic regressions were used to adjust for confounders. General estimated equation models were used to address intertwin correlation.Results: A total of 1297 twin pregnancies, including 213 spontaneous and 1084 IVF/ICSI DCDA pregnancies, met the inclusion criteria. Women with IVF/ICSI pregnancies were older and had higher body mass index, adherence with prenatal care and proportion of nulliparity. After adjustment for confounders, IVF/ICSI pregnancies were associated with a slight increase in preterm birth <37 weeks of gestation (adjusted odds ratio [aOR] 1.72; 95% CI 1.24-2.39), iatrogenic preterm birth <37 weeks of gestation (aOR 1.41; 95% CI 1.00-1.97) as well as NICU admission (aOR 1.34; 95% CI 1.00-1.80). IVF/ICSI pregnancies were associated with a decrease in PPROM (aOR 0.64; 95% CI 0.42-0.99). There were no differences between IVF/ICSI and spontaneous DCDA pregnancies in terms of spontaneous preterm birth, gestational diabetes mellitus, pregnancy-induced hypertensive disorder, preeclampsia, intrahepatic cholestasis of pregnancy, placenta previa, birthweight discordance, small for gestational age, neonatal respiratory distress syndrome, ventilator support, and perinatal death and/or severe morbidity.Conclusions: IVF/ICSI DCDA twin pregnancies were associated with a slight increase in preterm birth <37 weeks of gestation, iatrogenic preterm birth <37 weeks of gestation, and NICU admission but with a decrease in PPROM. Other outcomes were comparable between IVF/ICSI and spontaneous DCDA twin pregnancies. Multicenter studies with adequate power remain warranted. [ABSTRACT FROM AUTHOR]

Background: Velamentous cord insertion (VCI) has been proposed to be associated with some specific complications among monochorionic (MC) twin pregnancies. This meta-analysis and systematic review aims to determine the role of VCI in MC twin pregnancies.Methods: The PubMed, Embase and Web of Science databases and reference lists were searched for relevant studies. Outcomes of interest included twin-to-twin transfusion syndrome (TTTS), birthweight discordance (BWD) and selective intrauterine growth restriction (sIUGR). The methodological quality of the included studies was assessed by using the Newcastle-Ottawa Scale. The pooled results were calculated by means of a random or fixed effect model to obtain odds ratio with 95% confidential interval (CI). Subgroup analyses were utilized to detect the sources of heterogeneity.Results: Twenty studies were eligible for inclusion. The pooled result suggested a significant association between VCI and TTTS (OR, 1.542; 95% CI, 1.116-2.129) with a moderate level of heterogeneity (Q test: p = .024; I2 = 50.2%). Subgroup analysis reported single-center study, methodological quality and exclusion of laser-coagulated TTTS as the sources of heterogeneity. Another analysis revealed an increased risk of BWD among twin pregnancies with VCI (OR, 2.945; 95% CI, 2.176-3.984) with a low heterogeneity (Q test: p = .347; I2 = 10.5%). None of study level characteristics was found to be an influencing factor. Three studies reporting on sIUGR suggested a significant association between VCI and sIUGR.Conclusions: The meta-analysis and systematic review suggests an association between VCI and BWD and sIUGR. However, the association between VCI and TTTS may be overestimated and high-quality studies with a representative sample are needed in further research. [ABSTRACT FROM AUTHOR]

Background: Pathological skin scars, caused by cesarean section, affected younger mothers esthetically and psychosocially and to some extent frustrated obstetricians and dermatologists. Umbilical cord mesenchymal stem cells (UC-MSCs), as a population of multipotent cells, are abundant in human tissues, providing several possibilities for their effects on skin scar tissues. Herein, we performed a randomized, double-blind, placebo-controlled, three-arm clinical trial, aiming to assess the efficacy and safety of UC-MSCs in the treatment of cesarean section skin scars among primiparous singleton pregnant women. Methods: Ninety primiparous singleton pregnant women undergoing elective cesarean section were randomly allocated to receive placebo, low-dose (3 × 106 cells), or high-dose (6 × 106 cells) transdermal hydrogel UC-MSCs on the surface of the skin incision. The primary outcome was cesarean section skin scars followed after the sixth month, assessed by the Vancouver Scar Scale (VSS). Results: All the participants completed their trial of the primary outcome according to the protocol. The mean score of estimated total VSS was 5.52 in all participants at the sixth-month follow-up, with 6.43 in the placebo group, 5.18 in the low-dose group, and 4.71 in the high-dose group, respectively. No significant difference was found between-group in the mean scores for VSS at the sixth month. Additional prespecified secondary outcomes were not found with significant differences among groups either. No obvious side effects or adverse effects were reported in any of the three arms. Conclusion: This randomized clinical trial showed that UC-MSCs did not demonstrate the effects of improvement of cesarean section skin scars. Trial registration: ClinicalTrials.gov identifier, NCT02772289. Registered on 13 May 2016. [ABSTRACT FROM AUTHOR]

Objective: No recommendations are available for gestational weight gain (GWG) in underweight women with twin pregnancies. We aimed to evaluate whether underweight women with twin pregnancies should gain more weight than normal-weight women in order to optimize perinatal outcomes.Study Design: This retrospective cohort study compared the GWG and perinatal outcomes among normal-weight and underweight women who gave birth to viable twins between 2015 and 2018 at the Maternal and Child Health Hospital in Foshan, China. Gestational weight gain (GWG) was categorized as adequate or inadequate GWG, based on the US Institute of Medicine 2009 guidelines for normal-weight women (≥ 0.46 kg/week). The outcomes of interest included spontaneous preterm birth (sPTB) <37 weeks, <35 and <32 weeks, small for gestational age (SGA), gestational hypertensive disorder (GHD), gestational diabetes mellitus (GDM), birth weight discordance (BDW) ≥20%, neonatal intensive unit (NICU) admission and neonatal respiratory distress syndrome (NRDS). Propensity score matching (PSM, in a 1:1 ratio) was utilized to minimize the effects of confounders on the differences in the two cohorts. Multivariable logistic models were also used to verify the results from PSM analysis.Results: There were 475 normal-weight and 111 underweight women included in the analysis. Our results suggested that the incidence of adequate GWG was comparable between underweight and normal-weight women (37.5% vs. 45.1%, P = 0.141). The prevalence of GDM was significantly lower among underweight women (9.9%) than among normal-weight women (20.4%) (P = 0.010). There was no evidence of differences in other perinatal outcomes between the two groups. 102 underweight women and 102 normal-weight women were included in PSM analyses. There was a lower incidence of GDM in underweight women than in normal-weight women, but the difference was not significant (9.8% vs. 18.6%, P = 0.071). No evidence of any differences in the other outcomes, including sPTB, GHD, BWD≥20%, SGA, NICU admission and NRDS, was found between the underweight and normal-weight women. Multivariable logistic regression models yielded similar results.Conclusions: For Chinese twin pregnant women with twin pregnancies, our data does provide evidence to suggest underweight women need to gain more weight than normal-weight women to optimize perinatal outcomes. Future studies with larger number of underweight women with twin gestations are warranted to establish an optimal range of GWG. [ABSTRACT FROM AUTHOR]

This retrospective cohort study aimed to investigate the effect of placental location on birthweight discordance among diamniotic-dichorionic twin pregnancies. Medical records and sonographic reports of 978 diamniotic-dichorionic twin pregnancies delivered at Foshan Maternal and Fetal Health Hospital were reviewed. Pregnancies with congenital malformation, intrauterine death or placenta previa were excluded. The placental location for each twin was determined by last sonographic examination before delivery, and the pregnancies were grouped by different versus same placental location in each pregnancy. Maternal and fetal characteristics were summarized. The primary outcome of interest was birthweight discordance (BWD) ≥20%, and secondary outcomes included small for gestational age (SGA) as a binary outcome and mean value and absolute difference in birthweight as continuous outcomes. Student's t test and the chi-square test were used for univariate analyses, while multivariate regressions were used to adjust for confounders. General estimated equation (GEE) models were used to address the correlation between fetuses when assessing SGA. A total of 866 eligible subjects were included in the analysis. In total, 460 pregnancies had placentas with different locations, and 406 had placentas with same locations. The gestational age at delivery was slightly younger in the same placental location group than in the different placental location group (35.8 ± 0.1 vs. 36.1 ± 0.1 weeks, P = 0.067). Other maternal and fetal characteristics were comparable between the two study groups. There was no significant difference in BWD ≥20% (aOR = 1.06; 95% CI: 0.71–1.59) or SGA (aOR = 1.32; 95% CI: 0.76–2.28) between the same and different placental location groups. Neither the mean value nor the absolute difference in birth weight was associated with placental location combination (P = 0.478 and P = 0.162, respectively). In conclusion, discordant birthweight is not affected by same location of diamniotic-dichorionic placentas. [ABSTRACT FROM AUTHOR]

Background: Gestational weight gain (GWG) has implications for perinatal outcomes, the guidelines for maternal weight gain, however, remain understudied among twin pregnancies. This study aimed to assess the associations between perinatal outcomes and GWG among twin pregnancies, based on the US institute of Medicine (IOM) 2009 guidelines.Methods: A retrospective cohort study of pregnant women with viable twins ≥26 weeks of gestation, was conducted in Foshan, China, during July 2015 and June 2018. Maternal BMI was categorized based on Chinese standard and GWG was categorized as below, within and above the IOM 2009 recommendations. Underweight women were excluded for analysis. Perinatal outcomes were compared among these groups. To assess the independent impact of GWG on the perinatal outcomes, conventional multivariable regression and general estimated equation (GEE) were utilized for maternal outcomes and neonatal outcomes, respectively.Results: A total of 645 mothers with twin pregnancies were included, of whom 15.0, 41.4 and 43.6% gained weight below, within and above guidelines, respectively. Compared to weight gain within guidelines, inadequate weight gain was associated with increased risks in spontaneous preterm birth < 37 weeks (aOR:3.55; 95% CI: 1.73-7.28) and < 35 weeks (aOR:2.63; 95% CI: 1.16-5.97). Women who gained weight above guidelines were more likely to have gestational hypertension disorder (aOR: 2.36; 95% CI: 1.32-4.21), pre-eclampsia (aOR: 2.59; 95% CI: 1.29-5.21) and have fetuses weighted >90th percentile and less likely to have fetuses weighted < 2500 g and < 1500 g.Conclusions: Maintenance of gestational weight gain within the normal range could decrease the risk of adverse perinatal outcomes. However, the causality between pre-eclampsia and gestational weight gain requires further investigations. [ABSTRACT FROM AUTHOR]

Background: Cesarean delivery has already become a very common method of delivery around the world, especially in low-income countries. Hypertrophic scars and wound infections have affected younger mothers and frustrated obstetricians for a long time. Mesenchymal stem cells (MSCs) have strong potential for self-renewal and differentiation to multilineage cells. Previous studies have demonstrated that MSCs are involved in enhancing diabetic wound healing. Therefore, this study is designed to investigate the safety and efficacy of using MSCs in the treatment of Cesarean section skin scars.Methods: This trial is a prospective, randomized, double-blind, placebo-controlled, single-center trial with three parallel groups. Ninety eligible participants will be randomly allocated to placebo, low-dose (transdermal hydrogel MSCs; 3 × 106 cells) or high-dose (transdermal hydrogel MSCs; 6 × 106 cells) groups at a 1:1:1 allocation ratio according to a randomization list, once a day for six consecutive days. Study duration will last for 6 months, comprising a 1 week run-in period and 24 weeks of follow-up. The primary aim of this trial is to compare the difference in Vancouver Scar Scale rating among the three groups at the 6th month. Adverse events, including severe and slight signs or symptoms, will be documented in case report forms. The study will be conducted at the Department of Obstetric of Southern Medical University Affiliated Maternal & Child Health Hospital of Foshan.Discussion: This trial is the first investigation of the potential for therapeutic use of MSCs for the management of women's skin scar after Cesarean delivery. The results will give us an effective therapeutic strategy to combat Cesarean section skin scars, even with uterine scarring.Trial Registration: ClinicalTrials.gov, NCT02772289 . Registered on 10 May 2016. [ABSTRACT FROM AUTHOR]