Prevalence and influencing factors of anemia among pregnant women across first, second and third trimesters of pregnancy in monitoring areas, from 2016 to 2020: a population-based multi-center cohort study.

OBJECTIVE: To assess the prevalence of anemia among pregnant women across their entire pregnancy and the factors affecting it in the monitoring areas. METHODS: A total of 108,351 pregnant women who received antenatal health care and delivered from January 1, 2016 to December 31, 2020 in 15 monitoring counties of 8 provinces in the Maternal and Newborn Health Monitoring Program (MNHMP) of National Center for Women and Children's Health (NCWCH) were selected as the study subjects. The anemia status among the subjects across their first, second and third trimester of pregnancy and the influencing factors were analyzed. RESULTS: From 2016 to 2020, the prevalence of anemia at any stage during pregnancy in the monitoring areas was 43.59%. The prevalence of anemia among pregnant women across all three trimesters was 3.95%, and the prevalence of mild and moderate-to-severe anemia was 1.04% and 2.90%, respectively. Protective factors were living in the northern area (OR = 0.395) and being a member of an ethnic minority (OR = 0.632). The risk factors were residing in rural areas (OR = 1.207), with no more than junior high school education (OR = 1.203), having ≥ 3 gravidities (OR = 1.195) and multiple fetuses (OR = 1.478). CONCLUSIONS: Although the prevalence of anemia among pregnant women across all trimesters in the monitoring area was low, the severity of anemia was high. Since the prevalence of anemia among pregnant women across their entire pregnancy in the monitoring area is affected by many different factors, more attention should be paid to pregnant women living in rural areas, with low literacy, ≥ 3 gravidities and multiple fetuses for early intervention.

Increased risk of preterm birth due to heat exposure during pregnancy: Exploring the mechanism of fetal physiology.

BACKGROUND: Heat exposure during pregnancy can increase the risk of preterm birth (PTB) through a range of potential mechanisms including pregnancy complications, hormone secretion and infections. However, current research mainly focuses on the effect of heat exposure on pathophysiological pathways of pregnant women, but ignore that maternal heat exposure can also cause physiological changes to the fetus, which will affect the risk of PTB. OBJECTIVE: In this study, we aimed to explore the mediating role of fetal heart rate (FHR) in the relationship between maternal heat exposure and PTB incidence. METHODS: We assigned heat exposure to a multi-center birth cohort in China during 2015-2018, which included all 162,407 singleton live births with several times FHR measurements during the second and third trimesters. We examined the associations between heat exposure, FHR and PTB in the entire pregnancy, each trimester and the last gestational month. The inverse odds ratio-weighted approach applied to the Cox regression was used to identify the mediation effect of heat exposure on PTB and its clinical subtypes via FHR. FINDINGS: Exposure to heat significantly increased the risk of PTB during the third trimester and the entire pregnancy, hazard ratios and 95 % CIs were 1.266 (1.161, 1.379) and 1.328 (1.218, 1.447). Heat exposure during the third trimester and entire pregnancy increased FHR in the third trimester by 0.24 bpm and 0.14 bpm. The proportion of heat exposure mediated by FHR elevation on PTB and its subtype ranged from 3.68 % to 24.06 %, with the significant mediation effect found for both medically indicated PTB and spontaneous PTB. CONCLUSIONS: This study suggests that heat exposure during pregnancy has an important impact on fetal health, and FHR, as a surrogate marker of fetal physiology, may mediate the increased risk of PTB caused by extreme heat. Monitoring and managing physiological changes in the fetus would constitute a promising avenue to reduce adverse birth outcomes associated with maternal heat exposure.

Exploration of the preterm birth risk-related heat event thresholds for pregnant women: a population-based cohort study in China.

Background: Heat events increase the risk of preterm birth (PTB), and identifying the risk-related event thresholds contributes to developing early warning system for pregnant women and guiding their public health response. However, the event thresholds that cause the risk remain unclear. We aimed to investigate the effects of heat events defined with different intensities and durations on PTB throughout pregnancy, and to determine thresholds for the high-risk heat events. Methods: Using a population-based birth cohort data, we included 210,798 singleton live births in eight provinces in China during 2014-2018. Daily meteorological variables and inverse distance weighted methods were used to estimate exposures at a resolution of 1 km × 1 km. A series of cut off temperature intensities (50th-97.5th percentiles, or 18 °C-35 °C) and durations (at least 1, 2, 3, 4 or 5 consecutive days) were used to define the heat events. Cox regression models were used to estimate the effects of heat events on PTB in various gestational weeks during the entire pregnancy, and event thresholds were determined by calculating population attributable fractions. Findings: The hazard ratios of heat event exposure on PTB ranged from 1.07 (95% CI: 1.00, 1.13) to 1.43 (1.15, 1.77). Adverse effects of heat event exposure were prominently detected in gestational week 1-4, week 21-32 and the four weeks before delivery. The heat event thresholds were determined to be daily maximum temperature at the 90th percentile of the distribution or 30 °C lasting for at least one day. If pregnant women were able to avoid the heat exposures from the early warning systems triggered by these thresholds, approximately 15% or 17% of the number of total PTB cases could have been avoided. Interpretation: Exposure to heat event can increase the risk of PTB when thermal event exceeds a specific intensity and duration threshold, particularly in the first four gestational weeks, and between week 21 and the last four weeks. This study provides compelling evidence for the development of heat-health early warning systems for pregnant women that could substantially mitigate the risk of PTB. Funding: National Key R&D Program of China (No. 2018YFA0606200), National Natural Science Foundation of China (No. 42175183), Sanming Project of Medicine in Shenzhen (No. SZSM202111001).

c-Met is a chimeric antigen receptor T-cell target for treating recurrent nasopharyngeal carcinoma.

BACKGROUND AIMS: Radiation therapy is the standard treatment for patients with nasopharyngeal carcinoma (NPC), but relapse occurs in 10% to 20% of patients. The treatment of recurrent nasopharyngeal carcinoma (rNPC) remains challenging. Chimeric antigen receptors (CAR)-T-cell therapy has achieved good outcomes in the treatment of leukemia and seems to be a promising therapeutic strategy for solid tumors. c-Met has been found to be highly expressed in multiple cancer types, and the activation of c-Met leads to the proliferation and metastasis of cancer cells. However, the expression of c-Met in rNPC tissues and whether it can be used as a target for CAR-T therapy in rNPC remain to be investigated. METHODS: We detected the expression of c-Met in 24 primary human rNPC tissues and three NPC cell lines and constructed two different antibody-derived anti-c-Met CARs, namely, Ab928z and Ab1028z. To estimate the function of these two different c-Met-targeted CAR-T cells, CD69 expression, cytotoxicity and cytokine secretion of CAR-T cells were assessed after coculture with target cells. A cell line-derived xenograft mouse model also was used to evaluate these two anti-c-Met CAR-T cells. Furthermore, we determined whether combination with an anti-EGFR antibody could promote the antitumor effect of CAR-T cells in a patient-derived xenograft mouse model. RESULTS: High c-Met expression was detected in 23 of 24 primary human rNPC tissues by immunohistochemistry staining and in three NPC cell lines by flow cytometry. Ab928z-T cells and Ab1028z-T cells showed significantly upregulated expression of CD69 after coculture with targeted cells. However, Ab1028z-T cells showed superior cytokine secretion and antitumor activity. Furthermore, Ab1028z-T cells effectively suppressed tumor growth compared with control CAR-T cells, and the combination with nimotuzumab further enhanced the tumor-clearing ability of Ab1028z-T cells. CONCLUSIONS: We found that c-Met is highly expressed in rNPC tissues and confirmed its potential as a CAR-T target for rNPC. Our study provides a new idea for the clinical treatment of rNPC.

Effects of gestational ambient extreme temperature exposures on the risk of preterm birth in China: A sibling-matched study based on a multi-center prospective cohort.

BACKGROUND: Previous epidemiological findings on extreme temperature and preterm birth (PTB) were heterogeneous, especially for extreme cold exposure. Measured and unmeasured individual-level factors such as genetic factors or lifecourse exposures may constitute important contributors but have not been addressed. OBJECTIVES: We aimed to examine the association of gestational heat and cold exposure with PTB using a novel sibling-matched study. METHODS: Based on a multi-center population-based birth cohort across 16 counties in China, we included 10,826 sibling pairs born from March 2013 to December 2018. Conditional logistic and Cox Proportional Hazard regression models were used to estimate the effects of heat and cold exposure on PTB in each trimester, one and four weeks before delivery and the entire pregnancy. We also tested the heterogeneity in the association of temperature with PTB between siblings. FINDINGS: Exposure to heat during the third trimester and the entire pregnancy increased the risk of PTB. For heat (> 90th) defined with mean temperature, the odds ratios were 2.32 (1.63, 3.30) and 3.19 (2.22, 4.58), respectively. Cold exposure (< 10th) during the first, the third, and the entire pregnancy was associated with a higher PTB risk, with ORs (95%CIs) of 2.04 (1.43, 2.90), 3.13 (2.14, 4.58), and 4.26 (2.94, 6.19), respectively. We found slightly stronger associations of heat exposure during the entire pregnancy with the firstborn PTB, and stronger associations of cold exposure during one week and four weeks before delivery with secondborn PTB. CONCLUSIONS: Using a sibling-matched study, we took into account some mother-level unobserved confounding. Our research strengthens the evidence that gestational exposure to heat and cold increases the risk of PTB. Our findings may have important implications for improving the health of newborns in the context of climate change.

Relationship between Maternal Postpartum Intention to Breastfeed and Actual Breastfeeding Duration - Four Provinces, China, 2015-2017.

What is already known about this topic?: Several studies have reported that maternal antenatal intention to breastfeed is a strong predictor of actual breastfeeding duration. However, little research has investigated whether maternal postpartum intention also extends breastfeeding duration. What is added by this report?: Maternal postpartum intention to breastfeed was a protective factor for extending actual breastfeeding duration after controlling potential confounders. What are the implications for public health practice?: It is crucial to address and promote intrinsic and extrinsic factors that influence a mother's intention to breastfeed after delivery, thereby extending the actual breastfeeding duration.

Incidence and Risk Factors of Hypertensive Disorders of Pregnancy - 8 Provinces, China, 2014-2018.

What is already known about this topic? As a major cause of maternal and neonatal mortality and morbidity, hypertensive disorders of pregnancy (HDP) are a global public health problem affecting maternal and children's health. What is added by this report?The incidence of HDP was 6.40% among 277,632 pregnant women. With the progress of pregnancy, the proportion of pregnant women with high normal blood pressure (BP) and the incidence of HDP increased gradually. The incidence of HDP increased with pregnancy age, body mass index, and BP of pregnant women during first trimester. What are the implications for public health practice? To reduce the incidence of HDP effectively, we should pay more attention to older women who plan to become pregnant, measures should be taken to control BP and weight in pre-pregnancy.

The Distribution of Pregnant Women with Different Pregnancy Risks - 4 Cities, China, 2019.

SUMMARY: What is already known on this topic? Based on different pregnancy risk levels, the implementation of the "Five-Color Management" for pregnant women can prevent adverse pregnancy outcomes and ensure the safety of mothers and infants. What is added by this report? The proportions of being multipara and of advanced maternal age in the 4 cities (Beijing, Chengdu, Shenzhen, and Wuhan) were 47.4% and 13.3%, respectively. The proportions of "Yellow and above" pregnancy risk ranged from 54.5% to 65.0% and ranged from 7.4% to 16.3% for "Orange and above" pregnancy risk. Among women with "Orange and above" pregnancy risk, most of them gave birth in public tertiary institutions (71.8%-79.4%). What are the implications for public health practice? The implementation of the "Five-Color Management" for pregnant women with different pregnancy risks should be strengthened, especially those with "Orange and red" pregnancy risk who should be hospitalized for delivery in tertiary medical institutions if they have conditions.

Current status of antenatal care of pregnant women-8 provinces in China, 2018.

BACKGROUND: Antenatal care (ANC) played a crucial role in ensuring maternal and child safety and reducing the risk of complications, disability, and death in mothers and their infants. The objective of this study was to evaluate the current status of ANC emphasizing the number, timing, and content of examinations on a national scale. METHODS: The data was collected from maternal and newborn's health monitoring system at 8 provinces in China. After ethical approval, all pregnant women registered in the system at their first prenatal care visit, we included 49,084 pregnant women who had delivered between January 1, 2018 and December 31, 2018. Descriptive statistics of all study variables were calculated proportions and chi-square for categorical variables. RESULTS: Of the 49,084 women included in this study, the mean number of ANC visits was 6.95 ± 3.45. By percentage, 78.79% women received ANC examinations at least five times, 39.93% of the women received ANC examinations at least eight times and 16.66% of the women received ANC examinations at least 11 times. The proportion of first ANC examination in first trimester was 61.87%. The percentage of normative ANC examinations and the percentage of qualified ANC examinations were 30.98 and 8.03% respectively. Only 49.40% of the total women received all six kinds of examination items in first ANC examination: 91.47% received a blood test, 91.62% received a urine test, 81.56% received a liver function examination, 80.52% received a renal function examination, 79.07% received a blood glucose test, and 86.66% received a HIV/HBV/syphilis tests. 50.85% women received the first ANC examination in maternal and child health care (MCH) institutions, 14.07% in a general hospital, 18.83% in a township hospital, 13.15% in a community health services center, and 3.08% in an unspecified place. The proportion of women who received each of the ANC examination items in community health services center was the highest, but that in the MCH institutions was the lowest. CONCLUSIONS: There is a big difference between the results of this study and the data in official reports, this study found the current status of antenatal care is not optimal in China, findings from this study suggest that the systematization, continuity and quality of ANC examinations need to be improved.

Reference ranges and trajectories for blood pressure in pregnancy: findings from a follow-up study based on China Maternal and Newborn's Health Monitoring System.

Objectives: This study aimed to establish normal blood pressure reference ranges across gestation and maternal characteristics.Methods: We conducted a follow-up study including 29,200 Chinese normal pregnant women. Multilevel restrictive cubic spline models were used to calculate normal blood pressure reference ranges among all population and stratified groups.Results: In all normal pregnancies, the normal reference range of systolic blood pressure were 93.94-118.74 mmHg(2.5th-97.5th) and 97.35-124.63 mmHg at 12 and 37 weeks gestation, respectively while 58.79-74.21 mmHg and 59.19-78.25 mmHg were for diastolic blood pressure at 12 and 37 weeks gestation, which differed in subgroups stratified by prepregnancy body mass index and maternal age.Conclusion: This study provides evidence for blood pressure management in Chinese pregnant women.

Prevalence and Risk Factors of Anemia of Pregnant Women - 6 Provinces in China, 2014-2018.

What is already known about this topic? Anemia during pregnancy is a global public health problem affecting both maternal and children's health. The "National Nutrition Plan (2017-2030)" and "Healthy China Action (2019-2030)" issued by the State Council of China in 2017 and 2019, respectively, specified nutrition targets: by 2030, the anemia rate in pregnant women should be reduced to less than 10%. The anemia prevalence of pregnant women reported by the Chinese Nutrition and Health Surveillance in 2006 and 2010-2012 was 42.0% and 17.2%, respectively. What is added by this report? Past surveillance in 2010-2012 did not divide pregnant women by gestation week, and the sample size was only 4,315 cases. In this study, the information of 206,753 registered pregnant women from their first antenatal care (ANC) examination to childbirth was collected from 2014 to 2018. The overall prevalence of anemia among pregnant women was 41.98%. What are the implications for public health practice? The overall prevalence of anemia among pregnant women in the monitoring areas was high, far from the target of 10%. Anemia remains a serious health problem among pregnant women in China. It is urgent to develop effective strategies and take measures to reduce the prevalence of anemia in China.

The Impact of New Adjustments to the Family Planning Policy on the Number of Live Births in Four Developed Urban Areas - China, 2013-2019.

What is already known on this topic? Due to shifting circumstances in China, the government has adjusted the child-bearing policy to allow couples to have a second child. This has affected the total number of live births, especially in more developed urban areas. What is added by this report? The total number of live births in the 4 monitoring cities including Chengdu, Wuhan, Shenzhen, and Beijing during 2014-2019 increased by 33.0%, 20.3%, 10.7%, and 8.2%, respectively. From 2014 to 2017, the proportion of total live births that were policy related increased in each city: Chengdu (2.0% to 35.0%), Wuhan (1.0% to 25.1%), Shenzhen (0.6% to 39.4%), and Beijing (3.1% to 30.2%). What are the implications for public health practice? Our results showed that the implementation of the new adjusted family planning policy alleviated the downward trends in total live births and is unlikely to lead a baby boom as estimated by previous studies.

Gestational Weight Gain Charts by Gestational Age and Body Mass Index for Chinese Women: A Population-Based Follow-up Study.

BACKGROUND: Establishment of an unbiased association between gestational weight gain (GWG) and perinatal health is urgently needed in China, which has the largest population in the world. Our study aimed to create weight-gain-for-gestational-age charts using early pregnancy body mass index (BMI) to present selected percentiles of GWG in China. METHODS: A population-based follow-up study was conducted based on the Maternal and Newborn Health Monitoring System, which recruited 132,835 pregnant women between October 2013 and September 2016 in 12 districts/counties of 6 provinces in China. Multilevel analyses and restricted cubic splines were performed to model the longitudinal repeated maternal weight gain measurements and obtain smoothed curves for GWG. The internal and external validation of each model was also assessed. RESULTS: To develop models of GWG, 34,288 women were included. Smoothed percentiles of GWG in the 3rd, 10th, 50th, 90th, and 97th percentiles were estimated for each week of gestation. The median figures for GWG were 15.0 kg, 14.4 kg, 13.5 kg, and 12.1 kg in underweight, normal weight, overweight, and obese women, respectively, at 40 weeks. Of all the weight measurements, more than 70% and 95% fell within the expected 1 to 2 standard deviations, respectively. To accomplish external validation of the models, 20,458 women were included. The specificities of measurements in the 5th, 10th, 15th, 25th, 75th, 85th, 90th, and 95th percentiles in four BMI categories were between 90% and 100%. CONCLUSIONS: The population-based gestational weight gain Z-score charts performed well in providing guidance regarding expected gestational weight gain in Chinese women.

Blood pressure in early and mid-pregnancy and the risk of small-for-gestational-age birth: findings of a large cohort study in China.

The influences of blood pressure in early to mid-pregnancy on the risk of small-for-gestational-age (SGA) birth are not clear. Our objective was to examine the associations of the blood pressure levels at 10 and 18 gestational weeks with the risk of SGA birth. Data were obtained from the Chinese Maternal and Newborn's Health Monitoring System (MNHMS). In total, 50745 Chinese women who delivered a single live infant at a gestational age of between 28 and 42 weeks were included in this analysis. Blood pressure, birth outcome and other related information were obtained during antenatal visits by obstetricians. Logistic regression models were used to examine the associations, adjusting for potential confounders. The total incidence of SGA birth was 8.9%. High blood pressure levels at 10 gestational weeks significantly increased the risk of SGA birth (SBP: RR = 1.32, 95% CI: 1.11-1.56; DBP: RR = 1.10, 95% CI: 1.05-1.14). The incidence of SGA birth was not associated with the DBP at 18 gestational weeks but showed a U-shaped relationship with SBP. A decrease in blood pressure from 10 to 18 gestational weeks was associated with an increased risk of SGA birth (SBP: RR = 1.03, 95% CI: 1.00-1.07; DBP: RR = 1.05, 95% CI: 1.02-1.09). Our results provide evidence on the relationship of blood pressure in early and mid-pregnancy with SGA birth. Higher blood pressures during early pregnancy and greater decreases in blood pressure from early to mid-pregnancy increased the risk of SGA birth, indicating a continuum of risk for SGA birth based on blood pressure starting during early pregnancy.

Attendance at prenatal care and adverse birth outcomes in China: A follow-up study based on Maternal and Newborn's Health Monitoring System.

OBJECTIVE: to evaluate the independent association between attendance at prenatal care and adverse birth outcomes in China, measured either as the occurrence of preterm birth or low birth weight. DESIGN: a follow-up study. SETTING: the data was collected from maternal and newborn's health monitoring system at 6 provinces in China. PARTICIPANTS: all pregnant women registered in the system at their first prenatal care visit. We included 40152 registered pregnant women who had delivered between October 2013 and September 2014. MEASUREMENTS: attendance at prenatal care was evaluated using Kessner index. χ2 tests were used to examine the correlations between demographic characteristics and preterm birth or low birth weight. The associations between attendance at prenatal care and birth outcomes were explored using multilevel mixed-effects logistic regression models. FINDINGS: the prevalence for preterm birth and low birth weight was 3.31% and 2.55%. The null models showed region clustering on birth outcomes. Compared with women who received adequate prenatal care, those with intermediate prenatal care (adjusted OR 1.62, 95%CI 1.37-1.92) or inadequate prenatal care (adjusted OR 2.78, 95%CI 2.24-3.44) had significantly increased risks for preterm birth, and women with intermediate prenatal care (adjusted OR 1.31, 95%CI 1.10-1.55) or inadequate prenatal care (adjusted OR 1.70, 95%CI 1.32-2.19) had significantly increased risks for low birth weight. We found very significant dose-response patterns for both preterm birth (p-trend<0.001) and low birth weight (p-trend = 0.001). KEY CONCLUSIONS AND IMPLICATION FOR PRACTICE: This study shows that attendance at prenatal care in China has independent effects on both preterm birth and low birth weight. Appropriate timing and number of prenatal care visits can help to reduce the occurrence of preterm birth or low birth weight.

Rate of gestational weight gain and preterm birth in relation to prepregnancy body mass indices and trimester: a follow-up study in China.

BACKGROUND: To evaluate the association between rate of gestational weight gain and preterm birth varying prepregnancy body mass indices and trimester. METHODS: Data from Maternal and Newborn's Health Monitoring System on 17475 pregnant women who delivered live singletons at ≥ 28 weeks of gestation between October 2013 and September 2014 from 12 districts/counties of 6 provinces in China and started prenatal care at ≤ 12 weeks of gestation was analyzed. Gestational weight gain was categorized by rate of weight gain during the 2(nd) and 3(rd) trimester, based on the 2009 Institute of Medicine guidelines. Multivariable binary logistic regression models were conducted to investigate the association between rate of gestational weight gain and preterm birth stratified by prepregnancy body mass indices and trimester. RESULTS: Excessive weight gain occurred in 57.9 % pregnant women, and insufficient weight gain 12.5 %. Average rate of gestational weight gain in 2(nd) and 3(rd) trimester was independently associated with preterm birth (U-shaped), and the association varied by prepregnancy body mass indices and trimesters. In underweight women, excessive gestational weight gain was positively associated with preterm birth (OR 1.93, 95 % confidence interval (CI): 1.29- 2.88) when compared with women who gained adequately. While in overweight/obese women, insufficient gestational weight gain was positively associated with preterm birth (OR 3.92, 95 % CI: 1.13-13.67). When stratifying by trimester, we found that excessive weight gain in 3(rd) trimester had a significantly positive effect on preterm birth (OR 1.27, 95 % CI: 1.02-1.58). CONCLUSIONS: Excessive gestational weight gain among underweight pregnant women, insufficient gestational weight gain among overweight/obese women and excessive gestational weight gain in 3(rd) trimester were important predictors of preterm birth.

Dynamics of DNA Squeezed Inside a Nanochannel via a Sliding Gasket.

We use Brownian dynamics (BD) simulation of a coarse-grained (CG) bead-spring model of DNA to study the nonequilibrim dynamics of a single DNA molecule confined inside a rectangular nanochannel being squeezed with a sliding gasket piston or "nanodozer". From our simulations we extract the nonequilibrim density profile c ( x , t ) of the squeezed molecule along the channel axis (x-coordinate) and then analyze the non-equilibrium profile using a recently introduced phenomenological Nonlinear Partial Differential Equation (NPDE) model. Since the NPDE approach also fits the experimental results well and is numerically efficient to implement, the combined BD + NPDE methods can be a powerful approach to analyze details of the confined molecular dynamics. In particular, the overall excellent agreement between the two complementary sets of data provides a strategy for carrying out large scale simulation on semi-flexible biopolymers in confinement at biologically relevant length scales.

A matched case-control study of preterm birth in one hospital in Beijing, China.

BACKGROUND: Preterm birth is an unresolved global health issue. The etiologies of preterm birth are complex and multifactorial. To examine risk factors related to preterm birth, a matched case-control study was conducted in a hospital in Beijing, China where little data on preterm birth have been published in the scientific literature. METHODS: A 1:1 matched case-control study was conducted in 172 pairs of women with preterm birth (case group) and term delivery (control group). Eligible subjects were interviewed in person by well-trained investigators using a questionnaire. Information on obstetric diagnosis and newborns were abstracted from inpatients' medical records. Univariate and multivariate conditional logistic regression models were used to measure the associations between related factors and preterm birth. RESULTS: Univariate analysis showed that 6 of 12 factors were associated with preterm birth. Multivariate results showed that gestational hypertension (OR = 7.76), low gestational weight gain (OR = 3.02), frequent prenatal care (OR = 0.16), balanced diet (OR = 0.36), and high gestational weight gain (OR = 0.41) were associated with preterm birth. CONCLUSION: This study provides information on preterm birth in Beijing, China, and it also lends support to existing evidence about the role of maternal nutritional status, prenatal care and gestational hypertension as risk factors for preterm birth.

Semiflexible macromolecules in quasi-one-dimensional confinement: Discrete versus continuous bond angles.

The conformations of semiflexible polymers in two dimensions confined in a strip of width D are studied by computer simulations, investigating two different models for the mechanism by which chain stiffness is realized. One model (studied by molecular dynamics) is a bead-spring model in the continuum, where stiffness is controlled by a bond angle potential allowing for arbitrary bond angles. The other model (studied by Monte Carlo) is a self-avoiding walk chain on the square lattice, where only discrete bond angles (0° and ±90°) are possible, and the bond angle potential then controls the density of kinks along the chain contour. The first model is a crude description of DNA-like biopolymers, while the second model (roughly) describes synthetic polymers like alkane chains. It is first demonstrated that in the bulk the crossover from rods to self-avoiding walks for both models is very similar, when one studies average chain linear dimensions, transverse fluctuations, etc., despite their differences in local conformations. However, in quasi-one-dimensional confinement two significant differences between both models occur: (i) The persistence length (extracted from the average cosine of the bond angle) gets renormalized for the lattice model when D gets less than the bulk persistence length, while in the continuum model it stays unchanged. (ii) The monomer density near the repulsive walls for semiflexible polymers is compatible with a power law predicted for the Kratky-Porod model in the case of the bead-spring model, while for the lattice case it tends to a nonzero constant across the strip. However, for the density of chain ends, such a constant behavior seems to occur for both models, unlike the power law observed for flexible polymers. In the regime where the bulk persistence length ℓp is comparable to D, hairpin conformations are detected, and the chain linear dimensions are discussed in terms of a crossover from the Daoud/De Gennes "string of blobs"-picture to the flexible rod picture when D decreases and/or the chain stiffness increases. Introducing a suitable further coarse-graining of the chain contours of the continuum model, direct estimates for the deflection length and its distribution could be obtained.

Conformations, transverse fluctuations, and crossover dynamics of a semi-flexible chain in two dimensions.

We present a unified scaling description for the dynamics of monomers of a semiflexible chain under good solvent condition in the free draining limit. We consider both the cases where the contour length L is comparable to the persistence length ℓ(p) and the case L ≫ ℓ(p). Our theory captures the early time monomer dynamics of a stiff chain characterized by t(3/4) dependence for the mean square displacement of the monomers, but predicts a first crossover to the Rouse regime of t(2ν/1 + 2ν) for τ¹ ~ ℓ(p)³, and a second crossover to the purely diffusive dynamics for the entire chain at τ2 ∼ L(5/2). We confirm the predictions of this scaling description by studying monomer dynamics of dilute solution of semi-flexible chains under good solvent conditions obtained from our Brownian dynamics (BD) simulation studies for a large choice of chain lengths with number of monomers per chain N = 16-2048 and persistence length ℓ(p) = 1-500 Lennard-Jones units. These BD simulation results further confirm the absence of Gaussian regime for a two-dimensional (2D) swollen chain from the slope of the plot of ⟨R(N)²⟩/2Lℓ(p) ~ L/ℓ(p) which around L/ℓ(p) ∼ 1 changes suddenly from (L/ℓ(p)) → (L/ℓ(p))(0.5), also manifested in the power law decay for the bond autocorrelation function disproving the validity of the worm-like-chain in 2D. We further observe that the normalized transverse fluctuations of the semiflexible chains for different stiffness √(⟨l(⊥)²⟩)/L as a function of renormalized contour length L/ℓ(p) collapse on the same master plot and exhibits power law scaling √(⟨l(⊥)²⟩)/L ~ (L/ℓ(p))(n) at extreme limits, where η = 0.5 for extremely stiff chains (L/ℓ(p) ≫ 1), and η = -0.25 for fully flexible chains. Finally, we compare the radial distribution functions obtained from our simulation studies with those obtained analytically.