Peripheral thickening of the sarcomeres and pointed end elongation of the thin filaments are both promoted by SALS and its formin interaction partners.

During striated muscle development the first periodically repeated units appear in the premyofibrils, consisting of immature sarcomeres that must undergo a substantial growth both in length and width, to reach their final size. Here we report that, beyond its well established role in sarcomere elongation, the Sarcomere length short (SALS) protein is involved in Z-disc formation and peripheral growth of the sarcomeres. Our protein localization data and loss-of-function studies in the Drosophila indirect flight muscle strongly suggest that radial growth of the sarcomeres is initiated at the Z-disc. As to thin filament elongation, we used a powerful nanoscopy approach to reveal that SALS is subject to a major conformational change during sarcomere development, which might be critical to stop pointed end elongation in the adult muscles. In addition, we demonstrate that the roles of SALS in sarcomere elongation and radial growth are both dependent on formin type of actin assembly factors. Unexpectedly, when SALS is present in excess amounts, it promotes the formation of actin aggregates highly resembling the ones described in nemaline myopathy patients. Collectively, these findings helped to shed light on the complex mechanisms of SALS during the coordinated elongation and thickening of the sarcomeres, and resulted in the discovery of a potential nemaline myopathy model, suitable for the identification of genetic and small molecule inhibitors.

Maternal Periodontal Status as a Factor Influencing Obstetrical Outcomes.

Background and Objectives: Preterm birth as a complex phenomenon is influenced by numerous endogenic and exogenic factors, although its exact cause often remains obscure. According to epidemiological studies, maternal periodontal diseases, in addition to affecting general health, can also cause adverse pregnancy outcomes. Nonetheless, the existing results in the literature regarding this topic remain controversial. Consequently, our study aimed to determine the connection between poor maternal periodontal status and neonatal birth weight. Materials and Methods: A total of 111 primigravida-primiparous pregnant, healthy women underwent a periodontal examination in the second trimester of their pregnancies. Probing depth (PD) and bleeding on probing (BOP) were determined, and based on these diagnostic measurements, the patients were divided into three subgroups according to their dental status: healthy (H, n = 17), gingivitis (G, n = 67), and periodontitis (P, n = 27). Results: Considering that poor maternal oral status is an influencing factor for obstetrical outcomes, the presence of PD and BOP (characterized by the sulcus bleeding index, SBI) was evaluated. In the case of P, defined as PD ≥ 4 mm in at least one site and BOP ≥ 50% of the teeth, a significant correlation between BOP and a low neonatal birth weight at delivery (p = 0.001) was found. An analysis of the relationship between SBI and gestational age (GA) at the time of the periodontal examination in the different dental status groups showed a significant correlation between these parameters in the G group (p = 0.04). Conclusions: Our results suggest that a worse periodontal status during pregnancy may negatively affect obstetrical outcomes, especially the prematurity rate and newborn weight. Therefore, the importance of periodontal screening to prevent these complications is undeniable.

Machine learning framework to segment sarcomeric structures in SMLM data.

Object detection is an image analysis task with a wide range of applications, which is difficult to accomplish with traditional programming. Recent breakthroughs in machine learning have made significant progress in this area. However, these algorithms are generally compatible with traditional pixelated images and cannot be directly applied for pointillist datasets generated by single molecule localization microscopy (SMLM) methods. Here, we have improved the averaging method developed for the analysis of SMLM images of sarcomere structures based on a machine learning object detection algorithm. The ordered structure of sarcomeres allows us to determine the location of the proteins more accurately by superimposing SMLM images of identically assembled proteins. However, the area segmentation process required for averaging can be extremely time-consuming and tedious. In this work, we have automated this process. The developed algorithm not only finds the regions of interest, but also classifies the localizations and identifies the true positive ones. For training, we used simulations to generate large amounts of labelled data. After tuning the neural network's internal parameters, it could find the localizations associated with the structures we were looking for with high accuracy. We validated our results by comparing them with previous manual evaluations. It has also been proven that the simulations can generate data of sufficient quality for training. Our method is suitable for the identification of other types of structures in SMLM data.

Vertical distribution of soil seed bank and the ecological importance of deeply buried seeds in alkaline grasslands.

Background: Soil seed banks play a central role in vegetation dynamics and may be an important source of ecological restoration. However, the vast majority of seed bank studies examined only the uppermost soil layers (0-10 cm); hence, our knowledge on the depth distribution of seed bank and the ecological significance of deeply buried seeds is limited. The aim of our study was to examine the fine-scale vertical distribution of soil seed bank to a depth of 80 cm, which is one of the largest studied depth gradients so far. Our model systems were alkaline grasslands in East-Hungary, characterised by harsh environmental conditions, due to Solonetz soil reference group with Vertic horizon. We asked the following questions: (1) How do the seedling density and species richness of soil seed bank change along a vertical gradient and to what depth can germinable seeds be detected? (2) What is the relationship between the depth distribution of the germinable seeds and the species traits? Methods: In each of the five study sites, four soil cores (4 cm diameter) of 80 cm depth were collected with an auger for soil seed bank analysis. Each sample was divided into sixteen 5-cm segments by depth (320 segments in total). Samples were concentrated by washing over sieves and then germinated in an unheated greenhouse. Soil penetration resistance was measured in situ next to each core location (0-80 cm depth, 1-cm resolution). We tested the number and species richness of seedlings observed in the soil segments (N = 320), using negative binomial generalized linear regression models, in which sampling layer and penetration resistance were the predictor variables. We ran the models for morphological groups (graminoids/forbs), ecological groups (grassland species/weeds) and life-form categories (short-lived/perennial). We also tested whether seed shape index, seed mass, water requirement or salt tolerance of the species influence the vertical distribution of their seed bank. Results: Germinable seed density and species richness in the seed bank decreased with increasing soil depth and penetration resistance. However, we detected nine germinable seeds of six species even in the deepest soil layer. Forbs, grassland species and short-lived species occurred in large abundance in deep layers, from where graminoids, weeds and perennial species were missing. Round-shaped seeds were more abundant in deeper soil layers compared to elongated ones, but seed mass and ecological indicator values did not influence the vertical seed bank distribution. Our research draws attention to the potential ecological importance of the deeply buried seeds that may be a source of recovery after severe disturbance. As Vertisols cover 335 million hectares worldwide, these findings can be relevant for many regions and ecosystems globally. We highlight the need for similar studies in other soil and habitat types to test whether the presence of deep buried seeds is specific to soils with Vertic characteristics.

Laparoscopic management of adnexal torsion at 32th week of gestation / Torquálódott méhfüggelék laparoszkópos ellátása a 32. terhességi héten.

Összefoglaló. Terhességben az élettani és anatómiai változások miatt bizonyos patológiás szervi eltérések nem specifikus tünettannal járhatnak. A várandósság alatt fellépo hasi panaszok esetén lényeges felállítani a gyors és pontos diagnózist, a minél korábbi adekvát terápia érdekében. A klinikai tünetek hátterében többek között állhatnak szülészeti betegségek, illetve appendicitis, megnagyobbodott ovariumcysta, nephrolithiasis vagy diverticulitis is. Esetismertetésünkben egy 32 hetes gravida ellátását prezentáljuk, aki jobb alhasi panaszok miatt jelentkezett a Szegedi Tudományegyetem Szülészeti és Nogyógyászati Klinikáján. A magzati paraméterek megfeleloek voltak. A klinikai vizsgálatok appendicitis gyanúját vetették fel, mely miatt laparoszkópia történt. Torquálódott jobb oldali tuba uterina miatt jobb oldali salpingectomiát végeztünk, az appendix kóros elváltozása nem igazolódott. Magzati, illetve anyai szövodmény a posztoperatív szakban nem volt. A további terhesgondozás során szövodményt nem észleltünk, majd a betöltött 40. terhességi héten hüvelyi úton egészséges újszülött született. A méhfüggelék megcsavarodásának operatív megoldása laparoszkópos úton alkalmazható módszernek tekintheto terhességben is. Az adnexcsavarodás ritka sürgosségi nogyógyászati kórképnek számít, bár szakirodalmi adatok alapján az adnexum torsiójának rizikója fokozott lehet a terhesség korai szakaszában, kiváltképp asszisztált reprodukciós technikák alkalmazása esetén. Várandósság alatt hirtelen jelentkezo alhasi panaszok esetén az anamnesztikus adatok tükrében, a klinikai vizsgálatok során szükséges az adnextorsio lehetoségére is gondolni. Orv Hetil. 2021; 162(35): 1418-1421. Summary. Due to physiological and anatomical changes in pregnancy, certain pathological organ abnormalities may be associated with non-specific symptoms. In the case of abdominal complaints during pregnancy, it is important to make a quick and accurate diagnosis to apply an early adequate therapy. The cause of the clinical symptoms can be obstetrical diseases, appendicitis, large ovarial cyst, rarely nephrolithiasis or diverticulitis. Through our case study, we present the treatment of a 32-week gravida. Examination of the pregnant patient occured at the Department of Obstetrics and Gynecology of the University of Szeged due to right lower abdominal pain. The fetal parameters were satisfactory. We assumed appendicitis, so after proper preparation laparoscopy was performed. Salpingectomy was performed because of torqued right fallopian tube and no pathological changes were detected on the appendix. In the postoperative period, there were no fetal or maternal complications. During further care of pregnancy, there were no complications and a healthy newborn was born by vaginal delivery at the 40th week of gestation. The operative procedure of adnexal rotation by laparoscopy can be considered as an applicable method even in pregnancy. Adnexal torsion is a rare emergency gynecological disease, although literature data suggest an increased risk in early pregnancy, especially in the case of assisted reproductive technology. In the case of sudden abdominal pain during pregnancy, in the light of anamnestic data, it is recommended to consider the possibility of adnexal torsion, too. Orv Hetil. 2021; 162(35): 1418-1421.

Mapping Fluorescence Enhancement of Plasmonic Nanorod Coupled Dye Molecules.

Plasmonically enhanced fluorescence is a widely studied and applied phenomenon, however, only a comparative theoretical and experimental analysis of coupled fluorophores and plasmonic nanoresonators makes it possible to uncover how this phenomenon can be controlled. A numerical optimization method was applied to design configurations that are capable of resulting in an enhancement of excitation and emission, moreover, of both phenomena simultaneously in coupled Cy5 dye molecule and gold nanorod systems. Parametric sensitivity studies revealed how the fluorescence enhancement depends on the molecule's location, distance and orientation. Coupled systems designed for simultaneous improvement exhibited the highest (intermediate directional) total fluorescence enhancement, which is accompanied by intermediate sensitivity to the molecule's parameters, except the location and orientation sensitivity at the excitation wavelength. Gold nanorods with a geometry corresponding to the predicted optimal configurations were synthesized, and DNA strands were used to control the Cy5 dye molecule distance from the nanorod surface via hybridization of the Cy5-labelled oligonucleotide. State-of-the-art dSTORM microscopy was used to accomplish a proof-of-concept experimental demonstration of the theoretically predicted (directional) total fluorescence enhancement. The measured fluorescence enhancement was in good agreement with theoretical predictions, thus providing a complete kit to design and prepare coupled nanosystems exhibiting plasmonically enhanced fluorescence.

Could Poor Periodontal Status be a Warning Sign for Worse Pregnancy Outcome?

PURPOSE: The aim of the present study was to analyse the role of the main diagnostic signs of poor periodontal status, probing depth (PD) ≥4 mm and bleeding on probing (BOP) ≥50%, both simultaneously and individually in preterm birth (PB) and their effect on the birth weight (BW). Prematurity is a major health concern and it is the leading contributing factor to neonatal morbidity and mortality worldwide. Conflicting results exist on the relation between poor maternal, periodontal status and adverse pregnancy outcome, including preterm deliveries and low birth weight (LBW). MATERIALS AND METHODS: Seventy-seven PBs and 165 deliveries at term were analysed out of 242 patients. The perinatal factors such as gestational age (GA) and BW were analysed by BOP, categorised as ≥50% (high BOP) vs <50% (non-high BOP) and PD ≥4 mm vs <4 mm, in combination or separately. RESULTS: The obtained results suggest that maternal periodontal inflammation, represented particularly by BOP, might be a triggering factor and can be associated with PB and LBW. For women with high BOP the adjusted odds ratio (AOR) for LBW was 2.28-fold and they were likely to have PB, with a 2.02-fold higher rate. CONCLUSION: An increasing tendency of BOP seemed to be associated with a tendency to PB and LBW. Further investigations are necessary to underline this relationship, but the role of good oral health status in general, and particularly in case of pregnancy, is unequivocal.

Superresolution Microscopy of Drosophila Indirect Flight Muscle Sarcomeres.

Sarcomeres are extremely highly ordered macromolecular assemblies where proper structural organization is an absolute prerequisite to the functionality of these contractile units. Despite the wealth of information collected, the exact spatial arrangement of many of the H-zone and Z-disk proteins remained unknown. Recently, we developed a powerful nanoscopic approach to localize the sarcomeric protein components with a resolution well below the diffraction limit. The ease of sample preparation and the near crystalline structure of the Drosophila flight muscle sarcomeres make them ideally suitable for single molecule localization microscopy and structure averaging. Our approach allowed us to determine the position of dozens of H-zone and Z-disk proteins with a quasi-molecular, ~5-10 nm localization precision. The protocol described below provides an easy and reproducible method to prepare individual myofibrils for dSTORM imaging. In addition, it includes an in-depth description of a custom made and freely available software toolbox to process and quantitatively analyze the raw localization data.

Nanoscopy reveals the layered organization of the sarcomeric H-zone and I-band complexes.

Sarcomeres are extremely highly ordered macromolecular assemblies where structural organization is intimately linked to their functionality as contractile units. Although the structural basis of actin and Myosin interaction is revealed at a quasiatomic resolution, much less is known about the molecular organization of the I-band and H-zone. We report the development of a powerful nanoscopic approach, combined with a structure-averaging algorithm, that allowed us to determine the position of 27 sarcomeric proteins in Drosophila melanogaster flight muscles with a quasimolecular, ∼5- to 10-nm localization precision. With this protein localization atlas and template-based protein structure modeling, we have assembled refined I-band and H-zone models with unparalleled scope and resolution. In addition, we found that actin regulatory proteins of the H-zone are organized into two distinct layers, suggesting that the major place of thin filament assembly is an M-line-centered narrow domain where short actin oligomers can form and subsequently anneal to the pointed end.

mmSTORM: Multimodal localization based super-resolution microscopy.

Super-resolution localization microscopy provides a powerful tool to study biochemical mechanisms at single molecule level. Although the lateral position of the fluorescent dye molecules can be determined routinely with high precision, measurement of other modalities such as 3D and multicolor without the degradation of the original super-resolved image is still in the focus. In this paper a dual-objective multimodal single molecule localization microscopy (SMLM) technique has been developed, optimized and tested. The proposed optical arrangement can be implemented onto a conventional inverted microscope without serious system modification. The performance of the method was tested using fluorescence beads, F-actin filaments and sarcomere structures. It was shown that the proposed imaging method does not degrade the image quality of the original SMLM 2D image but could provide information on the axial position or emission spectra of the dye molecules.

[Effect of the treatment of periodontal disease on the outcome of pregnancy]. / Fogágybetegség kezelésének hatása a terhesség kimenetelére.

INTRODUCTION: Correlations between periodontitis and its effects on the outcome of pregnancies are actually more focused topics. Maternal motivation for a good oral hygiene and preventive dental treatment must be highlighted tasks during pregnancy care. AIM: The authors analysed the effect of the preventive dental treatment during pregnancy and its obstetrical effects. METHOD: In a prospective randomised study, including pregnant women observed for threatening preterm deliveries, patients with dental examination (n = 71) were compared with patients undergoing dental treatment at the same time (n = 79). STATISTICAL ANALYSIS: Univariate comparisons for categorical variables were assessed by χ2 tests and independent Student's t-tests for continuous variables. ORs were compared with Mantel-Haenszel tests. Multivariable logistic regression was performed to evaluate the factors determining the poor periodontal parameters and gingivitis separately. The two-tailed statistical significance level was set at 5%. RESULTS: In the dental treatment group, the neonatal birth weight was significantly higher than in the non-treated group, in case of patients with periodontitis (2990 ± 582.3 g vs 2568.1 ± 699.1 g, p = 0.005). Also the average age at delivery was significantly higher in the treated vs non-treated groups (37.3 ± 1.9 vs 36.0 ± 2.9 weeks, p = 0.027), and the treatment had a beneficial effect on the prolongation of pregnancy, with a higher level of significance in the gingivitis group vs patients with periodontitis groups (p = 0.02 vs p = 0.043). CONCLUSIONS: Dental treatment of expecting women has a beneficial effect on the prolongation of pregnancy by decreasing the rate of prematurity and perinatal complications. Orv Hetil. 2018; 159(24): 978-984.

Change in the Caries Status of Pregnant Women in Southeast Hungary and Its Background.

PURPOSE: To examine the caries status of pregnant women in southeast Hungary and compare the results with a similar study completed in the same region ten years earlier to determine whether any improvement has taken place in the past decade. Another objective was to assess the effects of age, socioeconomic status and number of pregnancies on oral health. MATERIALS AND METHODS: The dental examination of 130 pregnant women was carried out at the Dental Clinic of University of Szeged, Faculty of Dentistry in 2011-2013 (group 1). Caries status was examined according to WHO guidelines. In order to compare demographic and socioeconomic factors with DMF indices, find the decisive influencing factors and compare the results with the results of the previous study (group 2), two-way ANOVA and regression analyses were conducted. RESULTS: The number of highly educated, professional, urban participants included in the present group (group 1) was greater compared with that of group 2. Despite the higher age of the pregnant women in present study, statistically significantly lower DMFT (10.05 vs 12.57, p = 0.008) and DMFS (19.41 vs 26.26, p = 0.001) scores were found than ten years ago. In both studies, the regression analyses showed that women's age was the main contributing factor to caries status. CONCLUSION: The lower DMFT and DMFS values and the participants' willingness to participate in the dental screening in the present study group were probably the result of their higher educational background and that they worked as professionals.

TestSTORM: Versatile simulator software for multimodal super-resolution localization fluorescence microscopy.

Optimization of sample, imaging and data processing parameters is an essential task in localization based super-resolution microscopy, where the final image quality strongly depends on the imaging of single isolated fluorescent molecules. A computational solution that uses a simulator software for the generation of test data stacks was proposed, developed and tested. The implemented advanced physical models such as scalar and vector based point spread functions, polarization sensitive detection, drift, spectral crosstalk, structured background etc., made the simulation results more realistic and helped us interpret the final super-resolved images and distinguish between real structures and imaging artefacts.

[Pregnant women's oral hygiene knowledge and habits after the second millennium in South-East Hungary]. / Terhes nok szájhigiénés ismeretei, szokásai az ezredfordulón Délkelet-Magyarországon.

Among the predisposing agents for inflammatory periodontal lesion dental plaque is the most important, but different local and systemic factors may influence the seriousness or progression of periodontitis. Hormonal changes during pregnancy belong to the systemic aggravating factors. The aim of the present study was to assess pregnant women's oral hygiene knowledge and habits, and if these have a relationship with age, residence, educational level and profession/occupation. Questionnaires were used for the data collection. 275 pregnant women, who underwent prenatal care at the Department of Obstetrics and Gynecology in Szeged, volunteered to answer the questions. The results showed that almost all the women brushed their teeth daily, but only about one third of them used special oral hygiene tools, like dental floss. Many of the women claimed to have gingival bleeding when brushing their teeth. More then 70% visited a dentist during pregnancy. There was a significant relationship between educational level and the use of dental floss (p=0.004) and gingival bleeding (p=0.023) Oral hygiene education, dental and periodontal treatment of pregnant women need more emphasis during prenatal care.

Prevention of preterm delivery with periodontal treatment.

OBJECTIVE: To demonstrate the role of periodontal treatment (PT) in the prevention of preterm delivery (PD). METHODS: A comparative prospective study of two groups of pregnant women with threatening PD was carried out at the Department of Obstetrics and Gynaecology of the University of Szeged: group A (n = 39) comprised patients who were merely examined dentally for periodontitis, and group B (n = 44) consisted of patients who received periodontal treatment during pregnancy. RESULTS: Periodontitis was identified in 19 cases (48.7%) in group A and in 18 cases (40.9%) in group B. The mean birth weight of the newborns was significantly higher in group B (3,009.1 g) than in group A (2,580.8 g; p = 0.007). The rate of premature birth was significantly lower in the group who received PT (p = 0.012, odds ratio = 3.5, 95% confidence interval = 1.38-8.86). CONCLUSIONS: The PT of pregnant women can decrease the rate of premature birth and consequently lead to a better neonatal health outcome.

[The possible effect of basic periodontal treatment on the outcome of pregnancy]. / Egyszeru parodontológiai kezelés lehetséges hatása a terhesség kimenetelére.

More publications support the statement that maternal periodontitis may be a risk factor of preterm delivery and low birth-weight, than the number of those that suggest opposing evidence. The proving or rejecting of the questionable relationship may be carried out--among other methods--by analyzing the results of interventional studies. The aim of our study was to investigate whether or not it is possible to decrease the chance of preterm birth and low birth-weight in the case of healthy non-smoking women through the elimination of periodontal inflammation by providing professional oral hygiene treatment during pregnancy. After periodontal examination 80 pregnant women received professional oral hygiene treatment including plaque and calculus removal, root planing, motivation and instruction (treatment group); only the periodontal status was recorded in 79 cases (control group). The mean length of pregnancy and birth-weight in the treatment group were compared with similar data of the control group. Data were assessed using statistical methods. The mean weight of newborns was 3005.3 grams in the treatment group, while 2644.2 grams in the control group (p < 0.0001). The delivery occurred later in the treatment group (37.0 week), than among the control group (36.4 week), although the difference was not significant (p = 0.059). In the periodontal treated group, which had a statistically suitable number of members, the periodontal treatment might have contributed to a more optimal date of delivery and to achieving a larger birth-weight.

The oral health status of postpartum mothers in South-East Hungary.

OBJECTIVES: This study was carried out to assess the oral health status of new mothers, following not more than three days post-delivery, in South-East Hungary. An additional aim was to examine the effect of socioeconomic status on the oral health of the 169 women who volunteered, all of whom were healthy. MATERIAL AND METHODS: Socioeconomic data were collected via a questionnaire, and patients were examined according to WHO guidelines. The state of the periodontium was described by examining the plaque, calculus, probing depth and bleeding on probing. The mean age of the women was 27.5 yrs, representing all educational levels and professional categories of the country. RESULTS: The mean DMFT was 12.57, and the mean DMFS was 26.26. The plaque index was 0.68, the calculus frequency 20.22%, the mean probing depth 1.65mm and bleeding on probing occurred in 36.27% of teeth. Regression analyses demonstrated that caries levels were mostly related to age and plaque scores, while the state of the periodontium was mostly related to educational level, age and profession. The number of pregnancies had no significant influence on the caries nor on the periodontal status of these women. CONCLUSIONS: It was concluded that the oral health status of these mothers was mainly age- and socioeconomically-related, and that the dental needs of women during pregnancy must be emphasized, both to the dental profession and to the patients themselves.

Possible association between mother's periodontal status and preterm delivery.

BACKGROUND: A case-control study was undertaken to detect whether initial chronic localized periodontitis could be a risk factor for preterm birth (PB) and foetal growth restriction. METHODS: A PB case was defined if a patient had a threatening premature event during pregnancy pre-term premature rupture of membranes, or spontaneous pre-term delivery, before the 37th week of pregnancy, and/or the weight of the newborn was <2500 g. Into the PB (case) group, 77 women were allocated, while 84 were included in the control group, all of whom had delivery after the 37th gestational week and with a newborn weighing >or=2500 g. RESULTS: A significant association was found between PB and initial chronic localized periodontitis, the criteria being bleeding at >or=50% of the examined teeth and having at least at one site at >or=4 mm probing depth (p=0.0001). The adjusted odds ratio for initial chronic localized periodontitis was 3.32, 95% CI: 1.64-6.69. The average weight of newborns of mothers with periodontitis was significantly less than that of the women without periodontitis (p=0.002). CONCLUSIONS: The results support the hypothesis that initial chronic localized periodontitis of pregnant women could lead to PB, and birth-weight reduction.

Distribution of anaerobic bacteria among pregnant periodontitis patients who experience preterm delivery.

The preterm delivery of low-birth-weight (PLBW) infants remains a significant public health issue and a leading cause of neonatal death and of long-term neurodevelopmental disturbances and health problems. Epidemiological and immunological studies have suggested that periodontal disease may be an independent risk factor for PLBW. The incidence of periodontal disease during pregnancy has been found to be associated with a significantly lower birth weight for gestational age after adjustment for race, parity and baby gender. The present case-control study, carried out to examine the distribution of anaerobes in pregnant women with periodontitis who experienced preterm delivery, provides microbial evidence that maternal periodontal disease and the presence of key pathogens are significant contributors to the obstetric risk of preterm delivery.