A sonographic short cervix (length <25 mm during midgestation) is the most powerful predictor of preterm birth. Current clinical practice assumes that the same cervical length cutoff value should ...apply to all women when screening for spontaneous preterm birth, yet this approach may be suboptimal.
This study aimed to (1) create a customized cervical length standard that considers relevant maternal characteristics and gestational age at sonographic examination and (2) assess whether the customization of cervical length evaluation improves the prediction of spontaneous preterm birth.
This retrospective analysis comprises a cohort of 7826 pregnant women enrolled in a longitudinal protocol between January 2006 and April 2017 at the Detroit Medical Center. Study participants met the following inclusion criteria: singleton pregnancy, ≥1 transvaginal sonographic measurements of the cervix, delivery after 20 weeks of gestation, and available relevant demographics and obstetrical history information. Data from women without a history of preterm birth or cervical surgery who delivered at term without progesterone treatment (N=5188) were used to create a customized standard of cervical length. The prediction of the primary outcome, spontaneous preterm birth at <37 weeks of gestation, was assessed in a subset of pregnancies (N=7336) that excluded cases with induced labor before 37 weeks of gestation. Area under the receiver operating characteristic curve and sensitivity at a fixed false-positive rate were calculated for screening at 20 to 23 6/7, 24 to 27 6/7, 28 to 31 6/7, and 32 to 35 6/7 weeks of gestation in asymptomatic patients. Survival analysis was used to determine which method is better at predicting imminent delivery among symptomatic women.
The median cervical length remained fundamentally unchanged until 20 weeks of gestation and subsequently decreased nonlinearly with advancing gestational age among women who delivered at term. The effects of parity and maternal weight and height on the cervical length were dependent on the gestational age at ultrasound examination (interaction, P<.05 for all). Parous women had a longer cervix than nulliparous women, and the difference increased with advancing gestation after adjusting for maternal weight and height. Similarly, maternal weight was nonlinearly associated with a longer cervix, and the effect was greater later in gestation. The sensitivity at a 10% false-positive rate for prediction of spontaneous preterm birth at <37 weeks of gestation by a short cervix ranged from 29% to 40% throughout pregnancy, yet it increased to 50%, 50%, 53%, and 54% at 20 to 23 6/7, 24 to 27 6/7, 28 to 31 6/7, and 32 to 35 6/7 weeks of gestation, respectively, for a low, customized percentile (McNemar test, P<.001 for all). When a cervical length <25 mm was compared to the customized screening at 20 to 23 6/7 weeks of gestation by using a customized percentile cutoff value that ensured the same negative likelihood ratio for both screening methods, the customized approach had a significantly higher (about double) positive likelihood ratio in predicting spontaneous preterm birth at <33, <34, <35, <36, and <37 weeks of gestation. Among symptomatic women, the difference in survival between women with a customized cervical length percentile of ≥10th and those with a customized cervical length percentile of <10th was greater than the difference in survival between women with a cervical length ≥25 mm and those with a cervical length <25 mm.
Compared to the use of a cervical length <25 mm, a customized cervical length assessment (1) identifies more women at risk of spontaneous preterm birth and (2) improves the distinction between patients at risk for impending preterm birth in those who have an episode of preterm labor.
Dynamic online learning has been given great concerns as real-time and non-stationary systems develop and it can be used for solving many practical sequential decision problems like dynamic ...recommendation systems for online advertisement. Due to the large volume of big data in online learning, dynamic online learning is required to be deployed under the distributed framework where the communication among agents is time-varying and real-time. Meanwhile, since the information sharing among agents is vulnerable to interception by the adversary, the privacy protection problem is significant, but to the best of our knowledge, this work is the first to consider privacy-preserving distributed online learning under dynamic circumstances. Specifically, based on a differentially private distributed online gradient descent algorithm, we minimize the regret of the network. Moreover, via the rigorous mathematical analysis, we achieve the sublinear regret bound under ϵ-differential privacy, that is, we respectively obtain O(T+VT) and O(logT+VT) for convex and strongly convex function, where T is the time horizon and the path-length VT reflects the variation of the minimizer sequence. The experiments performed on the real datasets validate that the presented algorithm achieves acceptable optimization performance even when privacy protection is relatively strict.
Background
Measurement of cervical length by ultrasound is predictive of preterm birth (PTB). There are three methods of ultrasound cervical assessment: transvaginal (TVU), transabdominal (TAU), and ...transperineal (TPU, also called translabial). Cervical length measured by TVU is a relatively new screening test, and has been associated with better prediction of PTB than previously available tests. It is unclear if cervical length measured by ultrasound is effective for preventing PTB. This is an update of a review last published in 2013.
Objectives
To assess the effectiveness of antenatal management based on transvaginal, transabdominal, and transperineal (also called translabial) ultrasound screening of cervical length for preventing preterm birth.
Search methods
For this update, we searched the Cochrane Pregnancy and Childbirth’s Trials Register, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform (ICTRP) to 30 August 2018; reviewed the reference lists of all articles, and contacted experts in the field for additional and ongoing trials.
Selection criteria
We included published and unpublished randomised controlled trials (RCT) including pregnant women between the gestational ages of 14 to 32 weeks, for whom the cervical length was screened for risk of PTB with TVU, TAU, or TPU. This review focused on studies based on knowledge versus no knowledge of cervical length results, or ultrasound versus no ultrasound for cervical length. We excluded studies based on interventions (e.g. progesterone, cerclage) for short cervical length.
Data collection and analysis
We followed standard Cochrane methods.
Main results
We included seven RCTs (N = 923): one examined asymptomatic women with twin pregnancies; four included women with singleton pregnancies and symptoms of preterm labour (PTL); one included women with singleton pregnancies and symptoms of preterm premature rupture of membranes (PPROM); and one included asymptomatic singletons. All trials used TVU for screening.
We assessed the risk of bias of the included studies as mixed, and the quality of the evidence for primary outcomes as very low for all populations.
For asymptomatic women with twin pregnancies, it is uncertain whether knowledge of TVU‐measured cervical length compared to no knowledge reduces PTB at less than 34 weeks (risk ratio (RR) 0.62, 95% confidence intervals (CI) 0.30 to 1.25; 1 study, 125 participants) because the quality of the evidence is very low. The results were also inconclusive for preterm birth at 36, 32, or 30 weeks; gestational age at birth, and other maternal and perinatal outcomes.
Four trials examined knowledge of TVU‐measured cervical length of singletons with symptoms of PTL versus no knowledge. We are uncertain of the effects because of inconclusive results and very low‐quality evidence for: preterm births at less than 37 weeks (average RR 0.59, 95% CI 0.26 to 1.32; 2 studies, 242 participants; I² = 66%; Tau² = 0.23). Birth occurred about four days later in the knowledge groups (mean difference (MD) 0.64 weeks, 95% CI 0.03 to 1.25; 3 trials, 290 women). The results were inconclusive for the other outcomes for which there were available data: PTB at less than 34 or 28 weeks; birthweight less than 2500 g; perinatal death; maternal hospitalisation; tocolysis; and steroids for fetal lung maturity.
The trial of singletons with PPROM (N = 92) evaluated safety of using TVU to measure cervical length in this population as its primary outcome, not its effect on management. The results were inconclusive for incidence of maternal and neonatal infections between the TVU and no ultrasound groups.
In the trial of asymptomatic singletons (N = 296), in which women either received TVU or not, the results were inconclusive for preterm birth at less than 37 weeks (RR 1.27, 95% CI 0.61 to 2.61; I² = 0%), gestational age at birth, and other perinatal and maternal outcomes.
We downgraded evidence for limitations in study design, inconsistency between the trials, and imprecision, due to small sample size and wide confidence intervals crossing the line of no effect.
No trial compared the effect of knowledge of the CL with no knowledge of CL in other populations, such as asymptomatic women with singleton pregnancies, or symptomatic women with twin pregnancies.
Authors' conclusions
There are limited data on the effects of knowing the cervical length, measured by ultrasound, for preventing preterm births, which preclude us from drawing any conclusions for women with asymptomatic twin or singleton pregnancies, singleton pregnancies with PPROM, or other populations and clinical scenarios.
Limited evidence suggests that knowledge of transvaginal ultrasound‐measured cervical length, used to inform the management of women with singleton pregnancies and symptoms of preterm labour, appears to prolong pregnancy by about four days over women in the no knowledge groups.
Future studies could look at specific populations separately (e.g. singleton versus twins; symptoms versus no symptoms of PTL), report on all pertinent maternal and perinatal outcomes, and include cost‐effectiveness analyses. Most importantly, future studies should include a clear protocol for management of women based on TVU‐measured cervical length.
•A simple and effective strategy is proposed to measure the focal lengths.•It enables non-contact measurement and no need to measure the distance between optics components.•The entire measurement ...system occupies a small space that is easy to set up and operates.
This paper proposes a new method to measure the focal lengths of both convex and concave lenses based on vortex beam interference. Theoretical analysis illustrates that the maximum intensity distribution of the interferogram is in accordance with the Fermat's spiral, and the spiral coefficient is proportional to the difference between the focal length of the test lens and the distance from the test lens to the camera. In order to calculate the precise focal length, we separately block the light paths to obtain the reference and test beam spots, and get the ratio of these two spot sizes. Then, the ratio and the spiral coefficient are used to determine the focal length. For a biconvex lens with a focal length of 200 mm and a biconcave lens with a focal length of −100 mm, the relative measurement errors are 0.0892 % and 0.0800 %, respectively. This research provides a novel and convenient method for measuring the focal length, and no-sophisticated displacement devices and moving the lens to be measured are required in the measurement.
Progesterone and preterm birth Norman, Jane E.
International journal of gynecology and obstetrics,
July 2020, Letnik:
150, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Progestogens (vaginal progesterone and intramuscular 17‐hydroxyprogesterone acetate) are widely recommended for women at high risk of preterm birth. Typical regimens include 17‐hydroxyprogesterone ...caproate (250 mg intramuscularly weekly), starting at 16–20 gestational weeks until 36 weeks or delivery for women with a singleton gestation and a history of spontaneous preterm birth, or vaginal progesterone (90‐mg vaginal gel or 200‐mg micronized vaginal soft capsules) for women with a short cervix (typically ≤25 mm). Although some randomized trials support this approach, neither of the largest trials (PROLONG for 17‐hydroxyprogesterone acetate or OPPTIMUM for vaginal progesterone) demonstrated efficacy. There are almost no data on long‐term effects, and none that shows benefit beyond the neonatal period. Although some analyses suggest the cost‐effectiveness of the approach, a cervical length screening program followed by progesterone for those with a short cervix will reduce preterm birth rates by less than 0.5%. The present review assesses evidence on the efficacy, likely impact, and long‐term effects of implementing the recommendations for progestogens in full. Clinicians and pregnant women can look forward to resolution of the conflicting views on efficacy once the Patient‐Centered Outcomes Research Initiative (PCORI)‐funded individual patient data meta‐analysis is published.
The efficacy, probable impact, and long‐term effects of progesterone or 17‐hydroxyprogesterone acetate on the prevention of preterm labor are uncertain.
The efficacy of vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix has been questioned after publication of the OPPTIMUM ...study.
To determine whether vaginal progesterone prevents preterm birth and improves perinatal outcomes in asymptomatic women with a singleton gestation and a midtrimester sonographic short cervix.
We searched MEDLINE, EMBASE, LILACS, and CINAHL (from their inception to September 2017); Cochrane databases; bibliographies; and conference proceedings for randomized controlled trials comparing vaginal progesterone vs placebo/no treatment in women with a singleton gestation and a midtrimester sonographic cervical length ≤25 mm. This was a systematic review and meta-analysis of individual patient data. The primary outcome was preterm birth <33 weeks of gestation. Secondary outcomes included adverse perinatal outcomes and neurodevelopmental and health outcomes at 2 years of age. Individual patient data were analyzed using a 2-stage approach. Pooled relative risks with 95% confidence intervals were calculated. Quality of evidence was assessed using the GRADE methodology.
Data were available from 974 women (498 allocated to vaginal progesterone, 476 allocated to placebo) with a cervical length ≤25 mm participating in 5 high-quality trials. Vaginal progesterone was associated with a significant reduction in the risk of preterm birth <33 weeks of gestation (relative risk, 0.62; 95% confidence interval, 0.47–0.81; P = .0006; high-quality evidence). Moreover, vaginal progesterone significantly decreased the risk of preterm birth <36, <35, <34, <32, <30, and <28 weeks of gestation; spontaneous preterm birth <33 and <34 weeks of gestation; respiratory distress syndrome; composite neonatal morbidity and mortality; birthweight <1500 and <2500 g; and admission to the neonatal intensive care unit (relative risks from 0.47-0.82; high-quality evidence for all). There were 7 (1.4%) neonatal deaths in the vaginal progesterone group and 15 (3.2%) in the placebo group (relative risk, 0.44; 95% confidence interval, 0.18–1.07; P = .07; low-quality evidence). Maternal adverse events, congenital anomalies, and adverse neurodevelopmental and health outcomes at 2 years of age did not differ between groups.
Vaginal progesterone decreases the risk of preterm birth and improves perinatal outcomes in singleton gestations with a midtrimester sonographic short cervix, without any demonstrable deleterious effects on childhood neurodevelopment.
Distributed fiber-optic sensors are widely used for mining safety monitoring, civil engineering structural health monitoring and environmental monitoring. The position accuracy of measurements is of ...critical concern, as errors can lead to expensive decisions at the wrong location. Accurate fiber length measurement is key to calibrate distributed fiber-optic sensors. Existing methods suffer from time resolution or component delay errors. Optical time-domain reflectometry (OTDR) and its variants are widely used but needs calibration for practical applications. We propose two new methods that can self-calibrate, and can be used to calibrate other methods such as those based on OTDR. One based on a differential pulse loop using dual pulse statistical signal processing, and another is based on a differential pulse loop with multi-pulse sequence analysis, to enhance the timing accuracy. In addition, it is possible to determine the effective index of a single-mode fiber with known fiber length, which is important prerequisite information for practical applications in the field with uncertain laser wavelength and ambient temperature. When using a low-end oscilloscope with a nominal 26 MS/s sampling rate, compared with the measurement results of optical frequency domain reflectometer (OFDR) (LunaOBR4600), the double pulse method has an error of ±6 cm. For the multi pulse method, the measurement error can be as low as 1.75 mm for a fiber length of 2.049 km (relative error of 8.54 × 10 −7 ).
The multinode multibaseline interferometric synthetic aperture radar measurement system is the future development trend in the field of aviation remote sensing. The deformation error between the ...nodes directly affects the position and orientation error compensation of the load at the node, and the baseline length error directly affects the interferometric phase error compensation. Aiming at the particularity of the wing structure, a structural deformation measurement and baseline measurement method based on the strain mode is proposed. The fiber Bragg grating sensor is used to acquire the strain of each measuring point on the wing in real time, and the deformation of the wing is accurately measured by the modal superposition method, thereby realizing the high-precision measurement of the baseline between the nodes. The measurement result of the dual total station is the benchmark, and the validation of the method was carried out on the existing test system in the laboratory. Under static conditions, the experimental test results show that the wing deformation measurement accuracy is better than 1 mm, and the baseline measurement accuracy is better than 0.5 mm.
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