Objective: To compare the effect of early administration of aspirin on the risk of preterm and term preeclampsia. Method: A systematic review and meta-analysis of randomized controlled trials were performed. Women who were randomized to low-dose aspirin or placebo/no treatment at or before 16 weeks of gestation were included. The outcomes of interest were preterm preeclampsia (delivery <37 weeks) and term preeclampsia. Pooled relative risks (RR) with their 95% confidence intervals (CI) were computed. Results: The search identified 7,941 citations but only five trials on a combined total of 556 women fulfilled the inclusion criteria. When compared to controls, aspirin initiated ≤16 weeks of gestation was associated with a major reduction of the risk of preterm preeclampsia (RR 0.11, 95% CI 0.04–0.33) but had no significant effect on term preeclampsia (RR 0.98, 95% CI 0.42–2.33). Conclusion: Low-dose aspirin administrated at or before 16 weeks of gestation reduces the risk of preterm but not term preeclampsia.

Objective To study the effect of aspirin in the prevention of pre-eclampsia in high-risk women.Design Randomised, double-blinded, placebo-controlled trial.Setting Maternity clinics in ten Finnish hospitals participating in the PREDO Project.Sample A total of 152 women with risk factors for pre-eclampsia and abnormal uterine artery Doppler velocimetry.Methods Participants were randomised to start either aspirin 100 mg/day or placebo at 12 + 0 to 13 + 6 weeks + days of gestation. Because of the limited power of this trial, we also conducted a meta-analysis of randomised controlled trials that included data on 346 women with abnormal uterine artery Doppler flow velocimetry, and aspirin 50-150 mg/day started at or before 16 weeks of gestation.Main outcome measure Pre-eclampsia, gestational hypertension and birthweight standard deviation (SD) score. Outcome measures for the meta-analysis were pre-eclampsia, severe pre-eclampsia, preterm (diagnosed <37 + 0 weeks of gestation) and term pre-eclampsia.Results From the 152 randomised women, 121 were included in the final analysis. Low-dose aspirin did not reduce the rate of pre-eclampsia (relative risk [RR] 0.7, 95% CI 0.3-1.7); gestational hypertension (RR 1.6, 95% CI 0.6-4.2); early-onset pre-eclampsia (diagnosed <34 + 0 weeks of gestation) (RR 0.2, 95% CI 0.03-2.1); or severe pre-eclampsia (RR 0.4, 95% CI 0.1-1.3); and the results were not statistically significant in an intention-to-treat analysis. However, our meta-analysis, including the current data, suggested that low-dose aspirin initiated before 16 weeks of gestation reduces the risk of pre-eclampsia (RR 0.6, 95% CI 0.4-0.8) and severe pre-eclampsia (RR 0.3, 95% CI 0.1-0.7).Conclusions Our trial showed no statistically significant effect of aspirin in preventing pre-eclampsia in high-risk women. However, our meta-analysis suggested that aspirin may reduce the incidence of pre-eclampsia.Keywords Acetylsalicylic acid, aspirin, Doppler, intrauterine growth restriction, meta-analysis, pre-eclampsia, pregnancy, prevention, uterine artery.Please cite this paper as: Villa P, Kajantie E, Räikkönen K, Pesonen A-K, Hämäläinen E, Vainio M, Taipale P, Laivuori H. Aspirin in the prevention of pre-eclampsia in high-risk women: a randomised placebo-controlled PREDO Trial and a meta-analysis of randomised trials. BJOG 2013;120:64-74.

Monitoring of radiocarbon (C14) in carbon dioxide is demonstrated using mid-infrared spectroscopy and a quantum cascade laser. The measurement is based on cavity ring-down spectroscopy, and a high sensitivity is achieved with a simple setup. The instrument was tested using a standardized sample containing elevated levels of radiocarbon. Radiocarbon dioxide could be detected from samples with an isotopic ratio C14/C as low as 50 parts-per-trillion, corresponding to an activity of 5  kBq/m(3) in pure CO(2), or 2  Bq/m(3) in air after extraction of the CO(2) from an air sample. The instrument is simple, compact, and robust, making it the ideal tool for on-site measurements. It is aimed for monitoring radioactive gaseous emissions in a nuclear power environment, during the operation and decommissioning of nuclear power plants. Its high sensitivity also makes it the ideal tool for the detection of leaks in radioactive waste repositories.

An exceptional property of photo-acoustic spectroscopy is the zero-background in wavelength modulation configuration while the signal varies linearly as a function of absorbed laser power. Here, we make use of this property by combining a highly sensitive cantilever-enhanced photo-acoustic detector, a particularly stable high-power narrow-linewidth mid-infrared continuous-wave optical parametric oscillator, and a strong absorption cross-section of hydrogen fluoride to demonstrate the ability of cantilever-enhanced photo-acoustic spectroscopy to reach sub-parts-per-trillion level sensitivity in trace gas detection. The high stability of the experimental setup allows long averaging times. A noise equivalent concentration of 650 parts-per-quadrillion is reached in 32 minutes.

Nonlinear optical frequency conversion is one of the most versatile methods to generate wavelength-tunable laser light in the mid-infrared region. This spectral region is particularly important for trace gas detection and other applications of molecular spectroscopy, because it accommodates the fundamental vibrational bands of several interesting molecules. In this article, we review the progress of the most significant nonlinear optics instruments for widely tunable, high-resolution mid-infrared spectroscopy: continuous-wave optical parametric oscillators and difference frequency generators. We extend our discussion to mid-infrared optical frequency combs, which are becoming increasingly important spectroscopic tools, owing to their capability of highly sensitive and selective parallel detection of several molecular species. To illustrate the potential and limitations of mid-infrared sources based on nonlinear optics, we also review typical uses of these instruments in both applied and fundamental spectroscopy.

We report optical frequency comb generation by a continuous-wave pumped optical parametric oscillator (OPO) without any active modulation. The OPO is configured as singly resonant with an additional nonlinear crystal (periodically poled MgO:LiNbO3) placed inside the OPO for phase mismatched second harmonic generation (SHG) of the resonating signal beam. The phase mismatched SHG causes cascading χ(2) nonlinearities, which can substantially increase the effective χ(3) nonlinearity in MgO:LiNbO3, leading to spectral broadening of the OPO signal beam via self-phase modulation. The OPO generates a stable 4 THz wide (-30 dB) frequency comb centered at 1.56 μm.

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Low-dose aspirin initiated at or before 16 weeks reduces the risk of severe preeclampsia, but not mild preeclampsia.