Impact of Caesarean section on subsequent fertility: a systematic review and meta-analysis.

STUDY QUESTION: Is there an association between a Caesarean section and subsequent fertility? SUMMARY ANSWER: Most studies report that fertility is reduced after Caesarean section compared with vaginal delivery. However, studies with a more robust design show smaller effects and it is uncertain whether the association is causal. WHAT IS KNOWN ALREADY: A previous systematic review published in 1996 summarizing six studies including 85 728 women suggested that Caesarean section reduces subsequent fertility. The included studies suffer from severe methodological limitations. STUDY DESIGN, SIZE, DURATION: Systematic review and meta-analysis of cohort studies comparing subsequent reproductive outcomes of women who had a Caesarean section with those who delivered vaginally. PARTICIPANTS/MATERIALS, SETTING, METHODS: Searches of Cochrane Library, Medline, Embase, CINAHL Plus and Maternity and Infant Care databases were conducted in December 2011 to identify randomized and non-randomized studies that compared the subsequent fertility outcomes after a Caesarean section and after a vaginal delivery. Eighteen cohort studies including 591 850 women matched the inclusion criteria. Risk of bias was assessed by the Newcastle-Ottawa scale (NOS). Data extraction was done independently by two reviewers. The meta-analysis was based on a random-effects model. Subgroup analyses were performed to assess whether the estimated effect was influenced by parity, risk adjustment, maternal choice, cohort period, and study quality and size. MAIN RESULTS AND THE ROLE OF CHANCE: The impact of Caesarean section on subsequent pregnancies could be analysed in 10 studies and on subsequent births in 16 studies. A meta-analysis suggests that patients who had undergone a Caesarean section had a 9% lower subsequent pregnancy rate [risk ratio (RR) 0.91, 95% confidence interval (CI) (0.87, 0.95)] and 11% lower birth rate [RR 0.89, 95% CI (0.87, 0.92)], compared with patients who had delivered vaginally. Studies that controlled for maternal age or specifically analysed primary elective Caesarean section for breech delivery, and those that were least prone to bias according to the NOS reported smaller effects. LIMITATIONS, REASONS FOR CAUTION: There is significant variation in the design and methods of included studies. Residual bias in the adjusted results is likely as no study was able to control for a number of important maternal characteristics, such as a history of infertility or maternal obesity. WIDER IMPLICATIONS OF THE FINDINGS: Further research is needed to reduce the impact of selection bias by indication through creating more comparable patient groups and applying risk adjustment

Absence of correlation between nitrate reductase and symbiotic nitrogen fixation efficiency in rhizobium meliloti

Les activités spécifiques des nitrates réductases assimilatoires et "régulatoires" ont été étudiées chez 41 souches de Rhizobium meliloti ayant des activités différentes de fixation symbiotique d’azote. Les deux nitrates réductases ont été retrouvées chez les souches très efficaces ainsi que chez les souches inefficaces et aucune corrélation significative n’a été trouvée entre les activités spécifiques et le rendement de la matière sèche de la luzerne obtenu avec les 41 souches à l’essai. La détermination des activités spécifiques de ces deux nitrates réductases chez les bactéries végétatives ne peut donc pas être utilisée comme un test physiologique rapide pour la sélection de souches très efficaces de R. meliloti.Specific activities of the assimilatory and "regulatory" types of nitrate reductase were studied in 41 strains of Rhizobium m,eliloti naving ditierent symbiotic nitrogen fixation activities. Both nitrate reductase enzymes were present in very effective ind ineffective strains and no significant correlation was iound between the specific activities of the two enzymes and the dry matter yields of alfalfa obtained with the 41 strains. Measurements of the specific activities of the two nitrate reductase enzymes in the vegetative bacteria cannot be used as a rapid physiological test for the seiection of very effective strains of R. meliloti

An assessment of potential unintended consequences following a national antimicrobial stewardship programme in England: an interrupted time series analysis

Background: The 'Quality Premium' (QP) introduced in England in 2015 aimed to financially reward local healthcare commissioners for targeted reductions in primary care antibiotic prescribing. We aimed to evaluate possible unintended clinical outcomes related to this QP. Methods: Using Clinical Practice Research Datalink and Hospital Episode Statistics datasets, we examined general practitioner (GP) consultations (visits) and emergency hospital admissions related to a series of pre-defined conditions of unintended consequences of reduced prescribing. Monthly age and sex-standardised rates were calculated using a direct method of standardisation. We used segmented regression analysis of interrupted time series to evaluate the impact of the QP on seasonally adjusted outcome rates. Results: We identified 27,334 GP consultations and over five million emergency hospital admissions with pre-defined conditions. There was no evidence that the QP was associated with changes in GP consultation and hospital admission rates for the selected conditions combined. However, when each condition was considered separately, a significant increase in hospital admission rates was noted for quinsy, and significant decreases were seen for hospital-acquired pneumonia, scarlet fever, pyelonephritis and complicated urinary tract conditions. A significant decrease in GP consultation rates was estimated for empyema and scarlet fever. No significant changes were observed for other conditions. Conclusions: Findings from this study show that overall there was no significant association between the intervention and unintended clinical consequences, with the exception of a few specific conditions, most of which could be explained through other parallel policy changes or should be interpreted with caution due to small numbers

Igneous phosphate rock solubilization by biofilm-forming mycorrhizobacteria and hyphobacteria associated with Rhizoglomus irregulare DAOM 197198

Biofilm formation on abiotic and biotic surfaces was studied with two hyphobacteria, strongly attached to the surface of the arbuscular mycorrhizal fungus (AMF) Rhizoglomus irregulare (Ri) DAOM 197198 and two mycorrhizobacteria, loosely attached to the roots of different mycorrhizal plants. When the sparingly soluble igneous phosphate rock (PR) from Quebec, or when the chemical hydroxyapatite were used as sole phosphorus (P) source, hyphobacteria Rhizobium miluonense Rm3 and Burkholderia anthina Ba8 produced significantly more biofilms than mycorrhizobacteria Rahnella sp. Rs11 and Burkholderiaphenazinium Bph12, as indicated by the crystal violet assay or by quantifying biofilm exopolysaccharides. As previously observed with planktonic bacteria, biofilms mobilized P by lowering the pH and releasing gluconic acid. The high efficiency of P mobilization by the hyphobacteria Ba8 was linked to the presence of more viable cells in its biofilm as revealed by the hydrolysis of fluorescein diacetate. Scanning electron microscopy micrographs showed a high adherence of the best P-solubilizer hyphobacteria Ba8 on the surface of Quebec PR. Hydroxyapatite porous structure did not allow a good adherence of Ba8. Ba8 formed an important biofilm on the hyphae of Ri DAOM 197198 with low reactive Quebec PR while no biofilm was observed with the high reactive hydroxyapatite. Results confirm the possible presence of specificity between the Ri DAOM 197198 and the hyphobacteria and suggest that the interaction would be regulated by the availability of P

Response of Seven Crystallographic Orientations of Sapphire Crystals to Shock Stresses of 16 to 86 GPa

Shock-wave profiles of sapphire (single-crystal Al2O3) with seven crystallographic orientations were measured with time-resolved VISAR interferometry at shock stresses in the range 16 to 86 GPa. Shock propagation was normal to the surface of each cut. The angle between the c-axis of the hexagonal crystal structure and the direction of shock propagation varied from 0 for c-cut up to 90 degrees for m-cut in the basal plane. Based on published shock-induced transparencies, shock-induced optical transparency correlates with the smoothness of the shock-wave profile. The ultimate goal was to find the direction of shock propagation in sapphire that is most transparent as a window. Particle velocity histories were recorded at the interface between a sapphire crystal and a LiF window. In most cases measured wave profiles are noisy as a result of heterogeneity of deformation. Measured values of Hugoniot Elastic Limits (HELs) depend on direction of shock compression and peak shock stress. The largest HEL values were recorded for shock loading along the c-axis and perpendicular to c along the m-direction. Shock compression along the m- and s-directions is accompanied by the smallest heterogeneity of deformation and the smallest rise time of the plastic shock wave. m- and s-cut sapphire most closely approach ideal elastic-plastic flow, which suggests that m- and s-cut sapphire are probably the orientations that remains most transparent to highest shock pressures. Under purely elastic deformation sapphire has very high spall strength, which depends on load duration and peak stress. Plastic deformation of sapphire causes loss of its tensile strength.Comment: 18 pages, 18 figure

Age-related decline in antibiotic prescribing for uncomplicated respiratory tract infections in primary care in England following the introduction of a national financial incentive (the Quality Premium) for health commissioners to reduce use of antibiotics in the community: an interrupted time series analysis

Objectives: To assess the impact of the 2015/16 NHS England Quality Premium (which provided a financial incentive for Clinical Commissioning Groups to reduce antibiotic prescribing in primary care) on antibiotic prescribing by General Practitioners (GPs) for respiratory tract infections (RTIs). Method: Interrupted time series analysis using monthly patient-level consultation and prescribing data obtained from the Clinical Practice Research Datalink (CPRD), between April 2011 and March 2017. The study population comprised patients consulting a GP who were diagnosed with an RTI. We assessed the rate of antibiotic prescribing in patients (both aggregate and stratified by age) with a recorded diagnosis of uncomplicated RTI, before and after the implementation of the Quality Premium. Results: Prescribing rates decreased over the six year study period, with evident seasonality. Notably, there was a 3% drop in the rate of antibiotic prescribing (equating to 14.65 prescriptions per 1,000 RTI consultations) (p<0.05) in April 2015, coinciding with the introduction of the Quality Premium. This reduction was sustained, such that after two years there was a 3% decrease in prescribing relative to that expected had the pre-intervention trend continued. There was also a concurrent 2% relative reduction in the rate of broad-spectrum antibiotic prescribing. Antibiotic prescribing for RTIs diagnosed in children showed the greatest decline with a 6% relative change two years after the intervention. Of the RTI indications studied, the greatest reductions in antibiotic prescribing were seen for patients with sore throats. Conclusions: Community prescribing of antibiotics for RTIs significantly decreased following the introduction of the Quality Premium, with the greatest reduction seen in younger patients

Effets des souches de rhizobium meliloti et des coupes successives de la luzerne (medicago sativa) sur la fixation symbiotique d'azote

La fixation symbiotique d’azote chez 49 souches de Rhizobium meliloti a été étudiée sous un environnement contrôlé avec la variété de luzerne Saranac. Il a été mis en évidence que le rendement en poids sec de la plante peut être utilisé comme mesure indirecte de la fixation d’azote, et comme critère de sélection des souches efficaces de R. meliloti. L’étude statistique des rendements de trois coupes a établi que la deuxième coupe donne le plus d’information pour évaluer correctement l’efficacité symbiotique des souches. Six souches très efficaces ont été sélectionnées.Symbiotic nitrogen fixation with 49 isolates of Rhizobium meliloti was studied under controlled environment with alfalfa cv. Saranac. It was shown that plant yield in dry weight can be used as an indirect measurement of nitrogen fixation, and as a criterion for selecting efficient strains ofR. meliloti. Statistical study on yields of three cuttings has established that the second cutting gives the most necessary information to correctly evaluate the symbiotic efficiency of the isolates. Six very efficient strains were selected

Comparison of metabolic abnormalities and clinical lipodystrophy 48 weeks after switching from HAART to Trizivir versus continued HAART: the Trizal study

PURPOSE: To analyze the evolution of clinical lipodystrophy (LD) and metabolic abnormalities in patients continuing to receive HAART versus patients switched to Trizivir (zidovudine, lamivudine, abacavir) after 48 weeks. METHOD: Patients treated with HAART >6 months with plasma HIV-1 RNA viral load (VL) <400 copies/mL and <50 copies/mL at screening were randomly assigned to continue HAART (103 patients) or to receive Trizivir (106 patients). Clinical LD was evaluated using a standardized patient questionnaire only at baseline, weeks 4 and 8, and then every 8 weeks until Week 48. Laboratory evaluation was performed every 4 weeks. RESULTS: The proportion of patients exhibiting >or=1 LD symptom at baseline was 40% in the Trizivir arm and 50% in HAART arm (difference not significant). After 48 weeks, the prevalence was 28% and 42% respectively (p =.03), and the median number of LD symptoms per patient was 2 in the Trizivir arm and 4 in the continued HAART arm (p =.016). Median decreases in cholesterol levels over the 48-week study period were greater in the Trizivir arm than in the continued HAART arm (-0.80 vs. -0.44 mmol/L; p lt.001). Median triglyceride levels decreased in the Trizivir arm but increased in the continued HAART arm (-0.17 and +0.01 mmol/L; p =.006). Suppression of VL was maintained in most patients with no differences between the two arms. CONCLUSION: A switch from "standard" HAART to Trizivir was associated with an improvement in clinical LD and blood lipid abnormalities after 48 weeks