***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    ***EXAMPLES*** 
    Input: This study aim ed to determine the performance of screening for preeclampsia ( PE ) by maternal medical history and mean arterial pressure  (  MAP ) at 11 + 0 to 13 + 6 weeks . In 5590 women with singleton pregnancies attending for routine care at 11 + 0 to 13 + 6 week ’s gestation we recorded maternal variables and measured the MAP .  We excluded 397 because they had missing outcome data or the pregnancies result ed in miscarriage or termination . In 104 patients there was subsequent development of PE , 97 developed gestational hypertension , 574 delivered small-for-gestational-age newborns , and 4418 were unaffected by PE , gestational hypertension , or small for gestational age . A multivariate Gaussian model was fitted to the distribution of log multiple of the median MAP in the PE and unaffected groups . Likelihood ratios for log multiple of the median MAP were computed and used together with maternal variables to produce patient-specific risks for each case . Detection rates and false-positive rates were calculated by taking the proportions with risks above a given risk threshold . In the unaffected group , log MAP was influenced by maternal age , ethnic origin , smoking , family and personal history of PE , and fetal crown-rump length . In the prediction of PE , significant contributions were provided by log multiple of the median MAP , ethnic origin , body mass index , and personal history of PE . The detection rate of PE by log multiple of the median MAP and maternal variables was 62.5 % for a false-positive rate of 10 % . Maternal variables , together with MAP , at 11 + 0 to 13 + 6 weeks identify a group at high risk for development of PE Background Pre-eclampsia has an immense adverse impact on maternal and perinatal health especially in low- and middle-income setting s. We aim ed to estimate the associations between pre-eclampsia/eclampsia and its risk factors , and adverse maternal and perinatal outcomes . Methods We performed a secondary analysis of the WHO Global Survey on Maternal and Perinatal Health . The survey was a multi-country , facility-based cross-sectional study . A global sample consisting of 24 countries from three regions and 373 health facilities was obtained via a stratified multi-stage cluster sampling design . Maternal and offspring data were extracted from records using st and ardized question naires . Multi-level logistic regression modelling was conducted with r and om effects at the individual , facility and country levels . Results Data for 276,388 mothers and their infants was analysed . The prevalence of pre-eclampsia/eclampsia in the study population was 10,754 ( 4 % ) . At the individual level , sociodemographic characteristics of maternal age ≥30 years and low educational attainment were significantly associated with higher risk of pre-eclampsia/eclampsia . As for clinical and obstetric variables , high body mass index ( BMI ) , nulliparity ( AOR : 2.04 ; 95%CI 1.92–2.16 ) , absence of antenatal care ( AOR : 1.41 ; 95%CI 1.26–1.57 ) , chronic hypertension ( AOR : 7.75 ; 95%CI 6.77–8.87 ) , gestational diabetes ( AOR : 2.00 ; 95%CI 1.63–2.45 ) , cardiac or renal disease ( AOR : 2.38 ; 95%CI 1.86–3.05 ) , pyelonephritis or urinary tract infection ( AOR : 1.13 ; 95%CI 1.03–1.24 ) and severe anemia ( AOR : 2.98 ; 95%CI 2.47–3.61 ) were found to be significant risk factors , while having > 8 visits of antenatal care was protective ( AOR : 0.90 ; 95%CI 0.83–0.98 ) . Pre-eclampsia/eclampsia was found to be a significant risk factor for maternal death , perinatal death , preterm birth and low birthweight . Conclusion Chronic hypertension , obesity and severe anemia were the highest risk factors of preeclampsia/eclampsia . Implementation of effective interventions prioritizing risk factors , provision of quality health services during pre-pregnancy and during pregnancy for joint efforts in the areas of maternal health are recommended OBJECTIVES To examine the performance of screening for hypertensive disorders in pregnancy at 11 - 13 weeks by a combination of the maternal history , uterine artery Doppler imaging and blood pressure . METHODS This was a prospect i ve screening study for pre-eclampsia ( PE ) requiring delivery before 34 weeks ( early PE ) , late PE and gestational hypertension ( GH ) in women attending for their routine first hospital visit in pregnancy at 11 + 0 to 13 + 6 weeks of gestation . Maternal history was recorded , color flow Doppler imaging was used to identify the uterine artery with the lowest pulsatility index ( L-PI ) and automated devices were used to measure the mean arterial pressure ( MAP ) . The performance of screening for PE and GH by a combination of the maternal factor-derived a-priori risk , the uterine artery L-PI and MAP was determined . RESULTS There were 8061 ( 96.4 % ) cases unaffected by PE or GH , 165 ( 2.0 % ) that developed PE including 37 that required delivery before 34 weeks ( early PE ) and 128 with late PE , and 140 ( 1.7 % ) that developed GH . The MAP was higher in early PE , late PE and GH than in the unaffected group ( P < 0.0001 ) , and in early PE than in GH ( P = 0.002 ) . The uterine artery L-PI was significantly higher in early PE and late PE than in the unaffected group ( P < 0.0001 ) , in early PE than late PE or GH ( P < 0.0001 ) , and in GH than in the unaffected group ( P = 0.014 ) . In screening by a combination of the maternal factor-derived a-priori risk , uterine artery L-PI and MAP , the estimated detection rate at a 10 % false-positive rate was 89.2 % ( 95 % CI , 74.6 - 96.9 % ) for early PE , 57.0 % ( 95 % CI , 48.0 - 65.7 % ) for late PE and 50.0 % ( 95 % CI , 41.4 - 58.6 % ) for GH . CONCLUSIONS Effective screening for hypertensive disorders in pregnancy is provided by a combination of maternal history , uterine artery Doppler imaging and blood pressure at 11 - 13 weeks Objectives To develop a predictive model for pre-eclampsia based on clinical risk factors for nulliparous women and to identify a subgroup at increased risk , in whom specialist referral might be indicated . Design Prospect i ve multicentre cohort . Setting Five centres in Auckl and , New Zeal and ; Adelaide , Australia ; Manchester and London , United Kingdom ; and Cork , Republic of Irel and . Participants 3572 “ healthy ” nulliparous women with a singleton pregnancy from a large international study ; data on pregnancy outcome were available for 3529 ( 99 % ) . Main outcome measure Pre-eclampsia defined as ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg , or both , on at least two occasions four hours apart after 20 weeks ’ gestation but before the onset of labour , or postpartum , with either proteinuria or any multisystem complication .  Preterm pre-eclampsia was defined as women with pre-eclampsia delivered before 37 + 0 weeks ’ gestation . In the stepwise logistic regression the comparison group was women without pre-eclampsia . Results Of the 3529 women , 186 ( 5.3 % ) developed pre-eclampsia , including 47 ( 1.3 % ) with preterm pre-eclampsia . Clinical risk factors at 14 - 16 weeks ’ gestation were age , mean arterial blood pressure , body mass index ( BMI ) , family history of pre-eclampsia , family history of coronary heart disease , maternal birth weight , and vaginal bleeding for at least five days . Factors associated with reduced risk were a previous single miscarriage with the same partner , taking at least 12 months to conceive , high intake of fruit , cigarette smoking , and alcohol use in the first trimester . The area under the receiver operating characteristics curve ( AUC ) , under internal validation , was 0.71 . Addition of uterine artery Doppler indices did not improve performance ( internal validation AUC 0.71 ) . A framework for specialist referral was developed based on a probability of pre-eclampsia generated by the model of at least 15 % or an abnormal uterine artery Doppler waveform in a subset of women with single risk factors . Nine per cent of nulliparous women would be referred for a specialist opinion , of whom 21 % would develop pre-eclampsia . The relative risk for developing pre-eclampsia and preterm pre-eclampsia in women referred to a specialist compared with st and ard care was 5.5 and 12.2 , respectively . Conclusions The ability to predict pre-eclampsia in healthy nulliparous women using clinical phenotype is modest and requires external validation in other population s. If vali date d , it could provide a personalised clinical risk profile for nulliparous women to which biomarkers could be added . Trial registration ACTRN12607000551493 Background Preeclampsia ( PE ) increases  maternal and perinatal morbidity and mortality . Based on a multitude of data from r and omized clinical trials , clinical practice guidelines endorse using ASA to prevent PE in women who are “ at risk . ” However , data are lacking about the level of absolute risk to warrant starting ASA prophylaxis . Methods and Findings We present two approaches for objective ly determining the minimum absolute risk for PE at which ASA prophylaxis is justified . The first is a new approach — the minimum control event rate ( CERmin ) . The second approach uses a pre-existing concept — the minimum event rate for treatment ( MERT ) . Here we show how the CERmin is derived , and then use the CERmin and the MERT to guide us to a reasonable risk threshold for starting a woman on ASA prophylaxis against PE based on clinical risk assessment . We suggest that eligible women need not be at “ high risk ” for preeclampsia to warrant ASA , but rather at some modestly elevated absolute risk of 6–10 % . Conclusions Given its very low cost , its widespread availability , ease of administration and its safety profile , ASA is a highly attractive agent for the prevention of maternal and perinatal morbidity worldwide OBJECTIVE The aim of this study was to develop a multiparameter risk-based scoring system for first-trimester prediction of preeclampsia and to vali date this scoring system in our patient population . STUDY DESIGN Secondary analysis of a prospect i ve cohort of 1,200 patients presenting for first-trimester aneuploidy screening .  Maternal serum pregnancy-associated plasma protein A ( PAPP-A ) levels were measured and bilateral uterine artery ( UA ) Doppler studies performed . Using the first half of the study population , a prediction model for preeclampsia was created . Test performance characteristics were used to determine the optimal score for predicting preeclampsia . This model was then vali date d in the second half of the population . RESULTS Significant risk factors and their weighted scores derived from the prediction model were chronic hypertension ( 4 ) , history of preeclampsia ( 3 ) , pregestational diabetes ( 2 ) , body mass index ≥ 30 kg/m(2 ) ( 2 ) , bilateral UA notching ( 1 ) , and PAPP-A MoM < 10 th percentile ( 1 ) . The area under the curve ( AUC ) for the risk scoring system was 0.76 ( 95 % confidence interval [ CI ] , 0.69 - 0.83 ) , and the optimal threshold for predicting preeclampsia was a total score of ≥ 6 . This AUC did not differ significantly from the AUC observed in our validation cohort ( AUC , 0.78 [ 95 % CI , 0.69 - 0.86 ] ; p = 0.75 ] . CONCLUSION Our proposed risk factor scoring system demonstrates modest accuracy but excellent reproducibility for first-trimester prediction of preeclampsia OBJECTIVE To test the hypothesis that a combination of PP13 , PAPP-A and first-trimester uterine artery Doppler would improve the prediction of pre-eclampsia .  METHODS This is a prospect i ve cohort study of pregnant women followed from the first-trimester to delivery .  PP13 and PAPP-A were determined by immunoassay of maternal serum at 11 - 14 weeks ' , when uterine artery Doppler measurements were assessed . Cases identified with any form of pre-eclampsia were compared with a control group without pre-eclampsia . The sensitivity of each marker or their combinations in predicting pre-eclampsia for different fixed false positive rates was calculated from the ROC curves . RESULTS Forty two women were diagnosed with pre-eclampsia and 410 women with pregnancies not complicated by pre-eclampsia were used as controls . For a fixed false positive rate 
    Output:
    
A simple model achieved fewer false positives than a guideline recommended risk factor list , but sensitivity to classify risk for aspirin prophylaxis was not assessed .
Vali date d simple pre-eclampsia risk models demonstrate good risk discrimination that can be improved with specialised tests .
TWEETABLE ABSTRACT Pre-eclampsia risk models using maternal factors show good risk discrimination to guide aspirin prophylaxis