***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE This study was undertaken to compare rates and severity of gestational hypertension and preeclampsia , as well as perinatal outcomes when these complications develop , between women with twin gestations and those with singleton gestations . STUDY DESIGN This was a secondary analysis of prospect i ve data from women with twin ( n = 684 ) and singleton ( n = 2946 ) gestations enrolled in two separate multicenter trials of low-dose aspirin for prevention of preeclampsia . End points were rates of gestational hypertension , rates of preeclampsia , and perinatal outcomes among women with hypertensive disorders . RESULTS Women with twin gestations had higher rates of gestational hypertension ( relative risk , 2.04 ; 95 % confidence interval , 1.60 - 2.59 ) and preeclampsia ( relative risk , 2 . 62 ; 95 % confidence interval , 2.03 - 3.38 ) . In addition , women with gestational hypertension during twin gestations had higher rates of preterm delivery at both < 37 weeks ' gestation ( 51.1 % vs 5.9 % ; P < . 0001 ) and < 35 weeks ' gestation ( 18.2 % vs 1.6 % ; P < .0001 ) and also had higher rates of small-for-gestational-age infants ( 14.8 % vs 7 . 0 % ; P = .04 ) . Moreover , when outcomes associated with preeclampsia were compared , women with twin gestations had significantly higher rates of preterm delivery at < 37 weeks ' gestation ( 66.7 % vs 19.6 % ; P < .0001 ) , preterm delivery at < 35 weeks ' gestation ( 34.5 % vs 6.3 % ; P < .0001 ) , and abruptio placentae ( 4.7 % vs 0.7 % ; P = .07 ) . In contrast , among women with twin pregnancies , those who remained normotensive had more adverse neonatal outcomes than did those in whom hypertensive complications developed . CONCLUSIONS Rates for both gestational hypertension and preeclampsia are significantly higher among women with twin gestations than among those with singleton gestations . Moreover , women with twin pregnancies and hypertensive complications have higher rates of adverse neonatal outcomes than do those with singleton pregnancies PROBLEM : Effectiveness of early administered low‐dose aspirin in prevention of  pregnancy‐induced hypertension ( PIH ) and fetal growth retardation in twin pregnancies  was investigated in a r and omized placebo controlled , double‐blind trial in 47 twin pregnancies The National Institute of Child Health and Human Development conducts and supports research on all stages of human development from preconception to adulthood in order to better underst and the health of children , youths , adults , families , and communities . Health and human development information is made easily available on the site with a simple A to Z list , along with clinical trials and health education campaign information . Links to clinical trials , news releases , publications , and related web sites are also available , as well as information on research being conducted at present and supported by the National Institute of Child Health and Human Development OBJECTIVE To review the effect of assisted reproductive technology ( ART ) on perinatal outcomes , to provide guidelines to optimize obstetrical management and counselling of Canadian women using ART , and to identify areas specific to birth outcomes and ART requiring further research . OPTIONS Perinatal outcomes of ART pregnancies in subfertile women are compared with those of spontaneously conceived pregnancies . Perinatal outcomes are compared between different types of ART . OUTCOMES This guideline discusses the adverse outcomes that have been recorded in association with ART , including obstetrical complications , adverse perinatal outcomes , multiple gestations , structural congenital abnormalities , chromosomal abnormalities , imprinting disorders , and childhood cancer . EVIDENCE The Cochrane Library and MEDLINE were search ed for English- language articles from 1990 to February 2005 , relating to assisted reproduction and perinatal outcomes . Search terms included assisted reproduction , assisted reproductive technology , ovulation induction , intracytoplasmic sperm injection ( ICSI ) , embryo transfer , and in vitro fertilization ( IVF ) . Additional publications were identified from the bibliographies of these articles as well as the Science Citation Index . Studies assessing  gamete intrafallopian transfer ( GIFT ) and  zygote intrafallopian transfer ( ZIFT ) were excluded since they are rarely used in Canada . All study types were review ed . R and omized controlled trials were considered evidence of the highest quality , followed by cohort studies . Key studies and supporting data for each recommendation are summarized with evaluative comments and referenced . VALUES The evidence collected was review ed by the Genetics Committee and the Reproductive Endocrinology Infertility Committee of the Society of Obstetricians and Gynaecologists of Canada ( SOGC ) and quantified using the Evaluation of Evidence Guidelines developed by the Canadian Task Force on the Periodic Health Examination . BENEFITS , HARMS , AND COSTS The type and magnitude of benefits , harms , and costs expected for patients from guideline implementation . This guideline has been review ed by the Genetics Committee and the Reproductive Endocrinology and Infertility Committee , and approved by the Executive and Council of the Society of Obstetricians and Gynaecologists of Canada and the Board of the Canadian Fertility and And rology Society . RECOMMENDATIONS 1 . Spontaneous pregnancies in untreated infertile women may be at higher risk for obstetrical complications and perinatal mortality than spontaneous pregnancies in fertile women . Further research is required to clarify the contribution of infertility itself to adverse obstetrical and perinatal outcomes . ( II-2A ) 2 . All men with severe oligozoospermia or azoospermia should be offered genetic/ clinical counselling for informed consent and offered karyotyping for chromosomal abnormalities before attempting IVF-ICSI . They should be made aware of the availability of tests for Y chromosome microdeletion . Some patients may consider the option of donor insemination . ( II-3B ) 3 . Couples exploring IVF-ICSI when the man has obstructive azoospermia should be offered genetic/ clinical counselling for informed consent and offered genetic testing for alterations in genes associated with cystic fibrosis ( CF ) before attempting IVF-ICSI . ( II-2A ) 4 . Pregnancies achieved by ovarian stimulation with gonadotropins and intrauterine insemination are at higher risk for perinatal complications , and close surveillance during pregnancy should be considered . It remains unclear if these increased risks are attributable to the underlying infertility , characteristics of the infertile couple , or use of assisted reproductive techniques . Multiple gestations remain a significant risk of gonadotropin treatment . ( II-2A ) 5 . Pregnancies achieved by IVF with or without ICSI are at higher risk for obstetrical and perinatal complications than spontaneous pregnancies , and close surveillance during pregnancy should be considered . It remains unclear if these increased risks are attributable to the underlying infertility , characteristics of the infertile couple , or use of assisted reproductive techniques . ( II-2A ) 6 . Women undergoing ART should be informed about the increased rate of obstetrical interventions such as induced labour and elective Caesarean delivery . ( II-2A ) 7 . Couples suffering from infertility who are exploring treatment options should be made aware of the psychosocial implication s of ART . Further research into the psychosocial impact of ART is needed . ( II-2A ) 8 . Singleton pregnancies achieved by assisted reproduction are at higher risk than spontaneous pregnancies for adverse perinatal outcomes , including perinatal mortality , preterm delivery , and low birth weight , and close surveillance during pregnancy should be available as needed . ( II-2A ) 9 . A significant risk of ART is multiple pregnancies .  Infertile couples need to be informed of the increased risks of multifetal pregnancies . Although dichorionic twins are most common , the incidence of monochorionic twins is also increased . Risks of multiple pregnancies include higher rates of perinatal mortality , preterm birth , low birth weight , gestational hypertension , placental abruption , and placenta previa . Perinatal mortality in assisted conception twin pregnancies appears to be lower than in spontaneously conceived twin pregnancies . ( II-2A ) 10 . When multifetal reduction is being considered for high-order multiple pregnancies , psychosocial counselling should be readily available . Careful surveillance for fetal growth problems should be undertaken after multifetal reduction . ( II-2A ) 11 . To reduce the risks of multiple pregnancies associated with ART and to optimize pregnancy rates , national guidelines should be developed on the number of embryos replaced according to characteristics such as patient 's age and grade of embryos . ( II-2A ) 12 . Further epidemiologic and basic science research is needed to help determine the etiology and extent of the increased risks to childhood and long-term growth and development associated with ART . ( II-2A ) 13 . Discussion of options for prenatal screening for congenital structural abnormalities in pregnancies achieved by ART is recommended , including appropriate use of biochemical and sonographic screening . ( II-2A ) 14 . Further epidemiologic and basic science research is needed to help determine the etiology and extent of the increased risks of congenital abnormalities associated with ART . ( II-2A ) 15 . Couples considering IVF-ICSI for male-factor infertility should receive information , and if necessary formal genetic counselling , about the increased risk of de novo chromosomal abnormalities ( mainly sex chromosomal anomalies ) associated with their condition . Prenatal diagnosis by chorionic villus sampling ( CVS ) or amniocentesis should be offered to these couples if they conceive . ( II-2A ) 16 . Further epidemiologic and basic science research is needed to help determine the etiology and extent of the increased risks of chromosomal abnormalities associated with ART . ( II-2A ) 17 . Discussion of options for prenatal screening and testing for aneuploidy in pregnancies achieved by ART , adapted for maternal age and number of fetuses , is recommended , including appropriate use of biochemical and sonographic screening . ( II-2A ) 18 . The precise risks of imprinting and childhood cancer from ART remain unclear but can not be ignored . Further clinical research , including long-term follow-up , is urgently required to evaluate the prevalence of imprinting disorders and cancers associated with ART . ( II-2A ) 19 . The clinical application of preimplantation genetic diagnosis must balance the benefits of avoiding disease transmission with the medical risks and financial burden of in vitro fertilization . Further ethical discussion and clinical research is required to evaluate appropriate indications for preimplantation genetic diagnosis . ( III-B ) 
    Output:
    
Conclusion There is low level of evidence supporting the use of low-dose aspirin for the prevention of preeclampsia and SGA neonates in multiple gestations