***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: Estimates of the prevalence of the polycystic ovary syndrome ( PCOS )  in the general population have ranged from 2 - 20 % . The vast majority of these reports have studied White population s in Europe , used limited definitions of the disorder , and /or used bias population s , such as those seeking medical care . To estimate the prevalence of this disorder in the United States and address these limitations , we prospect ively determined the prevalence of PCOS in a reproductive-aged population of 369 consecutive women ( 174 White and 195 Black ; aged 18 - 45 yr ) , examined at the time of their preemployment physical .  Body measures  were obtained , and body hair was quantified by a modified Ferriman-Gallwey ( F-G ) method . All exams were initially performed by 2 trained nurses , and any subject with an F-G score above 3 was reexamined by a physician , the same for all patients . Of the 369 women , 277 ( 75.1 % ) also agreed to complete a question naire and have additional blood drawn . Subjects were studied regardless of current estrogen/progestin hormonal use ( 28.5 % ) . PCOS was defined as 1 ) oligoovulation , 2 ) clinical hyper and rogenism ( i.e. hirsutism ) and /or hyper and rogenemia , and 3 ) exclusion of other related disorders , such as hyperprolactinemia , thyroid abnormalities , and non-classic adrenal hyperplasia . Hirsutism was defined by a F-G score of 6 or more , and hyper and rogenemia was defined as a total or free testosterone , and rostenedione , and /or dehydroepi and rosterone sulfate level above the 95th percentile of control values [ i.e. all eumenorrheic women in the study , who had no hirsutism ( F-G < or = 5 ) or acne and were receiving no hormonal therapy ; n = 98 ] . Considering all 369 women studied , White and Black women had similar mean ages ( 29.4 + /- 7.1 and 31.1 + /- 7.8 yr , respectively ) , although White women had a lesser body mass than Black women ( 24.9 + /- 6.1 vs. 29.2 + /- 8.1 kg/m2 , respectively ; P < 0.001 ) . Of these 7.6 % , 4.6 % , and 1.9 % demonstrated a F-G score of 6 or more , 8 or 10 , respectively , and there was no significant racial difference , with hirsutism prevalences of 8.0 % , 2.8 % , and 1.6 % in Whites , and 7.1 % , 6.1 % , and 2.1 % in Blacks , respectively . Of the 277 women consenting to a history and hormonal evaluation , 4.0 % had PCOS as defined , 4.7 % ( 6 of 129 ) of Whites and 3.4 % ( 5 of 148 ) of Blacks . In conclusion , in our consecutive population of unselected women the prevalence of hirsutism varied from 2 - 8 % depending on the chosen cut-off F-G score , with no significant difference between White and Black women . Using an F-G score of 6 or more as indicative of hirsutism , 3.4 % of Blacks and 4.7 % of Whites had PCOS as defined . These data suggest that PCOS may be one of most common reproductive endocrinological disorders of women Gonadotrophin treatment in  clomiphene citrate resistant polycystic ovarian syndrome ( PCOS ) patients , using either low-dose step-up or low-dose step-down protocol s , is highly effective to achieve singleton live births . Concomitant use of gonadotrophin releasing hormone analogues ( GnRHa ) , which will block the endogenous feedback for monofollicular development during the low-dose step-up protocol , should not be employed . It is more difficult to induce ovulation in patients with more ' severe ' PCOS , characterized by obesity and insulin resistance . There is need for optimization of starting doses for both the low-dose step-up and step-down protocol s. Such optimization will prevent hyperstimulation due to a starting dose far above the FSH threshold , as well as minimize the time-consuming low-dose increments by starting with a higher dose in women with augmented FSH threshold . External validation of reported models for prediction of FSH response is warranted for tailoring and optimizing treatment for everyday clinical practice . Although preliminary , the partial cessation of follicular development , along with regression leading to atresia , lends support to the LH ceiling theory , emphasizing the delicate balance and need for both FSH and LH in normal follicular development . Future well- design ed r and omized controlled trials will reveal whether IVF with or without in-vitro maturation of the oocytes will improve safety and efficacy compared with classical ovulation induction strategies BACKGROUND Our aim was to investigate the effect of pre-treatment with metformin in women with polycystic ovary syndrome ( PCOS ) scheduled for IVF stimulation . METHODS Seventy-three oligo/amenorrhoeic women with polycystic ovaries and at least one of the following criteria : hyper and rogenaemia , elevated LH/FSH ratio , hyperinsulinism , decreased SHBG levels or hirsutism , were studied . Normal weight and overweight patients were r and omized separately in a prospect i ve , r and omized , double blind study . All patients were treated for at least 16 weeks with metformin ( 1000 mg bid ) or placebo ending on the day of HCG injection . RESULTS No differences were found in the primary end-points : duration of FSH stimulation 14.4 ( 13.1 - 15.7 ) versus 14.2 ( 12.6 - 15.7 ) days or estradiol on the day of HCG injection 6.8 ( 5.3 - 8.2 ) versus 7.6 ( 5.6 - 9.6 ) nmol/l in the metformin and placebo groups , respectively . The secondary end-points number of oocytes , fertilization rates , embryo quality , pregnancy rates and clinical pregnancy rates were equal . However , in the normal weight subgroup ( BMI < 28 kg/m(2 ) , n = 27 ) , pregnancy rates following IVF were 0.71 ( 0.63 - 0.79 ) versus 0.23 ( 0.15 - 0.31 ) in the metformin and placebo groups , respectively ( P = 0.04 ) . Overall clinical pregnancy rates were equal : 0.51 ( 0.34 - 0.68 ) versus 0.44 ( 0.27 - 0.62 ) in the metformin and placebo groups , respectively . However , in the normal weight subgroup , clinical pregnancy rates were 0.67 ( 0.43 - 0.91 ) and 0.33 ( 0.06 - 0.60 ) , respectively ( P = 0.06 ) . CONCLUSIONS Pre-treatment with metformin prior to conventional IVF/ICSI in women with PCOS does not improve stimulation or clinical outcome . However , among normal weight PCOS women , pre-treatment with metformin tends to improve pregnancy rates . Further studies in subgroups of PCOS women are required BACKGROUND Metformin appears to improve reproductive function in some women with polycystic ovary syndrome ( PCOS ) . We wished to explore the effect of metformin in women with PCOS undergoing IVF . METHODS A r and omized , placebo-controlled , double-blind study was carried out between 2001 and 2004 . Patients with PCOS undergoing IVF/ICSI treatment using a long GnRH agonist protocol were r and omized to receive metformin ( MET ) , 850 mg , or placebo ( PLA ) tablets twice daily from the start of the down-regulation process until the day of oocyte collection . The primary outcome was to be an improvement in the overall fertilization rate . RESULTS One-hundred and one IVF/ICSI cycles were r and omized to receive metformin ( 52 ) or to receive placebo ( 49 ) . There was no difference in the total dose of rFSH required per cycle ( median dose : MET = 1200 U , PLA = 1300 U ; P = 0.937 ) . The median number of oocytes retrieved per cycle ( MET = 17.2 , PLA = 16.2 ; P = 0.459 ) and the overall fertilization rates ( MET = 52.9 % , PLA = 54.9 % ; P = 0.641 ) did not differ . However , both the clinical pregnancy rates beyond 12 weeks gestation per cycle ( MET = 38.5 % , PLA = 16.3 % ; P = 0.023 ) and per embryo transfer ( MET = 44.4 % , PLA = 19.1 % ; P = 0.022 ) were significantly higher in those treated with metformin . Furthermore , a significant decrease in the incidence of severe ovarian hyperstimulation syndrome ( OHSS ) was observed ( MET = 3.8 % , PLA = 20.4 % ; P = 0.023 ) , and this was still significant after adjustment for BMI , total rFSH dose and age ( OR = 0.15 ; 95 % CI : 0.03 , 0.76 ; P = 0.022 ) . CONCLUSION Short-term co-treatment with metformin for patients with PCOS undergoing IVF/ICSI cycles does not improve the response to stimulation but significantly improves the pregnancy outcome and reduces the risk of OHSS OBJECTIVE To evaluate the effect of metformin therapy on hyper and rogenism , insulin resistance , cervical scores , ovulation , and pregnancy rates in clomiphene citrate-resistant women with polycystic ovary syndrome ( PCOS ) . DESIGN Prospect i ve , r and omized , double-blind , placebo-controlled study . SETTING Infertility clinic of a tertiary referral center . PATIENT(S ) Fifty-six women with clomiphene citrate-resistant PCOS . INTERVENTION(S ) Two cycles of oral metformin therapy ( 850 mg , twice daily ) in group I and placebo therapy ( twice daily ) in group II . Clomiphene citrate ( 100 mg/day ) on cycle days 3 - 7 of the second cycle in both groups . MAIN OUTCOME MEASURE(S ) Insulin , T , DHEAS , FSH , LH , body mass index ( BMI ) , waist-to-hip ratio , endometrial thickness , cervical score , ovulation , and pregnancy rates in clomiphene-induced cycles after metformin therapy . RESULT ( S ) Metformin therapy result ed in a significant decrease in total T , LH level , LH/FSH ratio , insulin resistance , and mean BMI . No difference in waist-to-hip ratio , DHEAS level , and fasting insulin level was observed . Clomiphene citrate induction result ed in higher ovulation rates and thicker endometrium in the metformin group than in the placebo group . There was higher cumulative pregnancy rate in the metformin group ; however , there was no significant difference in the pregnancy rate between the two groups . CONCLUSION ( S ) Metformin therapy not only decreases hyper and rogenism and insulin resistance but also improves ovulation rates , cervical scores , and pregnancy rates in clomiphene citrate-resistant women with PCOS This study was design ed to determine if metformin therapy improves ovarian stimulation and IVF outcomes in coasted patients with clomiphene-resistant polycystic ovarian syndrome ( PCOS ) . A retrospective data analysis was performed on women with clomiphene citrate-resistant PCOS treated with or without metformin , who underwent 72 cycles of IVF-embryo transfer with intracytoplasmic sperm injection ( ICSI ) .  In 59 cycles , patients were coasted to allow oestradiol concentrations to drop before human chorionic gonadotrophin administration . In patients undergoing coasting , the outcome of IVF with ICSI was compared in those who were treated and untreated . In patients treated with metformin , follicular fluid concentrations of testosterone and insulin were significantly lower ( 60.5 + /- 5 versus 79.1 + /- 6 ng/dl ; P < 0.05 and 18 + /- 2.5 versus 22 + /- 2.4 micro IU/ml ; P < 0.05 respectively ) , and the mean number of oocytes retrieved ( 22.3 + /- 2.4 versus 19.7 + /- 1.6 ) did not differ . The metformin-treated group showed an increase in the mean number of mature oocytes , oocytes fertilized and cleaving embryos ( 4-cell or greater by 72 h ) . However , in the group of patients undergoing coasting , maximum oestradiol concentrations and number of days of coasting were all lower in the metformin-treated group with increased clinical pregnancy rates ( 71 versus 30 % , P < 0.05 ) . Therefore , metformin use appears beneficial in improving IVF outcomes in clomiphene citrate-resistant PCOS patients Metformin effectively restores insulin sensitivity in insulin-resistant women with polycystic ovary syndrome ( PCOS ) . We examined whether metformin , given prior to and during ovarian 
    Output:
    
MAIN RESULTS This review found no evidence that metformin treatment before or during assisted reproductive technique ( ART ) cycles improved live birth or clinical pregnancy rates .
This review found no evidence that metformin treatment before or during ART cycles improves live birth or pregnancy rates .
The risk of OHSS  in women with PCOS and undergoing IVF or ICSI cycles was reduced with metformin .
Further large RCTs are necessary to definitively answer if the use of metformin in PCOS women undergoing ART improves live birth and pregnancy rates