***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 To study the effect of mifepristone and levonorgestrel on ovarian function and endometrial development in doses effective as emergency contraception . METHODS Twelve fertile women were treated with either 10 mg of mifepristone as a single dose ( n = 6 ) or two doses of 0.75 mg of levonorgestrel , 12 hours apart ( n = 6 ) before and after ovulation . An endometrial biopsy performed during the implantation period was analyzed for endometrial maturation and expression of markers of endometrial receptivity . The markers tested for were integrin α4 and β3 , cyclooxygenase‐1 and ‐2 , progesterone receptors , Dolichos biflorus agglutinin lectin binding , and pinopodes . Urinary excretion of luteinizing hormone , estrone , and pregnanediol were also determined RESULTS Treatment with mifepristone and levonorgestrel before ovulation inhibited the luteinizing hormone surge showing no significant differences between the means of luteinizing hormone measurements . When mifepristone was administered in the early luteal phase , downregulation of progesterone receptors was inhibited in five of six women . No significant alteration was found in any of the remaining markers of endometrial receptivity . CONCLUSION The mode of action of emergency contraception with mifepristone or levonorgestrel is primarily due to inhibition of ovulation rather than inhibition of implantation BACKGROUND The study was conducted to assess the effects of levonorgestrel ( LNG ) on hormonal behavior and on the secretory pattern of intrauterine glycodelin at the midcycle of ovulatory women . STUDY DESIGN Thirty healthy sterilized women with normal ovarian function were studied during one control untreated cycle and one LNG-treated cycle . In the treated cycle , each woman received two doses of 0.75 mg of LNG 12 h apart during the preovulatory phase approximately 2 days before the LH surge . Daily follicle development recordings were performed until follicle rupture was observed , and serum glycodelin , LH , estradiol , estrone and progesterone were measured as well . In addition , glycodelin concentrations were assayed in uterine flushing obtained on Days LH+1 and LH+12 . RESULTS LNG did not modify follicle rupture in 20 of 30 women . In spite of ovulatory progesterone and the occurrence of follicle rupture in these women , luteal phase length was significantly decreased , as well as the serum concentrations of LH , estradiol and estrone in the periovulatory phase . Glycodelin in serum and uterine flushings was significantly elevated in the periovulatory phase when compared to control cycles . CONCLUSIONS LNG taken at the dose used in emergency contraception before the LH surge increased prematurely serum and intrauterine concentrations of glycodelin at the time of ovulation . Since there are well established glycodelin inhibitory effects upon fertilization , these results may represent an additional action of LNG in situations where the intervention did not interfere with ovulation OBJECTIVE To determine whether transvaginal ultrasonography improves evaluation of conception time in women seeking emergency contraception . DESIGN Prospect i ve study . SETTING Obstetrics and Gynecology Department , Siena University , Siena , Italy . PATIENT(S ) One hundred sixty-three women seeking postcoital contraception . MAIN OUTCOME MEASURE(S ) Data on menstrual history and time of unprotected intercourse were recorded . Ultrasonographic variables evaluated were ovarian follicle or corpus luteum diameter , endometrial echopattern and thickness , and peritoneal fluid volume . Expected pregnancy rates were calculated according to the probability of conception as estimated from Dixon 's table of data , based solely on anamnestic data , or from endometrial or ovarian findings on transvaginal ultrasonography . RESULT ( S ) According to the menstrual history ( cut-off level < 0.03 ) we expected to find 7.6 pregnancies ( 7.9 in the high-risk group and 0.31 in the low-risk group ) . According to transvaginal ultrasonography ( at the same cut-off ) , we expected 11.2 pregnancies ( 0.3 in the low-risk group and 10.9 in the high-risk group ) . No more than 7 pregnancies were observed , all of which occurred in the high-risk group as determined by transvaginal ultrasonography . In contrast , on the basis of anamnestic data , 4 of 7 pregnancies were in the high-risk group and 3 of 7 were in the low-risk group . CONCLUSION ( S ) Transvaginal ultrasonography allows timely definition of the fertile period and is a reliable method of computing the day of ovulation . It improves therapeutic options by allowing treatment of only women at high risk of conception OBJECTIVE To examine the effects of a single-dose of 1.5 mg of levonorgestrel ( commonly used as emergency contraceptive ) on endometrial receptivity biomarkers through the oral or vaginal route . DESIGN Prospect i ve r and omized single-blinded trial . SETTING Affiliated Hospital and University Research Center . PATIENT(S ) Fertile normal women previously sterilized by tubal ligation . INTERVENTION(S ) Levonorgestrel ( 1.5 mg ) was administered on the day of LH surge either orally ( n = 14 ) or vaginally ( n = 13 ) . MAIN OUTCOME MEASURE(S ) Molecular assessment of endometrial progesterone receptors , L-selectin lig and , glicodelin-A and αvβ3 integrin by Immunohistochemistry and reverse transcriptase-polymerase chain reaction . RESULT ( S ) Plasma progesterone concentration and endometrial dating were not different . The pattern of progesterone receptors and glycodelin-A expression was not affected during the early and midsecretory phase . Some endometrial biopsies from the group in which levonorgetrel was orally administered showed areas of gl and ular atrophy and stromal decidualization . However , the expression of the progesterone receptor , L-selectin lig and , αvβ3 integrin , and glycodelin-A were not different between the groups . CONCLUSION ( S ) Levonorgestrel , given as emergency contraceptive on the day of LH surge , does not disrupt either ovulation or progesterone production by the corpus luteum . The contraceptive mechanism of levonorgestrel at the time of LH surge does not include changes in the progesterone receptors or the endometrial receptivity biomarkers BACKGROUND In  levonorgestrel intrauterine system ( LNG-IUS ) users , the prevention of sperm penetration through cervical mucus has not been demonstrated . STUDY DESIGN Subjects were enrolled in an investigator-blinded study to compare quality and sperm penetrability of mid-cycle cervical mucus between  LNG-IUS users and hormone-free controls . Cervical mucus was microscopically examined using World Health Organization ( WHO ) cervical mucus analysis ( CMA ) . CMA score ≥10 of 15 points indicated cervical mucus favoring sperm penetration . Mucus was incubated with sperm using the WHO simplified slide test ( SST ) and Kremer sperm cervical mucus penetration test ( SCMPT ) . RESULTS Data from 14 LNG-IUS users and 16 controls showed 14 % of LNG-IUS users had CMA score ≥10 % vs. 69 % of controls ( p=.004 ) . SST showed no sperm penetration for LNG-IUS users , significantly less than controls ( 0 % vs. 64.3 % , p<.001 ) . SCMPT demonstrated no sperm mucus penetration for LNG-IUS users at 2 and 6 h ( 0 % vs. 85 % in controls with 2-h score ≥6 , p<.001 ; 6 h 0 % vs. 79 % in controls , p<.001 ) . CONCLUSIONS Mid-cycle cervical mucus of LNG-IUS  users is poor quality and prevents endocervical sperm transport in vitro Spermatozoa have to swim through the oviduct and the cumulus oophorus before fertilization in vivo . In the oviduct , spermatozoa are exposed to glycodelin-A and -F that inhibit spermatozoa-zona pellucida binding . In this study , we determined whether these glycodelins would inhibit  fertilization . The data showed that the spermatozoa without previous exposure to glycodelin-A and -F acquired glycodelin immunoreactivity during their passage through the cumulus oophorus . On the other h and , when glycodelin-A or -F-pretreated spermatozoa were exposed to the cumulus oophorus , the zona pellucida binding inhibitory activity of glycodelin-A and -F was not only removed , but the spermatozoa acquired enhanced zona pellucida binding ability . These actions of the cumulus oophorus were due to the presence of a cumulus isoform of glycodelin , design ated as glycodelin-C. The cumulus cells could convert exogenous glycodelin-A and -F to glycodelin-C , which was then released into the surrounding medium . The protein core of glycodelin-C was identical to that in other glycodelin isoforms , as demonstrated by mass spectrum , peptide mapping , and affinity to anti-glycodelin antibody recognizing the protein core of glycodelin . In addition to having a smaller size and a higher isoelectric point , glycodelin-C also had lectin binding properties different from other isoforms . Glycodelin-C stimulated spermatozoazona pellucida binding in a dose-dependent manner , and it effectively displaced sperm-bound glycodelin-A and -F. In conclusion , the cumulus cells transform glycodelin-A and -F to glycodelin-C , which in turn removes the spermatozoazona binding inhibitory glycodelin isoforms and enhances the zona binding capacity of spermatozoa passing through the cumulus oophorus BACKGROUND Levonorgestrel ( LNG ) consistently prevents follicular rupture only when it is given before the onset of the ovulatory stimulus . As locally synthesized prostagl and in ( PG ) plays a crucial role in follicular rupture and cyclooxygenase-2 ( cox-2 ) catalyses the final step of PG synthesis , we reasoned that adding a cox-2 inhibitor to LNG would prevent follicular rupture even after the ovulatory process had been triggered by the gonadotrophin surge . METHODS Forty-one women were divided into two groups . One was treated when the size of the leading follicle was 15 - 17 mm ( n=10 ) and the other when it was > or=18 mm ( n=31 ) . Each woman contributed with one cycle treated with LNG 1.5 mg single dose plus placebo and another treated with LNG + meloxicam ( Melox ) 15 mg , in a r and omized order . Serial blood sampling for the assay of LH and follicular monitoring by transvaginal ultrasound were performed before and after treatment . RESULTS Follicular rupture failed to occur within the 5-day period that followed treatment in 50 and 70 % of cycles treated with LNG + Placebo and LNG + Melox , respectively , in the 15 - 17 mm group ( P=0.15 ) and in 16 and 39 % of cycles treated with LNG + Placebo and LNG + Melox , respectively , in the > or=18 mm group ( P < 0.052 ) . The overall proportion of cycles with no follicular rupture or ovulatory dysfunction increased significantly by the addition of Melox to LNG ( 66 versus 88 % , P < 0.012 ; n=41-matched pairs ) . CONCLUSIONS The trend towards increased incidence of no follicular rupture when Melox was combined with LNG suggests that the addition of a cox-2 inhibitor has the potential to improve the contraceptive efficacy of LNG by a pre-fertilization effect PURPOSE Multiple trials by the World Health Organization have established levonorgestrel as the gold st and ard in hormonal emergency contraception ( EC ) . However , changes in menstrual patterns following EC have been observed ; thus , we undertook this prospect i ve study to identify and determine the characteristics of these changes . MATERIAL S Women requesting EC at either any of two hospitals --1 family planning unit and 12 pharmacies in Yaoundé , Cameroon were enrolled if they had a history of regular menstrual cycles over the previous 3 months and if they agreed to follow-up until the end of the subsequent menstrual cycle . Pretreatment menstrual patterns were compared with those of the EC treatment cycle and the cycle after EC . RESULTS In a set of 232 participants ( mean age , 25 years ) , we observed 34 ( 14.7 % ) cases of incident intermenstrual bleeding and statistically significant changes in menstrual cycle length , menstrual period length and menstrual appearance compared to baseline patterns that differed according to whether EC was taken well before , close to or well after the expected ovulation for that cycle . The majority of these changes disappeared in the following cycle . CONCLUSION Levonorgestrel EC is associated with significant but transient changes in menstrual patterns in a significant proportion of users The effects of short-term administration of levonorgestrel ( 
    Output:
    
Luteal effects ( such as decreased progesterone , altered glycodelin levels , and shortened luteal phase ) present in the literature may suggest a pre-ovulatory induced post-fertilization drug effect .
The drug has no ability to alter sperm function and limited ability to suppress ovulation .
Further , data suggest that when administered pre-ovulation , it may have a post-fertilization MOA