***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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    Input: A 6-month prospect i ve study of 120 clients of the Bulgarian Family Planning Association was undertaken to document the use , effectiveness , and side effects of the postcoital contraceptive Postinor . 40 of the women used Postinor during 6 cycles , 31 during 5 cycles , 29 during 4 cycles , and 20 during 3 or fewer cycles ( total of 570 cycles ) . Most took 1 tablet within an hour of each intercourse ( they were instructed not to use the method more than 4 times per month ) , but some took 2 - 4 tablets simultaneously . This misuse result ed in badly tolerated side effects . Side effects occurred in 50 % of the clients and included bleeding , delayed menstruation , nausea , headaches , breast tenderness , severe menstrual bleeding , irritability , and weight gain . Four of the subjects became pregnant ( these women took the pill a day or more after intercourse ) . The side effects occurred more frequently in the women who took the most tablets during a month . It was concluded that Postinor should be reserved for emergency use and that clients must be properly counseled about its use and side effects BACKGROUND An oral dose of 0.75 mg levonorgestrel ( LNG ) taken shortly after sex was marketed as a routine , nonemergency contraceptive method until the 1990s . Because a hormonal method used only at the time of intercourse may be desirable for women who have infrequent sex , we conducted a study to reevaluate the potential of pericoital LNG as a primary means of contraception . METHODS We enrolled women aged 18 - 45 years in Brazil and the USA who expected to have sex 1 - 4 days per month for 6.5 months . Participants were instructed to take one tablet 0.75 mg LNG within 24 h before or after sex , with no more than one dose in any 24-h period . The primary efficacy measure was the Pearl Index among women aged 18 - 35 years . RESULTS The study was stopped after 72 of the planned 300 participants were enrolled due to slow recruitment and related feasibility considerations . In the primary analysis , three pregnancies occurred during 13.4 woman-years of follow-up , result ing in a Pearl Index of 22.4 ( 95 % confidence interval , 4.6 - 65.4 ) . No serious adverse events were reported , and vaginal bleeding patterns were generally acceptable . CONCLUSIONS Our estimated Pearl Index was noticeably higher than expected from previous research of LNG for pericoital contraception . Although the regimen was safe and generally acceptable , the study was challenged by slow enrollment and curtailed person-years of follow-up , result ing in poor precision for the estimated treatment effect . Future research may inform whether our results are symptomatic of the regimen , study design or characteristics of the population s from which we recruited . IMPLICATION S Our study failed to confirm prior data suggesting that 0.75 mg LNG for pericoital contraception could be more effective than typical use of barrier methods among women having infrequent sex . Characterizing population s most likely to adhere to , and benefit from , pericoital regimens is essential to future research on these methods The clinical contraceptive value of four oral progestogens was studied in two forms : a ) low-dosage , continuous ( 1472 women during 13,875 months ) ; b ) the same compounds at higher doses , but taken only before coitus ( 333 women , 1830 months ) . Subjects were of comparable age , parity , socioeconomic and educational background s. The precoital regimen was better tolerated , with less bleeding and cycle disturbance . Efficacy seems related to the agent and dosage administered . Norgestrienone and Clogestone showed higher efficacy in both regimens than did Retroprogestagen and Ethynodiol diacetate .  Modifications in cervical mucus , sperm tolerance , endometrium , and urinary pregnanediol were frequent but not constant . In 60 % of subjects accepted for elective tubal sterilization , signs of ovulation were found . Coital use of progestogens seems possible and effective if the proper compound and dose are given A pharmaceutical and pharmacokinetic study was carried out on  levonorgestrel tablets from two different sources ( Hungarian- and Chinese-made ) . Both preparations contained 0.75 mg levonorgestrel and had been shown to have similar contraceptive efficacy and side effects when used for postcoital contraception . Absorption and bioavailability of the Hungarian-made tablets were greater as evidence d by higher serum concentrations of levonorgestrel , a greater area under the concentration-time curve during the first 24 hours , and a more marked suppressive effect on SHBG levels . These differences most probably reflect differences in their pharmaceutical formulation , in particular the extent of tablet dissolution and the degree of micronisation of levonorgestrel Postcoital contraception aims at the avoidance of unwanted pregnancy in women who have a regimen of rare or accidental sexual contacts . For the 1st time in Bulgaria , the authors examined clinical ly an oral postcoital preparation , Postinor , which originated in Hungary . Each tablet contains 0.75 mcg of d-norgestrel . The observation included 49 volunteers , ages 19 - 38 , with proven fertility . The preparations were given during the course of 150 menstrual cycles . 1 women became pregnant as a result of improper dosage/multiple contacts during incomplete hormonal protection . There were 3 cases of bleeding ( 6.1 % ) and 1 required estrogen correction . The authors found that the best administration regimen was 1 tablet , with the exception of 2 tablets/week . The authors suggest that Postinor could be successfully combined with the rhythm method of Ogion-Knaus . They recommend it for daily contraceptive practice . ( author 's modified The experiences of 4 clinical research groups , 1 each in Mexico , Peru , Chile , and Argentina , using quingestanol acetate as a postcoital oral contraceptive is described . 2702 patients accumulated 18,531 cycles of postcoital therapy .  In Mexico with a 800 mcg dose , the pregnancy rate was .6 . In Chile and Peru at a dose of 750 mcg , pregnancy rates were over 20 . Differences in selection of patients may account for part of the difference BACKGROUND Although widely used , the mechanisms of action of the levonorgestrel emergency contraceptive pill ( LNG ECP ) are still unclear . There are increasing data to indicate that LNG is particularly effective as an ECP by interrupting follicular development and ovulation . An important outst and ing question is whether it has any effect on fertilization or implantation . METHOD Ninety-nine women participated ; they were recruited at the time they presented with a request for emergency contraception . All women took LNG 1.5 mg in a single dose during the clinic consultation . A blood sample was taken immediately prior to ingestion of the ECP for estimation of serum LH , estradiol and progesterone levels to calculate the day of ovulation . The specimens were analyzed in a single batch . Based on these endocrine data , we estimated the timing of ovulation to be within a + /-24-h period with an accuracy of around 80 % . Women were followed up 4 - 6 weeks later to ascertain pregnancy status . The effectiveness of ECP  when taken before and after ovulation was determined . RESULTS Three women became pregnant despite taking the ECP ( pregnancy rate , 3.0 % ) . All three women who became pregnant had unprotected intercourse between Days -1 and 0 and took the ECP on Day + 2 , based on endocrine data . Day 0 was taken as ovulation day . Among 17 women who had intercourse in the fertile period of the cycle and took the ECP after ovulation occurred ( on Days + 1 to + 2 ) , we could have expected three or four pregnancies ; three were observed . Among 34 women who had intercourse on Days -5 to -2 of the fertile period and took  ECP  before or on the day of ovulation , four pregnancies could have been expected , but none were observed . We found major discrepancies between women 's self-report of stage of the cycle and the dating calculation based on endocrine data . CONCLUSION These data are supportive of the concept that the LNG ECP has little or no effect on postovulation events but is highly effective when taken before ovulation A total of 1315 healthy women participated between August 1978 and February 1981 in Phase III and IV trials of Postinor a postcoital contraceptive tablet containing .75 mg levonorgestrel .  The women ranged in age from 14 - 40 years but 50.34 % were aged 15 - 19 . 62.51 % were single and 68.67 % were nulliparas . In the 8815 cycles of use coitus occurred 27253 times . 23 pregnancies occurred 6 attributed to ineffectiveness of the tablet and 17 to forgetting . The Pearl index had a raw mean value of 3.37 + or- .99 and a purified mean value of .83 + or- 44 . The effectivity of Postinor measured in terms of incidence of pregnancy in relation to number of copulations was on average 99.90 + or- .03 % . All pregnancies but 2 were terminated . The full-term babies were normal and healthy . Side effects included withdrawal bleeding in 9.1 % spotting in 15.1 % nausea in 5.7 % and temporary breast discomfort in 4.3 % . 60.3 % of the women had no complaints . 39 women discontinued tablet consumption because of side effects . A total of 120 women discontinued Postinor use 54.2 % because of changes in their sex life . Results of the multicenter tests indicate that Postinor is a safe and reliable postcoital  tablet whose only side effect in the majority of cases is mild spotting 
    Output:
    
Pericoital levonorgestrel was reasonably efficacious and safe .
Other hormonal drugs appeared promising but most of them were not studied extensively .
Menstrual irregularities were the most common side effects reported .
However , the studies provided no consistent evidence of a relationship between bleeding abnormalities and either frequency of pill intake or total dose of the drug .
Non-menstrual side effects were reportedly mild and not tabulated in most studies .
Most women liked the  pericoital method  in spite of frequent menstrual irregularities .
The studies of pericoital LNG regimens provided promising results but many had serious method ological issues .