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Efficacia di 5 giorni per la pillola del giorno dopo !!! |
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30/08/2001 |
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Effectiveness of emergency contraceptive pills between 72 and 120 hours after unprotected sexual intercourse Isabel Rodrigues, MD, MPH, Fabienne Grou, MD, and Jacques Joly, PhD Laval, Quebec, Canada OBJECTIVE: This article reopens the issue of a medical practice that has been well established for more than three decades by proposing an extension of the period during which treatment with the “morning-after pill is currently prescribed. The objective is to determine the effectiveness of the regimen of Yuzpe and Lancee when it is administered between 72 and 120 hours after sexual intercourse.
STUDY DESIGN: We conducted an observational study comparing 2 groups of women for whom the regi-men of Yuzpe and Lancee was administered after unprotected sexual intercourse. One group (usual time frame treatment group) sought consultation within 72 hours (n = 131), and the other (extended time frame treatment group) after 72 to 120 hours (n = 169).
RESULTS: The pregnancy rate was 0.8% for the <72-hour group and 1.8% for the 72- to 120-hour group.
The effectiveness rate varied from 87% to 90% for the <72-hour group and from 72% to 87% for the 72- to 120-hour group. In both groups the • 2 tests showed that emergency contraceptive pills significantly reduced the risk of pregnancy.
CONCLUSIONS: Women should be encouraged to seek consultation as quickly as possible after unprotected sexual intercourse. However, if the usual time limit (<72 hours) has expired, the so-called “morning-after pill should be recommended if an intrauterine contraceptive device is not available. Emergency contra-ceptive pills have a favorable success rate after 72 hours, with a pregnancy rate that is significantly lower than would be expected if no contraceptive were administered. (Am J Obstet Gynecol 2001;184:531-7.)
Key words: Clinical study, emergency contraception, hormonal contraception, postcoital contraception, relative biologic effectiveness ing emergency contraceptive pills. Our study design has many shortcomings, such as the absence of a placebo group, information that is based on recall, the absence of proven fertility, and the fact that sexually active women may have engaged in sexual intercourse more than once during the study period. The pregnancy tests at the beginning enabled us to detect pregnancies re-sulting from unprotected sexual intercourse earlier in the menstrual cycle. Such events would lower the effectiveness rate.
We changed the classification of 2 cases after we col-lected ultrasonographic data; this was not part of the pro-tocol.
Because we were interested in achieving good in-ternal validity in the effectiveness rate calculation, it was decided to take this information into account. Two cases would have been misclassified without this information.
Ultrasonographic data were not obtained differentially between groups. The results of ultrasonography made us realize the uncertainty of information based on recall and on the willingness to tell the truth. Even if patients are asked to adhere to a specific protocol, such as not having any sexual intercourse after treatment, young, sexually active women will have difficulty complying with this recommendation. Research studies concerning postcoital contraception will always be confronted with this dilemma.
Without a placebo control group, the use of probability tables such as those proposed by Wilcox et al 10 is the only way to estimate what would have occurred in the absence of any contraception.
It was also decided to include additional analysis of data on women who, in other studies, would have been considered protocol violators,11, 12 such as women who had 2 instances of unprotected sexual intercourse and irregular menstrual cycles. It is interesting to note that even when the lowest probability of pregnancy was used we found a significantly lower pregnancy rate than would be expected if no contraception had been administered Including these women increases the study’s external va-lidity Statistical significance was achieved when the observed and the expected pregnancy rates were compared. The effectiveness rates were comparable between the ex-tended time frame and the usual time frame groups in the selected population. Direct comparisons of these groups were not performed because the lack of power to detect small differences between them was known beforehand.
We noted that women who had had sexual intercourse 72 hours before dosing were less likely to use any con-traceptive method. They seemed less concerned by their sexual risk-taking behavior in that they did not consult the family planning clinic because of unprotected sexual intercourse; most of them consulted the clinic for other reasons. In our study the systematic evaluation of unprotected sexual intercourse by the clinicians allowed the de-tection of these situations and in some cases prevented unwanted pregnancies.
Studies in which the target population is difficult to recruit and the outcome is a rare event require further con-firmation by other studies involving other populations.
Even though our study shows that the effectiveness was equally as good before and after 72 hours for the selected subgroup, we observed in all the groups a trend toward a decrease in the effectiveness rate after 72 hours. We show that emergency contraceptive pills are still effective after 72 hours, but we believe that they are probably less effec-tive as the time before treatment increases.
In conclusion, we agree that women should be encour-aged to seek consultation as soon as possible after an un-protected coital act. However, after 72 hours, the regimen of Yuzpe and Lancee has a favorable effectiveness rate and therefore should be recommended when an intrauterine contraceptive device cannot be used. A recent study confirmed that levonorgestrel 5 is more effective than the method of Yuzpe and Lancee. It also revealed a higher effectiveness rate when the medication was given early after unprotected sexual intercourse. Studies with mifepristone and levonorgestrel are interesting and seem to show higher efficacy rates; however, they are not yet available in many countries. Future research should chal-lenge this new time frame with these regimens, which might offer some advantages over the method of Yuzpe and Lancee. They should include ultrasonography as part of the protocol for all pregnancies and pregnancy tests before treatment. These measures should help prevent misclassification of failure or success attributable to the emergency contraceptive pills.
We thank the following participating clinics: the Local Center for Community Services (CLSC) de Gramby, CLSC Pierrefond, CLSC Centreville, Clinique des Jeunes Saint-Denis, Hôpital Sainte-Justine, CLSC du Marigot, CLSC Sainte-Thérèse, CLSC J.O. Chénier, CLSC Hochelaga-Maisonneuve, CLSC des Faubourgs, CLSC Lamater, CLSC Villeray, CLSC Saint-Hubert, CLSC Mon-tréal Nord, CLSC Métro, CLSC Saint-Eustache, CLSC Rosemont, CLSC Lasalle, CLSC Verdun, CLSC Saint-Henri, CLSC Haute-Laurentide, CLSC de Matane, CLSC Soc, CLSC Normand Bethune, Haute Yamaska, and Université Concordia.
REFERENCES
1. OCs provide emergency contraception option. Network 1996;16:14-7.2. Yuzpe AA, Lancee WJ. Ethinylestradiol and dl–norgestrel as a postcoital contraceptive. Fertil Steril 1977;28:932–6.3. Glasier A, Thong KJ, Dewar M, Mackie M, Baird DT. Mifepris-tone(RU 486) compared with high-dose estrogen and progestogen for emergency postcoital contraception. N Engl J Med 1992; 327:1041-4.4. Ho PC, Kwan MSW. A prospective randomized comparison of levonorgestrel with the Yuzpe regimen in postcoital contraception.
Hum Reprod 1993;8:389-92.536 Rodrigues, Grou, and Joly March 2001 Am J Obstet Gynecol |
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