Contraceptive efficacy of emergency contraception with levonorgestrel given before or after ovulation

Gabriela Noé, Horacio B. Croxatto, Ana María Salvatierra, Verónica Reyes, Claudio Villarroel, Carla Muñoz, Gabriela Morales, Anita Retamales

Resultado de la investigación: Article

40 Citas (Scopus)

Resumen

Background: The contraceptive efficacy of emergency contraceptive pills containing levonorgestrel (LNG-EC) has been estimated in most previous studies by judging the day of ovulation from presumptive menstrual cycle data, thus providing poorly reliable estimates. Methods: In the present study, the efficacy of LNG-EC was determined in 393 cycles by dating ovulation on the basis of reliable hormonal and ovarian parameters validated by a database constructed in a separate study. In addition, the efficacy was determined separately for cycles in which LNG-EC was given before or after ovulation. Results: For the 148 women who had sexual intercourse during the fertile days, the overall accumulated probability of pregnancy was 24.7, while altogether 8 pregnancies were observed. Thus, the overall contraceptive efficacy of LNG-EC was 68%. Among the 103 women who took LNG-EC before ovulation (days -5 to -1), 16 pregnancies were expected and no pregnancy occurred (p<.0001). Among the 45 women who took LNG-EC on the day of ovulation (day 0) or thereafter, 8 pregnancies occurred and 8.7 were expected (p=1.00). These findings are incompatible with the inhibition of implantation by LNG-EC in women. The same cases were also analyzed using the presumptive menstrual cycle data, and important discrepancies were detected between the two methods. Conclusion: The efficacy of LNG-EC has been overestimated in studies using presumptive menstrual cycle data. Our results confirm previous similar studies and demonstrate that LNG-EC does not prevent embryo implantation and therefore cannot be labeled as abortifacient.

Idioma originalEnglish
Páginas (desde-hasta)486-492
Número de páginas7
PublicaciónContraception
Volumen84
N.º5
DOI
EstadoPublished - 1 nov 2011

Huella dactilar

Postcoital Contraception
Levonorgestrel
Contraceptive Agents
Ovulation
Pregnancy
Menstrual Cycle
Postcoital Contraceptives
Abortifacient Agents
Coitus
Databases

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynaecology

Citar esto

Noé, Gabriela ; Croxatto, Horacio B. ; Salvatierra, Ana María ; Reyes, Verónica ; Villarroel, Claudio ; Muñoz, Carla ; Morales, Gabriela ; Retamales, Anita. / Contraceptive efficacy of emergency contraception with levonorgestrel given before or after ovulation. En: Contraception. 2011 ; Vol. 84, N.º 5. pp. 486-492.
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title = "Contraceptive efficacy of emergency contraception with levonorgestrel given before or after ovulation",
abstract = "Background: The contraceptive efficacy of emergency contraceptive pills containing levonorgestrel (LNG-EC) has been estimated in most previous studies by judging the day of ovulation from presumptive menstrual cycle data, thus providing poorly reliable estimates. Methods: In the present study, the efficacy of LNG-EC was determined in 393 cycles by dating ovulation on the basis of reliable hormonal and ovarian parameters validated by a database constructed in a separate study. In addition, the efficacy was determined separately for cycles in which LNG-EC was given before or after ovulation. Results: For the 148 women who had sexual intercourse during the fertile days, the overall accumulated probability of pregnancy was 24.7, while altogether 8 pregnancies were observed. Thus, the overall contraceptive efficacy of LNG-EC was 68{\%}. Among the 103 women who took LNG-EC before ovulation (days -5 to -1), 16 pregnancies were expected and no pregnancy occurred (p<.0001). Among the 45 women who took LNG-EC on the day of ovulation (day 0) or thereafter, 8 pregnancies occurred and 8.7 were expected (p=1.00). These findings are incompatible with the inhibition of implantation by LNG-EC in women. The same cases were also analyzed using the presumptive menstrual cycle data, and important discrepancies were detected between the two methods. Conclusion: The efficacy of LNG-EC has been overestimated in studies using presumptive menstrual cycle data. Our results confirm previous similar studies and demonstrate that LNG-EC does not prevent embryo implantation and therefore cannot be labeled as abortifacient.",
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Noé, G, Croxatto, HB, Salvatierra, AM, Reyes, V, Villarroel, C, Muñoz, C, Morales, G & Retamales, A 2011, 'Contraceptive efficacy of emergency contraception with levonorgestrel given before or after ovulation', Contraception, vol. 84, n.º 5, pp. 486-492. https://doi.org/10.1016/j.contraception.2011.03.006

Contraceptive efficacy of emergency contraception with levonorgestrel given before or after ovulation. / Noé, Gabriela; Croxatto, Horacio B.; Salvatierra, Ana María; Reyes, Verónica; Villarroel, Claudio; Muñoz, Carla; Morales, Gabriela; Retamales, Anita.

En: Contraception, Vol. 84, N.º 5, 01.11.2011, p. 486-492.

Resultado de la investigación: Article

TY - JOUR

T1 - Contraceptive efficacy of emergency contraception with levonorgestrel given before or after ovulation

AU - Noé, Gabriela

AU - Croxatto, Horacio B.

AU - Salvatierra, Ana María

AU - Reyes, Verónica

AU - Villarroel, Claudio

AU - Muñoz, Carla

AU - Morales, Gabriela

AU - Retamales, Anita

PY - 2011/11/1

Y1 - 2011/11/1

N2 - Background: The contraceptive efficacy of emergency contraceptive pills containing levonorgestrel (LNG-EC) has been estimated in most previous studies by judging the day of ovulation from presumptive menstrual cycle data, thus providing poorly reliable estimates. Methods: In the present study, the efficacy of LNG-EC was determined in 393 cycles by dating ovulation on the basis of reliable hormonal and ovarian parameters validated by a database constructed in a separate study. In addition, the efficacy was determined separately for cycles in which LNG-EC was given before or after ovulation. Results: For the 148 women who had sexual intercourse during the fertile days, the overall accumulated probability of pregnancy was 24.7, while altogether 8 pregnancies were observed. Thus, the overall contraceptive efficacy of LNG-EC was 68%. Among the 103 women who took LNG-EC before ovulation (days -5 to -1), 16 pregnancies were expected and no pregnancy occurred (p<.0001). Among the 45 women who took LNG-EC on the day of ovulation (day 0) or thereafter, 8 pregnancies occurred and 8.7 were expected (p=1.00). These findings are incompatible with the inhibition of implantation by LNG-EC in women. The same cases were also analyzed using the presumptive menstrual cycle data, and important discrepancies were detected between the two methods. Conclusion: The efficacy of LNG-EC has been overestimated in studies using presumptive menstrual cycle data. Our results confirm previous similar studies and demonstrate that LNG-EC does not prevent embryo implantation and therefore cannot be labeled as abortifacient.

AB - Background: The contraceptive efficacy of emergency contraceptive pills containing levonorgestrel (LNG-EC) has been estimated in most previous studies by judging the day of ovulation from presumptive menstrual cycle data, thus providing poorly reliable estimates. Methods: In the present study, the efficacy of LNG-EC was determined in 393 cycles by dating ovulation on the basis of reliable hormonal and ovarian parameters validated by a database constructed in a separate study. In addition, the efficacy was determined separately for cycles in which LNG-EC was given before or after ovulation. Results: For the 148 women who had sexual intercourse during the fertile days, the overall accumulated probability of pregnancy was 24.7, while altogether 8 pregnancies were observed. Thus, the overall contraceptive efficacy of LNG-EC was 68%. Among the 103 women who took LNG-EC before ovulation (days -5 to -1), 16 pregnancies were expected and no pregnancy occurred (p<.0001). Among the 45 women who took LNG-EC on the day of ovulation (day 0) or thereafter, 8 pregnancies occurred and 8.7 were expected (p=1.00). These findings are incompatible with the inhibition of implantation by LNG-EC in women. The same cases were also analyzed using the presumptive menstrual cycle data, and important discrepancies were detected between the two methods. Conclusion: The efficacy of LNG-EC has been overestimated in studies using presumptive menstrual cycle data. Our results confirm previous similar studies and demonstrate that LNG-EC does not prevent embryo implantation and therefore cannot be labeled as abortifacient.

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KW - Levonorgestrel

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