Since the publication of the first edition of the WHO (World Health Organization) Laboratory Manual for the examination of Human Semen in 1980, the reference values of sperm parameters have been updated on four occasions. Currently and globally, most of the laboratories analyzing semen samples use the latest, 5th edition of the manual that recommends ejaculatory abstinence from two to seven days before producing the sample for examination. While this standardized interval of time facilitates the interpretation of the results and research, no solid evidence exists to support the WHO-recommended abstinence time for a semen analysis in order to optimize clinical outcomes after assisted reproduction. Most of the studies refer to different clinical outcomes, different groups of patients and different editions of the WHO Laboratory Manual, including heterogeneous intervals of abstinence or sperm parameters. The aim of the current systematic review was to evaluate available evidence correlating ejaculatory abstinence time with clinical outcomes and sperm parameters analyzed according to the last edition of the World Health Organization Laboratory Manual reference values in different male populations. The results from the included studies indicate that WHO abstinence recommendations may need revision, given that a shorter ejaculatory abstinence interval appears to be associated with improved sperm parameters, such as sperm DNA fragmentation, progressive motility or morphology, while evidence suggests a potential increase in embryo euploidy rates and pregnancy outcomes.

Desde la introducción de los tratamientos de reproducción asistida, hace ya más de 40 años, ha habido un creciente interés por conocer la función de la P, tanto en los ciclos naturales como en los de FIV y de transferencia de embriones criopreservados. Su impacto directo en los resultados clínicos en varios niveles activó varias líneas de investigación, con algunas de ellas aún abiertas hoy en día. En este capítulo describimos la evidencia disponible actualmente para valorar la implicación de la P en TRA y revisamos los factores que pueden modificar los niveles de P sérica, así como los que pueden interferir en su lectura correcta a la hora de analizar el resultado obtenido del laboratorio.