Migration sedimentation technique as a predictive test for the fertilizing capacity of spermatozoa in an in‐vitro fertilization programme

The migration‐sedimentation technique (MST) has been proposed as a means of separating high quality motile spermatozoa. The present study was conducted in order to evaluate whether sperm performance following separation by MST predicts their fertilizing capacity in an in‐vitro fertilization (IVF) programme. Ninety semen specimens were analysed for use in an IVF‐embryo transfer (ET) programme. Each specimen was divided into two parts: one was processed in the IVF programme and was used after sperm swim‐up separation for insemination of human ova. The other aliquot (0.2 ml) was separated by MST, and the sperm then characterized by their concentration, motility, degree of motility and morphology. Sperm characteristics after separation by MST were then correlated with the results of the IVF‐fertilization rates. In 79 of 90 IVF‐ET cycles, at least one oocyte was fertilized. All post‐MST sperm characteristics were significantly higher in cycles with fertilizations compared to IVF cycles without fertilization. A larger percentage of the total motile spermatozoa were recovered after MST in semen specimens with fertilization, compared to semen specimens without fertilization (39.9 ± 3.6 and 20.6 ± 6.6%, respectively; P<0.05). This value was correlated with the percentage of fertilized oocytes (r= 0.24; P<0.02). More IVF cycles with fertilizations were recorded in cases in which the recovery of motile sperm was >25%(P<0.005), or when more than 1.5 times 10⁶ motile spermatozoa were recovered after MST (P <0.0001). As sperm characteristics after MST correlated significantly with their fertilizing capacity, the MST test could be used in evaluation of the fertilizing capacity of spermatozoa.