Factors Affecting Sperm Form Defined
Infertility not linked to a strict set of factors; instead, researchers are surprised at findings.
Increased sperm concentration and total motility are associated with increased percentages of normal sperm forms, whereas increasing age is linked to a decreased percentage of normal forms, researchers conclude.
Abstinence interval, volume, pH, and presence of white blood cells do not affect sperm morphology.
“Usually, morphology is the best predictor for good outcome in IVF (in vitro fertilization),” said lead investigator Laura Detti, MD, a clinical fellow in the division of reproductive endocrinology and infertility at
She and her colleagues retrospectively studied 1,667 men from infertile couples who presented to her institution's clinical andrology laboratory between January 2001 and March 2006 for semen analysis. The researchers evaluated only one ejaculate per patient (the first one collected correctly); semen analysis was performed manually using the modified World Health Organization criteria.
Her group looked at correlations between the variable sperm morphology and other parameters evaluated in the semen analysis, including age, abstinence interval, concentration, volume, pH, white blood cells, and motility. The analysis examined subcategories of motility: progression A (forward movement), progression B (slow forward movement), and progression C (non-progressive motility), total motility (motility x concentration x volume). All patients were divided into two groups based on their sperm morphology evaluation: “general” (387 patients) and “strict” (1,260 patients).
Progression A, progression B, and total motility correlated positively with increasing percentages of normal forms, whereas age correlated negatively with morphology in the “strict” morphology group only.
“Our study shows that the percentage of motile sperm should be almost as good as morphology at predicting the outcome of IVF,” Dr. Detti said. “However, other correlation studies should be performed to confirm these findings.”
Rebecca Sokol, MD, MPH, president of the Society of Male Reproduction and Urology, said the new study is important because it included so many semen samples from infertile couples. She cautioned that prospective studies are needed. “No definitive conclusions can be drawn about the correlation between sperm motility and IVF success until the investigators can report the predictive value of the percentage of motile sperm with IVF outcomes in a prospective study,” Dr. Sokol indicated.