Weber W. Chuang

Increased chromosome X, Y, and 18 nondisjunction in sperm from infertile patients that were identified as normal by strict morphology: implication for intracytoplasmic sperm injection

OBJECTIVE To determine the incidence of nondisjunction for chromosomes X, Y, and 18 using fluorescence in situ hybridization (FISH) on morphologically normal sperm from infertile men who are candidates for ICSI. DESIGN After standard hematoxylin staining, sperm with normal morphology were identified using Krugers strict morphology criteria. The location of each normal-appearing sperm was recorded using an electronic microstage locator. Slides were subsequently subjected to FISH for detection of chromosomes X, Y, and 18 (control probe). Nuclei were relocated and analyzed under the fluorescent microscope. SETTING University-affiliated IVF and intracytoplasmic sperm injection program. PATIENT(S) Men classified as infertile on the basis of abnormal strict morphology (<4% by Krugers criteria). For controls, normal fertile men (n=6) were also analyzed. INTERVENTION(S) Semen smears were obtained retrospectively from infertile (n=8) and fertile (n=6) men. MAIN OUTCOME MEASURE(S) Ploidy of each cell was determined according to the number of signals detected for each probe. RESULT(S) Approximately 100-150 morphologically normal sperm were identified and located in each case. Subsequent FISH analysis of these normal sperm showed aneuploidy to range from 1.8% to 5.5% in the infertile group as compared with 0 to 2.6% among the control fertile group. Statistically significant differences in the incidence of aneuploidy for the sex chromosomes as well as for all three (X, Y, and 18) chromosomes was observed. CONCLUSION(S) Although 95% to 98% of the sperm were found to be normal for X, Y, and 18, our findings show that infertile couples undergoing ICSI are likely to be at an increased risk for having a genetically abnormal conceptus as compared with the fertile controls. These results demonstrate that normal morphology is not an absolute indicator for the selection of genetically normal sperm. Hence, observed pregnancy failures among ICSI patients may in part be due to the selection of aneuploid sperm.