Effect of injected spermatozoa morphology on theoutcome of intracytoplasmic sperm injection inhumans

The development of intracytoplasmic sperm injection (ICSI) has meant that severe male factor infertilitythat was previously untreatable can be treated successfully. None of the classic sperm parameters, such asconcentration, motility, or morphology, have been correlated with ICSI fertilization rates, and the onlyrequirement for achieving a satisfactory result is the presence of a living, motilespermatozoon. When therelationship between spermmorphology and ICSI success was analyzed, with the use of the percentage ofnormal spermatozoa in the whole semen sample as the predictor value, no relationship was found. WhenTasdemir et al. (1) analyzed the effect of the morphology of the injected spermatozoa on ICSI outcome in 17cases, the fertilization, pregnancy, and implantation rate were found to be reduced.

We present the results of a retrospective clinical study in which the effect of the morphology of the injectedspermatozoon was determined in a large series of ICSI treatments in a well-established infertility clinic.

ICSI was performed in 170 cycles. In 85 cycles that showed no morphologically normal spermatozoa, anabnormal spermatozoon was injected into each oocyte. Immediately following each ICSI treatment, oocytesinjected with normal spermatozoa were chosen as controls. On the day of oocyte retrieval, the spermmorphology was determined. In the abnormal morphology group, all patients had zero normal forms. Aspermatozoon was considered abnormal when it had defects in the head (globozoospermia—large, small,round; tapering or pyriform). Cycles in which spermatozoa had great defects (double head, double tail, oramorphous heads) were not used in the study. A single motile spermatozoon of normal morphology (orabnormal if no normal spermatozoon was found) was injected into an oocyte. Only cycles in which clearlyabnormal spermatozoa were observed at magnification3400 were used for the study; if the spermatozoaappeared only slightly abnormal, the cycle was not considered for the analysis (because at magnification3400it was not clear whether these spermatozoa were normal). Fertilization was assessed 18 hours after injectionby seeking the presence of pronuclei. Embryo cleavage was assessed 24 hours later. The embryo quality wasevaluated under the dissecting microscope before transfer, which was performed two days after oocytepick-up. All of the embryos transferred in the abnormal spermatozoa group had developed from an abnormalspermatozoon. Clinical pregnancy was diagnosed by the presence of a gestational sac with fetal echoes andpulsation.

A total of 1828 oocytes were injected in the 170 cycles analyzed. When normal spermatozoa were used,the fertilization rate was significantly higher than when abnormal spermatozoa were used. The abnormalfertilization rate (1 or 3 pronuclei) was the same in both cases. The cleavage rate and the embryo quality weresimilar in the two groups, as was the number of transferred embryos. No differences were observed in clinicalpregnancy, implantation, or miscarriage rates (Table 1). In the group of normal spermatozoa, 17 babies—11(64.7%) females and 6 (35.3%) males—were born after treatment; 25 babies—16 (64%) females and 9 (36%)males—were born in the abnormal spermatozoa group. No genetic or structural abnormalities were observedin the offspring.

When our ICSI results with morphologically abnormal spermatozoa were analyzed, we found differencesonly in the fertilization rate; no other parameter (embryo development, pregnancy, implantation, or miscar-riage rate) was affected. Mansour et al. (2) reported eight ICSI cases with 100% teratozoospermia. In two ofthese patients, amorphous sperm heads were microinjected and resulted in a complete failure of fertilization.These amorphous head spermatozoa could be the result of deficient spermatogenesis and their ability tofertilize could be reduced for this reason. In 1996, Lee et al. (3) showed that the incidence of structuralchromosomal aberrations was about four times higher in spermatozoa with amorphous heads than in thosewith morphologically normal heads. No increase in chromosome aberrations in spermatozoa with small orlarge heads was found. In an analysis of 17 cases with 100% abnormal sperm heads, Tasdemir et al. (1)observed low pregnancy and implantation rates; in two patients with 100% amorphous sperm heads there wasa complete failure of fertilization. This could result from the high incidence of structural chromosomalaberrations in these severely abnormal spermatozoa or from other sperm defects that may impair fertility.

In our study, no amorphous sperm heads where injected because we were always able to find some “good”

Received February 22,2000; revised andaccepted April 24, 2000.Reprint requests: E.Gomez, Ph.D., IVI-MURCIAc/Navegante Macias delPoyo No. 5-Bajo. 30007Murcia (Spain). (FAX: 34-968-23 78 11; E-mail:ivimur@forodigital).

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abnormal spermatozoa. The lowest fertilization rate (26.8%) in ourseries was observed in two cycles from the same patient with adiagnosis of total globozoospermia. Similar results have been ob-served previously and may be related to the type of globozoosper-mia present in the patient or to the absence or down-regulation ofthe sperm-associated oocyte-activating factor in these spermatozoa.No sperm karyotype abnormalities were seen in these spermatozoa(4). The results are not divided into different abnormality categoriesbecause of the low number of cases (85) in this study, and nostatistical analysis could be performed.

The absence of differences in embryo development or in im-

plantation, pregnancy, or miscarriage rates could mean that thefertilization process acts as a filter for “bad” spermatozoa, afterwhich no embryo parameters are affected. Structural aberrationmay be responsible for this phenomenon. On the other hand, theabnormal spermatozoa that were used for ICSI and which achievedfertilization did not have any chromosomal defects that couldinhibit embryo development or result in a baby with genetic defects.This may have been because we did not use amorphous heads forICSI since these spermatozoa may have structural chromosomalaberrations (3).

The present findings show that normal babies can be producedusing spermatozoa with morphologically abnormal heads, with norisk of genetic defects.

Emilio Gomez, Ph.D.a

Inmaculada Pe´rez-Cano, Ph.D.a

Beatriz Amorocho, Ph.D.a

JoseLanderas, M.D.a

Agustın Ballesteros, M.D.a

Antonio Pellicer, M.D.b,c

IVI-MURCIA, Murcia, Spain,a; Instituto Valenciano deInfertilidad, Valencia, Spain.b; Department of Paediatrics,Obstetrics and Gynaecology, Valencia University Schoolof Medicine, Valencia, Spainc

References1. Tasdemir I, Tasdemir M, Tavukcuoglu S, Kahraman S, Biberoglu K.

Effect of abnormal sperm head morphology on the outcome of intracy-toplasmic sperm injection in humans. Hum Reprod 1997;12:1214–17.

2. Mansour RT, Aboulghar MA, Serour GI, Amin YM, Ramzi AM. Theeffect of sperm parameters on the outcome of intracytoplasmic sperminjection. Fertil Steril 1995;64:982–6.

3. Lee JD, Kamiguchi Y, Yanagimachi R. Analysis of spermatozoa con-stitution of human spermatozoa with normal and aberrant head morphol-ogies after injection into mouse oocytes. Hum Reprod 1996;1:1942–6.

4. Rybouchkin A, Dozortsev D, Pelinck MJ, De Sutter P, Dhont M. Anal-ysis of the oocyte activating capacity and chromosomal complement ofround-headed human spermatozoa by their injection into mouse oocytes.Hum Reprod 1996;11:2170–5.

T A B L E 1

ICSI outcome when normal and abnormal humanspermatozoa were injected into oocytes.

NormalSpermatozoa

(n 5 85)a

AbnormalSpermatozoa

(n 5 85)a

Normal fertilization rate,2 pronuclei 79.7b (627/787) 72.5b (613/845)

Abnormal fertilization rate, 1–3pronuclei 7.1 (56/787) 6.4 (54/845)

Division rate 87.6 (549/627) 86.6 (531/613)Number of blastomers 3.06 0.7 3.06 0.6Fragmentation degree 1.56 0.4 1.96 0.4Number of transferred embryos 3.66 1.0 3.56 1.3Pregnancy rate per cycle 25.9 (22/85) 29.4 (25/85)Implantation rate 8.3 11.0Miscarriage rate 18.2 (4/22) 12.0 (3/25)a n 5 no. of cycles.b P , .05.

Gomez. Injected spermatozoa morphology on ICSI. Fertil Steril 2000.

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