Analysis of factors contributing to success in a program of micromanipulation-assisted fertilization

OBJECTIVE: To determine factors important to clinical success in micromanipulation-assisted in vitro fertilization (IVF). DESIGN: Procedures invoked in two separate series of micromanipulation-assisted IVF cycles, one unsuccessful (series I) and the other successful (series II), were compared in an effort to identify changes that led to clinical success. SETTING: University-based IVF clinic. PATIENTS: In both IVF series involving micromanipulation, patients consisted of infertile couples who fit any of five categories of male-factor related infertility. The female patients underwent controlled hyperstimulation for oocyte retrieval and the oocytes were inseminated normally or were subjected either to partial zona dissection or subzonal sperm insertion to assist fertilization. Results in all groups were compared between the two patient series. RESULTS: In the successful series II, a noticeable improvement in fertilization rate and embryo quality was observed compared with series I. A significant increase in the percentage of patients reaching embryo transfer, the pregnancy rate per transfer, and the pregnancy rate per retrieval were noted in series II; a 25% ongoing pregnancy rate per retrieval was observed overall in this successful group, with "ongoing" defined as manifestation of at least a fetal sac on ultrasound with no detectable problems. Patients with a mixed transfer of embryos derived from manipulated and normally inseminated oocytes had a 75% rate of pregnancy per transfer in series II. Differences between the two series could not be attributed to patient selection or biases in selection of oocytes relegated to micromanipulation. However, oocyte handling, micromanipulation, and culture protocols differed significantly between the two series in that temperature and pH of oocytes was better controlled, and micromanipulation time was minimized in series II. CONCLUSION: Success in micromanipulation depends on maintenance of the oocyte in a stable and supportive environment throughout the micromanipulation procedure. It is also important to minimize trauma to the eggs by performing micromanipulation rapidly and with minimal distortion of the egg. Patients with a poor fertilization rate in standard IVF may experience a substantial increase in the likelihood of pregnancy when micromanipulation-assisted fertilization is performed on some eggs.     

The effects of coculture with autologous cryopreserved endometrial cells on human in vitro fertilization and early embryo morphology: a randomized study

PURPOSE: The aim of this study was to examine the influence of endometrial cells on the fertilization rate and early embryonic morphology following routine in vitro fertilization (IVF). Cryopreservation with subsequent thawing allowed the use of autologous somatic cells, thus minimizing the risk of transmission of infective agents. Interpatient variability was eliminated by randomizing oocytes from each cycle into the control or coculture group. RESULTS: Two hundred ninety-four oocytes from 24 IVF cycles (21 patients) were included in the study (145 coculture and 149 control). The normal fertilization rate of control oocytes (56.4%) was not significantly different from that of oocytes cocultured with endometrial cells (61.4%). The mean number of blastomeres in cocultured embryos (3.65) was not significantly different from the number in control embryos (3.46) 2 days after insemination, but the proportion of embryos with minimal or no fragmentation was significantly higher in the coculture group [34/84 (40.5%) vs. 17/80 (21.3%); P < 0.01]. CONCLUSIONS: The inclusion of cryopreserved autologous endometrial cells in routine clinical IVF procedures does not influence fertilization or the early cleavage rate but may reduce the extent of embryo fragmentation during the early cleavage divisions.     

The correlation between follicular measurements, oocyte morphology, and fertilization rates in an in vitro fertilization program

OBJECTIVE: To explore the relationship between follicle size and the morphology of the oocyte-cumulus-corona complex with fertilization rates in stimulated cycles of IVF. DESIGN: Retrospective comparison of measurements and observations of 2,429 oocytes from 215 patients undergoing 324 stimulated IVF cycles. SETTING: A large hospital-based IVF program. MAIN OUTCOME MEASURES: Individual follicles were measured by ultrasound before transvaginal aspiration and the size was recorded. The oocyte-cumulus-corona complex from each follicle was examined and classified. The oocytes were checked for evidence of fertilization 17 to 22 hours after insemination. RESULTS: The fertilization rate of all oocytes regardless of morphological type revealed a positive linear correlation with increasing follicle diameter. The fertilization rates of type I oocytes was marginally higher than type II oocytes, controlling for follicle diameter; however, this difference did not achieve statistical significance. Oocytes from follicles with a mean diameter > or = 16 mm had significantly higher fertilization rates than did oocytes from follicles with a mean diameter < or = 14 mm. CONCLUSIONS: Follicle size is a better predictor of fertilization than is morphological characterization of the oocyte-cumulus-corona complex in IVF.     

In vitro fertilization in women age 40 and older: the impact of assisted hatching

PURPOSE: To assess the impact of assisted hatching on in vitro fertilization (IVF) outcome in women age 40 and older. METHODS: A retrospective analysis was performed to compare 28 cycles of IVF without assisted hatching to 38 cycles of IVF with assisted hatching. All patients in both groups were age 40 or older and the mean age was similar. RESULTS: The delivery rate per oocyte retrieval was significantly higher in the assisted hatching group (18/38; 48%) compared to the nonhatched controls (3/28; 11%, P = 0.0003). The implantation rate of hatched embryos (40/175; 22%) was clearly enhanced, compared to the nonhatched embryos (7/126; 6%, P < 0.001). The fertilization rate, number of oocytes and the number of embryos per patient were comparable in the two groups. CONCLUSIONS: Assisted hatching dramatically improves embryonic implantation and term pregnancy rates in women age 40 and older undergoing IVF.     

Intracytoplasmic sperm injection as a routine indication in low responder patients

The aim of this study was to determine if a low response to gonadotrophin stimulation could be considered as an indication for intracytoplasmic sperm injection (ICSI). This prospective study included a total of 96 non-male infertile couples with six or fewer retrieved oocytes, who underwent 104 in-vitro fertilization (IVF) cycles between January 1996 and April 1997. They were randomly divided into two groups for fertilization, one by IVF and the other by ICSI. Groups were compared in terms of fertilization rates, fertilization failure, embryo quality, embryos transferred and reproductive outcome. ICSI provided similar fertilization rates per inseminated oocyte (77.7 versus 70.2%) and per obtained oocyte (56.5 versus 58.8%) as IVF. Furthermore, equal numbers (2.2 versus 2.5) and quality of embryos were obtained and comparable pregnancy (21.1 versus 17.3%) and implantation (14.0 versus 11.1%) rates. Neither the number of retrieved oocytes, nor patient age was relevant for the fertilization rates obtained with both techniques. The number of cases with complete fertilization failure was similar in both procedures. We conclude that the technique of fertilization is not related to the reproductive outcome of low responders, and the routine use of ICSI is not indicated.     

Implications of complete fertilization failure after intracytoplasmic sperm injection for subsequent fertilization and reproductive outcome

With the introduction of intracytoplasmic sperm injection (ICSI), couples with severe male factor infertility have achieved fertilization and clinical pregnancy rates comparable to other in-vitro fertilization (IVF) patients. However, failure of fertilization still occurs in some patients despite the utilization of microsurgical sperm injection techniques. How such fertilization failure after ICSI might impact later ICSI treatment(s) is unknown. In this investigation, couples with complete fertilization failure after ICSI treated from August 1993 to August 1996 were identified (index cycle, n = 21). Additionally, fertilization data from any previous or subsequent infertility treatments were evaluated. Seven patients (33%) had at least one IVF treatment before the index cycle, although no deliveries occurred. Of patients with complete fertilization failure in the index cycle, 48% (n = 10) underwent at least one subsequent ICSI cycle which proceeded to oocyte retrieval. The remainder (n = 11) elected to discontinue treatment. Although six subsequent cycles were cancelled due to poor follicular response (< or = 2 mature oocytes), all patients electing to continue treatment eventually achieved a subsequent embryo transfer. The clinical pregnancy rate per transfer was 45.4% for this group; the delivery and ongoing pregnancy rate per transfer was 36.3%. Review of semen parameters, superovulation characteristics or other clinical parameters during the three study cycles (pre-index, index, and post-index) was not prognostic of fertilization success or reproductive outcomes in later treatments. Fertilization failure with ICSI therefore could not be predicted by prior cycle performance, although total immotility of spermatozoa at time of oocyte retrieval, total teratozoospermia, and low oocyte yield were common characteristics of couples experiencing complete fertilization failure with ICSI. These findings suggest that fertilization failure in one ICSI cycle does not preclude successful fertilization and delivery in a later ICSI treatment.     

Sub-zonal insemination for extreme male factor infertility

When in-vitro fertilization (IVF) is used for severe male infertility, the zona pellucida constitutes a major barrier to sperm-oocyte interaction, a barrier that may, in principle, be overcome by micro-injecting one or more spermatozoa into the sub-zonal perivitelline space ('sub-zonal insemination' or SZI). We have defined suitable patients for SZI as having 'extreme' male factor in that they have either shown a failure of fertilization in previous IVF cycles or had < 50 000 motile spermatozoa recoverable after semen preparation. (This is distinct from those with only 'severe' male factor in whom sufficient (> 50 000) motile spermatozoa could be recovered from a semen preparation.) A total of 213 SZI cycles were performed at Sydney IVF in the 4 year period September 1988 to September 1992, for extreme male factor patients with previous IVF failures or extremely low sperm numbers for whom SZI was the first option (about two-thirds and one-third of cases respectively). A total of 138 embryo transfers are reported, producing 20 clinical pregnancies after performing SZI on 1899 oocytes. One patient miscarried at 12 weeks gestation and there have been nine normal deliveries (so far) of 10 healthy infants. The first delivery was in February 1990. One pregnancy was achieved in the only patient in whom spermatozoa were obtained by epididymal aspiration, and transfer of three cryopreserved embryos in another patient resulted in a singleton pregnancy. Of the 492 oocytes fertilized, 282 had two pronuclei (57.3%) and normal embryos were transferred in 138/213 (64.8%) treatment cycles, giving an overall pregnancy rate of 14.5% per embryo transfer or 9.4% per cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

The relationship between follicular fluid aspirate volume and oocyte maturity in in-vitro fertilization cycles

As a consequence of multiple follicular growth during ovarian stimulation for in-vitro fertilization (IVF), follicles of varying sizes often yield oocytes that vary in maturity and morphology of the oocyte-cumulus-corona complex. The objective of this prospective study was to explore the relationship between follicular fluid aspirate volume and the oocyte's developmental potential in an IVF treatment cycle. In total 9933 follicles were studied from 400 patients who underwent 535 consecutive IVF treatment cycles at St James's University Hospital, Leeds, UK, between February 1995 and February 1996. The volume of each individual follicle aspirated was recorded and related to the probability of obtaining an oocyte, its fertilizing capacity, the cleavage rate and the quality of embryos derived. We found no statistically significant difference in oocyte recovery rates between follicles with an aspirate volume < or = 1 ml and follicles with a volume > 1 ml. Although oocytes obtained from follicles with an aspirate volume > or = 1 ml showed a significantly lower fertilization rate, they went on to cleave at the same rate as oocytes obtained from larger follicles and resulted in embryos of comparable quality. Furthermore, there was no statistically significant difference in the implantation, clinical pregnancy or live birth rates per cycle between embryos derived from follicles with an aspirate volume < or = 1 ml and those derived from follicles with an aspirate volume > 1 ml. We conclude that follicular size and the oocyte's developmental potential in the stimulated ovary are not closely related and can be independent. This is in contrast to the Graafian follicle and the pre-ovulatory oocyte in the natural cycle.     

Transrectal electroejaculation combined with in-vitro fertilization: effective treatment of anejaculatory infertility due to spinal cord injury

Infertility due to spinal cord injury (SCI) in young men is a frequent complication of their injury. When the simpler methods of management of the erectile and ejaculatory dysfunction that invariably follow the more severe types of SCI are not effective, then semen production by transrectal electroejaculation (TREE) combined with in-vitro fertilization (IVF) and embryo transfer is effective. A retrospective analysis is presented of data on the treatment and outcome of 35 couples who wished to have a family but in whom the male partner had suffered SCI. These 35 couples had 71 attempts at IVF with spermatozoa obtained following TREE. Normal fertilization and cleavage of the embryos occurred in 48.2% of the oocytes. Fresh embryos were transferred in 54 cycles and frozen-thawed embryos in 14 cycles. In all, 18 clinical pregnancies were achieved in 54 fresh and 14 frozen embryo transfer cycles, with a live birth rate of 16.5% (14/85) per treatment cycle started, 20.6% (14/68) per transfer cycle and 40.0% (14/35) per couple who started treatment, in a mean of 1.9 transfer cycles. We conclude that TREE combined with IVF and embryo transfer is an effective treatment for the infertility problems associated with SCI.     

Dizygotic twin pregnancy after intracytoplasmic sperm injection of 1 day old unfertilized oocytes

We report on a case where late intracytoplasmic sperm injection (ICSI) on unfertilized oocytes after standard in-vitro fertilization (IVF) cycles resulted in a dizygotic twin pregnancy. Fifteen oocytes were harvested from a patient with a history of salpingotomy. After a single cycle of IVF, only one oocyte showed two pronuclei. Subsequently ICSI was performed on six unfertilized metaphase II oocytes, and three of these oocytes showed two pronuclei. Three fertilized embryos were transferred (two derived from ICSI and one from IVF). A normal twin pregnancy resulted, and after delivery of two healthy boys the twins were confirmed to be dizygotic by DNA analysis of several loci. We conclude that at least one of the embryos was derived from the reinsemination by 'second day ICSI'.     

Outcome from consecutive in-vitro fertilization/intracytoplasmic sperm injection attempts in the final group treated with urinary gonadotrophins and the first group treated with recombinant follicle stimulating hormone

In the absence of specific dose equivalency data, the aim of this study was to compare the clinical results during the cross-over from menopausal urinary products (human menopausal gonadotrophin; HMG) to recombinant follicle stimulating hormone (FSH) follitrophin beta (FSHr) in order to determine whether the manufacturer's recommendation for equivalence of ampoule to ampoule (50 IU FSHr:75 IU HMG) would prove clinically correct. A total of 353 consecutive in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) treatment cycles was studied between 1st September 1996 and mid-February 1997. This included cycles in the last 191 women receiving HMG and the first 162 taking FSHr. All were down-regulated using a gonadotrophin releasing hormone (GnRH) agonist long protocol method from day 1 of the cycle. Greater efficacy was seen in the HMG group in terms of days of stimulation required, need to increase dosage, cycle discontinuation, number of follicles punctured, the numbers of oocytes retrieved and their quality. The hormonal response to stimulation assessed by oestradiol concentrations on days 5, 8 and day of human chorionic gonadotrophin (HCG) was significantly lower in the FSHr group. The ratio of oestradiol per follicle and per oocyte was significantly lower in the FSHr group. There was a highly significant increase in cost with FSHr therapy. Clinical pregnancy rates were 14% per cycle with FSHr and 20% per cycle with HMG.     

The role of histone acetylation in the allelic expression of the imprinted human insulin-like growth factor II gene

This study examines the relationship between the first cycle of in-vitro fertilization (IVF) and subsequent cycles. The results of all IVF cycles conducted at The Hammersmith Hospital or The Royal Masonic Hospital between 1988 and 1995 were studied including those cycles where egg recovery was abandoned due to poor ovarian response. All patients underwent a standardized treatment protocol. Of those women who achieved a clinical pregnancy during their first IVF attempt, 33% achieved a pregnancy during their second cycle, statistically significantly different from the 24% of patients conceiving during a second cycle who had failed to conceive during their first. 36% of those who achieved a biochemical pregnancy in their first cycle became pregnant in their second. Age was an important factor in the success of IVF treatment, with pregnancy rates of 48% in the 20-25 year age group falling to 8% in those aged > or =41 years. Cumulative pregnancy rates were 26% after one cycle, increasing to 43% after two cycles and reached 80% after seven cycles. A previous pregnancy significantly improved a couple's probability of conception in a later IVF cycle. Overall pregnancy rates per cycle were constant for the first three attempts. Cumulative pregnancy rates continued to rise to 72% after six cycles. Thus the more cycles a couple undergo (up to six) the greater their chance of a pregnancy.     

An evaluation of the effect of pentoxifylline on sperm function and treatment outcome of male-factor infertility: a preliminary study

OBJECTIVE: Our objective was to study the effect of pentoxifylline (PF) on fertilization rates in couples with previous failure of fertilization and male-factor infertility and to determine the predictive value of conventional semen analysis parameters in selecting the couples who would benefit from the elective use of PF in IVF. DESIGN: This prospective controlled study was conducted in an assisted conception METHODS: Sixty-nine couples with previous failed IVF cycle, who had a low fertilization rate and/or male-factor infertility, were recruited to the study. Multiple follicular development was induced using the same protocol of human menopausal gonadotropin and gonadotropin releasing hormone analogue in both cycles. The oocytes were inseminated with spermatozoa treated with PF. The fertilization rates in the PF cycle were compared to the reference cycle based on semen analysis parameters and previous fertilization rates. RESULTS: In couples with male infertility, the fertilization rate improved significantly, from 17 to 50% in PF cycles (P < 0.001). A significant improvement in fertilization rate was also demonstrated in couples with previous poor fertilization, < 30% (P < 0.01), particularly in those with a very low fertilization rate, < 20% (P < 0.001). Although there was an overall improvement in fertilization rates in couples with male-factor infertility, there was no cutoff value in sperm motility that would make a significant difference in the impact of PF on fertilization rates. CONCLUSION: Couples with poor fertilization rates in vitro benefit with a significant improvement in fertilization by the elective use of PF. The improvement is most significant in couples with previous complete failure of fertilization and poor fertilization rates, < 30%.     

The outcome of in-vitro fertilization treatment by egg donation and intracytoplasmatic sperm injection for severe male factor infertility: a preliminary report

Due to a paucity of donated eggs, we have excluded, until recently, couples with severe male factor infertility from our egg donation programme, except for those who accepted insemination with donor spermatozoa. The purpose of this study was to assess the feasibility of a shared in-vitro fertilization (IVF)-embryo transfer treatment whenever the recipients have severe oligoasthenoteratozoospermia (OTA) and need intracytoplasmic sperm injection (ICSI) for egg fertilization. The results from 163 consecutive couples with ovarian failure who underwent 273 cycles of IVF with donated eggs and augmented with ICSI were analysed. The rate of diploid fertilization was 54.7%; in 92.3% of the cycles, at least one embryo was available for transfer. Forty-seven clinical pregnancies were achieved, representing 18.6% conceptions per transfer. The highest pregnancy rate was achieved in menopausal patients aged 40-45 years (26.2% per cycle) and the lowest in patients >45 years old (10.8% per cycle, P = 0.03). Overall, 28.8% of the couples achieved a clinical pregnancy. A total of 196 treatment cycles resulted in 46 clinical pregnancies (23.5%) among the donors. No statistical differences were found in pregnancy rate achieved by the donors when compared with the recipients. We conclude that ICSI with egg donation is a reliable treatment in patients with ovarian failure and severe OTA.     

Reparation activity and neurogenesis

OBJECTIVE: To study the outcome in poor responders to three ampules (225 IU) of hMG per day in subsequent IVF treatment cycles in which six ampules (450 IU)of hMG per day were administered. DESIGN: Retrospective chart review. SETTING: Academic tertiary center. PATIENTS: Between January 1988 and May 1995, 126 poor response patients had a first treatment cycle on three ampules and a second cycle on six ampules of hMG per day. MAIN OUTCOME MEASURES: Numbers of follicles, oocytes, and embryos, and pregnancy rates. RESULTS: On six ampules, patients had significantly more follicles and oocytes. The number of embryos did not differ significantly. The pregnancy rate on six ampules were low (3.2% pregnancies per cycle started). CONCLUSION: Poor responders do not benefit from high-dose hMG stimulation; their reproduction outcome is poor.     

Results from in vitro fertilization and intracytoplasmic sperm injection with purified gonadotrophins (Metrodin HP)

Purified urinary follicle-stimulating hormone (uFSH-HP; Metrodin HP, Serono Ltd.) was compared with a combination of pure FSH and human menopausal gonadotrophin (hMG; Pergonal, Serono Ltd.) in patients undergoing standard in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). In standard IVF, pure FSH gave a significantly higher pregnancy rate per started cycle than did the combination with hMG (35 vs. 18%, p < 0.05). No differences between standard IVF and ICSI were seen which could be associated with hormonal stimulation in an open non-randomized series of patients. In 11 ICSI cycles, the use of recombinant FSH (Gonal F, Serono Ltd.) resulted in 4 ongoing pregnancies.     

The results of an in vitro fertilization program: two regimens of superovulation

Gonadotropin-releasing hormone (GnRH) agonists are increasingly used in ovarian hyperstimulation protocols in in vitro fertilization (IVF) programs. From March 1992 to June 1993, 565 patients attending our Institute underwent superovulation in 1104 IVF program cycles. Of these cycles, 650 were stimulated with clomiphene citrate and gonadotropins (human menopausal gonadotropin/hMG), and 454 with the GnRH agonist buserelin and hMG in a group of patients who had earlier failed to respond or did not conceive after clomiphene citrate/hMG stimulation. The ovarian response was similar in both groups, however, with the use of buserelin more oocytes were recovered -4.9 +/- 3.2 and 3.5 +/- 2.3 oocytes, respectively. The clinical pregnancy rate per transfer in the group of patients superovulated with buserelin/hMG was twice that of the clomiphene citrate/hMG group (21.0% vs. 10.4%). The relatively high pregnancy rate with the buserelin/hMG regimen in the group of 'poor responders' may be connected with GnRH agonist-induced pharmacological hypophysectomy and the sequelae thereof: normalization of some endocrinopathies, absence of an endogenous luteinizing hormone (LH) surge and better endometrium receptivity, oocytes and embryo quality.     

Extended induction of ovulation by human menopausal gonadotropins and a gonadotropin-releasing hormone analog in high responders for in vitro fertilization and oocyte donation

OBJECTIVE: To examine the efficacy of extending ovulation induction for the in vivo maturation of oocytes. STUDY DESIGN: Fifty-nine high responders underwent 72 in vitro fertilization (IVF) cycles with a conventional protocol of human menopausal gonadotropin and a gonadotropin-releasing hormone analog. These patients donated oocytes to 81 recipients. The same 59 patients underwent 90 subsequent cycles in which the duration of induction was extended by two to three days. The oocytes were also donated to 138 patients. RESULTS: With the extended protocol, significantly more oocytes were retrieved (29.1 vs. 20.6), and a greater proportion of them were mature. Fertilization rates were significantly higher for both donors (67.7% vs. 36.2%) and recipients (67.5% vs. 47.1%). Conception rates were also significantly higher for both donors (24.4% vs. 11.1%) and recipients (38.4% vs. 24.7%). CONCLUSION: Extending the duration of ovulation induction in high responders is associated with in vivo maturation of oocytes and improved success rates in IVF and ovum-donation programs.     

An oocyte donation program with goserelin down-regulation of voluntary donors

BACKGROUND: In ovum donation programs oocytes can be requested from infertile women going through an in vitro fertilization cycle. Currently, when embryos can be cryopreserved, these donors have virtually disappeared. Instead, most donors have been healthy fertile volunteers willing to go through an IVF attempt solely for the purpose of donating all oocytes. METHODS: Sixty-four patients had 93 started cycles of oocyte donation from 59 donors. Twenty recipients had primary ovarian failure, 24 had secondary ovarian failure, 15 had had repeated failures in earlier IVF attempts and five were carriers of genetic diseases. The donors were 51 healthy volunteers recruited through the press. Eight patients from an IVF program donated excess oocytes. Donors were not paid and their mean age was 30 years. To minimize discomfort of the treatment, a long-acting GnRH-agonist, goserelin, was used for down-regulation. RESULTS: The pregnancy rate per transfer with fresh embryos was 28.4% (23/81) and with frozen-thawed embryos, 17% (3/18). Twenty-one healthy infants have been born including one set of triplets and three sets of twins. Nine pregnancies ended in abortion and one in intrauterine fetal death. The most common complications of pregnancy were pre-eclampsia and pregnancy-induced hypertension (41.2%, 7/17). Ten of 17 patients delivered by cesarean section (58.8%). CONCLUSION: It was possible, through the press, to obtain highly motivated oocyte donors, who go through IVF treatment solely for altruistic reasons. Oocyte recipients appear to have many complications in their pregnancies. Until more data are available, these patients need a high standard of obstetric care.     

Human menopausal gonadotropin during in vitro maturation of human oocytes retrieved from small follicles enhances in vitro fertilization and cleavage rates

OBJECTIVES: To compare the IVF rates of oocytes retrieved from small follicles (< 2 mL in volume) with those of oocytes retrieved from large follicles and to test the effect of adding gonadotropins to the IVF medium on the fertilization rates of oocytes from small follicles. DESIGN: Oocytes were retrieved with endovaginal ultrasound (US) guidance from patients undergoing infertility treatment in our IVF program. Oocytes were grouped according to the volume of the originating follicle and subjected to our routine procedure for IVF. HMG was added to the IVF medium for some of the oocytes from small follicles. SETTING: Toronto Fertility and Sterility Institute is affiliated with the University of Western Ontario and University of Toronto and is equipped for RIA, endovaginal US monitoring and oocyte retrieval, and for processing and culturing gametes and embryos. PATIENTS: Infertile patients admitted to our IVF program. INTERVENTIONS: Patients underwent ovarian stimulation with hMG before oocyte retrieval. No other interventions were introduced to the processing and culturing the gametes and embryos except the addition of hMG to the medium of some of the small follicle-originated oocytes with the informed consent from the patients. MAIN OUTCOME MEASURES: Rates of fertilization, cleavage of the fertilized embryos before replacement, and meiotic status of some of the oocytes from small follicles. RESULTS: Most of the oocytes from small follicles did not complete the first meiotic division; they had low rates of fertilization and cleavage compared with oocytes from large follicles, and these rates were improved by the addition of hMG to the IVF medium. CONCLUSIONS: Oocytes from small follicles are probably less mature and require a more physiological environment to achieve normal rates of fertilization and cleavage.