Cryopreservation of human oocytes and fertilization by two techniques: in-vitro fertilization and intracytoplasmic sperm injection

Human oocyte cryopreservation results in poor survival and subsequentfertilization rates. It has been suggested that freeze-thaw-inducedchanges in the zona pellucida may impair sperm penetration orattachment. The aim of this study was to compare fertilizationand cleavage rates in cryopreserved oocytes inseminated by conventionalin-vitro fertilization (IVF) or intracytoplasmic sperm injection(ICSI). A total of 220 oocytes, obtained from volunteers whohad undergone ovarian stimulation, were cryopreserved usinga slow freeze-rapid thaw protocol with 1.5 M propanediol asthe cryoprotectant. Surviving oocytes (n= 74, 34.4%) were randomlyallocated for fertilization by conventional IVF (group 1) orICSI (group 2) using cryopreserved spermatozoa from a singledonor of proven fertility. Fertilization was achieved in five(13.5%) of the oocytes in group 1 and 17 (45.9%) in group 2(P < 0.005), with only one oocyte in group 1 exhibiting normalfertilization as opposed to 16 (43.2%) in group 2 (P < 0.001).Similarly, one oocyte fertilized by IVF cleaved, while all fertilizedwith ICSI cleaved (P < 0.001). We conclude that althoughthe survival of oocytes is poor following cryopreservation,fertilization and cleavage rates can be enhanced significantlyusing ICSI. These data also suggest that the method of cryopreservationused in this study affected the zona pellucida, such that normalsperm attachment or penetration was impaired.     

Prevention of twin pregnancy after in-vitro fertilization or intracytoplasmic sperm injection based on strict embryo criteria: a prospective randomized clinical trial.

A prospective randomized study comparing single embryo transfer with double embryo transfer after in-vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) was carried out. First, top quality embryo characteristics were delineated by retrospectively analysing embryos resulting in ongoing twins after double embryo transfer. A top quality embryo was characterized by the presence of 4 or 5 blastomeres at day 2 and at least 7 blastomeres on day 3 after insemination, the absence of multinucleated blastomeres and <20% cellular fragments on day 2 and day 3 after fertilization. Using these criteria, a prospective study was conducted in women <34 years of age, who started their first IVF/ICSI cycle. Of 194 eligible patients, 110 agreed to participate of whom 53 produced at least two top quality embryos and were prospectively randomized. In all, 26 single embryo transfers resulted in 17 conceptions, 14 clinical and 10 ongoing pregnancies [implantation rate (IR) = 42.3%; ongoing pregnancy rate (OPR) = 38.5%] with one monozygotic twin; 27 double embryo transfers resulted in 20 ongoing conceptions with six (30%) twins (IR = 48.1%; OPR = 74%). We conclude that by using single embryo transfer and strict embryo criteria, an OPR similar to that in normal fertile couples can be achieved after IVF/ICSI, while limiting the dizygotic twin pregnancy rate to its natural incidence of <1% of all ongoing pregnancies.     

Controlled comparison of conventional in-vitro fertilization and intracytoplasmic sperm injection in patients with asthenozoospermia.

A controlled comparison between conventional in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) has been carried out for patients with 相似文献   

Endometrial thickness as a predictor of pregnancy after in-vitro fertilization but not after intracytoplasmic sperm injection

An ultrasonographic evaluation of the endometrium was performedin 158 patients undergoing ovarian stimulation for an in-vitroassisted reproduction programme. Endometrial thickness was evaluatedin 109 patients undergoing in-vitro fertilization (IVF) forfemale indications and in 49 patients undergoing intracytoplasmicsperm injection (ICSI) for male indications. The maximal endometrialthickness was measured on the day of human chorionic gonadotrophin(HCG) administration by longitudinal scanning of the uteruson the frozen image using electronic callipers placed at thejunction of the endometrium-myometrium interface at the levelof the fundus. Cases in which the endometrial thickness was10 mm were included in group A; cases in which the endometrialthickness was <10 mm were assigned to group B. The age ofthe patients, serum 17- oestradiol concentrations on the dayof HCG administration, the length of follicular stimulation,the number of follicles, 17- oestradiol concentrations per follicleon the day of HCG and the number of embryos transferred wereanalysed in each case. When comparing endometrial thicknessand results in IVF and ICSI patients, an endometrium <10mm predominated in IVF patients (27.5%) compared with thoseundergoing ICSI (16.7%) (P=0.05); conversely an endometrium10 mm was more frequent in ICSI than in IVF patients. The incidenceof pregnancy was higher in IVF group A patients (32/79; 41%)than in IVF group B patients (5/30; 17%) (P=0.03), whereas nosignificant difference was found between ICSI group A (13/42;31%) and ICSI group B (3/7; 43%) patients. Thus, a higher percentageof IVF patients had thin endometrium when compared with ICSIpatients; thin endometrium was a prognostic indicator of pregnancyonly in the case of a female indication for infertility (IVF).A thin endometrium in cases of female infertility may reflecta previous or present uterine pathology, whereas in indicationsof male infertility (i.e. cases using ICSI), in the absenceof any associated uterine pathology, the presence of a thinendometrium is not predictive.     

Comparison of in-vitro development of embryos originating from either conventional in-vitro fertilization or intracytoplasmic sperm injection

In this retrospective study on 1628 consecutive cycles performed during a period of 4 years, development in vitro is compared of embryos obtained after either conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). At 39-42 h after insemination or injection, embryos obtained after ICSI were significantly (P < 0.01) further developed (mean cell number 3.48 +/- 0.03) as compared with those obtained after IVF (3.22 +/- 0.03), whereas after 63-66 h of in-vitro development this difference was no longer present (mean cell number 6.11 +/- 0.15 versus 6.09 +/- 0.13 respectively). Culture of surplus embryos obtained after IVF resulted in a significantly higher (P < 0.001) mean incidence of blastocyst formation per cycle as compared with the ICSI group (31.8 +/- 1.9 versus 23.0 +/- 1.4 respectively). Blastocysts from both groups consisted of comparable numbers of cells. Blastocyst formation was also significantly higher when embryos were cultured in groups (31.2 +/- 1.8) compared to single culture (23.1 +/- 1.5; P < 0.01), in human tubal fluid (HTF) medium (29.2 +/- 1.7) compared with IVF-50(TM) medium (24.2 +/- 1.6; P < 0.01), and when they were cultured under 5% O(2) (30.3 +/- 1.5) compared with 20% O(2) (21.7 +/- 1.7; P < 0.01). In all culture conditions used, the mean incidence of blastocyst formation per cycle showed comparable differences in favour of the IVF group as compared with the ICSI group.     

Clinical experience with ultrarapid cryopreservation of human embryos resulting from intracytoplasmic sperm injection: brief communication.

A total of 41 patients requested thawing of supernumerary embryos in an intracytoplasmic sperm injection (ICSI) programme. Mean patient age was 30.8 +/- 3.8 years. Embryo freezing by the ultrarapid method was performed at room temperature in 3 mol/l DMSO and 0.25 mol/l sucrose. Total freezing time was 2.5 min including filling of the straw. In the thawing process, the embryos were removed from liquid N(2), left at room temperature for 30 s, immersed for 40 s at 30 degrees C, and then successively transferred at room temperature for 10 min to each of three sucrose solutions of decreasing concentration. The embryos were kept in culture and only those that presented cleavage after 24 h were transferred. Embryos from 42 cycles were thawed and a total of 24 transfers was performed. The mean number of thawed embryos was 5.0 +/- 3.2 per cycle and the mean number of transferred embryos was 2.83 +/- 1.3. The clinical pregnancy rate per cycle obtained after the thawing process was 16. 6%. The clinical pregnancy rate per transfer was 29.2% and the implantation rate was 13.2%. The abortion rate was 14.3%. Six deliveries have been performed, with the birth of seven infants.     

Embryo transfer under ultrasound guidance improves pregnancy rates after in-vitro fertilization

Between October 1998 and January 1999, we examined the influence of ultrasound guidance in embryo transfer on pregnancy rate in 362 patients from our in-vitro fertilization (IVF)-embryo transfer programme. These patients were prospectively randomized into two groups: 182 had ultrasound-guided embryo replacement, and 180 had clinical touch embryo transfer. There were no statistically significant differences between the two groups with respect to age, cause of infertility and in the characteristics of the IVF cycle. The pregnancy rate was significantly higher among the ultrasound-guided embryo transfer group (50%) compared with the clinical touch group (33.7%) (P < 0.002). Furthermore, there was also a significant increase in the implantation rate: 25.3% in the ultrasound group compared with 18.1% in the clinical touch group (P < 0.05). In conclusion, ultrasound assistance in embryo transfer significantly improved pregnancy and implantation rates in IVF.     

Cumulative probability of achieving an ongoing pregnancy after in-vitro fertilization and intracytoplasmic sperm injection according to a woman's age, subfertility diagnosis and primary or secondary subfertility

The aim of this study was to estimate reliable cumulative probabilities of achieving an ongoing pregnancy after successive in-vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) cycles, according to a woman's age, subfertility diagnosis and primary or secondary subfertility. Therefore reasons for quitting treatment without achieving an ongoing pregnancy were taken into account. Moreover, we studied whether there were trends in cumulative probabilities after adjustment for potential confounding effects of the other two characteristics, duration of subfertility, year of first treatment and reason for quitting treatment. In total, 2984 IVF/ICSI cycles were performed in 1315 couples at the University Hospital Nijmegen, The Netherlands, between 1991 and 1998. The 'realistic' cumulative probability of achieving an ongoing pregnancy was 54.5% after five consecutive IVF/ICSI cycles, which was about 10% lower (absolute value) than the optimistic probability calculated by life-table analysis and about 10% higher (absolute value) than the most pessimistic estimate. Women of 35 years or younger had a higher probability of achieving an ongoing pregnancy than the older women. As ICSI is now an option, there were no obvious differences between the subfertility diagnosis subgroups. The cumulative probability after the first two IVF/ICSI cycles was higher in women with secondary subfertility than in those with primary subfertility; this advantage disappeared after further treatment. These trends remained valid after adjustment for confounding factors.     

Maternal serum alpha-fetoprotein and human chorionic gonadotrophin in pregnancies conceived after intracytoplasmic sperm injection and conventional in-vitro fertilization.

Data in the Caucasian population suggest that maternal serum alpha-fetoprotein (AFP) and unconjugated oestriol concentrations are reduced and human chorionic gonadotrophin (HCG) concentrations are elevated in pregnancies conceived after in-vitro fertilization (IVF), leading to a higher than expected Down's syndrome screen-positive rate. There are no previous reports on the serum marker values in pregnancies conceived after intracytoplasmic injection (ICSI). Between 1996 and 1998, we measured maternal serum total HCG and AFP concentrations between 15 and 20 weeks gestation in 42 in-vitro fertilization (IVF) pregnancies and 23 ICSI pregnancies with known normal outcome. The results were compared with that of 2799 naturally occurring singleton pregnancies who were known to have a normal outcome. Median AFP multiple of the median (MOM) in ICSI pregnancies was significantly reduced to 0.76 compared with both that of the controls and that of the IVF pregnancies. For the IVF pregnancies, median HCG MOM was elevated to 1.15, and median AFP MOM was reduced to 0.88 compared with the controls, but these differences were not statistically significant. In both the IVF and ICSI pregnancies the changes might result in a falsely high Down's syndrome risk. In particular, the reduced AFP concentration in ICSI pregnancies was substantial. If this preliminary finding is substantiated by other series, the appropriate adjustment needs to be made to allow for valid interpretation of the screen result and to avoid an unnecessarily high false positive rate.     

Conventional in-vitro fertilization versus intracytoplasmic sperm injection in sibling oocytes from couples with tubal infertility and normozoospermic semen.

An auto-controlled study was conducted in couples with tubal infertility and normozoospermic semen. The fertilization rates and embryonic development in sibling oocytes treated, using the same semen sample, either by conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) at the same time were compared. Sibling oocyte-cumulus complexes (OCC) of 56 different couples with tubal infertility and normozoospermic semen were randomly divided in order of retrieval into two groups inseminated either by conventional IVF or by ICSI. Of the retrieved OCC in the same cohort, 53.0 +/- 31.2 and 62.0 +/- 26.6% showed two distinct pronuclei after conventional IVF and ICSI respectively (not significant). Complete fertilization failure occurred after conventional IVF in 12.5% (7/56 couples). After ICSI, the comparable figure was 3.6% (2/56). The number of cases was too small to apply a statistical test to this difference. Total cleavage rates were quite similar: 86.7 +/- 28.0 and 90.1 +/- 21% of the zygotes developed into transferable embryos after IVF and ICSI respectively (not significant). Similarly, no difference in embryo quality was observed. Although injection and insemination of the oocytes were performed at the same time in the two groups, at 42 h post-insemination more embryos were at the four-cell stage after ICSI (P < 0.001) than after conventional IVF, where more embryos were still at the two-cell stage (P < 0.02). Embryo transfer was possible in all 56 couples, resulting in 16 positive serum human chorionic gonadotrophin tests (28.6% per embryo transfer), from which a clinical pregnancy resulted in 15 couples. The best embryos were selected for transfer independently of the insemination procedure, but preferably from the same origin. There appeared to be no difference in implantation potency of the embryos obtained with either technique after the non-randomized transfers.     

Chromosomal status of uni-pronuclear human zygotes following in-vitro fertilization and intracytoplasmic sperm injection

Uni-pronuclear embryos (n = 42) were analysed by fluorescencein-situ hybridization (FISH) with two to four chromosome pair-specificprobes. Half of these embryos resulted from conventional inseminationand half from intracytoplasmic sperm injection (ICSI). The majorityof uni-pronuclear embryos from conventional insemination werenormally diploid (61.9%) whereas only 9.5% of uni-pronuclearICSI embryos (P < 0.001) were diploid. In addition, a significantlyhigher number of uni-pronuclear embryos from conventional inseminationhad a Y chromosome (10/21, 47.6%) when compared with ICSI embryos(2/21, 9.5%) (P = 0.015). It is concluded that the majorityof uni-pronuclear embryos following regular in-vitro fertilizationare fertilized, whereas those from ICSI are parthenogeneticallyactivated. The latter embryos should not be considered for embryoreplacement.     

Infertility: Avoidance of triplet pregnancies by elective transfer of two good quality embryos

Attempts to increase the probability of a successful pregnancyin in-vitro fertilization (IVF) treatment by increasing thenumber of embryos transferred automatically also increase theprobability of multiple pregnancies and their attendant risks.Even where the number of transferred embryos is limited to amaximum of three as in this and other centres, there is a highincidence of twins and triplets. The question therefore ariseswhether the number of transferred embryos should be furtherlimited to a maximum of two in cases where the prognosis isotherwise good. The only objection to this idea is a possiblelowering of pregnancy rate. The present study set out to investigatethis question. No significant lowering of pregnancy rate wasfound, so that limiting the number of transferred embryos totwo where the prognosis is otherwise good has now become standardpractice in our centre. A good IVF prognosis was defined bythe following criteria: first attempt for IVF, less than 37years old, and good embryo development. From 183 patients fulfillingthese criteria, 80 agreed to the transfer of two embryos (group1) and 103 opted for a triple transfer (group 2). Patient characteristicsand embryology results were similar in the two groups. In group1, 34 patients (42.5%) became pregnant and in group 2, 50 (48.5%).This difference is not significant. Similarly, twin pregnancyrates in both groups were high; eight twin pregnancies (23.5%)in group 1 and 12 (24%) in group 2. For the triplet pregnancyrate of 18% (nine triplet pregnancies) in group 2, there wasobviously no parallel in group 1. After thawing about half ofthe cryopreserved embryos and subsequently replacing them, preliminarycumulative pregnancy rates of 52.5% in group 1 and 53.4% ingroup 2 were obtained. Future results from cryopreservationshould provide relatively better outcomes for group 1 sinceall the patients in this group had at least one embryo frozenand fewer embryos replaced in the fresh cycle.     

Luteal phase and clinical outcome after human menopausal gonadotrophin/gonadotrophin releasing hormone antagonist treatment for ovarian stimulation in in-vitro fertilization/intracytoplasmic sperm injection cycles.

The luteal phase hormonal profile and the clinical outcome of 69 patients undergoing in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) after ovarian stimulation with human menopausal gonadotrophin (HMG) and the gonadotrophin-releasing hormone (GnRH) antagonist Cetrorelix were analysed. Twenty-four patients received Cetrorelix 0.5 mg (group I) while in 45 patients Cetrorelix 0.25 mg was administered (group II). Human chorionic gonadotrophin (HCG) was used as luteal support. Nine clinical pregnancies were obtained in group I (37.5%) and 12 in group II (26. 6%). These results were not significantly different. Serum progesterone and oestradiol concentrations did not differ between the two groups either in pregnant or non-pregnant patients. An expected decrease of the same hormones was observed 8 days after the pre-ovulatory HCG injection in non-pregnant women. With regard to serum luteinizing hormone concentrations, a decrease was observed 2 days after the pre-ovulatory HCG injection and was maintained at almost undetectable levels throughout the entire luteal phase in both conception and non-conception cycles of group I and group II. This study demonstrates that different doses of GnRH antagonist do not have any impact on the luteal phase of IVF/ICSI cycles when hormonal support is given.     

Implantation: Two instead of three embryo transfer in in-vitro fertilization

The rational of transferring two instead of three embryos wasstudied through 468 in-vitro fertilization (IVF) treatment cyclesin 287 couples. The quality of 1224 embryos was determined accordingto the fragmentation rate and the morphology as good (A) andpoor (B). The influence of the number of embryos transferred(two or three) on the pregnancy rate when the same quality orcombinations of good and poor quality embryos transferred wasexamined. When only good quality embryos were transferred thepregnancy rates in double (AA) and triple (AAA) embryo transferwere 40.5 (17/42) and 42.9% (30/70) respectively (not significant).When only poor quality embryos were transferred, the pregnancyrates in double (BB) and triple (BBB) embryo transfers were11.0% (11/ 100) and 22.9% (16/70) respectively (P < 0.001).On the other hand, when good and poor quality embryos were transferredtogether as AB in double and as AAB and ABB in triple embryotransfer, the pregnancy rates were 36.8 (14/38) and 39.9% (59/148)respectively (not significant). There was no difference in themiscarriage rate between double and triple embryo transfers;16.7 and 18.1% respectively. The multiple pregnancy rate was14.3% for double embryo transfers and 32.4% for triple embryotransfers (P < 0.001). This study demonstrates that if thereis at least one good quality embryo available for transfer,then double instead of triple embryo transfer will not yielda significantly lower pregnancy rate. The influence of the numberof embryos transferred on the pregnancy rate became significantwhen only poor quality embryos were transferred. In conclusion,as long as at least one good quality embryo is available fortransfer, we may consider the transfer of double instead oftriple embryos.     

A prospective randomized study comparing the outcome of in-vitro fertilization and embryo transfer following culture of human embryos individually or in groups before embryo transfer on day 2.

A prospective randomized trial of in-vitro fertilization and embryo transfer was undertaken to investigate the reported beneficial effects of culturing preimplantation human embryos in groups, rather than individually. A total of 159 treatment cycles, in which the women were matched for age, basal gonadotrophin concentrations and number of previous attempts, were included in the study. Of these, 78 cycles were randomized to the 'individual culture' group, and 81 cycles were randomized to the 'group culture' group. The groups did not differ in terms of the median number of oocytes or embryos obtained per cycle. There was no statistically significant difference between the two groups in terms of treatment outcome, as assessed by pregnancies or clinical pregnancies.     

A comparative analysis of embryo implantation potential in patients with severe teratozoospermia undergoing in-vitro fertilization with a high insemination concentration or intracytoplasmic sperm injection

The objective of this study was to assess fertilization, implantationand pregnancy rates in infertile patients with severe teratozoospermia[P (poor prognosis) pattern sperm morphology assessed by strictcriteria] treated by in-vitro fertilization (IVF) using a highinsemination concentration (HIC), or by intracytoplasmic sperminjection (ICSI). This was a retrospective cohort study performedin an academic tertiary institution. The outcome of 115 consecutiveICSI cycles was compared to that of a similar number of cyclesof IVF with HIC performed during a similar time frame and matchedby woman's age and basal serum (cycle day 3) follicle stimulatinghormone concentrations. The inclusion criteria were sperm morphology4% normal forms (P pattern) and 1 x106 total motile spermatozoaper ejaculate. The diploid fertilization rate in the HIC-IVFgroup was 86% and in the ICSI group 68% (P < 0.05). Importantly,an equal number of embryos was transferred to both groups ofpatients. The morphological quality of the embryos (proportionof transfers having superior morphology embryo scores) was significantlybetter in the ICSI group than in the patients receiving HIC-IVF.Although there was a clear trend for better implantation andpregnancy rates in the ICSI group, these differences were notstatistically significant We conclude that, although HIC-IVFresulted in a higher fertilization rate than ICSI in patientswith severe teratozoospermia, ICSI produced a significantlyhigher proportion of morphologically superior embryos with atendency towards a higher implantation potential. Therefore,teratozoospermic patients having adequate numbers of motilespermatozoa should be offered ICSI as an alternative to modified(HIC) IVF treatment.     

Cryopreservation of human embryos obtained after gamete intra-Fallopian transfer and/or in-vitro fertilization

During a one-year period 636 excess embryos obtained after in-vitrofertilization and gamete intra-Fallopian transfer combined within-vitro fertilization were cryopreserved using two differentprotocols. For early stage embryos including the pronucleatestage, 1,2-propanediol was used as cryoprotectant (procedureA, adapted from Renard) and for later stage embryos dimethylsulphoxidewas used in protocol B, adapted from Trounson and Mohr. Afterthawing 288 embryos, half of them were of sufficient qualityto be replaced. After cryopreservation, procedure A gave thebest survival in embryos having 2 blastomeres; for later stageembryos best survival was obtained using the dimethylsulphoxideprotocol. Survival after cryopreservation was also clearly relatedto the quality of the embryos prior to freezing. Embryos werereplaced during endocrinologically monitored natural cyclesand were transferred in synchrony between endornetrial and embryonicage. After replacement of 126 embryos in 110 patients, 20 pregnanciesoccurred. So far six healthy children have been born, two patientsaborted and 12 pregnancies are ongoing. In this series no statisticaldifference was observed between the implantation rate of embryoscryopreserved by procedure A or B. Six pregnancies occurredin patients from the oocyte and embryo donation programme. Anadequate cryopreservation programme circumvents the difficultproblem of synchronizing the ovarian cycles of donor and acceptorpatients.     

Minimizing embryo expulsion after embryo transfer: a randomized controlled study

BACKGROUND: The aim of this work was to modify the embryo transfer technique to prevent expulsion of the embryos by exerting gentle mechanical pressure on the cervix using the vaginal speculum. METHODS: A total of 639 infertile patients undergoing ICSI were prospectively randomized into two groups using sealed dark envelopes. In the study group (n=325) the screw of the vaginal speculum was loosened in order to exert a gentle pressure on the portiovaginalis of the cervix before ejecting the embryos, and was maintained for 7 min afterwards. In the control group (n=314) no pressure was applied on the cervix during embryo transfer and the vaginal speculum was removed after transferring the embryos. RESULTS: The clinical pregnancy rate was significantly higher in the study group than in the control group [207/325 (67%) versus 150/314 (47.8%); odds ratio (OR) 1.39; 95% confidence interval (CI) 1.11-1.74]. The implantation rate was also significantly higher in the study group [304/913 (33.3%) versus 198/920 (21.5%); OR 1.54; 95% CI 1.26-1.89]. CONCLUSIONS: Applying gentle mechanical pressure on the portiovaginalis of the cervix using the vaginal speculum during and after transferring the embryos significantly improved clinical pregnancy and implantation rates.     

Obstetric outcome of pregnancies after the transfer of cryopreserved and fresh embryos obtained by conventional in-vitro fertilization and intracytoplasmic sperm injection.

This study reports the obstetric outcome of pregnancies obtained after the transfer of cryopreserved or fresh embryos where the initial procedure was standard in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Pregnancies obtained after frozen IVF (n = 245) or frozen ICSI (n = 177) were compared with a control group of pregnancies after fresh embryo transfer in standard IVF (n = 245) and ICSI (n = 177) cycles were selected as controls. The controls were matched according to maternal age, parity and date of embryo transfer. In the standard IVF group, the biochemical pregnancy rates in the cryopreserved and fresh groups were 18.8 and 9.8% respectively (P < 0.01). In the ICSI group, the biochemical pregnancy rates in the cryopreserved and fresh groups were 16.4 and 6.8% respectively (P < 0.01). The miscarriage rates were comparable between the cryopreserved and fresh groups. However, in the frozen ICSI group the miscarriage rate (26.0%) was significantly higher than in the frozen conventional IVF group (13.1%) (P = 0.001). The frequencies of preterm deliveries, infants with very low birthweight and intrauterine deaths were similar in the groups. The low birthweight rates in the frozen IVF (16.1%) and ICSI (12.1%) groups were significantly lower than those in the fresh IVF (32.2%) and ICSI (32.7%) groups (P < 0.001). The major malformation rates in the frozen IVF (2.4%) and ICSI (2.9%) groups were not different from the major malformation rates in the fresh IVF (4.5%) and ICSI (2.4%) groups. In conclusion, the cryopreservation process had no negative impact on the outcome of pregnancies over 20 weeks of gestation. Long-term follow-up studies are needed in order to prove the safety of the freezing-thawing process.     

Day 2 elective single embryo transfer in clinical practice: better outcome in ICSI cycles

BACKGROUND: Single embryo transfer (SET) after IVF/ICSI has been shown to result in an acceptable pregnancy rate in selected subjects. In our unit, SET is routinely carried out among women under the age of 36 in the first or second treatment cycle when a top-quality embryo is available. In order to define further the selection criteria for SET, we have analysed the outcome of elective SET (eSET), including the cumulative pregnancy rate after frozen embryo transfers, performed in the years 2000-2002 in the Oulu Fertility Center. METHODS: During the study period, a total of 1271 transfers were performed, and in 468 cycles SET (39% of all transfers) was carried out. Of the SET cycles, in 308 cases a top-quality embryo was transferred on day 2 and extra embryos were frozen. Of these eSET cycles, ICSI was carried out in 87 cycles (28%). RESULTS: The overall clinical pregnancy rate per transfer was 34.7% in the eSET cycles. In the eSET ICSI cycles, the clinical pregnancy rate was significantly higher than in the corresponding IVF cycles (50.6 versus 28.5%, P < 0.001). The cumulative pregnancy rate per patient after fresh and frozen embryo transfers was also significantly higher after ICSI (71.2 versus 53.4%, P < 0.01). CONCLUSIONS: A high cumulative pregnancy rate per oocyte retrieval can be achieved after eSET in daily clinical practice. The implantation rate of fresh top-quality embryos in the ICSI cycles was significantly higher than in the IVF cycles, possibly due to more successful selection of the embryo for embryo transfer on day 2 after ICSI. In addition, our data suggest that embryo quality is a more important determinant of outcome than the age of the woman.