Effects Of Transplanting Human Early-cleavage Embryo On Pregnancy Outcomes In Vitro Fertilization-embryo Transfer

Background and ObjectiveHow to choose high-quality embryo with development potential to improve clinical pregnancy rate has become a focal point in vitro fertilization-embryo transfer (IVF-ET). Embryo morphology score has occupied a leading place in the choice of embryoes. In recent years, a great deal of attention has been paid to early cleavage. It has been reported that early cleavage is an indicator of embryo quality and embryo development potential. The mechanism of early cleavage is unclear, scholars have different point about it. In some research patients were aparted into two groups whether had early cleavage embryos on D2 or D3, so implantation capacity of early cleavage embryo is not intuitive, so as in mixed embryo transfers. Research about different controlled ovarian hyperstimulation programs, transplanting early cleavage embryos from patients with gonadotropin-releasing hormone antagonist would not improve implantation pregnance rate. Although most studies support the role of early cleavage, but in recent years reported that high-quality embryo transfer have similar pregnancy outcome, while have nothing to do with early cleavage. If this is true, then observing the early cleavage was meaningless. All subjects of this study were selected high-quality embryo depend on morphology of D2/D3 days, fertility and excellent embryo rate were statistically analyzed, and just because littile research has been done about the effects of early cleavage on pregnancy outcomes in ICSI or IVF. The purpose of this study was to observe the effects of early cleavage on pregnancy outcomes in ICSI or IVF, and further confirm that early cleavage possesses better embryo development potential. This study has a cetain significance for improvement in IVF-ET pregnancy outcomes.Materials and methods1. Early vleavage was observed in all IVF and ICSI cycles performed in our Center between March and September 2011. The data of 1027 cycles were retrospectively analyzed. Inclusion criteria included (1) patients were less than 40-year-old; (2) the first to two OPU cycles (3) day 2 and 3 high-quality embryoes were transferred; Exclusion criteria were (1) donor oocytes or sperm used in IVF; (2) rescue ICSI.2. Controlled ovarian hyperstimulation (COH) was accomplished using standard long or ultralong-protocols. The choose of IVF or ICSI was determined on the infertily cause.Pronuclei were observed according Scott and Smith scoring system. Conventionally early cleavage was observed after ICSI 24h-25h and IVF 27h-28h splitting into≥2 cells were recorded early cleavage embryos.Embryo quality was evaluated accoding to Peter scoring system 48h and 72h after ovum pick-up. Embryos will be transferred in Day 2 when normal zygotes≤2.GradeⅠorⅡnormal zygotes with 6 cells or more were transferred 72 h after ovum pick-up. Two embryoes or less were transferred in the patients with the first cycle, three embryoes or less were transferred in the patients with the age≥35 years or more than 2 cycles. Progesterone was intramuscularly injected and duphaston was orally given for luteal support. HCG in urine and blood were determined 14 days and 18 days after embryo transfer, respectively. It was diagnosed as clinical prenancy that B-mode ultrasound showed embryo sac and fetal heart beat 35 days after embryo transfer.3. Grouping:In the 7663 cleavage embryos,3386 were early cleavage embryoes and 4277 were late cleavage embryoes. Of the 1027 cycles, clinical pregnancy group 551 cycles and non-clinical pregnancy group 476 cycles; early-cleavage embryoes were used in 448 cycles (early-cleavage group:IVF-381, ICSI-67), late-cleavage embryoes were used in 284 cycles (late-cleavage group:IVF-147, ICSI-137), and both early and late-cleavage embryoes were used in 295 cycles (mixed group: IVF-209, ICSI-86); three groups with 0-1-2 early-cleavage embryoes transfer in 734 cycles which have 2PN early cleavage embryoes and have 2 embryoes transfer.4. Statistical analysis:Statistical analysis was performed with SPSS 16.0 software. Measurement data were expressed as mean±standard deviation (x±s) and were analyzed with t test. Numeration data were expressed as rate (%) and were analyzed withχ2 test. Test criterion was set atα=0.05 and statistical significance was established at P<0.05.5. CPR was determined as the presence of a gestational sac by abdominal ultrasound 35 days after ET. IR was defined as the ratio of the number of gestational sacs to the embryos transferred. Multiple pregnancy rate (twins and triplet was included) was defined as multiple pregnancies divided by clinical pregnancies. Miscarriage rate was defined as a pregnancy loss during the whole pregnancy period.Results1 Relation between early cleavage and embryo qualityIn 1027 patients with the age of 30.93±4.47 years,9804 MⅡooyctes,fertility rate was 81.0%(7943/9804) and cleavage rate was 96.5%(7663/7943), early cleavage rate was 42.6%(3386/7943).In the 7663 cleavage embryos,2PN rate of early cleavage embryos was 93.5%, excellent embryo rate was 87.2%, significantly higher than 82.1% of the late cleavage embryos and 58.8%(P<0.01), the same result was observed in IVF and ICSI cycles (IVF:87.5% vs.57.2%, P<0.001; ICSI:86.1% vs. 61.5%, P<0.001), and there were no significant differences between different fertilization.2 Relation between early cleavage rate and pregnancy outcomesPregnant compared to non-pregnant group in this study:there was no significant differences in age, infertility period, bFSH, GN days and the dosage, E2, P on HCG day, endometrial thickness on transplant day, etc. In laboratory parameters, the mean number of oocytes, fertilization rate, cleavage rate, early cleavage rate and high quality embry rate are all higher than those in non-pregnant group, the difference was statistically significant (P<0.05) except fertilization rate, but the number of embryoes transferred were no significant differences (P>0.05). In the two groups, no significant difference in Day 2 transplant ratio, but higher proportion of ICSI cycles and early cleavage embryoes transplant in pregnancy group.The differences were statistically significant (P<0.05).3 Pregnancy outcomes in IVFThis study included 737 IVF cycles. There were no statistical differences in age, duration of infertility, dose of gonadotropin (Gn), basal follicle stimulating hormone (FSH), levels of E2 and P on HCG day and endometrial thickness on the day of embryo transfer (ET) between the three groups (all P>0.05). The number of retrieved oocytes were no significantly different between groups (P>0.05). Fertility rate was higher in EC group than in late group (84.8% vs.81.2%, P<0.05).Cleavage rate and high-quality embryo rate were all significantly lower in late-cleavage group (92.7% and 54.0%) than in other two groups (all P<0.01). There was no significant difference in the number of transferred high-quality embryoes between the three groups. Clinical pregnancy rate and implantation rate were significantly higher in early-cleavage group (61.4% and 39.9%) than in other two groups (all P<0.05). Clinical pregnancy rate and implantation rate were similar in late-cleavage group and mixed group. There were no significant differences in multiple pregnance rate and spontaneous abortion rate between the three groups.4 Pregnancy outcomes in ICSIThis study included 290 ICSI cycles. There were no statistical differences in general status, oocyte retrieval and fertility rate between the three groups (all P>0.05). Cleavage rate was lower in late-cleavage group compared with other groups (P<0.01).Top-quality embryo rate was a little lower, but there was no significantly difference. Clinical pregnancy rate and implantation rate were significantly higher in early-cleavage group (73.1% and 42.8%) and mixed group (64.0% and 39.2%) than late-cleavage group (all P<0.05). Clinical pregnancy rate (73.1%) and implantation rate (42.8%) in early-cleavage group were higher compared with mixed group but wothout statistical significance (all P>0.05). There were no significant differences in high-order birth rate and spontaneous abortion rate between the three groups.5 Pregnancy outcome with different number of early cleavage embryoesAccording to the number of early-cleavage embryo transfer,734 from 841 cycles which have 2PN early-cleavage embryoes to choose and at last have 2 embryoes transfer were divided into three groups:ETO-1-2, comparative clinical pregnancy rate, implantation rate were significantly difference, the abortion rate and multiple pregnancy rate were not. Group ET2 has higher clinical pregnancy rate and implantation rate not only than ETO but also than ET1 group, the difference between the groups were significantly (P<0.05).Conclusions1 Early-cleavage embryos have the higher potential to develop into good quality embryos and nomal fertilization rate compared to late cleavage embryos.2 Early cleavage rate of clinical pregnancy group was significantly higher than non-pregnant group, inferred that the patients with higher early cleavage rate may presage a better pregnancy outcome.3 Despite good quality embryos were transplanted, both clinical pregnancy rate and implantation rate in IVF or ICSI were significantly higher in early-cleavage group than in late-cleavage group, suggesting that early cleavage is a potential objective indicators of evaluation of embryonic development, transplantation of early cleavage embryos will get better pregnancy outcomes.4 In ICSI, both clinical pregnancy rate and implantation rate were significantly higher in mixed group than in late-cleavage group. Inferred more obviously impact on ICSI pregnancy outcome by early cleavage.5 With increasing number of transplantation of early-cleavage embryos, clinical pregnancy rate and implantation rate tended to increase, the multiple rate and abortion rate were not affected, suggesting that embryos with superior morphology are preferred early cleavage embryos can improve pregnancy outcomes without increasing multiple births and the risk of miscarriage.