Comparison of cryopreservation of supernumerary pronuclear human oocytes obtained after intracytoplasmic sperm injection (ICSI) and after conventional in-vitro fertilization

Abstract

A comparison was made of pronuclear stage human oocytes obtained either after classical in-vitro fertilization (IVF) or after intracytoplasmic sperm injection (ICSI). After ICSI or IVF, three fertilized oocytes from each patient were kept in culture for a further 24 h before embryo transfer. The surplus oocytes were cryopreserved using the 'open freezing system' and 1,2-propanediol and sucrose as cryoprotectants. A cohort of 817 and 1626 oocytes in pronuclear stage were frozen after IVF and ICSI respectively. Of these, 333 and 744 zygotes have been thawed, of which 78 and 76.5% were morphologically intact zygotes after IVF and ICSI respectively. From the 204 (ICSI) and 89 (IVF) zygote transfers performed, 34 (17%) and 18 (20%) pregnancies were established. Both groups showed a similar abortion rate of approximately 20%. It is concluded that pronuclear stage oocytes resulting from ICSI can be successfully frozen/thawed and the survival and pregnancy rates achieved are comparable to those for zygotes obtained after IVF.

Comparison of cryopreservation outcome following intracytoplasmic sperm injection and conventional in vitro fertilization

“…The abortion rate of clinical pregnancies was 22% for frozen-thawed conventional IVF embryos and 26.8% for ICSl-derived embryos. These rates were comparable and corroborate previous studies demonstrating that the abortion rates for frozen-thawed ET cycles ranged between 20 and 23% for conventional IVF embryos and 18 and 25% for lCSl-derived embryos (8,9,13).…”

“…We, therefore, refrain from using clomiphene citrate for endometrial preparation in a frozenthawed ET cycle. Although previous studies (7,8) have not indicated what the power of their analysis was, our results suggest that larger samples than that being reported have to be assessed to reach a firm and clinically significant conclusion.…”

“…Only a small number of studies directly address this question. A1-Hasani et al (8) reported a pregnancy rate of 17% (204 transfers) and 20% (89 transfers) for transfers of frozen-thawed pronuclear-stage embryos resulting from ICSI and conventional IVF, respectively. Van Steirteghem et al (7) reported a comparable clinical pregnancy rate of 12.9 and 14.6% for transfers of multicellular frozen-thawed embryos derived from either ICSI (101 cycles) or conventional IVF (253 cycles), respectively.…”

“…However, as mentioned previously, the two studies differ in their methodology of freezing and thawing, which may account for such differences. A1-Hasani et al (8) reported a survival rate of 78 and 76.5% for zygotes derived from conventional IVF and ICSI, respectively. A higher survival rate for freezing of pronuclear-stage zygotes, 94.8 and 93.2% for IVFand ICSI-derived zygotes, was recently reported by Hoover et al (9).…”

“…For fresh ET the pregnancy rate for ICSI cycles seems to be comparable to that of conventional IVF attempts (5,6). This rate is somewhat lower for frozen-thawed ET cycles of both ICSI and conventional IVF and is reported to range between 12.9 and 21% (7)(8)(9)(10)(11)(12)(13).…”