[Effects of cryopreservation time and thawing method of human oocyte vitrification on the outcome of assisted reproduction].

OBJECTIVE

To evaluate the effects on pregnancy outcome of freezing time from oocyte retrieval and thawing method for metaphaseII human oocytes vitrification.

METHODS

From Mar 2007 to Mar 2009, the clinical outcome of 30 infertile women undergoing vitrified-thawing oocytes of in vitro fertilization-embryo transfer (IVF-ET) in the Reproductive Medical Center of the First Affiliated Hospital of Zhengzhou University was studied retrospectively, including 21 women with double fallopian tube obstruction and 9 women's husband azoospermia. All infertile women were divided into three groups, including 5 cases in group A (freezing between 4 and 5 hours from oocyte retrieval and conventional thawing method), 9 cases in group B (freezing within 2 hours from retrieval and conventional thawing method) and 16 cases in group C (freezing within 2 hours from retrieval and improved thawing method). The vitrified oocytes were preserved for 2 months to 1 year and thawed for Intracytoplasmic sperm injection (ICSI) and embryo transfer. The outcome of IVF and pregnancy were recorded.

RESULTS

(1) The rates of oocyte survival was (65 ± 33)% in group B and (72 ± 23)% in group C and the rate of transfer cycle was 9/9 in group B and 16/16 in group C, which were all significantly higher than (16 ± 17)% of oocyte survival and 1/5 of transfer cycle in group A (P = 0.001, 0.021). However, the rate of oocyte survival and transfer cycle between group B and group C did not reach statistical difference (P > 0.05). The rate of implantation and clinical pregnancy of (33 ± 38)% and 9/16 in group C were significantly higher (4 ± 11)% and 1/9 in group B (P = 0.033, 0.040). (2) The mean age of women in group C were (28.6 ± 2.1) in oneself oocyte, (28.0 ± 4.6) in donor oocyte and (28.1 ± 3.4) in donor sperm. The rate of oocyte survival was (73 ± 25)%, (88 ± 10)% and (66 ± 25)%. The rate of fertilization rate was (84.6 ± 0.9)%, (79.3 ± 2.0)% and (82.8 ± 15.0)%. The rate of implantation was (20.0 ± 44.7)%, (33.0 ± 0.1)%, (41.6 ± 41.7)%. The rate of clinical pregnancy was 1/5 in oneself cycles, 3/3 in donor oocyte cycles, 5/8 banked donor sperm cycles in group C. All above clinical parameters were not statistically different (P > 0.05). (3) In group A, one women underwent IVF-ET and no clinical pregnancy was observed. One women pregnancy was terminated at two months in group B. The clinical pregnancies rate of group C was 9/16, late abortion occurred in 1 woman, the other 8 women underwent term pregnancy, including 5 male infants and 4 female infants. All of infants showed normal Karyotype. Live-birth rates per warmed oocyte was 5.9%(8/135). The mean gestational weeks and birth weight of the infants were (39.4 ± 0.9) weeks and (3574 ± 569) g, respectively.

CONCLUSIONS

Embryo quality and clinical outcome of thawing cycles could be significantly improved when oocyte vitrification was performed within 2 hours from oocyte retrieval and improved thawing method.