OBJECTIVE: To compare the multiple pregnancy rates of frozen-thawed embryos transfer (FET) or fresh embryos transfer, analyze the factors related to multiple pregnancies after IVF and study pregnancy rates with different number of embryos transferred in FET cycle. METHODS: A retrospective analysis was performed upon multiple pregnancies from 1235 and 1561 clinical pregnancies conceived by FET or fresh embryo transfers. RESULTS: No correlation was found between fresh or cryopreserved embryos transfer and multiple pregnancy rates. There were significant effects of woman's age, number of embryos transferred and stage of embryos upon multiple pregnancy rates. When the same number of cleavage-stage embryos was transferred to women with the same age, twin pregnancy rate or triplet pregnancy rate was the same between FET and fresh cycles. Triplet pregnancy rate with three embryos transferred was significantly higher than that of two embryos transferred. In women under 35 years old, the pregnancy rate with two embryos transferred reached 36.1%. CONCLUSION: Frozen-thawed embryos or fresh embryos transfer has no effect upon the multiple pregnancy rate. Women under 35 years old can achieve acceptable pregnancy rates when two cryopreserved embryos are transferred. It is helpful to reduce the triplet pregnancy rate.
OBJECTIVE: To compare the multiple pregnancy rates of frozen-thawed embryos transfer (FET) or fresh embryos transfer, analyze the factors related to multiple pregnancies after IVF and study pregnancy rates with different number of embryos transferred in FET cycle. METHODS: A retrospective analysis was performed upon multiple pregnancies from 1235 and 1561 clinical pregnancies conceived by FET or fresh embryo transfers. RESULTS: No correlation was found between fresh or cryopreserved embryos transfer and multiple pregnancy rates. There were significant effects of woman's age, number of embryos transferred and stage of embryos upon multiple pregnancy rates. When the same number of cleavage-stage embryos was transferred to women with the same age, twin pregnancy rate or triplet pregnancy rate was the same between FET and fresh cycles. Triplet pregnancy rate with three embryos transferred was significantly higher than that of two embryos transferred. In women under 35 years old, the pregnancy rate with two embryos transferred reached 36.1%. CONCLUSION: Frozen-thawed embryos or fresh embryos transfer has no effect upon the multiple pregnancy rate. Women under 35 years old can achieve acceptable pregnancy rates when two cryopreserved embryos are transferred. It is helpful to reduce the triplet pregnancy rate.