体外受精中单卵双胎的成因及相关因素分析

目的探讨体外受精-胚胎移植（IVF—ET）中单卵双胎的发生及其成因与机制。方法回顾性分析2006年9月至2010年10月间于我院进行IVF-ET并获得临床妊娠的1，782个周期，其中常规IVF—ET1，076周期，卵胞浆内单精子注射（ICSI）技术706周期，新鲜胚胎移植1，232周期，冷冻解冻胚胎移植550周期，统计单卵双胎、双卵3胎及三卵4胎等的发生情况，分析相关影响因素。结果1，782个周期中，单卵双胎共28例，发生率为1.57％。单卵双胎与非单卵双胎患者的年龄、不育年限、基础卵泡刺激素（FSH）和雌二醇（E2）水平有显著性差异（P〈0．05），而超排卵方案中，促性腺激素释放激素（GnRH）与促性腺激素释放激素激动剂（GnRH—a）总量及使用时间、黄体酮（P）剂量、基础黄体生成素（LH）、取卵日雌孕激素水平无显著性差异（P〉0．05）；患者胚胎移植前子宫内膜修整与否其单卵双胎的发生率有差异（P〈0．05）；常规IVF-ET和ICSI周期、冷冻胚胎周期和新鲜胚胎周期与单卵双胎的发生率均无显著性差异（P〉0．05）。结论IVF及其衍生技术中单卵双胎的发生率高于自然妊娠，可能与患者的年龄、基础激素水平、移植胚胎质量、子宫内膜同步化等因素相关。

Causes and related factors of monozygotic twins in vitro fertilization

Objective： To study the incidence and potential mechanism of monozygotic twins （MZT） pregnancies in IVF-ET cycles. Methods： One thousands seven hundred and eighty two IVF-ET cycles gained clinic pregnancy from Sep. 2006 to Oct. 2010, including 981 conventional in vitro fertilization and embryo transfer （IVF-ET） cycles and 801 intra-cytoplasmic sperm injection （ICS1） cycles, were reviewed. Among them, 1,232 cycles underwent flesh-embryos transfer and the 550 thawed cycles. The incidence and potential causes of MZT in IVF-ET were investigated. Results： Twenty eight cases of MZT occurred in 1,782 cycles with a incidence of 1, 57%. There were significant differences in maternal age, duration of infertility, basal FSH, E2 between MZT and non-MZT pregnancies （P〈0.05）; but no significant differences were found in dosage used of gonadotropin （Gn）, gonadotropin-releasing hormone antagonist （GnRH-a） and progesterone, and the levels of basal LH, E2, P, E2/P at hCG administration day （P〉0.05）. There was no significant difference in incidence of MZT between fresh and thawed cycles, neither between conventional IVF-ET and ICSI cycles （P〉0.05）, but there was significant difference between performed mechanical stimulation to endometrium or not （P〈 0.05）. Conclusions： The incidence of MZT in IVF-ET cycles was much higher than spontaneous conception, which was possibly related with maternal age, basal hormone levels, embryonic quality, embryonic development rate, assisted hatching, opening time of endometrial implantation window, and the difference between embryonic development and endometrial synchronization.