摘要目的：探讨辅助生殖技术（ART）治疗后单卵双胎（MZT）的发生、处理及妊娠结局。方法回顾性分析2011年1月至2014年1月在温州医科大学附属第一医院生殖医学中心行ART治疗后获得临床妊娠患者的临床资料，分析其MZT的发生、处理及妊娠结局。结果（1）获得临床妊娠的5908个胚胎移植周期中，多胎妊娠2169例（36.71%，2169/5908），其中双胎妊娠2012例（34.06%，2012/5908）、三胎及三胎以上妊娠（HOMP）157例（2.66%，157/5908）；MZT妊娠51例（0.86%，51/5908）。51例MZT妊娠患者中，19例为单纯MZT妊娠，32例为伴有MZT的HOMP。MZT妊娠在卵裂期胚胎或囊胚期胚胎移植中的发生率[分别为0.86%（38/4420）、0.87%（13/1488）]比较，差异无统计学意义（P=0.960）；在体外受精（0.93%，28/3022）、卵母细胞胞质内单精子注射法（0.72%，10/1384）和冻融胚胎移植（0.87%，13/1502）后的发生率比较，差异也无统计学意义（P=0.794）。（2）单纯MZT妊娠与非MZT的双胎妊娠患者间比较，更易发生流产[分别为6/19和5.11%（101/1976）]和出现低出生体质量儿[分别为73.91%（17/23）和42.89%（1453/3388）；P<0.01]。29例伴有MZT的三胎妊娠行减胎术后，8例减为单胎妊娠的患者中，无低出生体质量儿，与21例减为双胎妊娠患者的低出生体质量儿发生率[56.00%（14/25）]比较，差异有统计学意义（P=0.021）。伴有MZT的三胎妊娠减为双胎妊娠的21例患者中，双胎活产率为（42.86%，9/21）；同期非MZT的三胎妊娠减为双胎妊娠的121例患者中，双胎活产率为（75.21%，91/121），前者明显低于后者（P=0.003）。结论 ART治疗后MZT的发生率较高，是造成HOMP的重要原因，易引起不良妊娠结局。为减少MZT的发生，首要措施选择单胚胎移植，当HOMP合并MZT时宜减去MZT。

abstractsObjective To analysis the incidence and management of monozygotic twin (MZT) conceived by assisted reproductive techniques (ART). Methods A retrospective analysis of clinical pregnancies and MZT that resulted from ART was performed in Reproductive Medical Center,the First Affiliated Hospital,Wenzhou Medical University between January 2011 and January 2014. Results A total of 5 908 pregnancies were diagnosed: 2 012 twins, 157 high-order multiple pregnancy (HOMP), including 4 quadruplets. Overall, 51 MZT pregnancies were identified of them including 32 cases HOMP and 19 cases MZT. The incidence of MZT resulting from cleavage-stage embryo transfer was similar to blastocyst transfer (P=0.960). The percent of MZT resulting from in vitro fertilization [0.93% (28/3 022)], frozen-thawed embryo transfer [0.87% (13/1 502)] and intracytoplamic sperm injection [0.72% (10/1 384)] did not show statistical significance (P=0.794). The expectantly managed MZT was associated with a significantly greater likelihood of miscarriage [6/19 vs 5.11% (101/1 976)], and low birth weight infant [73.91% (17/23) vs 42.89% (1 453/3 388), P<0.01], when compared with dizygotic twin (DZT) did not undergo selective embryo reduction(SER). In monozygotic (MZ)-triplets with SER to 2 fetuses or to 1 fetus, there was no cases of preterm birth or low birth weight infant observed in MZ-triplets with SER to 1 fetus;when compared with MZ-triplets with SER to 2 fetuses, the low birth weight infant [56.00% (14/25), P=0.021] has statistical significance. The likelihood of the survival of two babies was lower in MZ-triplets with SER to 2 fetuses when compared with non-MZ triplets with SER to 2 fetuses [42.86%(9/21)vs 75.21%(91/121), P=0.003]. Conclusions The incidence of MZT pregnancies following ART is high. It plays a significant role in the occurrence of HOMP. MZT pregnancies are at an increased risk of adverse outcomes , it should transform to a single embryo thansfer (SET) program to reduce them incideuce. Reduction of MZT contained in multiple pregnancies appears to be a safe option.