Dichorionic diamniotic (DCDA) twin pregnancies after single blastocyst embryo transfer have been reported recently, although a blastocyst ovum is generally believed to divide into monochorionic twin pregnancy. We investigated the incidence of DCDA twin pregnancy after single blastocyst embryo transfer and their zygosity. This prospective cohort study included 655 consecutive twin pregnancies that were managed from 2006 to 2014 at our institution. Chorionicity and amnionicity were determined using first-trimester ultrasonography and/or placental pathology. Zygosity was analyzed if the cases were DCDA twins after single blastocyst embryo transfer. Among 655 twin pregnancies, there were 348 DCDA cases, 295 monochorionic diamniotic (MCDA) cases and 12 monochorionic monoamniotic cases. Single blastocyst embryo transfer was performed in 43 cases. Six out of the 43 (14%) cases involved DCDA twin pregnancies and the other 37 cases involved MCDA twin pregnancies. Three DCDA twins born after single blastocyst embryo transfer, wherein frozen embryo transfer (FET) was performed in the natural cycle, were dizygotic, and the other three cases, wherein FET with hormone replacement therapy was performed, were monozygotic. DCDA twin pregnancy occurred in 14% (7% for monozygotic and 7% for dizygotic) of twin pregnancies after single blastocyst embryo transfer cases.

中文翻译：

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单囊胚移植和接合性后绒毛膜双羊膜双胎妊娠的发生率：8 年单中心经验

最近报道了单囊胚移植后双绒毛膜双羊膜（DCDA）双胎妊娠，尽管通常认为囊胚卵分为单绒毛膜双胎妊娠。我们调查了单囊胚移植后DCDA双胎妊娠的发生率及其合子性。这项前瞻性队列研究包括我们机构从 2006 年到 2014 年管理的 655 例连续双胎妊娠。使用孕早期超声检查和/或胎盘病理学确定绒毛膜性和羊膜性。如果病例是单囊胚移植后的 DCDA 双胞胎，则分析接合性。655例双胎妊娠中，DCDA 348例，单绒毛膜双羊膜（MCDA）295例，单绒毛膜单羊膜12例。单囊胚移植43例。43 例 (14%) 病例中有 6 例涉及 DCDA 双胎妊娠，其他 37 例涉及 MCDA 双胎妊娠。单胚泡胚胎移植后出生的三对DCDA双胞胎，其中在自然周期中进行冷冻胚胎移植（FET），为双卵子，另外三例，其中进行了激素替代疗法的FET，为单卵子。DCDA双胎妊娠在单囊胚移植病例后的双胎妊娠中发生率为14%（单卵子为7%，双卵子为7%）。其中进行了激素替代疗法的 FET 是同卵异体。DCDA双胎妊娠在单囊胚移植病例后的双胎妊娠中发生率为14%（单卵子为7%，双卵子为7%）。其中进行了激素替代疗法的 FET 是同卵异体。DCDA双胎妊娠在单囊胚移植病例后的双胎妊娠中发生率为14%（单卵子为7%，双卵子为7%）。