title: [Outcome analysis of monozygotic twin pregnancy conceived by assisted reproductive techniques].
abstract: OBJECTIVE
  To analyze the incidence, management, and outcomes of monozygotic twin (MZT) pregnancy conceived by assisted reproductive techniques (ART).
  
  
  METHODS
  A retrospective analysis was performed of clinical pregnancies after in vitro fertilization and embryo transfer (IVF-ET) and introcytoplasmic sperm injection and embryo transfer (ICSI-ET) from January, 2010 to June 2015 at our center. We investigated the incidence, managements and outcomes of 94 MZT pregnancies. Comparison of the pregnancy outcomes was made between the expectantly managed MZT pregnancies, dizygotic twin (DZT) pregnancies, monozygotic (MZ)-triplet pregnancies with selective embryo reduction (SER) to 2 fetuses and 1 fetus, and non-MZ triplet pregnancies with SER to 2 fetuses.
  
  
  RESULTS
  Ninety-four MZT pregnancies occurred in the total of 6257 clinical pregnancy cycles with an incidence of 1.5%. No significant difference was found in the incidence of MZT pregnancies between IVF and ICSI cycles or between fresh and thawed cycles (P>0.05). Of the 94 MZT pregnancies, 45 were MZT pregnancy cycles, 43 were MZ-triplet pregnancy cycles, 3 were MZ-quadruplet pregnancy cycles and 3 were ectopic pregnancies. The expectantly managed MZT was associated with a significantly greater rate of miscarriage and malformation and a lower rate of live birth and term birth (P<0.05) in comparison with DZT pregnancy cycles that did not undergo SER. Similar outcomes were found between MZ-triplet pregnancies with SER to 2 fetuses and MZ-triplet pregnancies with SER to 1 fetus (P>0.05), and between MZ-triplets with SER to 2 fetuses and non-MZ triplet pregnancies with SER to 2 fetuses (P>0.05).
  
  
  CONCLUSIONS
  ART is associated with a much higher incidence of MZT pregnancies than spontaneous conception. MZT pregnancies are at high risk of adverse outcomes, and reduction of MZT in multiple pregnancies may help to improve the outcomes.
authors.affiliation: Center for Reproductive Medicine, Department of Gynecology and Obstetrics, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China.E-mail: michellefeng64@163.com.
authors.forename: Shu-Xian
authors.initials: SX
authors.lastname: Feng
authors.forename: Xue-Lan
authors.initials: XL
authors.lastname: Li
authors.forename: Xing-Yu
authors.initials: XY
authors.lastname: Zhou
authors.forename: Yu-Dong
authors.initials: YD
authors.lastname: Liu
authors.forename: Ping-Ping
authors.initials: PP
authors.lastname: Guo
authors.forename: De-Sheng
authors.initials: DS
authors.lastname: Ye
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.forename: Shi-Ling
authors.initials: SL
authors.lastname: Chen
mesh_terms: D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D015994:Incidence; D050498:Live Birth; D011247:Pregnancy; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D027724:Reproductive Techniques, Assisted; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic; D014430:Twins, Monozygotic