On the origin of zygosity and chorionicity in twinning: evidence from human in vitro fertilization


DİRİCAN E. K., OLGAN Ş.

JOURNAL OF ASSISTED REPRODUCTION AND GENETICS, vol.38, no.11, pp.2809-2816, 2021 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Review
  • Volume: 38 Issue: 11
  • Publication Date: 2021
  • Doi Number: 10.1007/s10815-021-02294-y
  • Journal Name: JOURNAL OF ASSISTED REPRODUCTION AND GENETICS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, ATLA Religion Database, BIOSIS, Biotechnology Research Abstracts, CAB Abstracts, EMBASE, MEDLINE, Veterinary Science Database
  • Page Numbers: pp.2809-2816
  • Keywords: Multifetal gestations, Zygosity, Chorionicity, In vitro fertilization, Inner cell mass, Trophectoderm, SINGLE EMBRYO-TRANSFER, INTRACYTOPLASMIC SPERM INJECTION, MONOCHORIONIC DIZYGOTIC TWINS, THAWED BLASTOCYST TRANSFER, DIAMNIOTIC DD TWINS, INNER CELL MASS, MONOZYGOTIC TWINS, ASSISTED REPRODUCTION, MOUSE EMBRYO, RISK-FACTORS
  • Akdeniz University Affiliated: Yes

Abstract

Assisted reproduction is presumed to increase monozygotic twin rates, with the possible contribution of laboratory and medical interventions. Monozygotic dichorionic gestations are supposed to originate from the splitting of an embryo during the first four days of development, before blastocyst formation. Single embryo transfers could result in dichorionic pregnancies, currently explained by embryo splitting as described in the worldwide used medical textbooks, or concomitant conception. However, such splitting has never been observed in human in vitro fertilization, and downregulated frozen cycles could also produce multiple gestations. Several models of the possible origins of dichorionicity have been suggested. However, some possible underlying mechanisms observed from assisted reproduction seem to have been overlooked. In this review, we aimed to document the current knowledge, criticize the accepted dogma, and propose new insights into the origin of zygosity and chorionicity.