Live birth from a blastocyst derived from a conjoined oocyte in a frozen embryo transfer cycle: a case report and a literature review

Abstract

The significance of conjoined oocytes in the clinical in vitro fertilization (IVF) laboratory setting has been questionable due to the extremely limited data available. This issue is discussed by presenting one case for conjoined oocyte observed in the program of the assisted reproduction and by including a review of corresponding literature. This report describes a successful clinical pregnancy with subsequent live birth from a conjoined oocyte. To our knowledge, there are only three reported cases of successful live birth from conjoined oocytes, but this is the first case of live birth from a blastocyst derived from a conjoined oocyte fertilized using intracytoplasmic sperm injection (ICSI) in a frozen embryo transfer cycle. Moreover, this study reports the first time that live birth of a conjoined oocyte is achieved without removing the degenerated immature oocyte prior to transfer. It demonstrates that the degenerated immature oocyte has no adverse effect on subsequent embryo development and pregnancy outcome. In addition, we reviewed the literature to evaluate the origin, incidence, safety, and significance of conjoined oocytes in reproductive health. We further confirm previous reports that demonstrate that a mature oocyte from conjoined-oocyte complexes can be fertilized by standard IVF or ICSI and lead to the development of a blastocyst, subsequent pregnancy, and live birth.

Keywords: Binovular follicle; Conjoined oocyte; Frozen embryo transfer cycle; Intracytoplasmic sperm injection.

Fig. 1

A pair of conjoined oocytes arise from binovular follicles, which include a mature oocyte (MII) and an immature oocyte containing a large vacuole on day 0. The connected region of the zona pellucida is indicated by black arrow

Fig. 2

The high-quality embryo from a conjoined oocyte and the hatching blastocyst from a separated oocyte. a A high-quality 8-cell embryo derived from the conjoined oocyte on day 3 after ICSI. b A high-quality expanded blastocyst (4BB) derived from the conjoined oocyte on day 5. c The hatching blastocyst (5BC) derived from a separated oocyte. d The hatching blastocyst derived from the conjoined oocyte and the degenerated immature oocyte still attached