Split happens: a case of consecutive monozygotic twin pregnancies following elective single-embryo transfer in a 40-year old woman using donor oocytes
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Monozygotic twins derive from a single zygote that undergoes division at varying stages of development, the timing of which ultimately determines placental sharing. Morula stage (days 1–4) division results in dichorionic-diamniotic twins that cannot be differentiated from dizygotic twins in utero. Blastocyst stage (days 4–8) division results in monochorionic-diamniotic twins. Division at the 8–12-day stage results in monochorionic-monoamniotic twins, and division after day 12 leads to conjoined twins [1, 2]. Monozygotic twinning is seen at a rate of 0.4% in natural conceptions, though that rate is significantly higher, ranging from 1.57–5.6%, when blastocysts are transferred using assisted reproductive technologies (ART) [3, 4, 5]. Although consensus has not been reached in the literature, it is thought that factors such as intracytoplasmic sperm injection (ICSI), blastocyst transfer, assisted hatching (AH), and individual embryologist technique may play a role in the...
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Conflict of interest
The authors declare that they have no conflict of interest.
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