Monozygotic twins in assisted reproduction treatment

Authors: E. Oráčová;  P. Trávník;  G. Tauwinklová;  K. Veselá;  L. Hromadová;  J. Veselý
Authors‘ workplace: Sanatorium REPROMEDA s. r. o., Brno 1;  Výzkumný ústav veterinárního lékařství, v. v. i., Brno 2
Published in: Prakt Gyn 2010; 14(3): 133-136
Category: Original Article


By definition, monozygotic (MZ) twins arise from one single zygote splitting into two separate individuals. MZ twinning is rare in nature, occurring in approximately 0.4% of all births. The incidence following assisted reproduction varies between 0.2% and 12.5%. Factors which appear to influence MZ twinning may be intrinsic factors (age, skewed X chromosome inactivation and inherited defects in zona pellucida proteins) and extrinsic factors (ovulation induction, artificial breach of the zona pellucida, embryo culture conditions and transfer of blastocyst stage embryos).

Materials and methods:
In this retrospective cohort study, including data from January 2000 to August 2009, we analyzed the incidence of MZ twin pregnancies in a cohort of consecutive IVF treatment cycles with ICSI, PGD and egg donation.

Of 1 255 pregnancies, 25 (1.99%) were MZ twins. In all these cases Day 5 embryos were transferred. The majority of transferred embryos were expanding and hatching blastocysts. Compared to the entire set, higher number of oocytes were gained in the MZ twins group (16.9 vs. 14.9) and the patients were of lower age (29.5 vs. 32.4). Over the last three years, an increasing tendency in MZD per pregnancy ratio was noted; 2.80% (year 2007), 3.33% (year 2008) a 3.39% (part of year 2009).

The incidence of MZ twin pregnancies in assisted reproduction treatment conceptions is several-fold higher compared to pregnancies after spontaneous conception. Due to an incomplete detection the true incidence of MZ twin pregnancies is probably even higher. We found association between the incidence of MZ twins and lower maternal age, higher number of obtained oocytes, ovarian stimulation and transfer of high quality blastocysts.

Key words:
monozygotic – twins – monochorionic – assisted reproductive treatment


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Paediatric gynaecology Gynaecology and obstetrics Reproduction medicine
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