Risk of monozygotic twinning associated with different blastocyst transfer strategies in single embryo transfer
Yaxin Song1, Yapeng Wang1, Lin Zeng2
1Centre for Reproductive Medicine, Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, People's Republic of China; National Clinical Research Center for Obstetrics and Gynecology (Peking University Third Hospital), People's Republic of China; State Key Laboratory of Female Fertility Promotion, Department of Obstetrics and Gynecology, Peking University Third Hospital, People's Republic of China; Key Laboratory of Assisted Reproduction (Peking University), Ministry of Education, People's Republic of China; Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproductive Technology, People's Republic of China.
Research Question:
To explore which embryo transfer plan is the risk factor of monozygotic twinning in in vitro fertilization and embryo transfer.
Design:
This retrospective analysis included 25,202 patients who achieved clinical pregnancy following single embryo transfer. According to different embryo transfer protocols, patients were divided into five groups: fresh cleavage-stage embryo transfer (Group A), thawed cleavage-stage embryo transfer (Group B), fresh blastocyst transfer (Group C), thawed cleavage embryos then blastocyst transfer (Group D), and thawed blastocyst transfer (Group E). The incidence of monozygotic twinning was compared among the five groups.
Results:
The overall incidence of monozygotic twinning in this study was 1.79% (451/25,202). The incidences of monozygotic twinning in Groups C and D were 3.02% and 4.38%, respectively, significantly higher than those in Groups A, B, and E (1.01%, 1.93%, and 1.65%, respectively). The incidence of monozygotic twinning following transfer of early blastocysts (stage ≤ 3) was significantly higher than that following transfer of stage 4, 5, and 6 blastocysts (3.58% vs. 1.93%, 1.57%, and 1.04%, respectively; P < 0.001). The proportion of stage ≤ 3 blastocysts in Group E was 1.40% (272/19,446), significantly lower than that in Groups C (16.31%, 205/1,257) and D (20.67%, 250/1,210). Multivariate logistic regression analysis showed that thawed cleavage embryos then blastocyst transfer (Group D) was an independent risk factor for MZT (OR = 2.837, 95% CI: 1.280-6.288, P = 0.010).
Conclusions:
Compared with frozen-thawed blastocyst transfer, thawing and extended culture of cleavage-stage embryos to blastocysts may be a risk factor for monozygotic twinning.
