Comparison Single Embryo Transfer (SET) and Fetal Reduction (Three to One) Outcomes of Pregnant Women After Fetal Reduction

1. Background and Purpose Compared with multiple births, single embryo transfer pregnancies are not as high as risk of significant child morbidity, particularly cerebral palsy, after high-order fetal reduction. This is termed the vanishing-twin syndrome, and is an important etiology of cerebral palsy. Antenatal corticosteroid therapy (CCT) is widely used during preterm labor to enhance lung maturity, the use of dexamethasone, however, increase the risk for detrimental long-term neurodevelopmental effects. Thus, in this study we assess the effect of CCT on neurological disability and congenital abnormality in SET and control group after fetal reduction and over 2 years of age. 2. Methods The CCT (38 sets of SET) and control (56 sets) groups were compared for the incidences of cerebral palsy and congenital abnormalities, as well as mean birth weight, maternal age, and mean gestational age at delivery and at fetal reduction using records from Shin-Kong Memorial Hospital for the period 2008-2017. 3. Results There were 94 quadruplet-reduced sets of SET in our study. All of these SET were alive and aged over 2 years at the time of this writing. The gestational age at the time of delivery was 39+-2.4 weeks for the SET group vs. 36 ± 2.9 weeks for the controls, with mean birth weights of 2798 ± 555g vs. 2685 ± 519g, respectively (p<0.01). All 94 sets of twins were delivered by cesarean section, with only 1 case of cerebral palsy in Control group, while the others had developed normally by the age of 2 years. Only mean birth weight and gestational age at delivery showed significant differences in comparisons of the 2 groups of twins. 4. Conclusion The reasons why IVF treatment sometimes results in twin or triplet births – even though only one embryo is used – have been found by the largest study to date on single embryo transfer (SET) and multiple pregnancy. However, despite performing SET, multiple pregnancies do happen due to a phenomenon known as ‘zygotic splitting’, when one embryo divides resulting in twins or triplets. It is more prevalent following SET than in spontaneous conception.