A new mind-set for selective reduction in Dichorionic twin pregnancy discordant for chromosomal aneuploidy: a rare case report

Abstract Background Selective reduction is usually performed when one of dichorionic twins has a chromosomal abnormality.However, significant challenges arise when dichorionic twins exhibit identical features and lack definitive sonographic markers. we report a case of selective fetal reduction in structurally normal twin with chromosomal abnormalities in one of the dichorionic, and discusses the reduction strategy in the absence of clear ultrasonographic markers for selective reduction. Case presentation A 37-year-old women conceived dichorionic diamniotic twins via assisted reproductive technology, and underwent amniocentesis at 17 weeks of gestation, which confirmed trisomy 21 in one fetus. Both twin fetuses demonstrated concordant structural anatomy, biometric parameters, and phenotypic sex, with no discernible differences in placental architecture or umbilical cord insertion patterns. The couple chose selective reduction.We considered relying on the intrauterine position of the fetus as twin labeling for selective reduction.However, The position changes of the two fetuses were detected by ultrasound before the planned selective reduction. We attempted to have the patient change positions, move around, and hold her urine.Finally,the fetus spontaneously returned to its original position, successful reduction was achieved, with post-procedural genetic analysis confirming the terminated fetus exhibited trisomy 21. Conclusion In the absence of other evident sonographic markers, it is reasonable to consider relying on the intrauterine position of the fetus as twin labeling for reduction, However, the intrauterine position of the fetus is subject to change, we found it can be anticipated that the intrauterine positions of the two fetuses will recover spontaneous within a short time. Changes in fetal intrauterine position were tracked using continuous ultrasound monitoring.This approach effectively circumvents the requirement for secondary amniocentesis and reformulation of reduction protocols.