Abstract Objective: To understand phenotyping and prognosis for fetuses with 16p13.11 deletion/duplication in East Asian population. Design: Retrospective prenatal and patient cohort study in southern China. Setting: Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region. Population: All fetuses and patients underwent chromosomal microarray analysis between April 2013 and July 2024. Methods: We conducted a comprehensive ultrasound phenotypic analysis, pedigree analysis and long-term postnatal outcome follow-up on 201 fetuses, as well as phenotypic manifestations on 14 patients with 16p13.11 deletion/duplication. Descriptive statistical analysis was used. Main outcome measures: Prenatal ultrasound characteristics and postnatal clinical phenotypes. Results: The detection rates were 0.08% and 0.18%, the frequencies of de novo occurrence were 26.9% and 14.5%, the rates of abnormal postnatal phenotypes were 25% and 17.5% in our prenatal cohort of deletion and duplication. 28.6% of deletions and 15.9% of duplications exhibited abnormal postnatal phenotypes even if inherited from a phenotypically normal parent. Developmental delay was the most common clinical abnormality. Immune disorders, torticollis, concealed penis and cryptorchidism were closely related phenotypes that had previously gone unnoticed. The deletion was closely associated with isolated choroid plexus cysts. Thickened nuchal translucency and choroid plexus cysts were the Top 2 ultrasound characteristics for duplication. Conclusion: The largest East Asian prenatal cohort is conducive to enhancing genetic counseling for 16p13.11 deletion/duplication syndrome by facilitating a more accurate prediction of fetal prognosis and developmental potential. Keywords 16p13.11 deletion/duplication, Prenatal diagnosis, Postnatal outcome follow-up, Genetic counsel