Pfeiffer syndrome，an extremely rare autosomal dominant disorder in prenatal settings，is caused by pathogenic variants in Fibroblast Growth Factor Receptor 1（ FGFR1）or Fibroblast Growth Factor Receptor 2（ FGFR2）. In this article，a 33-year-old pregnant woman whose fetus was diagnosed with Pfeiffer syndrome type Ⅱ was reported. Initial ultrasound at 23 +1 weeks revealed temporal skull depression and spinal alignment abnormalities. By 29 +3 weeks，subsequent ultrasound identified additional findings：a cloverleaf-shaped skull，midface hypoplasia，elbow joint fusion，and broad thumb/toe deformities. Fetal MRI confirmed cranial deformities and sacral kyphosis. Postpartum，a CT 3D reconstruction demonstrated craniosynostosis and humeroulnar fusion. Whole exome sequencing（WES）identified an FGFR2 pathogenic variant. This case dynamically illustrates the phenotypic evolution of Pfeiffer syndrome type Ⅱ from subtle to classic triads during gestation，highlighting that multimodal imaging combined with WES enables precise diagnosis and facilitates genetic counseling.

Pfeiffer syndrome，an extremely rare autosomal dominant disorder in prenatal settings，is caused by pathogenic variants in Fibroblast Growth Factor Receptor 1（ FGFR1）or Fibroblast Growth Factor Receptor 2（ FGFR2）. In this article，a 33-year-old pregnant woman whose fetus was diagnosed with Pfeiffer syndrome type Ⅱ was reported. Initial ultrasound at 23 +1 weeks revealed temporal skull depression and spinal alignment abnormalities. By 29 +3 weeks，subsequent ultrasound identified additional findings：a cloverleaf-shaped skull，midface hypoplasia，elbow joint fusion，and broad thumb/toe deformities. Fetal MRI confirmed cranial deformities and sacral kyphosis. Postpartum，a CT 3D reconstruction demonstrated craniosynostosis and humeroulnar fusion. Whole exome sequencing（WES）identified an FGFR2 pathogenic variant. This case dynamically illustrates the phenotypic evolution of Pfeiffer syndrome type Ⅱ from subtle to classic triads during gestation，highlighting that multimodal imaging combined with WES enables precise diagnosis and facilitates genetic counseling.