Objectives To summarize and analyze the characteristics ofspina bifida occulta in prenatal ultrasound scan in order to improve the accuracy of diagnosis.Methods Sixteen singleton pregnant women with fetal spina bifida occulta who were diagnosed in the Ultrasonography Department of Dalian Maternal and Child Health Hospital from January 2014 to April 2015,were enrolled in this study.Diagnosis was made based upon the abnormalities found in the spinal column of fetus during routine ultrasound scan,followed by a close examination on the fetal spinal column and the position of conus medullaris by using multiple scan.Descriptive analysis was used to summarize the characteristics of spina bifida occulta in ultrasonic images.Results Among the 16 cases,12 had subcutaneous mass (nine cases had follicle-like anechoic mass and three cases had masses with strong echoes).The other four cases without subcutaneous mass manifested signs of disappeared physiological curvatures or disordered arrangement of spinal column,angulation deformity or scoliosis,or asymmetry in ossification centers of spinal column on both sides of lesions and lowered position of conus medullaris.Lemon shaped head and banana shaped cerebellum were seen in one case,while the other 15 cases were found no cerebral abnormalities.Eight cases had tethered cord (the position of conus medullaris was lower than the second lumber vertebra),six cases had unclear position of conus medullaris and the other two were normal.Diagnoses for all of the 16 cases were confirmed by MRI after delivery or autopsy or neonatal operation.Conclusions Abnormalities such as subcutaneous mass and tethered cord observed in prenatal ultrasound scan are significant indicators for suspected closed spinal dysraphism and further multiple scan is required to confirm the diagnosis.

We reported one fetus who was identified with significantly short humeri and femora,bulging abdomen and narrowed chest at 22+2 weeks' gestation,which was consistent with clinical findings at birth.Genetic analysis revealed that this was a case of short-rib thoracic dysplasia syndrome (type Ⅲ) caused by compound heterozygous mutation in DYNC2H1.We summarized the features of prenatal ultrasound imaging and results of postpartum genetic analysis of this case to provide information for prenatal ultrasound diagnosis and postpartum consultation.