To summarize prenatal two-dimensional ultrasound examination results of different types of fetal limb deformity, and emphasise on some rare deformity disease such as phocomelia and sirenomelia. To investigate the value of systematic continuous sequence approach in the examination of fetal limb during pregnancy periods.

Eighteen thousand seven hundred and eight cases of fetus were selected from September 2014 to August 2016 in the 105^th Hospital of Chinese People′s Liberation Army, which were screened by routine and systematic ultrasonography. The systematic continuous sequence approach was used to focus on examination of the fetal limb. All fetuses with abnormal limbs were followed up. The ultrasonographic images were compared with the results of pathological examination and X-ray examination to summarize the ultrasonographic features of fetal limb deformities.

Seventy-six cases of fetal limb deformity were detected by prenatal ultrasound system in 18 708 cases. Three cases were detected at 11-13^{+ 6} weeks of gestation, 18 at 14-19^{+ 6} weeks, 38 at 20-27^{+ 6} weeks, 17 at 28-35^{+ 6} weeks. Types of limb deformities are as fllowing, 11 cases of abnormal number of fingers (adactylism, polydactyly, syndactyly), 2 cases of cleft hand deformity, 45 cases of foot varus, 1 case of sirenomelia and 4 cases of short limbs. Thirty-seven cases of fetal limb deformity combined with other system malformations and 12 cases were with multiple system malformations. Karyotypes were abnormal in 11 cases, including 3 cases of trisomy 21, 6 cases of trisomy 18 and 3 cases of trisomy 13. One case of prenatal ultrasound diagnosis of twins with sirenomelia. An autopsy of twin fetus indicated that there were epactal toes at the left foot. Prenatal ultrasonography.

The systematic continuous sequence approach in early and middle pregnancy play the advantages of each pregnancy examination. The fetal limb deformity can be detected early by combining application of systematic continuous sequence approach.