[Clinical analysis of 21 cases with short fetal femur in the third trimester].

Objective: To analyze the clinical features and to explore the etiology of short fetal femur during the third trimester. Methods: From January 2010 to June 2016, 21 singleton pregnancies with short fetal femur detected by ultrasonography during the third trimester were referred to the Chinese PLA General Hospital. Clinical data were collected, karyotype or single nucleotide polymorphism microarray was carried out to detect chromosomal abnormalities, and FGFR3 c.1138G>A mutation detection was carried out to detect achondroplasia (ACH) via invasive procedure, respectively. The deviation of femur length from the mean value of the gestational age in ultrasonography was expressed as the Z-score. The difference between ACH and isolated short femur (ISF, in the absence of associated structure abnormality or genetic abnormality) was then explored. Results: In the 21 fetuses, 11 had abnormal genetic test results(52%, 11/21), including 9 cases of ACH, 1 case of Ellis-van Creveld Syndrome and 1 case of Pallister-Killian syndrome. In the 10 ISF fetuses (48%, 10/21), 3 cases were fetal growth restriction, 1 was normal small for gestational age infant and 6 cases were unexplained. The median Z-scores for 9 cases of ACH and 10 cases of ISF in the third trimester were -5.04, -3.20, respectively. The short femur in ACH was more severe than in ISF (P=0.005) in the third trimester. Conclusions: The etiology of short fetal femur is complicated, including skeletal dysplasia, chromosomal abnormality, fetal growth restriction, as well as normal variants during fetal development. Genetic test should be considered during the antenatal consultation.目的： 对妊娠晚期发现的股骨短小胎儿的临床特征进行分析，并探讨其病因。 方法： 收集2010年1月至2016年6月因妊娠晚期超声检查诊断"胎儿股骨短小"就诊或转诊至解放军总医院的21例单胎妊娠孕妇的临床资料；通过侵入性产前诊断对胎儿进行染色体核型分析或单核苷酸多态性微阵列检测，明确胎儿有无染色体异常，同时行Sanger测序明确胎儿是否携带软骨发育不全（ACH）的致病基因FGFR3基因c.1138G>A突变以确诊ACH。以Z值反映胎儿股骨长度的超声测量值偏离相应孕周均值的程度，比较ACH胎儿与孤立性股骨短小（ISF；无胎儿结构畸形及遗传学检测异常）胎儿的股骨长度的差异。 结果： 21例妊娠晚期股骨短小胎儿中，11例胎儿（52%，11/21）遗传学检测发现异常，其中ACH 9例（9/21），软骨外胚层发育不全综合征1例，12号染色体短臂四体所致的Pallister-Killian综合征1例；另有ISF胎儿10例（48%，10/21），其中胎儿生长受限3例，正常的小于胎龄儿1例，原因未明的股骨短小者6例。妊娠晚期9例ACH与10例ISF胎儿股骨长度Z值的中位数分别为-5.04、-3.20；与ISF胎儿相比，ACH胎儿妊娠晚期股骨短小更为严重（P=0.005）。 结论： 妊娠晚期胎儿股骨短小的原因复杂，可能为ACH等先天性骨骼畸形、染色体异常以及胎儿生长受限等，或为胎儿生长发育过程中的正常变异，需要结合遗传学检测进行咨询。.