国内、外多数人体解剖学教科书或人体胚胎学专著，对胎儿次级骨化中心（ｓｅｃｏｎｄａｒｙｏｓｓｉｆｉｃａｔｉｏｎｃｅｎｔｅｒ，ＳＯＣ）出现的时间比较一致的看法是在胎儿出生以后，或仅比较含糊地指出是在出生前后出现。作者对３４６例受精龄为１２～３８整周的正常妊娠中胎儿进行了超声检测，测量记录了多项生长值和ＳＯＣ出现的情况，并配合了部份胎儿标本５６例实地解剖观察。超声检测结果显示，自２９周龄开始，股骨远端有ＳＯＣ出现，此后ＳＯＣ的百分率逐周递增，到３４周出现率为１００％。 At home and abroad, most human anatomy textbooks or human embryology monographs, a consistent view of the timing of appearance of secondaryossification centers (SOCs) is the appearance of the fetus after birth or only vaguely before and after birth . The author of 346 cases of fertilization age of 12 to 38 weeks of normal pregnancy in the fetus was detected by ultrasound measurements were recorded a number of cases and the occurrence of SOC, and with part of the fetus in 56 cases of field anatomy. Ultrasound results showed SOC began to appear at the distal femur since 29 weeks of age, and the percentage of SOC increased gradually from week to week, with an incidence of 100% at 34 weeks.