O'Rahilly R, Müller F
Anat Rec. 1984 Jun;209(2):265-71. doi: 10.1002/ar.1092090212.
The greatest length (GL) and the crown-rump (C-R) length were compared in 43 staged human embryos. It was found that point C, which overlies the middle of the midbrain, was sometimes difficult to locate and that point R is not precise. These disadvantages render the C-R measurement unsatisfactory. At 4 weeks (stage 13) the GL comes to exceed the C-R and continues to do so until about 7 weeks (stages 17-19). The maximum difference is approximately 1.5 mm. Thereafter, the two lengths are basically equal and coincide from about stages 18 and 19 onward. In a series of 100 embryos of stages 19-23, female embryos at stages 21 and 22 were found to be shorter (by a mean of 1 mm) than male embryos, but not at stages 19, 20, and 23. The greatest length, which is independent of fixed points, is much simpler to measure than the C-R length, and it is recommended that it be used instead. It is pointed out that Streeter had already made that substitution. The greatest length has the further advantage of being a practicable measurement from two postovulatory weeks (stage 6) throughout the remainder of the embryonic and also in the fetal period. The lower limbs are excluded from measurement.
在43个分期的人类胚胎中对最大长度（GL）和顶臀长度（C-R）进行了比较。发现覆盖中脑中部的C点有时难以定位，且R点不准确。这些缺点使得C-R测量结果不尽人意。在4周（第13阶段）时，GL超过C-R，并一直保持这种状态直到约7周（第17 - 19阶段）。最大差值约为1.5毫米。此后，这两个长度基本相等，从大约第18和19阶段起重合。在一系列100个第19 - 23阶段的胚胎中，发现第21和22阶段的雌性胚胎比雄性胚胎短（平均短1毫米），但在第19、20和23阶段并非如此。最大长度不依赖于固定点，比C-R长度测量起来要简单得多，建议使用最大长度来替代。需要指出的是，斯特里特早已进行了这种替换。最大长度还有一个优点，即从排卵后两周（第6阶段）直至胚胎期剩余时间以及胎儿期，它都是一种可行的测量方法。测量时不包括下肢。
