Laboratories of The Rockefeller Institute for Medical Research.
J Exp Med. 1936 May 31;63(6):901-21. doi: 10.1084/jem.63.6.901.
Observations were made on 475 fetuses carried by 71 pregnant rabbits. 63 or 88.7 per cent of the 71 does were sacrificed from 28 to 31 days after the last fertile mating, and these does bore 401 or 88.2 per cent of the total of 455 fully developed fetuses. The following information was available with reference to each fetus: age, weight, weight of corresponding placenta, horn, i.e., right or left, presentation, and position or order. The presentation indicated that part, head or breech, which was directed toward the vagina, and position or order, the relative locus of the fetus in the horn, the first position being that nearest the ovary. As the gestation period approached its normal limit of 31 days, the relative daily increase in mean fetal weight was progressively retarded. There was no significant difference between the number of fetuses in each uterine horn. Head presentation was significantly more frequent than breech, but the uterine horn in which the fetus was located had no influence on its presentation. A greater relative number of breech presenting fetuses was observed in the third position than in the other positions. Presentation did not exert a significant influence on fetal weight. Fetal weight at or near term was significantly influenced by the position or order in the uterine horn. In general, the weights of fetuses implanted high up nearest the ovary were greater than those developing nearest the outlet, and fetuses occupying intermediate positions had intermediate weights. When, however, only two fetuses were present in a horn, position had no effect on their weights. A significant positive coefficient of correlation was observed between fetal and placental weights. Moreover, placental weight was influenced by position in the uterine horn in exactly the same manner that fetal weight was so influenced. The factors which produced variability in fetal weight at or near term, did not account for the abnormally low birth weights of the dwarf rabbits observed in this laboratory.
对 71 只怀孕的母兔所怀的 475 只胎儿进行了观察。71 只母兔中有 63 只（占 88.7%）在最后一次交配后 28-31 天被处死，这些母兔产下了 455 只完全发育的胎儿中的 401 只（占 88.2%）。每只胎儿都有以下信息：年龄、体重、相应胎盘的重量、角（即右角或左角）、分娩部位和位置或顺序。分娩部位表示朝向阴道的胎儿头部或臀部，位置或顺序表示胎儿在角中的相对位置，第一位置是最靠近卵巢的位置。随着妊娠期接近正常的 31 天，胎儿体重的日相对增长率逐渐减慢。两个子宫角中的胎儿数量没有显著差异。头部分娩的频率显著高于臀部分娩，但胎儿所在的子宫角对其分娩部位没有影响。在第三位置观察到的臀位分娩胎儿数量相对较多。分娩部位对胎儿体重没有显著影响。接近足月时的胎儿体重受子宫角位置或顺序的显著影响。一般来说，靠近卵巢的植入位置较高的胎儿体重较大，而靠近出口的胎儿体重较小，占据中间位置的胎儿体重居中。然而，当一个角中只有两个胎儿时，位置对它们的体重没有影响。胎儿体重和胎盘重量之间存在显著的正相关系数。此外，胎盘重量受子宫角位置的影响与胎儿体重的影响完全相同。在接近足月时导致胎儿体重变化的因素，并不能解释在本实验室观察到的矮兔异常低出生体重的现象。
