Statistics analysis result showed that there was a high correlation between the size of gestational sac and body,crown-rump length,head,biparietal diameter(BPD),thoracic depth,heart diameter of embryo or feta and the days after mating.

• 观察胎囊、胎儿、胎心、胎动、胎儿脏器、胎儿骨骼出现时间和测量胎囊大小、冠臀长、胎儿身长、头长、双顶径、胸深和心区大小 ,证明胎囊大小、胎儿冠臀长、身长、头长、双顶径、胸深与胎龄呈显著正相关。