This change in morphology is associated with important physical and cytochemical changes and with an increase in their capacity for motility and their fertilizing ability. 这种形态学的变化是与重要的物理学和组织化学的变化以及活力和受精能力的增强有关。
When it is not, then availability of IVF depresses the birth rate because women balance the cost of a child against the extra income they could earn in employment outside the home. 当它得不到巨额补助的时候，试管受精便使生育率越发低下，因为妇女会对生育孩子的成本和她们在外受雇所挣的额外收入进行比较。
