It is significant that Anna's announcement of her pregnancy occurs at the same time Vronsky's passion for horses bears fruit, his imminent victory at the steeplechase. Both situations demand all the resources of which Vronsky is capable in order to meet the challenge. Both crises are confrontations with destiny.
With obvious significance, Tolstoy remarks that Anna and Vronsky appear to him as a fine mare and full-blooded stallion (an analogy which other critics have also pointed out). Mahotin's stallion wins the race, but the sensitive mare loses her life. The close relationship between rider and mount is akin to Vronsky's bond with Anna. The intensity of their unlawful love is like the intensity of the steeplechase with their life running a course of obstacles which both, as one, must overcome until their race against moral law is won.
But Frou-Frou's entire being exists for racing, Anna's for loving; that the mare breaks her back in fulfilling the purpose of her existence prefigures Anna's subsequent doom. Vronsky, however, does not share his horse's commitment to the race. Though he loves Frou-Frou while they are in the run, his passion for racing is basically frivolous and self-indulgent. The analogy applies to his love affair, where Vronsky, though deeply in love, is not committed to Anna as she is committed to him. That Vronsky's lack of commitment can make him destructive when his mount flounders (he kicks the mare) presages his hostility to Anna when their relationship becomes irritating.
