At demography.matters.blog Edward Hugh discusses what appears to be an emerging "birth rebound" in China attributed by the Chinese government to the idea that "Newly rich couples can afford to pay fines to have more than one child, while rural couples are marrying earlier."
It strikes me that one aspect of China's fertility policy that will have unpredictable social consequences sometime in the near(next twenty or so years) future is the gender imbalance that has resulted from the combination of the official one child policy and the well documented preference of Chinese couples for having a boy rather than a girl.
I also think that the gender imbalance will have an impact on future fertility rates as there will be a meaningful proportion of the Chinese population that will be unable to reproduce (i.e. all of those males that can't find a wife), and that any particular cohort that one might choose to look at will have lower than expected fertility due to the lack of females in the cohort. To me, this will skew fertility rates lower than a basic "size of the population of reproductive age" analysis might predict.