Would women have really been married off as young as 12 during antiquity?

In the novel creation which is set during the reign of Xerses I the protagonist a Persian nobel marry's the daughter of an Indian king when she is 12 years old and consumate there marriged three nights after marrying her and she gives birth to his son 9 months later. Would that have been common? Was it not know back then that women getting pregnant and giving birth that young would have massively increased the chances of either her or the baby or both dying?