The main impact that can be seen from the time period on the characters' lives is through the societal conventions that existed. In the time period of the story, slavery was a common practice in the south, and so slaves were considered as lesser people, with no rights or say of their own. As a result, the white people often took advantage of them, and treated them poorly. This results in many of the pregnancies and unique relationships between the characters in the novel. The slave women were manipulated by the white owners, and because of their "lower" class in society, they didn't have control over the situation. The mixed-race dynamic plays a role too, where the children of these relationships are not afforded full status either because of their partial slave lineage. So, the social conventions of slavery at the time played the largest role in the lives of the characters.
I hope that helped to get you started; good luck!