We first see slavery in The Joys of Motherhood when the senior wife of Nnu Ego's father dies, and her slave woman is buried alive with her despite the slave's protests that she wants to live. Nnu Ego is born some months later, and it turns out that the slave woman has become Nnu Ego's chi, her personal god. This god takes revenge on Nnu Ego years later when she struggles to get pregnant. The slave woman has become Nnu Ego's curse. After Nnu Ego finally is able to get pregnant, she struggles her entire life to keep her kids clean, clothed, and well fed. The slave woman/god continues to have her way with Nnu Ego, even after Nnu Ego's father frees all of his slave and adopts them as his own children.
But literal slaves aren't the only slaves in this novel. Ibo men who work for white masters in Lagos have ceased being "men." They no longer command their wives' respect in the same way because their wives see that they are not their own masters. Nnu Ego is also a slave, not only to her husband Nnaife who keeps claiming that he "owns" her because he paid bride price for her, but also to her children. Her love and sense of duty to the children she bore keeps her enslaved, even when they seem to disregard her well being.
Even though Nnu Ego is at first considered a failed woman without children, she soon discovers that having children enslaves her.
Although the prospect of making lots of money working for the white men entices Ibo men to come to Lagos, they soon discover that being a servant emasculates and enslaves them.