Professor Yesenia Barragan (History) has produced a major website dedicated to the study of the "free womb"--the practices in many countries of "freeing" the children of enslaved women:

"This project is a resource for students and scholars of slavery and emancipation in the Atlantic World. Each law has been translated into English and Spanish and can be accessed in the “Laws” section. On this website, visitors can also find a brief introductory historical essay, a “Suggested Readings” list, and an “Image Gallery” featuring an assortment of historical images relating to the process of gradual abolition in the Atlantic World."

The website includes a database of laws and a bibliography.

in her introductory essay she notes that:

"While the history of abolition often evokes images of the sudden, immediate termination of chattel slavery, the majority of governments in the Atlantic World—from the state of Pennsylvania in the northern United States to the Empire of Brazil—actually implemented policies of gradual rather than outright abolition in the late eighteenth and nineteenth centuries.

What exactly was meant by the “gradual abolition” of slavery? “Gradual abolition” was a legislative approach to terminating chattel slavery through gradual, and not immediate, means. Specifically, it legislated that the children of enslaved women born after a specific date would be freed immediately or after serving their mother’s master under a particular period of bondage—for example, until the age of twenty-five in the case of the Connecticut law of 1784 or the age of eighteen in the case of the Gran Colombian (encompassing modern-day Colombia, Ecuador, Venezuela, and Panama) law of 1821. This generation of children would therefore be the last formally bonded peoples of African descent in the Atlantic World. In practice, gradual abolition laws abolished the longstanding logic of slavery: partus sequitur ventrem, or the (enslaved) status of the child derives from that of the mother. As such, no chattel slaves would be born in these different states, republics, imperial regimes, or colonies, thus amounting to the protracted, gradual abolition of slavery."