Slavery is usually worse than you think

The men were allowed to come on deck night and day if they wished, but it was the rule to whip the Negro men if they went in the hold with the women.  Aboard the Creole, sex was apparently (and, it turned out, wrong) deemed a greater threat than slave rebellion.  Gonorrhea, according to slaveholding commonplace, was a disease “generally contracted among Negroes en route who are brought for sale.”  A number of different traders had their slaves aboard the ship, and segregating them by sex was a way to keep one slaveholder’s slaves from diminishing the value of another’s by passing a disease — or starting a pregnancy.

That is from Walter Johnson, Soul By Soul: Life Inside the Antebellum Slave Market.