A situation when a female is disillusioned into thinking that having a man's baby will keep him from leaving her.
She purposely gets pregnant by him in hopes that things will improve or work out but the seldom do.
"Tonya knows that Lil' Ray is a 'keep a nigga baby' in that she got pregnant right before James was to go to Australia and start working for 2 years before he came home"
"Yeah, Terry got trapped with a 'keep a nigga baby' -- he told Wendy he didn't want anything more to do with her so after 5 years, she coincidentally got pregnant right at the end".
When a nigga' gets inside a bitch, and that bitch be keepin' the baby.
John fucked Sally. Sally got pregnant. Sally decided to keep the baby, to keep John around. You ask, "Hey, why's John still dating Sally?" Response? "Sally had a Keepanigga baby, and that nigga' got screwed."