None of those mods are likely to be a problem. Unique slaves are created on the base of a normal slave, so they are not anything of note. It's possible that your save file may have data that indicates if playing in vanilla was the problem, but otherwise it may not help in determining the cause.
Viewing post in Aric's Expansion Rebred
Slaves impregnated in vanilla gameplay will have a baby ID in the "baby" field but will have "is_preg" still set to false. Slaves impregnated in this mod will have at least one baby ID in the "unborn_baby" field and the "is_preg" entry set to true. However, if the slave was added during vanilla gameplay but not expanded to have the addition data for the mod, then the "is_preg" entry will be missing, which is your primary problem.