You have no right to be on their property: you are not a tenant. A landlord or property owner can control who may enter their property, and an employer can refuse to let workers/employees have guests at their property--employers may also   ban former employees from their location. For all these reasons, they can refus to let you on or at their property and have you arrested for trespassing if you do enter. Your finance's pregnancy is irrelevant and does not affect their rights.