they dont engage fully like first babies, but subsequant can start to engage at around 34 weeks and up. Im sure baby CRX was starting to engage like that around the same time and she was born at 40+4.
make sure your bags are packed ready though, hope youre not kept waiting too long
when this happened to my mate her midwife told her not to be dissapointed if it disengaged itself by the next appointment. I think they move around more freely than with your first.