maclover - I wish you luck in getting your wife back yo HK prior to giving birth.

If I was in your position, I would be calling anyone and everyone at CX, explaining position, the timings you require, and to get a contact who you can turn to in an emergency if needed.

Not sure of the exact rules on pregnant fliers, but all airlines have different requirements for medical letters certifying fit to fly, and also cut off dates after which they will not allow such passengers to fly.

Time does not sound to be on your side, so please just be proactive in constantly contacting the airlines.

Good luck.