Well the 1st thing to do, is go to the municipal registry in the district where you married and obtain a shortened form of SECPA this is NSO Security papers showing the your marriage entry in the register of marriages, even though ou may not have your NSO Marriage contract, you may still be still apply for SECPA.
Once having done this, you will need to have a good bank balance on your bank statements, showing your last 6 months income, you will need to prove to the ECO that you can support your wife in the UK when resident and that your will not be the subject of a public funds request on returning into the UK.
If you have worked in China, its unlikely that you would qualify for public funds in any event, however there is an unwritten rule that if your wife gets into distress, she may make an emergency application for public funds, this is what the government is not keen for you to know.
Hence the need to prove you must be able to support your wife without recourse to public funds.
In any event, why the rush back to UK ? your child does not have to be born in the UK just because you are worried about British Nationality, the fact is, if your child is born in the Philippines, you simply go along with your wife to the British Embassy Consular section and apply to register your child as a British Citizen, which by the way regardless of marriage is the right of all Fathers under the BRITISH NATIONALITY ACT which was amended last year.
If its the matter of the pregnancy and flying, suggest your submit your application following the procedures asap, and explain the urgency to the UKVACS centre in Makati, as you are in the Philippines now, at least you can go around and organize your paperwork on site, and get your application in asap.
Bank statements will be the key to your application being successful, you could also show that you are a professional person, and that you intend to take up employment on your return, i.e. networking with your former employers, or similar.
All I can give you in the form of reassurance is to say, don't be unduly worried and just get on with it, there is no reason why you cannot receive a visa for your wife to settle in UK.
The only thing I would say to you, is that if you are overdrawn at the bank or your bank statements don't show a healthy outlook, don't bother applying and wasting a P50,000 fee, thats my advice.