Here is some information that I found about chest infections from Love Life Matters:
Chest Infection During Pregnancy?
I'm 24 weeks pregnant and have a chest infection. Firstly, I'm worried that all my coughing will distress the baby – is this reasonable? Secondly, what medicines can I take that are safe to the baby, but will ease my cough and cold? I have been taking blackcurrant linctus 3-4 times a day.
Unfortunately there is no way to avoid infections in pregnancy. In fact, women are slightly more prone to infection in pregnancy than they would otherwise be.
It is normal to be concerned about the baby throughout pregnancy, and many women worry about the effects of excessive coughing. The baby is remarkably resilient and will not be affected by your cough and cold. I would not advise that you take any medicines apart from paracetamol for any fever or discomfort that you might have. Usually symptoms such as yours will last for a couple of weeks and will then begin to settle. If you are coughing up phlegm or your symptoms are not easing after this time, it would be a good idea to arrange to see your GP so that you can be examined. If there is evidence of bacterial infection a course of antibiotics may be needed, and there are several antibiotics that can be safely used in pregnancy. If this is not the case, drinking plenty of fluids and using some steam inhalation is likely to help, and over a period of weeks your symptoms will settle.