You should manage your asthma in the same way as usual during pregnancy. Your inhalers are safe for you and are not know to harm your baby.
You can increase your dose of inhaler as indicated in your asthma plan if you start to feel more breathless. For example you may need to increase the dose of your preventer inhaler if you feel a cold coming on. You should make a check up appointment with your doctor.
If you need a steroid course while you are pregnant, this is also safe and will not harm your baby.
If you have any concerns about your asthma medicines see your doctor before you stop any medicines. You should also check before you buy any over the counter medicines.