How Can Asthma During Pregnancy Be Treated?

My daughter, 36 years old, pregnant with her 5th baby due in june (a boy) They are thrilled! She has a history of asthma since childhood (was hospitalized a couple of time between ages 6 and 9) Since around early September, she has been having exacerbation of her asthma to the point where she has been to the pulmonologist twice, put on steroids for 10 days, takes home treatments etc... she was cleared cardiac-wise in beginning of September (she had ekg stress test and echo) she had a CT chest at that time too... which all checked out ok. she has nothing new in her environment and has not changed her diet (eats very healthy) she says there is something wrong yet docs say they cannot find anything wrong. her husband bought a pulse oxymeter over the counter and she registers between 96 97 after treatment. she says she cleans the nebulizer daily, could it be old and need to be taken apart or cleaned differently? she has had it for about twenty years r more...I am wondering if other organs need testing like kidneys liver etC i cant think of any reasons why but maybe we are missing something...what would you recommend? further heart, lung testing? Any help would be appreciated My daughter does not panic easily and she knows her body and says something else is going on...Thank you