If I just accepted a new job that is fully physical (airport), can I be terminated within my probationary period because I need special accommodations and cannot perform the job I was hired for?

Unfortunately, yes--you may be terminated if you can't do the job for which you were hired. While employers must make certain "reasonable accommodations" for disabled employees--and pregnancy is considered a disability for this purpose--a reasonable accommodation is one that is neither too expensive nor too disruptive for the employer and which lets the employee do her job. A common example is letting a diabetic employee have brief snack breaks so she can balance her blood sugar, or lettting a cashier who would normally stand but who has a back or leg problem have a stool to sit. If the employee's condition simply does not let her do her job, the employer may terminate her, because employers do not need to pay people for not working, or transfer employees to different jobs, other than the ones they were hired for. 

Unfortunately, yes--you may be terminated if you can't do the job for which you were hired. While employers must make certain "reasonable accommodations" for disabled employees--and pregnancy is considered a disability for this purpose--a reasonable accommodation is one that is neither too expensive nor too disruptive for the employer and which lets the employee do her job. A common example is letting a diabetic employee have brief snack breaks so she can balance her blood sugar, or lettting a cashier who would normally stand but who has a back or leg problem have a stool to sit. If the employee's condition simply does not let her do her job, the employer may terminate her, because employers do not need to pay people for not working, or transfer employees to different jobs, other than the ones they were hired for.