Ay, maganda ang tanong mo! Based sa experience ng ilan sa amin, most hospitals will only bill to one primary HMO card during delivery kaya hindi mo pwedeng gamitin pareho simultaneously, usually ang card ng hospital network nila ang priority, tapos ang iba ay considered secondary lang. Best approach is to call both your HMO providers directly and ask kung sino ang magiging primary sa maternity benefits, then inform the hospital kung saan mo gustong i-bill ang delivery nang walang confusion on the day itself. One of my mum friends did this and naka-save pa siya ng time at stress during admission dahil lahat na-clear na beforehand!