What Lead To Miscarriages In My Last Two Pregnancies?

Doctor, i had a history of two miscarriages, one at 6 weeks, inevitabe and another at 16 weeks, missed miscarriage.i had my blood tests done on cardiolipin. everything normal, but doctor said it happened may be becoz i had a normal high la screen and la confirm, 40.7 and 38.5 respectively and the ratio to be 1.05. the doctor has asked me to take aspirin just after i get concieved...can u please tell me is it becoz of my high normal value of la i had the mc,s??