This study investigated the association between miscarriage karyotype and body mass index, maternal age, and mode of conception. Miscarriages after IVF and/or intracytoplasmic sperm injection were less frequently aneuploid; advanced maternal age was associated with an increase in aneuploid products of conception; overweight and obese women aged <35 years were less likely to have aneuploid miscarriages than women in a healthy weight range, suggesting alternate mechanisms for miscarriage in this population.