Infertility treatment
The exposure of interest was the mode of conception recorded in BORN, namely, i) unassisted conception (the reference group); ii) subfertility without infertility treatment (i.e., a history of an infertility consult with a physician, defined as an ICD-9 628 OHIP diagnosis in the 2 years prior to the estimated date of conception, and in the absence of receipt of infertility treatment); iii) non-invasive infertility treatment (i.e., ovulation induction [OI] or intrauterine insemination [IUI] alone); and iv) invasive infertility treatment (i.e., In Vitro fertilization [IVF] or intracytoplasmic sperm injection [ICSI]).