I was taking zoloft (sertraline) when i had 3 miscarriages could this have been the cause? all tests were fine.

Yes, it is possible.: According to a study published in a canadian study of more than 5, 000 women, there was an association between taking antidepressants, particularly the selective serotonin reuptake inhibitors (ssris) such as paxil, (paroxetine) prozac, and zoloft, and an increased risk for miscarriage. But researchers caution that this association does not imply a cause-and-effect relationship.