Original: One study testing hormones for ovulation and pregnancy found that 61.9% of conceptuses were lost prior to 12 weeks, and 91.7% of these losses occurred subclinically, without the knowledge of the once pregnant woman.
Simplified: One particular study showed a rate of pregnancy in exposed ovulatory cycles of 59.6%; with 61.9% of conceptuses lost before twelve weeks. 91.7% of these occuried subclinically, without the knowledge of the mother.