Three in four, according to Guttmacher. Half are due to failure to implant, and go by undetected.

But part of the problem is women who miscarry often suffer from mental illness, including an unreasonable belief that somehow they are at fault. (Selection is part of the gestation process. Many, many conceptions are incompatible with life even in perfect conditions.) So law enforcement may be capitalizing on a demographic that already feels guilty.