I have a crazy question that requires a (crazy?) medical professional's attention.

[Arkansas Granny]

4. I found some information, but I don't think it answers your specific question.

A miscarriage is a pregnancy loss that occurs before 20 weeks, well before the fetus is able to survive outside the womb. About 10 to 15 percent of recognized pregnancies end this way (1, 2). As many as 40 percent of all pregnancies may end in miscarriage, because many losses occur before a woman realizes she is pregnant (3).

http://www.marchofdimes.com/baby/loss_miscarriage.html

These stats are for miscarriages due to any cause, not just failure to implant. I've always wondered how people could claim that each fertilized egg is so precious to god when so many of them are shed so early in pregnancy, sometimes before a woman even knows she is pregnant.