Well, sure. I have a theory.
I'm thinking that KC may have been (falsely) claiming to be pregnant to get sympathy/attention/money for baby clothes/money for an abortion/whatever. Later, when she was having her period, she forgot about supposedly being pregnant and borrowed feminine supplies from a friend then had to come up with the miscarriage story.
Alternatively, KC really was pregnant and told everyone except Cindy - as we have all heard on the tapes, KC really, really likes to hear herself talk - then she decided to get an abortion but knew people would be more sympathetic if she claimed to have miscarried.
A genuine miscarriage would normally have involved 1) medical diagnosis of the pregnancy by a health care provider and 2) medical treatment after the miscarriage. I have never met a woman who miscarried who did not seek medical treatment, because: What it if wasn't a miscarriage? What is if was only a threatened miscarriage and the woman needs hospitalization and/or bedrest to protest the fetus and herself? What if it was an incomplete miscarriage and some of the placenta was retained in the uterus, causing potentially life-threatening continued bleeding and sepsis? How would Casey afford to pay for these things without Cindy's help? After all, Cindy's help was required to pay for Casey's medical expenses with Caylee. So, if there had really been a miscarriage, Casey would have had to tell Cindy about the prior pregnancy and presumably Cindy would have been able to figure out that Casey had been having sex.
Bottom line: Since the miscarriage story was complete fiction, Casey KNEW because she was the one who made up the story.
Katprint
Always only my own opinions