What if all we ever find out is that they hid two pregnancies, completely isolated two babies, all because of some vague, nonsensical fear of parental/family scorn since they weren't married (even though they were living together)? What if that is ALL there is to the story? What if there is no sexual abuse, no incest, no unnamed biological parents, no super-religious-to-the-point-of-crazy inlaws, no underage sex cover-up, no gender discrimination, no child trafficking, nothing? Just "Well, we were kind of worried what our families would think." Even Shannon's lawyer said it didn't make sense, but that was their minimal reasoning.
Shannon DID conceal and deny at least one pregnancy, making her very unusual -- especially because she kept concealing the babies alive instead of killing or abandoning them. Personally, I don't think Shannon is the naive young woman pushed around by the older guy. I don't picture a man saying, "We can't tell our families!" and any normal pregnant woman saying, "Okay, I won't tell anyone I'm pregnant. I'll hide it and then we can hide the babies too." No, this is the kind of crazy business specially reserved for women.
When a study was done to find out what kind of women conceal and/or mentally deny their pregnancies, the researchers were surprised at their findings. They found that these women "were predominantly over the age of 18 and were multigravidas" (had multiple pregnancies, miscarriages, abortions, even other living children). The women didn't all claim that their parents or baby-daddies were unusually judgmental where they wouldn't have been supportive. Also, "contrary to our hypothesis, abuse histories were not commonly noted." They also noticed these women were usually kind of quiet.
There is an assumption that a woman who conceals/denies mentally that she is pregnant does so because a) she has abusive parents, or b) she has no support system, or c) she's never been pregnant before and is clueless -- but none of these assumptions holds true. I don't think any of these assumptions will hold true with Shannon either.
One study found that of women with pervasive denial of pregnancy (meaning they denied it even to themselves all the way thru to delivery) "48% had some documented mental disorder, and ...10% were mentally retarded." So schizophrenia, personality disorders, or diminished intelligence were found in 58% of the women. But that leaves 42% who did NOT have any obvious mental problem.
I don't think Shannon was completely nuts or profoundly retarded -- it takes a lot of planning to conceal two children. I'm afraid there is no easy explanation, just as there is no easy explanation when a normal-seeming, diligent student with loving, supportive parents dumps a baby in the bathroom at the prom (Melissa Drexler). She blankly, unemotionally admitted it when questioned. Something missing there, as with Shannon.
Study:
http://psy.psychiatryonline.org/cgi/content/full/48/2/117
Melissa Drexler:
http://www.people.com/people/archive/article/0,,20122470,00.html