For Mad Men fans, you may have been shocked to find out that Peggy could go into labor after spending her entire pregnancy not realizing she was going to have a child. But even now, some women don't realize they're pregnant, giving new meaning to the phrase "unexpected pregnancy."

It seems obvious that pregnancy symptoms would have you thinking you may need to see a doctor. But as it turns out, studies in Ireland and Germany revealed that about one in 600 babies is born to a woman who has no idea she was pregnant until really late in her term, or when she went into labor.

The Times Online relays stories of women who showed no obvious signs of pregnancy, until after she learned the news. "It's as if I'd been unconsciously holding everything in," one woman reports.

Cases of older women believing they are entering initial stages of menopause find themselves with a positive pregnancy test at the doctor's office. Perhaps most surprisingly of all, one woman went to her doctor complaining of appendicitis pain. A few minute later, a crying lump in her pajama pants revealed something quite different.

The little research that has been done to explain this gap in knowing when you're pregnant points to some sort of repressed feelings or denial - an unconscious desire to not acknowledge their pregnancy. One German study goes so far to say that "intense psychological conflicts about the pregnancy" may keep women from seeing that they are in fact in term.

Let's not dilute all explanations down to psychosis, however. Women with irregular periods, who may often fluctuate in weight, and have been using some sort of birth control, may not easily recognize the difference between their day to day lives and suddenly becoming pregnant. The bump may not be suddenly there. The mood swings may already have been there.

Times Online goes on to report that there is little difference statiscally between the babies whose mothers receive care from health professional throughout their pregnancies and babies whose mothers come in later in their term.

What can we take away from this information? One wonders if there was more openness about reproductive health and abortion, if women would be less anxious and terrified about pregnancies and thus acknowledge an unplanned pregnancy if it happened.

Have you experienced the stories above? Have you been completely unaware of your pregnancy until months later? What do you think causes these occurrences?