Like most health care professionals who come in contact with obstetrics, I have seen this phenomenon many times before, and I always wonder where the level of denial is. I suspect that some who claim they didn't know they were pregnant really do know it but find it convenient or easier to deny it. The frightened single teen who just doesn't know how to handle telling her parents comes to mind. Others perhaps know that something is afoot but deny it to themselves. Then, maybe, there are those who have mental illness that makes them not recognize the pregnancy. Finally, there are probably some who really just don't figure it out that they are pregnant, although I suspect that's a minority of pregnancy deniers.
I guess I should be glad that this woman didn't continue to deny it after the baby was born. Now and then you hear about parents trying to flush a newborn down the toilet or throwing them in the garbage, although most of the time that's probably not a denial but just an act of desperation.
This mother had a diagnosis of schiziphrenia, although you sure wouldn't know it from talking to her. She seemed very lucid and rational. This was her fourth pregnancy, and it turns out it was the second time she didn't realize she was pregnant, which I guess makes her a serial pregnancy denier.
P.S. Shinga has asked me to remind people about the next Pediatric Grand Rounds. Submit your post to him by July 1, 1500 London time, at breath dot spa at googlemail dot com.