DP didn't know she was pregnant until she went into labour.
She has a titled uterus, which was apparently responsible for the fact she didn't feel any movement, and she didn't show (helped by a bit of new relationship weight gain).
She was on the pill so having light periods, and had a bit of breakthrough bleeding during the pregnancy, which made her think periods were continuing.
The only symptoms she had were some bad indigestion for the last month of the pregnancy, which was being investigated by her GP, and some breast soreness for the last couple of weeks, at which point she did take a pregnancy test. However it came back negative as they're not designed to be taken that late.
While I know in some cases like this the pregnancy is being hidden, I can categorically say this isn't the case with DP. She behaved normally throughout, we went ice skating a few weeks before she gave birth, to Alton towers a few weeks before that. She drank throughout, going on two hen dosnwhile pregnant. She was in work the night before she gave birth, lifting heavy boxes.
This is a woman who is incapable of killing a fly, there's no way she'd knowingly do anything that might hurt her child.
I do get the disbelief that a lot of women get when they hear this story. When you've felt your child move inside you, or had an absolutely horrendous pregnancy, it's hard to imagine someone else could go through it without even knowing. But it does happen.